Applied Science, Faculty of
Civil Engineering, Department of
DSpace
UBCV
Anderson, Christopher D.
Master of Applied Science - MASc
University of British Columbia
Permanent ground deformations (PGD) are a major cause o f damage to buried natural gas pipeline systems, particularly in areas of ongoing ground deformation. A new testing apparatus was designed and constructed specifically to meet the requirements of full-scale physical modeling research on typical polyethylene natural gas pipeline configurations subjected to lateral ground displacements. The apparatus essentially comprised a large soil testing chamber in which pipeline configurations could be monitored with an instrumentation array measuring pullout resistance, pipeline displacement, and local strain within the pipe specimens. Specialized methods were developed for mounting strain gauges to polyethylene to obtain reliable readings, and to reduce imposed drag forces. A series of tests performed on straight pipeline sections indicated that peak axial pullout resistance predicted using published design equations tended to over-predict pullout resistance of polyethylene pipes in uncompacted sand, and to underestimate pullout resistance in dense sand. Significant limitations were found in the applicability of current design equations, developed from tests on rigid steel pipelines, to the prediction of axial pullout resistance of relatively "flexible" polyethylene pipelines. Several soil-pipeline interaction mechanisms have been suggested that seem to account for the observed differences in behaviour between polyethylene and steel pipelines. Axial tests on trunk lines with tee connections to smaller size branch pipes indicated that branched configurations experience a complex interaction with the soil. The branch pipe initially deflected and elongated in close proximity to the tee connection, then with increasing displacement, pipe deformation transitioned to axial pullout of the branch. The contribution to pullout resistance from the branches was similar in both uncompacted and dense sand, and also was not significantly affected by the diameter of the trunk line. The anchoring effect of the branch pipe generates significant strain concentrations in both trunk line and branch pipes. In relatively large diameter (115 mm) trunk lines, the highest vulnerability to such strain concentrations was in the smaller diameter (15 mm) branched pipe. In small diameter (60 mm) trunk lines these strain concentrations were observed to induce yielding of the trunk line.
27712000 bytes
application/pdf
RESPONSE OF BURIED POLYETHYLENE NATURAL GAS PIPELINES SUBJECTED TO L A T E R A L GROUND DISPLACEMENT B y Chris topher D . Anderson r-B . A . S c , Un ive r s i ty o f B r i t i s h C o l u m b i a , 1998 A THESIS S U B M I T T E D I N P A R T I A L F U L F I L L M E N T O F T H E R E Q U I R E M E N T S F O R T H E D E G R E E O F M A S T E R O F A P P L I E D S C I E N C E i n T H E F A C U L T Y O F G R A D U A T E S T U D I E S Department o f C i v i l Eng inee r ing W e accept this thesis as conforming to the required standard T H E U N I V E R S I T Y O F B R I T I S H C O L U M B I A A p r i l 2 0 0 4 © Chris topher D . Anderson , 2 0 0 4 Library Authorization In presenting this thesis in partial fulfillment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Ofr&sroVH&g. D . AVVGH&OM %3 /of/Zoo^ Name of Author (please print) Date (dd/mm/yyyy) Title of Thesis: H BSVO^SS O F 1$UQ-I&?> To<-r & T ^ ^ ^ ^ e ^ATIA^U D e S r e e : MASTERS OF AVPU&I> ^ g g ^ g Department of Q.w^ f / u g i ^ g i ^ The University of British Columbia Vancouver, BC Canada Year: ^ G O f ABSTRACT Permanent ground deformations ( P G D ) are a major cause o f damage to bur ied natural gas pipel ine systems, par t icular ly in areas o f ongo ing ground deformation. A new testing apparatus was designed and constructed specif ical ly to meet the requirements o f fu l l -scale phys ica l mode l i ng research on typica l polyethylene natural gas pipel ine configurations subjected to lateral ground displacements. The apparatus essentially comprised a large so i l testing chamber i n w h i c h p ipel ine configurat ions cou ld be monitored w i t h an instrumentation array measuring pul lout resistance, p ipel ine displacement, and loca l strain w i t h i n the pipe specimens. Spec ia l i zed methods were developed for mount ing strain gauges to polyethylene to obtain rel iable readings, and to reduce imposed drag forces. A series o f tests performed on straight pipel ine sections indicated that peak axia l pullout resistance predicted us ing publ ished design equations tended to over-predict pullout resistance o f polyethylene pipes in uncompacted sand, and to underestimate pul lout resistance i n dense sand. Signif icant l imitat ions were found i n the appl icab i l i ty o f current design equations, developed f rom tests on r ig id steel pipelines, to the predict ion o f ax ia l pullout resistance o f re la t ive ly " f l ex ib l e " polyethylene pipel ines. Several soi l -p ipel ine interaction mechanisms have been suggested that seem to account for the observed differences in behaviour between polyethylene and steel pipel ines. A x i a l tests on trunk l ines w i t h tee connections to smaller size branch pipes indicated that branched configurations experience a complex interaction w i t h the soi l . The branch pipe in i t i a l ly deflected and elongated in c lose p rox imi ty to the tee connect ion, then w i t h increasing displacement, pipe deformation transitioned to axia l pul lout o f the branch. i i The contr ibut ion to pul lout resistance f rom the branches was s imi la r i n both uncompacted and dense sand, and also was not signif icantly affected by the diameter o f the trunk line. The anchoring effect o f the branch pipe generates significant strain concentrations i n both trunk line and branch pipes. In relat ively large diameter (115 mm) trunk lines, the highest vulnerabi l i ty to such strain concentrations was i n the smaller diameter (15 mm) branched pipe. In smal l diameter (60 mm) trunk lines these strain concentrations were observed to induce y i e l d i n g o f the trunk line. i i i T A B L E OF CONTENTS A B S T R A C T i i L I S T OF T A B L E S v i L I S T OF F I G U R E S v i i N O M E N C L A T U R E x A C K N O W L E D G E M E N T S x i i C H A P T E R 1 I N T R O D U C T I O N 1 1.1 B a c k g r o u n d 1 1.2 Object ives o f the Thesis 3 1.3 S cope o f the Thes i s 4 1.4 Organ iza t ion o f the Thesis 4 C H A P T E R 2 L I T E R A T U R E R E V I E W 6 2.1 Introduction 6 2.2 F u l l - S c a l e Labora tory Test ing 7 2.3 F u l l Scale F i e l d Test ing 9 2.4 A n a l y t i c a l M o d e l l i n g 9 2.5 F i e l d Performance and M o d e l i n g 11 2.6 P ipe l ine D e s i g n 12 2.7 Research N e e d s Identified from Literature R e v i e w 13 C H A P T E R 3 E X P E R I M E N T A L A P P A R A T U S , M A T E R I A L P R O P E R T I E S & T E S T P R E P A R A T I O N 15 3.1 Exper imen ta l Apparatus 15 3.1.1 Tes t ing Chamber 15 S o i l B o x 16 Sand H a n d l i n g 19 L o a d i n g M e c h a n i s m s 19 3.1.2 Instrumentation 21 Forces 22 Strains 22 Disp lacements 23 Pos i t iona l Surveys 23 D a t a A c q u i s i t i o n 24 3.2 Test Mater ia l s 24 3.2.1 Properties and Di rec t Shear Test ing o f Fraser R i v e r Sand 25 iv 3.2.2 Propert ies and Compress ion Tes t ing o f Po lye thy lene Na tu ra l G a s P ipes 27 3.3 P u l l o u t Test Preparat ion 29 3.3.1 P i p e Spec imen Preparat ion 29 3.3.2 Strain G a u g i n g Polyethylene 30 Strain Gauge Select ion 30 A p p l i c a t i o n Procedure 32 Surface Preparat ion 32 G a u g e A p p l i c a t i o n 33 G a u g e Pro tec t ion 33 3.3.3 Sand Placement 35 C H A P T E R 4 S T R A I G H T P I P E L I N E P U L L O U T T E S T I N G 37 4.1 Introduct ion 37 4.2 Resul ts o f Straight Sect ion Pu l lou t 38 4.2.1 Tests i n M e d i u m L o o s e Sand 40 4.2.2 Tests in Dense Sand 48 C H A P T E R 5 B R A N C H E D P I P E L I N E P U L L O U T T E S T I N G 58 5.1 Introduction 58 5.2 Resul ts o f B ranched Sect ion Pul lou t 59 5.2.1 Tests in M e d i u m - L o o s e Sand 59 5.2.2 Tests in Dense Sand 68 C H A P T E R 6 A N A L Y S I S A N D D I S C U S S I O N O F R E S E A R C H R E S U L T S 79 6.1 Introduct ion 79 6.2 M e c h a n i s m s o f S o i l Resistance on Polyethylene P ipe l ines 79 6.3 R e v i e w o f Exper imen ta l Observations w i t h Respect to E x i s t i n g Approaches 81 6.4 Correspondence o f Measu red Strains and Disp lacements 83 6.5 Strain Dis t r ibu t ions in Branched P ipe l ine Conf igura t ions 85 C H A P T E R 7 S U M M A R Y A N D C O N C L U S I O N S 89 7.1 Summary 89 7.2 F u l l Scale Tes t ing F a c i l i t y 90 7.3 Pu l lou t Test ing o f Straight P ipe Configurat ions 90 7.4 Pu l lou t Tes t ing o f Branched P ipe l ine Conf igura t ions 91 7.5 Recommenda t ions for Future Research 93 R E F E R E N C E S 95 A P P E N D I X A P I P E S P E C I M E N C O M P R E S S I O N T E S T I N G 102 A P P E N D I X B P U L L O U T T E S T R E S U L T S 107 A P P E N D I X C P H O T O G R A P H S 169 v LIST OF TABLES Page Table 3.1: Comparison o f Soi l Parameters for the Current and Previous Studies 26 Table 3.2: Strain Gauge Properties 31 Table 4.1: Straight Pipeline Test Matr ix 37 Table 4.2: Test Parameters for Straight Sections in Medium-Loose Sand 40 Table 4.3: Pullout Force Results for Straight Sections in Medium-Loose Sand 43 Table 4.4: Interpreted Interface Friction Angles for Straight Sections in Medium-Loose Sand 47 Table 4.5: Test Parameters for Straight Sections in Dense Sand 49 Table 4.6: Pullout Force Results for Straight Sections in Dense Sand 54 Table 4.7: Interpreted Interface Friction Angles for Straight Sections in Dense Sand 56 Table 5.1: Branched Pipeline Test Matr ix 58 Table 5.2: Test Parameters for Branched Sections in Loose Sand 60 Table 5.3: Pullout Force Results for Branched Sections in Medium-Loose Sand 63 Table 5.4: Approximate Branch Contributions to Peak Pullout Resistance 64 Table 5.5: Test Parameters for Branched Sections in Dense Sand 69 Table 5.6: Pullout Force Results for Branched Sections in Dense Sand 72 Table 5.7: Approximate Branch Contributions to Peak Pullout Resistance 73 Table 6.1: Measured versus Predicted Strains 85 vi LIST OF FIGURES Page Figure 3.1: Testing Chamber Configuration for A x i a l Pullout Testing 17 Figure 3.2: Load Cel l to Pipe Connection Detail 21 Figure 3.3: Grain Size Distribution o f Fraser River Sand 25 Figure 3.4: Compression Testing o f Pipe Specimens 27 Figure 3.5: Typical Pipe Specimen Compression Test Results at 1 mm/min 28 Figure 3.6: Original and Modif ied StrainGauge Installation and Protection Technique 34 Figure 4.1: Density Testing Summary for Straight Tests in Medium-Loose Sand 41 Figure 4.2: Pullout Resistance for Test on 115 mm Straight Section in Medium-Loose Sand (115 a L - R T ) 42 Figure 4.3: Pullout Resistance for Tests on 60 mm Straight Sections in Medium-Loose Sand (60aL) 43 Figure 4.4: Normalized Pullout Resistance for Tests on 115 mm and 60 mm Straight Sections in Medium-Loose Sand (115al-RT and 60aL) (uncorrected for gasket fiction) 45 Figure 4.5: Observed Point Strains, 115 mm Diameter Pipeline Specimen 46 Figure 4.6: Density Testing Summary for Straight Tests in Dense Sand 49 Figure 4.7: Pullout Resistance for Tests on 115 mm Straight Sections in Dense Sand 50 Figure 4.8: Pullout Resistance for Tests on 60 mm Straight Sections in Dense Sand 50 v i i Figure 4.9: Pullout Resistance for Tests on 15 mm Straight Sections in Dense Sand 51 Figure 4.10: Observed Point Strains, 115 mm Diameter Pipeline Specimen 52 Figure 4.11: Normalized Pullout Resistance for Tests on 115 mm and 60 mm Straight Sections in Dense Sand (uncorrected for gasket fiction) 53 Figure 4.12: Normalized Pullout Resistance for Tests on 15 mm Straight Section in Dense Sand (uncorrected for gasket fiction) 53 Figure 4.13: Inferred Elongation from End Displacements, 15 mm Diameter Pipeline Specimen 55 Figure 4.14: Variation o f Apparent Interface Friction Angle R a t i o , / with Diameter, D 57 Figure 5.1: Typical Instrumentation Layout for Branched Pipeline Specimen in Medium-Loose Sand 60 Figure 5.2: Density Testing Summary for Branched Tests in Medium-Loose Sand 61 Figure 5.3: Pullout Resistance for Tests on 115 mm Branched Section in Medium-Loose Sand 62 Figure 5.4: Pullout Resistance for Tests on 60 mm Branched Section in Medium-Loose Sand 63 Figure 5.5: Relative Displacements o f Pipe Ends, Test 115baL (see Figure 4.15 for Instument Locations) 65 Figure 5.6: Relative Displacements o f Pipe Ends, Test 60baL (see Figure 4.15 for Instument Locations) 65 Figure 5.7: Local Strain Readings Along Trunk Line for Tests on 115mm Branched Section in Medium-Loose Sand 66 Figure 5.8: Local Strain Readings Along Trunk Line for Tests on 60mm Branched Section in Medium-Loose Sand 67 Figure 5.9: Surveyed Locations Before and After Testing (115baL) 67 Figure 5.10: Surveyed Locations Before and After Testing (60baL) 68 vi i i Figure 5.11: Typical Instrumentation Layout for Branched Pipeline Specimen in Dense Sand 69 Figure 5.12: Density Testing Summary for Branched Tests in Dense Sand 70 Figure 5.13: Pullout Resistance for Tests on 115 mm Branched Section in Dense Sand 71 Figure 5.14: Pullout Resistance for Tests on 60 mm Branched Section in Dense Sand 72 Figure 5.15 Relative Displacement of Pipe Ends, Test 115baD (see Figure 5.1 for Instrument Locations) 74 Figure 5.16 Relative Displacement of Pipe Ends, Test 60baD (see Figure 5.1 for Instrument Locations) 74 Figure 5.17: Local Strain Readings Along Trunk Line for Test on 115 mm Branched Section in Dense Sand 75 Figure 5.18: Local Strain Readings Along Trunk Line for Test on 60 mm Branched Section in Dense Sand 76 Figure 5.19: Surveyed Locations Before and After Testing for 115 mm Branched Section in Dense Sand 77 Figure 5.20: Surveyed Locations Before and After Testing for 60 mm Branched Section in Dense Sand 77 Figure 5.21: Surface Soi l Disturbance from Tee, Test 115baD 78 Figure 6.1: Comparison o f Normalized Experimental Pullout Resistance to Predictions 82 Figure 6.2: Comparison o f Predictions Based on Different k 0 conditions, Test 60aD 83 Figure 6.3: Typical Strain Response in Branch Section, Test 115aD 86 Figure 6.4: Plastic Deformation o f Branch Section at Point of Attachment 88 i x NOMENCLATURE 5 Interface F r i c t i o n A n g l e Diameter o f P ipe Interface F r i c t i o n A n g l e Ra t io U n i t W e i g h t o f S o i l D / y H Dep th to P ipe Center l ine H c Dep th to P ipe C r o w n Hj Dep th to P ipe Invert k 0 Coeff ic ient o f La tera l Ear th Pressure L E m b e d d e d L e n g t h o f P ipe § Internal A n g l e o f F r i c t i o n o f So i l P Transverse H o r i z o n t a l Fo rce Q Transverse V e r t i c a l Fo rce t P i p e W a l l Th i cknes s t u A x i a l Pu l lou t Resistance per U n i t L e n g t h o f P ipe T u A x i a l Pu l lou t Resistance T m a x Peak A x i a l Pu l lou t Resistance T ' N o r m a l i z e d A x i a l Pu l lou t Resistance x A x i a l Disp lacement x m a x A x i a l Disp lacement at Peak A x i a l l Pu l lou t Resistance y Transverse H o r i z o n t a l Disp lacement z Transverse V e r t i c a l Disp lacement x A C K N O W L E D G E M E N T S A number o f people are deserving o f m y sincerest gratitude and appreciat ion for p rov id ing the support, assistance and advice necessary to complete m y research and wri te this thesis. A b o v e a l l others, D r . D h a r m a W i j e w i c k r e m e provided me w i t h unfa i l ing encouragement, enthusiasm and support as w e embarked upon an avenue o f research new to both m y s e l f and to the Geotechn ica l G r o u p . A s m y supervisor, he a l l owed me to advance the research w i t h the freedom to make it m y o w n , w h i l e p r o v i d i n g his invaluable knowledge and experience at any t ime, and often anywhere. Wi thou t his patience and advice this project w o u l d hardly have been possible. M y gratitude is also extended to D r . Car los Ventura for his support and encouragement o f a geotechnical engineer de lv ing into the domain o f structural engineers. H i s knowledge o f the structural aspects o f the project proved indispensable i n understanding the interaction between the geotechnical and structural elements. H i s confidence and posit ive out look, as w e l l as his abi l i ty to help me see beyond the routine effort o f the research was an inspirat ion. This research was made possible by sponsorship from Terasen Gas . In particular, the personal involvement M r . A l l e n M i t c h e l l is deeply appreciated, as his counsel and perspective gave d i rec t ion to the path o f the research. In addit ion, M r . D a v e M i l l e r was instrumental i n p r o v i d i n g materials and informat ion pertaining to the particular pipel ine installations investigated. I am grateful for the endless assistance provided by the technical staff o f the Department o f C i v i l Engineer ing . These inc lude M r . Hara ld Schrempp, D o u g Smith , B i l l L e u n g , x i D o u g Hudn iuk , and M a x N a z a r w h o assisted w i t h construct ion and set up o f the test chamber, as w e l l as fabricat ing many o f the special ized components required for the test apparatus. E lec t ron ics technicians Scott Jackson and John W o n g were influential in assisting the development o f techniques for instal lat ion o f instrumentation on polyethylene pipes, and for set up o f the control and data acquis i t ion systems. M y thanks must also be extended to the manager o f the Structural Eng inee r ing Laboratory , M r . F e l i x Y a o , as w e l l as the other technical staff, w h o were except ional ly tolerant o f the dust storms that often accompanied m y test preparations. The size o f the ful l-scale testing specimens meant that m y test preparations w o u l d have been nearly imposs ib le wi thout the assistance o f f e l low graduate student H a m i d K a r i m i a n and undergraduate student M a r k Forsyth . In addit ion, assistance was provided by undergraduate students B e n Tang and Jennifer Scott in deve lop ing design drawings and performing tests to determine sand properties. M y appreciation goes out to Mathers B u l l d o z i n g for their generous donation o f the large quantities o f sand required for the research and for compl imentary del ivery to U B C . X l l C H A P T E R 1 INTRODUCTION 1.1 Background The performance o f bur ied natural gas p ipel ine systems i n areas subjected to ground deformations is an important engineering considerat ion since geotechnical hazards can be a major cause o f damage to these ut i l i t ies . Where permanent ground deformation hazards are ident if ied, major t ransmission pipel ines are routed or re-al igned so as to a v o i d potential damages resul t ing f rom ground movements . H o w e v e r , smal ler diameter p ipel ine dis t r ibut ion networks de l iver to numerous specif ic locations, and because o f their regional nature there is an increase l i k e l i h o o d for such networks to encounter zones o f potential ground movements . Furthermore, i n areas where very s l o w ground displacements are occur r ing over t ime, the land m a y be developed and bur ied service networks instal led p r io r to any knowledge o f the ongoing permanent g round deformation. In such instances, changes to the al ignment and loca t ion o f the dis t r ibut ion ne twork are general ly not feasible. The end result o f p ipe l ine systems i n creeping ground displacement zones is increased moni to r ing and maintenance requirements dur ing operation o f the system. In a technical context, a detai led understanding o f the associated soi l -pipe interaction p rob lem w o u l d be the k e y to deve lop ing the needed cri ter ia or guidel ines for des ign and performance evaluat ion. A l t h o u g h soi l -pipe interaction models exist, there is on ly l imi t ed experience w i t h p ipel ine materials other than steel, and i n part icular polyethylene. Current practices for polyethylene p i p i n g systems are based on tradit ional des ign methods typ i ca l ly used for installations o f steel pipel ines . In recent years it has become the industry standard to construct natural gas p ipel ine dis tr ibut ion networks us ing Chapter 1. Introduction polyethylene pipe. The lower mater ial cost and ease o f handl ing , instal lat ion and maintenance have made polyethylene economica l ly advantageous over older steel pipel ines , and have contributed to many older p ipel ine networks be ing replaced w i t h polyethylene installations. Further, the increased f l ex ib i l i t y o f polyethylene pipe is often considered to be superior to steel i n resist ing rupture o f the p ipel ine due to ground displacements. S ince soi l -p ipel ine interaction is a complex prob lem, laboratory testing plays an important role i n deve lop ing a fundamental understanding o f the performance o f pipel ines subject to ground movements . The required laboratory tests w o u l d range f rom element type tests to phys i ca l mode l ing that a l lows examinat ion o f the response o f an integrated system. W i t h respect to phys i ca l mode l ing , leading research facil i t ies (Traughtman and O ' R o u r k e , 1983; P a u l i n et a l . , 1998) have made use o f full-scale testing tanks to investigate the effects o f ax ia l , lateral and uplif t load ing o n bur ied steel pipel ines . The majori ty o f the testing performed to date has investigated m i d - to large-diameter steel pipel ines , however , for sma l l diameter pipel ines , and par t icular ly for p o l y m e r pipes, l i t t le i f any research has been carr ied out. Relat ionships developed f rom phys ica l m o d e l testing has been subsequently adopted for use i n the A S C E Commit tee o n Gas and L i q u i d F u e l L i n e s Guide l ines for the Se i smic D e s i g n o f O i l and Gas P ipe l ine Systems (1984) and for the A m e r i c a n L i fe l ines A l l i a n c e ( A L A ) Guide l ines for the D e s i g n o f B u r i e d Steel P ipe (2001). A n a l y t i c a l models developed for soi l -p ipe interaction have p r imar i l y been cal ibrated us ing data f rom full-scale laboratory testing. In the current design guidel ines, A S C E (1984) and A L A (2001), the p ipe l ine is often mode led as a structural beam, and s o i l -p ipel ine interaction is accounted for us ing s imple design equations appl ied to h igh ly idea l ized condi t ions. H o w e v e r , as observed i n m u c h o f the literature, there are numerous discrepancies between laboratory tests and these s imple equations. Further, as addi t ional observations are made, it becomes apparent that addi t ional m i c r o - and macroscopic behaviours o f soils such as strain softening and arching (Petroff, 1990) are not accounted for i n the models . Chapter 1. Introduction W i t h this background, a detailed research program i n v o l v i n g full-scale phys i ca l mode l i ng has been undertaken at the Un ive r s i t y o f B r i t i s h C o l u m b i a ( U B C ) , Canada, i n partnership w i t h Terasen Gas Inc., B r i t i s h C o l u m b i a , Canada , to study so i l -p ipe l ine interact ion dur ing permanent ground displacements affecting dis t r ibut ion networks o f polyethylene p ip ing . W i t h operational considerations leading to adopt ion o f polyethylene as the industry standard for natural gas dis t r ibut ion systems, a detailed invest igat ion into the interaction o f these materials w i t h the surrounding so i l was needed to ensure that the responses o f both p ipel ine and so i l components are properly accounted for dur ing design. T h e purpose o f this research is to determine the contr ibut ing factors and key parameters in f luenc ing the behaviour o f polyethylene pipe bur ied i n so i l . W h i l e the w o r k stems f rom potential concerns i n gas dis t r ibut ion areas where s low, cont inual ground movements such as slope creep are anticipated, the research findings are considered to be equal ly appl icable to other forms o f ground deformations, i nc lud ing those induced b y earthquakes. 1.2 Objectives of the Thesis The purpose o f this research is to determine the response o f polyethylene p ipe l ine configurations to induced permanent ground deformations. W i t h this i n m i n d , the specif ic research objectives described herein are as fo l lows : i ) to des ign and construct a testing faci l i ty capable o f testing ful l-scale, typ ica l bur ied p ipel ine configurations under s imulated f i e ld instal la t ion and P G D condit ions, i i ) to examine the behaviour o f polyethylene pipel ines exper iencing induced permanent ground deformations by testing basic p i p i n g configurations that are c o m m o n l y encountered i n dis t r ibut ion systems, i i i ) to determine the magnitude o f the forces act ing o n polyethylene pipel ines and the resul t ing structural deformations occurr ing dur ing permanent ground deformations, and Chapter 1. Introduction i v ) to r ev iew the appl icab i l i ty o f so i l -p ipel ine interaction models developed for steel to installations o f polyethylene. 1.3 Scope of the Thesis T o accompl i sh the research objectives, the scope o f w o r k conducted for, and discussed w i t h i n this thesis is as fo l lows : • a n e w test chamber and load ing mechanisms for testing polyethylene pipes was designed and constructed based o n cri ter ia der ived f rom considerat ion o f both p ipe l ine and so i l deformation mechanisms, • an instrumentation array and specia l ized instal la t ion procedures were devised such that pul lout resistance, displacement and strain a long the pipel ines c o u l d be measured and observed i n real-t ime, • a total o f 8 pul lout tests were performed o n straight polyethylene pipel ine specimens i n both uncompacted and dense sand b a c k f i l l to provide baseline comparisons to exis t ing analyt ical models , • a total o f 4 p ipe l ine pul lout tests were conducted on polyethylene p ipe specimens that each contained two tee connections and branch pipes. Tests were performed i n both uncompacted and dense sand b a c k f i l l condi t ions, and • test results were ana lyzed w i t h respect to so i l -p ipel ine interaction models avai lable i n the literature and/or used i n design equations, and a method o f ana lyz ing branched configurations was developed. 1.4 Organization of the Thesis This thesis is organized into s ix chapters and 4 Append ices , w i t h the contents o f each described be low. Chapter 1. Introduction Chapter 2 A rev iew o f the literature that contributed to the development o f the research program and that pertains to the phenomena o f soi l -p ipel ine interaction and permanent ground deformation is presented. Chapter 3 The details o f the full-scale experimental apparatus, mater ial properties and test preparation procedures are described. Chapter 4 T h e quantitative results, a long w i t h qualitative observations o f p ipel ine behaviour f rom the full-scale p ipe l ine pul lout tests are presented i n detail . Chapter 5 T h e results o f the testing program are discussed relative to exis t ing models and design methods, and the impl ica t ions for f ie ld installations are explored. Chapter 6 The findings o f the research are summarized , and recommendations are made for possible future research and for addi t ional applications to field installations. Appendices A p p e n d i x A provides typ ica l test results f rom compress ion tests performed o n the pipe specimens i n order to determine the elastic modulus . A p p e n d i x B contains the test results for the complete series o f tests performed dur ing the research program. F i n a l l y , A p p e n d i x C contains a number o f photographs o f the test apparatus, test specimens, and deformed p ipe l ine sections. C H A P T E R 2 L I T E R A T U R E R E V I E W 2.1 Introduction A rela t ively large body o f w o r k exists i n the literature s temming f rom previous research i n the area o f soi l /p ipel ine interaction for m i d - to large-diameter steel t ransmission pipel ines . The leading research facil i t ies i n this f i e ld have been C o r n e l l Un ive r s i t y , and more recently C - C O R E . B o t h facil i t ies have made use o f full-scale testing tanks to investigate the effects o f ax ia l , lateral, and uplif t load ing on bur ied steel pipel ines . The majori ty o f the testing performed to date has investigated m i d - to large-diameter steel pipel ines , however , for smal l diameter pipel ines , and par t icular ly for p o l y m e r pipes, l i t t le i f any research has been carried out. In testing programs performed at other faci l i t ies , pipe strains and pressures are rout inely moni tored, al though actual failure cri teria for the p ipe l ine have not been proposed. A l t h o u g h mechanica l ly , the failure cri ter ia are typ ica l ly ident i f ied b y the y i e l d stress/strain, w i t h the pipe cont inuing to deform un t i l rupture, there have been few attempts to specify so i l displacements as a measure o f pipe failure cri teria. T h i s m a y be due, i n part, b y the l imi t s o f the available so i l /p ipe l ine interaction models currently avai lable . The literature rev iew contained i n this section provides an ove rv i ew o f both research pertaining direct ly to, and support ing the design o f the current research program, and also research relat ing to complementary areas o f bur ied pipel ine design and performance. In particular, the works related to full-scale lab testing o f bur ied pipel ine segments has been instrumental i n gu id ing the design o f the test chamber at U B C . The works concerning design, f ie ld performance, and/or remediat ion o f bur ied pipel ines Chapter 2. Literature Review exper iencing slope movement have also been inc luded because o f their relevance to the p r o b l e m investigated i n the current research and to the supply and dis t r ibut ion o f natural gas. 2.2 F u l l - S c a l e L a b o r a t o r y T e s t i n g F u l l scale laboratory testing o f soi l -p ipel ine interaction w i t h regard to relative movements between pipe and so i l was first performed at C o r n e l l U n i v e r s i t y b y Traughtman & O ' R o u r k e (1983, 1985). These investigations focused on lateral and uplif t loadings o n steel pipel ines i n sand, and i n part icular the in i t i a l por t ion o f the force-displacement response. These studies were carr ied out us ing re la t ively rap id displacements (20 m m / m i n ) meant to simulate the effects o f fault displacements o n steel t ransmiss ion pipel ines . The researchers found that models for comput ing m a x i m u m lateral so i l forces adapted f rom ver t ica l and strip anchors were reasonably adequate for representing laboratory results. H o w e v e r , it was found that predicted loads for loose, contractive sands were underestimated, and that the m a x i m u m s o i l forces were i n fact near ly equal to those i n m e d i u m dense sand f o l l o w i n g large ground movements , par t icular ly for lateral pipel ines displacement. F o r ax ia l pul lout o f pipel ines , the m a x i m u m pul lout resistances were achieved w i t h i n very sma l l p ipe l ine displacements, on the order o f 2.5 m m (0.1 in.) for sand. The equation for m a x i m u m pul lout resistance per unit length o f p ipe was determined to be based o n fr ic t ional contact at the p ipe-so i l interface, and was presented i n the form: tu = —jH{\ + k,)\m8 [2.1] Where : D t, H Y -u = ult imate ax ia l force on pipe (soi l resistance) = external p ipe l ine diameter = effective unit weight o f s o i l = depth f rom ground surface to center o f the p ipel ine Chapter 2. Literature Review ko = coefficient o f s o i l pressure at rest 8 = interface angle o f f r ic t ion between so i l and pipel ine T h i s relat ionship, as w e l l as the relationships for lateral pul lout proposed by the researchers at C o r n e l l Un ive r s i ty , was subsequently adopted for the A S C E Commit tee o n Gas and L i q u i d F u e l L i n e s Guide l ines for the Se i smic D e s i g n o f O i l and Gas P ipe l ine Systems (1984) and the A m e r i c a n L i f e l ines A l l i a n c e Guide l ines for the D e s i g n o f B u r i e d Steel P ipe (2001). Further, the so i l - spr ing m o d e l p rov ided by these relationships have been implemented i n numerous numer ica l models relat ing to so i l -p ipel ine interaction, i nc lud ing the c o m m o n l y used programs A N S Y S , A B A Q U S and P I P L I N (Swanson A n a l y s i s Systems Inc., 1992; Hibb i t t et a l . , 2000; Stuctural Software Deve lopment Inc. 1981). M o r e recently, several col laborat ive efforts have been undertaken i n order to refine the geotechnical parameters contr ibut ing to the current soi l -p ipel ine interaction models . Research centers include the Center for C o l d O c e a n Research Eng inee r ing ( C - C O R E ) (Pau l in et a l . , 1998), Italgas, G a z de France, and A d v a n t i c a Technologies L t d . representing the involvement o f Canadian , European and Japanese contributors. These studies investigated so i l type, so i l condi t ion , bur ia l geometry and load ing rate o n force response o f steel t ransmission p ipe l ine segments. It was found that force-displacement i n loose sand over-predicted the ax ia l pul lout forces b y as m u c h as 4 0 % , w h i l e i n dense sand, these forces were under-predicted b y as m u c h as 2 0 % (Paul in et a l . , 1998). Explanat ions for the discrepancy are not discussed i n the avai lable literature, and no signif icant attempts have been made to careful ly investigate these differences. A s imi la r testing apparatus was u t i l i zed by researchers i n T a i w a n to investigate rate effects on lateral pipe displacement restraint (Hsu , 1993). The results indicated that for tests i n dry sand, a mod i f i ed vers ion o f the lateral so i l restraint m o d e l proposed b y Traughtman and O ' R o u r k e (1983) was able to predict s o i l resistance at va ry ing speeds. A l t h o u g h not direct ly appl icable to the current research focus o f ax ia l ly loaded pipel ines , the results o f these tests indicate that rate effects may be o f concern even i n dry sand, where rate-dependent effects f rom changes i n pore pressure normal ly are not a concern. Chapter 2. Literature Review The most c o m m o n method o f app ly ing a displacement to the p ipel ine i n the research has been b y app ly ing a l oad direct ly to the p ipel ine v i a hydrau l ic pistons and steel cables. Y o s h i z a k i et a l . (2001) have recently reported investigations at C o r n e l l U n i v e r s i t y o f relat ive displacements and strains i n the p ipe l ine caused by shearing two s o i l boxes past each other. The w o r k performed at each o f these facil i t ies has also inc luded significant computer m o d e l i n g and cal ibrat ion i n order to attempt to reproduce the s o i l failure mechanisms observed i n the test tanks. It should be noted that the testing at C o r n e l l U n i v e r s i t y has been performed at re la t ively rap id load ing rates, i n order to simulate the effects o f slope failures due to so i l l iquefact ion. In compar ison, the phys i ca l m o d e l testing at C - C O R E was performed at rates ranging f rom 0.5 mm/hr to 10 mm/hr (Popescu et a l . , 2002) . 2.3 Full Scale Field Testing The results o f full-scale laboratory testing have begun to extend into f ield-based ax i a l pu l lout tests, i n w h i c h out o f service or abandoned pipelines have been ax i a l l y loaded to induce movement (Cappallet to et a l . , 1998). L i m i t e d informat ion regarding the results o f these tests is avai lable i n the literature, as most o f these tests have been performed for private agencies, the results o f w h i c h are se ldom publ ished. It is l i k e l y that a significant amount o f informat ion m a y exist i n various private databases. The few results that are avai lable , however , appear to be consistent w i t h laboratory test results. 2.4 Analytical Modelling A n a l y t i c a l models developed for soi l -pipe interaction have p r imar i l y been der ived f rom fu l l scale laboratory testing results. The bi - l inear soi l -spr ing representation presented i n Equa t ion 2 .1 , above, is c o m m o n l y accepted as adequate for analysis and design purposes. H o w e v e r , as observed i n m u c h o f the literature, there are numerous discrepancies between laboratory tests and these s imple equations. It appears that m i c r o - and macroscopic s o i l behaviours, i nc lud ing strain softening and arching (Petroff, 1990), Chapter 2. Literature Review w h i c h are not exp l i c i t l y accounted for i n the models contribute to these discrepancies to a significant degree. A n a l y t i c a l models have addi t ional ly been developed for descr ib ing the geometric dis tr ibut ion o f permanent ground deformations imposed on pipel ines . One such m o d e l has been developed based on typ ica l earthquake-induced l iquefact ion f low failures ( O ' R o u r k e and Nordberg , 1990). The geometry o f a f l ow sl ide is mode led as a probabi l i ty density function, w i t h the largest s o i l displacements occurr ing at the center o f the s o i l displacement zone. The shape o f such a dis t r ibut ion o f ground displacements is s ignif icant ly different f rom the other typ ica l ground deformation m o d e l used, w h i c h is that o f a fault-offset. The fault-offset type ground deformation comprises a distinct shear zone w i t h two reasonably intact b locks o n either side (Kennedy et a l . , 1977). T o date, full-scale soi l -pipe research has been restricted to fault-offset or b l o c k type ground displacements, the reason for w h i c h is l i k e l y due to the d i f f icul ty o f reproducing a distr ibuted type s o i l displacement w i t h avai lable laboratory equipment. F o r experimental studies o n pipel ine components, a b lock-displacement type ground deformation is a reasonable s impl i f i ca t ion for reproducing the so i l displacement condit ions occur r ing around a re la t ively loca l i zed section o f p ipel ine . N u m e r i c a l models developed f rom laboratory testing typ i ca l ly incorporate the s imple analyt ica l soi l-springs developed dur ing laboratory tests, and as found i n the A S C E (1985) guidel ines, into computer programs such as A B A Q U S and A N S Y S , i n order to assess strains experienced by the p ipel ine (Kobayash i , 1989). In order to determine movement o f the pipe i n through the so i l , par t icular ly dur ing lateral movement , cont inuum models , such as F L A C have been used to va ry ing degrees o f success (Popescu et a l . 1999) al though pipe elements are often mode led as r i g i d bodies i n these models . There remains some dif f icul ty i n numer ica l ly mode l ing the so i l deformation and pipe strain s imultaneously. - 1 0 -Chapter 2. Literature Review 2.5 Field Performance and Modeling In order to r ev iew the performance o f numer ica l tools for structural mode l ing , several researchers have compared numer ica l analysis w i t h field data on slope movements and pipel ine strain ( B u g h i et a l . , 1996; B r u s c h i et a l . , 1996). These researchers have presented several case studies o f numer ica l m o d e l l i n g performed for areas exper iencing s low slope movements o n the order o f 1 to 10 m m per year. The researchers indicate that the accuracy o f their numer ica l models was l imi t ed b y the ava i lab i l i ty o f an accurate phys i ca l m o d e l o f so i l -p ipel ine interaction and b y an accurate representation o f the slide front. W i t h addi t ional understanding o f the slide mechanics and soi l -p ipel ine interaction it appears l i k e l y that significant progress cou ld be made i n m o d e l l i n g pipel ine networks. In other studies attempting to define patterns o f ground deformation act ing o n pipel ines , par t icular ly i n earthquake l iquefact ion events, researchers have appl ied s inusoidal , or probabi l i ty dis t r ibut ion functions to predict the var ia t ion o f ground displacement across the w i d t h o f the peak ground displacement ( P G D ) zone ( O ' R o u r k e , 1998; S u z u k i et a l . , 1989; L i u and O ' R o u r k e , 1997). Th i s w o r k has been undertaken us ing both analyt ica l and numer ica l mode l l i ng approaches, and, i n both instances, it is found that the most c r i t i ca l parameter inf luencing the forces o n pipel ines is the w i d t h o f the P G D zone. Further, the behaviour o f the system is found to act i n both ' beam- l ike ' and ' c ab l e - l i ke ' manners, depending on the loca t ion relative to the P G D zone. F o r ground displacement events o f re la t ively large aerial extent, the p ipe l ine typ ica l ly responds a predominant ly cable- l ike element. Several researchers have also investigated the field performance o f pipel ines f o l l o w i n g permanent ground displacement resul t ing f rom earthquake-induced l iquefact ion ( O ' R o u r k e and T a w f i k , 1983; O ' R o u r k e and O ' R o u r k e , 1995; N i s h i o , 1995). These researchers investigated t ransmission pipel ine performance dur ing the 1971 San Fernando and 1994 Nor thr idge Earthquakes. A key f inding i n these works was that i n large displacement events, the geometry o f the spread had a greater influence on the magnitude o f strains induced i n the pipe than d i d the s o i l type. It should be noted, Chapter 2. Literature Review however , that the pipel ines investigated i n these studies were typ ica l ly large diameter steel pipel ines w i t h significant structural capacity. 2.6 Pipeline Design F o r the major p ipel ine design guidelines under considerat ion, A S C E (1984) and A L A (2001), the p ipel ine is most often mode led as a structural beam, and soi l -p ipel ine interaction is accounted for us ing s imple design formulas appl ied to h igh ly idea l ized condit ions. The equations, as noted above, are generally mod i f i ed versions o f p i le or s o i l anchor theoretical and analyt ical c losed-form solutions. Further, the guidelines have been developed to provide a methodology for character izing r isks associated w i t h potential , re la t ively rapid ground displacements impac t ing specific steel p ipe l ine installations. There has been little attempt to develop the guidel ines as a means o f p rov id ing input for assessing serviceabi l i ty over longer t ime frames, as is t yp i ca l ly required i n instances o f long-term landsl ide creep deformation. Several general observations are made i n the guidel ines regarding p ipe l ine behaviour dur ing transverse lateral and ax ia l p ipe l ine displacements. In particular, it is noted that even dur ing lateral permanent ground deformation relative to the p ipel ine , the p ipe l ine strain response is typ ica l ly that o f a cable, w i t h a beam-l ike response l im i t ed to w i t h i n the shearing zone. The structural response associated w i t h f lexural bending o f the p ipel ine w h e n subjected to bending forces t yp i ca l ly results i n an increased ax ia l tension d iametr ica l ly opposed b y a compressive strain. The guidelines observe that i n both f i e ld and laboratory settings, pipel ines perform far better i n tension than i n compress ion. P ipe l ine compress ion typ ica l ly results i n w r i n k l i n g , w h i c h consequently causes h i g h l y elevated l o c a l i z e d strains i n the wr ink les . F o r des ign purposes, internal p ipe l ine pressure is rout inely neglected i n order to provide an added degree o f conservat ism to the design ( A S C E , 1984). Internal p ipe l ine pressure w i l l general ly reduce ova l iza t ion o f the p ipel ine dur ing normal operation, however , i n dynamic events a loss o f pressure i n one area m a y result i n progressive addi t ional failures - 1 2 -Chapter 2. Literature Review at other locations a long the pipel ine as the re inforc ing effect o f the internal pressure is lost. N a t i o n a l and international standards for p ipel ine design, such as Canad ian standard C S A Z 6 6 2 - 9 6 , B r i t i s h Standard B S 8 0 1 0 , typ ica l ly provide strain-based serviceabi l i ty cr i ter ia for o i l and gas pipel ines (Dinovi tze r , 1998). The strain l imi ts for ova l i ty o f the p ipe l ine are typ ica l ly imposed to reduce the r i sk o f b u c k l i n g o f the p ipel ine , and for larger pipel ines , to a v o i d restrictions o f inspect ion (pigging) operations. P ipe l ine deflections and strains imposed by ground displacements are typ ica l ly beyond the scope o f these standards, however . A s m a y be noted, m u c h o f the above has been developed to understand the performance o f bur ied steel pipes, whereas litt le informat ion is currently avai lable pertaining to bur ied polyethylene pipel ines . 2.7 Research Needs Identified from Literature Review F r o m the r ev iew o f research literature and industry standards sources out l ined above, several research needs have been identif ied i n order to better understand the behaviour of, and the r isks associated w i t h , polyethylene natural gas pipel ine networks exper iencing long term landsl ide creep induced s o i l deformations. These research and invest igat ion needs are summar ized as fo l lows : • Since most exis t ing models are based on the response o f steel p ipel ines , it is important to check the appl icabi l i ty o f analyt ical models exis t ing i n the literature to the design and assessment o f polyethylene p ipe l ine networks. It should be conf i rmed that the soi l -spr ing representations used for steel pipel ines are appl icable to the more f lexible polyethylene materials. • Labora tory testing should be conducted to observe strains and deformations a long full-scale p ipe l ine specimens, rather than mode l on ly pul lout resistance and average strains. It is considered possible that complex so i l responses m a y on ly be - 13 -Chapter 2. Literature Review observed i n fu l l scale specimens, par t icular ly for f lex ib le p ipe l ine specimens w i t h h igh elongat ion potential . • A n examina t ion should be made o f the discrepancy between pul lout resistances predicted by analyt ica l models and prototype performance. • A ful l-scale laboratory assessment o f the response to ground displacements o f pipel ines w i t h complex geometry is required. In particular, understanding o f the behaviour o f layouts typ ica l o f dis t r ibut ion networks is needed. • A n account ing o f the effects o f rate o f displacement on pul lout resistances o f pipel ines should be investigated to determine the appl icab i l i ty o f analyt ica l and numer ica l models to ground displacements at differ ing rates, par t icular ly consider ing the rate dependant response typ ica l ly experienced by polyethylene. The scope o f the current research project is to address the above research needs focusing o n laboratory testing o f fu l l scale polyethylene pipel ine networks, and va l ida t ion o f exis t ing models for f lexible p ipel ine assessment i n zones o f permanent ground deformation. It was recognized that a fac i l i ty capable o f conduct ing the requisite testing was required, and consequently, des ign and construct ion o f such a fac i l i ty was incorporated into the current research objectives. - 14-CHAPTER 3 EXPERIMENTAL APPARATUS, MATERIAL PROPERTIES & TEST PREPARATION 3.1 Experimental Apparatus A testing apparatus has been designed and constructed spec i f ica l ly to meet the requirements for full-scale phys ica l m o d e l i n g research o n p ipe - so i l interaction problems. The objectives o f the research presented herein were to determine force-displacement and strain responses o f polyethylene pipel ines i n sand subjected to ax i a l load ing i n configurations typ ica l o f natural gas dis t r ibut ion networks. The new system a l lows study o f the stress, strain and displacement responses o f a var iety o f typ ica l bur ied p ipe l ine configurations subjected to ax ia l and transverse s o i l loadings, corresponding to mul t ip le in-s i tu condi t ions. The details o f the testing chamber, so i l handl ing system, and load ing mechanisms are described i n section 3.1.1. The instrumentation and data acquis i t ion system used to measure the appl ied loads, p ipe l ine strain, p ipe l ine displacement and s o i l displacement are described is section 3.1.2. 3.1.1 Testing Chamber T h e components o f the testing chamber have been designed and constructed to make use o f avai lable space and equipment i n the U B C Structural Eng inee r ing Labora tory . It was required that the testing apparatus be able to reproduce plane strain condit ions i n order to calibrate the test results w i t h typ ica l results obtained at other faci l i t ies , as w e l l as be able to test fu l l s ized branched pipel ine sections that are currently used i n f ie ld applicat ions. The sections b e l o w present the design cri teria and as-built details for each component o f the test fac i l i ty . - 15 -Chapter 3. Experimental Apparatus, Material Properties & Test Preparation S o i l B o x The design o f the so i l b o x was based on several cr i ter ia that were der ived f rom considerat ion o f both p ipe l ine and s o i l deformation mechanisms. The p r inc ipa l cr i ter ia govern ing the design o f the b o x were: 1) The length and w i d t h o f the b o x should a l l o w fu l l development o f active and passive s o i l zones i n the v i c i n i t y o f either the m a i n por t ion or branched sections o f pipe for sizes up to 500 m m ; 2) The size o f the b o x should permit development o f significant changes i n strain w i t h length (stretching o f the pipe) for ax ia l pu l lout specimens, and should a l l o w fu l l development o f bending strains over a reasonable length for sections o f pipe perpendicular to pul lout direct ion; 3) The wa l l s o f the b o x should provide " r i g i d " boundary condi t ions; and 4) The size and configurat ion o f the b o x should be reasonably easi ly mod i f i ed i n order to meet alternative test configurations. B u i l d i n g u p o n the experience o f the w o r k performed at C o r n e l l U n i v e r s i t y (Traughtman and O ' R o u r k e , 1983), and C - C O R E (Pau l in et a l . , 1997), the testing chamber has been designed to accommodate fu l l development o f the active and passive wedges adjacent to the p ipe l ine that t yp i ca l ly develop dur ing lateral displacement o f sha l low bur ied pipel ines i n plane strain condit ions. Further, the size o f the chamber is such that s imi la r deformation zones are a l l owed to develop around the pipes i n the testing o f the dis t r ibut ion branches. The length o f the chamber, 5 m , a l lows for observat ion o f the tensile strain decay a long the length o f the p ipel ine dur ing ax ia l pul lout testing, g i v i n g a direct ind ica t ion o f anchor ing behaviour o f the polyethylene p ipel ine . In addi t ion, the height o f the chamber permits up to 2 m o f so i l cover above the p ipe l ine . The modular construct ion o f the chamber provides the abi l i ty to change the configurat ion o f the chamber to best accommodate mul t ip le testing configurations and applicat ions. - 1 6 -Chapter 3. Experimental Apparatus, Material Properties & Test Preparation The skeleton o f the so i l box is constructed from steel W l 5 0 x 3 7 H-scc t ion uprights we lded to C 2 5 0 x 3 0 channel base plates and reinforced wi th we lded H S S 89x89x3.8 tubular braces. The base plates arc bol ted direct ly to the reinforced concrete floor o f the structural engineering laboratory. Hor izon ta l cross-beams consis t ing o f 90 m m by 140 m m structural t imber connect the steel frames at 300 m m centers. The timber cross-beams arc notched to fit the internal d imension o f the H-sections, and arc then sh immed to provide a uni form bearing surface across the steel and t imber sections. The internal wa l l s o f the box arc constructed o f 19 m m (3/4 in.) treated p l y w o o d bolted to the H -scct ion uprights. The internal chamber dimensions employed in axia l pul lout testing were 2.4 m x 5.0 m . The layout o f the testing chamber for ax ia l pullout is shown in Figure 3.1. Figure 3.1: Testing Chamber Configuration for Axial Pullout Testing - 1 7 -Chapter 3. Experimental Apparatus, Material Properties & Test Preparation W h e n p laced i n the s o i l box , the p ipel ine test specimen extended f rom either end o f the box , rather than be fu l ly contained w i t h i n the test chamber, i n order to provide a un i fo rm contact surface area dur ing the test. T o prevent unacceptable amounts o f s o i l loss f rom where the p ipe l ine entered and exi ted the box , a lubricated rubber gasket was pos i t ioned at either exit locat ion. The gasket consisted o f a 50 m m th ick hard rubber, w i t h a hole cut to match the external diameter o f the pipe. The thickness and stiffness o f the rubber a l l owed the gasket to main ta in shape as the pipe was pu l l ed through, and to resist deforming and b ind ing against the pipe. Tes t ing o f the fr ic t ional resistance between the polyethylene p ipe and lubricated rubber gaskets indicated a peak fr ict ional force o f 0.3 k N , and a large displacement f r ic t ional force o f 0.2 k N , for tests carr ied out on 60 m m pipes. H o w e v e r , it was observed dur ing the testing that the lubricants used at the interface q u i c k l y became c logged w i t h sand, resul t ing i n uncertainty i n cont inued smooth operation o f the gasket interface. A s such, the interface was generally kept un-lubricated, w i t h result ing fr ic t ional forces o f 0.4 k N and 0.3 k N for peak and residual values, respectively. S i m i l a r tests were conducted o n 115 m m pipe specimens, and the resul t ing fr ic t ional pul lout forces due to the gaskets were 0.5 k N peak and 0.3 k N residual . B ranched p ipe l ine sections were s imi l a r ly extended beyond the boundaries o f the b o x (see Sec t ion 3.3 for details o n pipe layout) . Because the branched sections were compr i sed on ly o f 16 m m diameter pipe, the required access holes were m u c h smal ler (18 m m ) than the main l ine access holes, and sand w o u l d not freely pass through the annulus around the pipe. Therefore, the access holes for the branches d i d not require rubber gaskets, and on ly smal l amounts o f lubr ica t ion was p rov ided to assist the pipe i n passing through the p l y w o o d . F o r r emova l o f the sand specimen f o l l o w i n g each test, two access holes were p rov ided near the base o f the test chamber, one at either end. E a c h access measured approximate ly 450 m m b y 300 m m , and was covered by a p l y w o o d panel dur ing the tests. Chapter 3. Experimental Apparatus, Material Properties & Test Preparation Sand H a n d l i n g F o r the tests performed dur ing the research, approximately 15 m 3 o f sand was required for each test to achieve the required depth o f cover above the p ipel ine . P r io r to each test, w h i l e the p ipe l ine was be ing p laced i n the b o x and instrumented, the sand was stored outside o f the b o x i n large bulk-storage bags, each o f w h i c h contained approximately 0.9 m o f so i l . O n c e the p ipe l ine was configured for the test, the overhead crane at hand i n the structures lab was used to lift the bags into the chamber. E m p t y i n g o f the sand f rom the bags was accompl i shed through a draw-str ing chute i n the base o f the bag, w h i c h was opened once the bag was inside the box . Once the chute was opened, it was possible to spread the sand throughout the chamber b y us ing the movement o f the crane. The drop height o f the sand f rom the base o f the bags was l imi t ed to less than about 1 m due to safety concerns and also for m i n i m i z i n g the generation o f dust i n the lab. L o a d i n g M e c h a n i s m s The load ing system for the tests required displacement contro l led movement o f the pipe specimen through so i l at ve ry s low displacement rates i n order to simulate the natural si tuation o f landsl ide creep deformation. The displacement rate chosen for this testing was 10 m m per hour, however , it was desired that the load ing mechan i sm be able to accommodate faster displacement rates, and also be able to vary the displacement rate dur ing the test. The pul lout load ing system chosen to meet these requirements consists o f a double-act ing hydraul ic cyl inder , an analog hydrau l ic control system, and a c l amping arrangement that permits on ly uni -d i rec t ional pipe displacement. The actuator for ax ia l load ing is a single 225 k N (50 k ip ) hydrau l ic cy l inder w i t h an integrated l inear var iable displacement transducer ( L V D T ) . The hydraul ic cyl inder , manufactured b y R o y a l Cy l inde r s Inc., N e w Westminster , B C , Canada, has a 175 m m (7 in.) bore diameter, w i t h a fu l l stroke o f 900 m m (36 in.) . The cy l inder is t runnion-mounted to a load ing pedestal w h i c h is attached to the reinforced concrete floor, separate f rom the s o i l box . The mount ing arrangement provides a connect ion height o f 450 m m above the concrete floor. - 1 9 -Chapter 3. Experimental Apparatus, Material Properties & Test Preparation H y d r a u l i c power for the cy l inder is p rov ided b y a 75 litres per minute, 21 M P a (3000 PSI ) b u i l t - i n hydrau l ic system i n the structures lab. A 40 litre per minute backup hydrau l ic power supply was also used for several tests w h i l e the m a i n supply was be ing serviced. B o t h hydraul ic pumps were manufactured by M T S Inc., and actuator response f rom the two pumps was nearly ident ical . D u r i n g the testing, on ly 0.0037 litres per minute were i n fact required to achieve a displacement rate o f 10 mm/hr . The control system for the hydraul ic cy l inder consisted o f the f o l l o w i n g components: • A n a l o g s ignal generator, m o d e l 3 4 0 A , manufactured b y Exac t ; • Integrated l inear var iable displacement transducer ( L V D T ) , m o d e l L P , manufactured by Temposon ic ; • Servo C o n t r o l S igna l Interface, manufactured by the U B C Dept . o f C i v i l Eng inee r ing Elec t ronics shop; • Servo controller, manufactured b y M T S ; and • Servo control valves , manufactured by M o o g . The analog s ignal generator provides a un i fo rm ramp load ing s ignal representing a displacement o f 10 mm/hr , w h i l e the integrated L V D T o n the cy l inder and feedback unit provides a feedback s ignal representing the actual cy l inder pos i t ion . T h e servo control ler compares the two signals, and w h e n necessary, sends a c o m m a n d s ignal to the control valves to adjust the f l ow o f hydraul ic o i l into and out o f the cyl inder . T h e c l a m p i n g mechanisms for attaching the pipe specimens to the load c e l l were compr i sed o f a two piece outer metal col lar that bol ted around the end o f the pipe, and a c i rcu lar insert that was p laced i n the pipe-end to prevent crushing or induc ing stresses other than tension. Because the displacement rates for the testing were at or b e l o w the threshold l imi t s o f the hydraul ic control system, some instabi l i ty i n cy l inder pos i t ion ing was observed dur ing testing. In order to compensate for this instabi l i ty, it was decided to - 2 0 -Chapter 3. Experimental Apparatus, Material Properties & Test Preparation provide a " loose" connect ion between the load ce l l and c l amping assembly. Th is connect ion a l lows axia l load to be appl ied in on ly one direct ion, so that i f the actuator moves in the direct ion opposite to the test, the pul lout load is reduced or dropped altogether, but the pipe is not m o v e d in the reverse direct ion. The attachment details arc shown in Figure 3 .2. A l l components o f the c l amping assembly were custom manufactured in the U B C C i v i l Engineer ing M a c h i n e shop. L o a d C e l l U n i - D i r c c t i o n a l C o u p l i n g Figure 3.2: Load Cell to Pipe Connection Detail 3.1.2 Instrumentation The focus o f the research is the deformation o f the pipel ine segments, and as such, most o f the instrumentation is focused on and around the pipel ines. The pipel ine instrumentation array is able to measure pullout forces, displacements o f the ends o f the pipe and o f points a long the pipe specimen buried in the so i l , and strains w i t h i n the pipe specimen. - 2 1 -Chapter 3. Experimental Apparatus, Material Properties & Test Preparation Forces The ax ia l pul lout force appl ied to the p ipel ine by the actuator was measured us ing an i n -l ine load c e l l mounted to the cy l inder rod . The load c e l l was a Sensotec m o d e l 41/573, w i t h a m a x i m u m load capacity o f 225 k N (50,000 lbs). The load ce l l was operated at an exci ta t ion voltage o f 1 0 V volts , and was calibrated over the range o f expected ax ia l loads, that is to say up to 25 k N . Strains Poin t strains were measured at mul t ip le locations a long the m a i n trunk o f the p ipe l ine and also a long the branches. Strains were measured us ing K y o w a type K F E L - 5 - 1 2 0 - C 1 strain gages w h i c h have a w o r k i n g strain range o f ± 1 5 % . Further details o n strain gauge selection, and specia l ized procedures for surface preparation and mount ing procedures for bond ing to polyethylene can be found i n Sect ion 3.3.2, be low. In some instances i n w h i c h strain gauges are located o n plastic specimens, a l oca l i zed strengthening and stiffening o f the mater ial is often noted (Br iassoul i s and Schet t ini , 2002) . It was recognized that strain gauges mounted to the polyethylene p ipe specimens w o u l d l i k e l y cause a s imi la r l oca l i zed stiffening o f the p ipel ine , resul t ing i n lower recorded strain measurements. A s such, the strain gauge measurements were used to provide relative strain and deformation profi les o f the pipe as the test progressed, and displacement transducers attached di rect ly to the p ipe l ine p rov ided g loba l strain values. In p re l iminary tests, it was shown that mul t ip le strain gauges mounted at 0 ° , 9 0 ° , 180° and 2 7 0 ° around the pipe gave essentially ident ical results. Th i s indicates that the dis t r ibut ion o f tensile strain throughout the cross section o f the pipe is re la t ively un i fo rm, w h i c h decreases the number o f strain gauges required. It was found that increased numbers o f strain gauges mounted to the pipe affected the required pul lout force for a g iven set o f test parameters. T h i s was due to the resistance generated b y the increased cross sectional area result ing f rom the strain gauges and associated abrasion protect ion - 2 2 -Chapter 3. Experimental Apparatus, Material Properties & Test Preparation measures, and due to the increased drag forces result ing f rom the lead wires f rom the strain gauges i n the s o i l . Displacements The displacement o f the actuator was moni tored us ing the integrated L V D T , w h i c h was a Tempson ic type L P analog magnetostrictive L i n e a r Disp lacement Transducer. Po in t displacements were measured at several locations a long the pipe specimen, at the front and back ends o f the pipe specimen, and at the ends o f the branches. In a l l cases, the specif ic points o n the p ipe that were moni tored were attached to str ing potentiometers us ing ve ry th in extension cables, w h i c h were found to have negl ig ib le resistance w h e n p u l l e d through the sand. In this w a y , points on the pipe bur ied w i t h i n the sand c o u l d be moni to red us ing externally mounted, and therefore protected, instruments. The displacement o f the front end o f the pipe was moni tored separately f rom actuator displacement i n order to account for any stretching o f the free end o f the pipe extending f rom the box . Pos i t iona l Surveys Spat ia l displacements o f the var ious pipe specimen configurations were measured us ing survey measurements o f the specimen before and after the test. P r io r to bur ia l , the layout o f the configurat ion was accurately mapped us ing a theodolite w i t h a laser range finder w h i c h p rov ided angular and distance accuracy o f ± 2 m m . U p o n comple t ion o f the test, the pipel ine was carefully uncovered and again surveyed. Strains and displacements were moni tored dur ing bur ia l and excavat ion o f the pipe specimen i n order to record any movement o f the p ipe f o l l o w i n g the in i t i a l survey o r p r io r to the f ina l survey that was unrelated to the pul lout test. Surveys were addi t ional ly taken o f the sand surface pr ior to and f o l l o w i n g testing i n order to capture any change i n surf ic ia l geometry related to p ipel ine movement . - 2 3 -Chapter 3. Experimental Apparatus, Material Properties & Test Preparation Data A c q u i s i t i o n A l l measurements f rom the instrumentation array moni to r ing the pipe spec imen were recorded at 2 H z ( 2 samples per second) i n order to moni tor any rapid sudden strain or displacement changes that c o u l d result f rom specimen failure. A d d i t i o n a l l y , as noted earlier, the very s low displacement rate required b y the tests resulted i n some instabi l i ty o f the control system, and as such, it was deemed necessary to moni tor any sudden strains or displacements due to unstable appl ied loads. Signals f rom the instrumentation array were col lec ted v i a a N a t i o n a l Instruments N I S C X I - 1 0 0 1 s ignal condi t ion ing board, and del ivered to the c o m m e r c i a l l y avai lable software package Da i sy l ab for real-time plot t ing o f a l l data. The system was powered b y a dedicated Pen t ium III computer system running M S W i n d o w s X P Profess ional . D u e to an acquis i t ion rate o f 2 H z and very long testing periods, post processing o f the data required reducing the data to a more manageable number o f data points. In general, w h e n tests functioned properly , the data set c o u l d be reduced to approximately 10% or less o f the o r ig ina l number o f data points and s t i l l main ta in very h igh resolut ion o f the plot ted curves. In instances where system instabili t ies were noted, test results were evaluated for acceptabil i ty, w i t h the results f o l l o w i n g the instabi l i ty general ly considered to be disturbed tests. 3.2 Tes t M a t e r i a l s The s o i l used for the testing program is l oca l l y obtained Fraser R i v e r Sand, w h i c h has been extensively tested and documented dur ing numerous laboratory testing programs performed at U B C i n the past (i.e. V a i d and Thomas , 1995). M a t e r i a l properties for the polyethylene pipe specimens were obtained f rom testing performed b y Terasen, f rom laboratory testing carr ied out at U B C , and f rom the manufacturer 's literature. The properties o f these materials are reported be low. - 2 4 -Chapter 3. Experimental Apparatus, Material Properties & Test Preparation 3.2.1 P rope r t i e s a n d D i r e c t S h e a r T e s t i n g o f F r a s e r R i v e r S a n d The so i l can be characterized by a number o f relevant engineering properties, inc lud ing mineral compos i t ion , grain size distr ibut ion, density and angle o f internal fr ict ion. Based on the avai lable literature, the compos i t ion o f Fraser R i v e r sand is understood to be 4 0 % quartz, 1 1 % feldspar, 4 5 % unaltered rock fragments, and 4 % other minerals ( V a i d and Thomas , 1995). Th is fine to med ium sand has an angle o f internal friction reported in the literature o f 32° loose and 38° dense. T h e average grain size, D 5 0 , is 0.23 m m , wi th a coefficient o f uniformity , C u o f 1.5. The m i n i m u m particle size is 0.074 m m and m i n i m u m and m a x i m u m v o i d ratios for the material arc 0.68 and 1.00, respectively The grain s ize distr ibution o f the sand obtained for the current test program was dry sieved in order to conf i rm that the above parameters w o u l d be appropriate for appl icat ion to test results. Detai ls o f the dry s iev ing technique can be found in L a m b c (1991). The grain size distr ibution curve for the material tested is shown in Figure 3.3. 10 1 0.1 0.01 0.001 Grain Size (mm) Figure 3.3: Grain Size Distribution of Fraser River Sand - 2 5 -Chapter 3. Experimental Apparatus, Material Properties & Test Preparation The angle o f internal f r ic t ion o f the s o i l was addi t ional ly conf i rmed us ing direct shear testing, w h i c h c lose ly simulates the shearing mechan i sm be l ieved to occur at and near the interface between the pipe and s o i l dur ing ax ia l pul lout . The importance o f accurately k n o w i n g the angle o f f r ic t ion is i l lustrated i n theoretical equations for estimates o f ax ia l pul lout resistance, where a 1° change i n (j) results i n approximately 3.5% change i n ax ia l pul lout resistance. The internal angle o f fr ic t ion, (j), for Fraser R i v e r sand used i n this study varies f rom 32° for loose samples to 38° for dense samples. A compar i son o f basic parameters for soi ls used by Traughtman & O ' R o u r k e (1983) are compared w i t h those for the current study i n Table 3.1. Table 3.1: Comparison of Soil Parameters for the Current and Previous Studies Traughtmann and O'Rourke, 1983 Current Study Dso 0.50 m m 0.23 m m D i o 0.20 m m 0.15 m m D 8 5 2.00 m m 0.35 m m C u 2.6 N / A emax 0.74 1.00 0.48 0.68 <|> (Loose - Dense) 33° - 4 2 ° 32° - 3 8 ° S G 2.74 2.70 The moisture content o f the sand was a l l owed to stabil ize at less than 1% moisture before the testing program began. Since considerable effort w o u l d have been required to moisture cond i t ion such large vo lumes o f sand, the sand was kept dry throughout this testing program i n order to negate the effects o f var iable moisture content. - 2 6 -Chapter 3. Experimental Apparatus, Material Properties & Test Preparation 3.2.2 P rope r t i e s a n d C o m p r e s s i o n T e s t i n g o f Po lye thy l ene N a t u r a l G a s P ipes The polyethylene pipe specimens were provided by Terasen Gas, and branched and joined sections were constructed on their premises prior to delivery to UBC. The specimens consist of three sizes, with outside diameters of 15 mm, 60 mm and 115 mm, and wall thicknesses of 2.3 mm, 6.2 mm and 11.0 mm, respectively. The resulting wall thickness to diameter ratios, t/d, arc 0.15, 0.10, and 0.10, respectively. Testing of polyethylene pipe sections was carried out in order to determine the clastic modulus of full size the pipe specimens. The samples were trimmed to provide a length to diameter ratio of approximately 2.5. This ratio was considered suitable in order to mobilize compressive resistance with minimal effect from the end platens, while at the same time avoiding buckling failure of the specimen. For 60 mm diameter pipe sections the resulting sample length was 150 mm, while for 115 mm diameter sections, the sample length was 250 mm. Specimens were tested in a universal compression testing machine. The standard machine set up was modified by attaching an L V D T to the end platens in order to measure the displacement of the platens, and therefore the global strain of the sample. The test setup is shown in Figure 3.4. Figure 3.4: Compression Testing of Pipe Specimens - 2 7 -Chapter 3. Experimental Apparatus, Material Properties & Test Preparation F o r testing o f the pipe sections, the rate o f displacement was set to 1 m m per minute. T h i s results i n a rate o f strain o f approximate ly 0 .7% per minute for 60 m m diameter pipes, and 0 .4% per minute for 115 m m diameter samples. T y p i c a l test results are presented i n Figure 3.5. In order to provide some indica t ion o f the effects o f rate o f strain on the load response o f polyethylene pipes, a test was performed at a rate o f displacement one order o f magnitude faster than the previous tests. Fo r this test the rate o f displacement, 10 mm/minute , resulted i n a rate o f strain o f approximate ly 6 .5% per minute on a 60 m m pipe. 25 20 ^ 15 5 - Typical Respt ^ " T y p i c a l Resp( )nse, 60 mm )nse, 115 mm 0 5 10 15 20 25 30 Displacement (%) Figure 3.5: T y p i c a l Pipe Specimen Compress ion Test Results at 1 mm min The elastic modulus o f the polyethylene was determined from relat ively s imple compress ion testing o f pipe specimens. It has been found that w i t h i n 2 % compressive strain, the modulus o f elasticity is generally equivalent to the tensile modulus o f elasticity (Plastic Pipe Institute, 1998). The testing o f specimens p rov ided to U B C indicated an - 2 8 -Chapter 3. Experimental Apparatus, Material Properties & Test Preparation elastic M o d u l u s o f 325 M P a . A summary o f results f rom compress ion testing o f the polyethylene specimens is contained i n A p p e n d i x A . 3.3 Pullout Test Preparation The test parameters for the current series o f tests were mainta ined re la t ively constant throughout the tests. A s such, the test preparation procedures, once established, required li t t le modi f i ca t ion throughout the testing program. The test preparation techniques for instrumentation attachment and preparation o f loose and dense so i l condit ions are discussed be low. 3.3.1 Pipe Specimen Preparation Pipe specimens for the fu l l scale pul lout tests consisted o f two basic configurations. The first configurat ion consisted o f 7 m long straight sections o f 15 m m , 60 m m or 115 m m diameter pipe. The second configurat ion consisted o f a p ipel ine " t runk" section w i t h two smaller diameter pipes branching o f f perpendicular f rom the m a i n l ine . T h e m a i n trunk consisted o f 7 m long sections o f either 60 m m or 115 m m diameter pipe, and the branching sections were 3 m long sections o f 15 m m pipe. The branching sections both d iverged f rom the trunk toward the same side, and were separated by 2.0 m . The connect ion o f the branching sections to the trunk was achieved through a fusion bonded "tee" w h i c h extends above the c r o w n o f the trunk by some 100 m m . Photographs o f typ ica l p ipel ine configurations are presented i n A p p e n d i x C . The majori ty o f the pipe specimens were outfitted w i t h several strain gauges a long the length o f the trunk section, as w e l l as a long the branches, w h e n present. Strain gauge instal la t ion procedures were ident ical regardless o f whether the strain gauge was located o n the trunk or branch sections. The detai led surface preparation and strain gauge mount ing procedure is described i n Sec t ion 3.3.2, be low. The strain gauges were isolated f rom induced strains result ing f rom drag forces on the lead wires b y p rov id ing a strain re l ief- loop adjacent to the gauge. L e a d wires f rom the strain gauges were typ ica l ly pos i t ioned such that drag forces on the wires w o u l d be reduced, and i n addi t ion, were - 2 9 -Chapter 3. Experimental Apparatus, Material Properties & Test Preparation located several pipe diameters away f rom the pipe i n order to a v o i d dis turbing the s o i l shear zone around the pipe. The lead wires were a l l ow ed to exit through the so i l surface, and were l ed over the top o f the chamber wa l l s to the data acquis i t ion system. The locations where string potentiometer extension wires were attached were p rov ided w i t h a mechan ica l anchorage consis t ing o f smal l screws ho ld ing the extension w i r e to the pipe. The crew thread measured approximately 2 m m , and generally penetrated to a depth o f roughly 4 m m . Anchorage locations were selected suff iciently distant f rom strain gauges such that any concentrations o f stresses around the disturbance caused by the smal l screws d i d not impact on the strain readings. The extension wires were approximate ly 0.5 m m i n diameter and p rov ided very litt le resistance w h e n p u l l e d through the so i l . The wires exited the box through sma l l holes d r i l l ed through the p l y w o o d wa l l s . Once the pipe specimen was supported on a prepared bed o f sand, the configurat ion was surveyed for both lateral and ver t ica l pos i t ion o f specific points marked o n the pipe us ing an indel ib le marker. P r i o r to sand placement, a l l instrumentation was attached to the pipe and proper operation o f the instrumentation array was ver i f ied . The data acquis i t ion system was employed dur ing the sand placement and compac t ion i n order to moni tor any potential displacement o f the p ipe l ine f rom the in i t i a l surveyed posi t ion. 3.3.2 Strain Gauging Polyethylene Strain Gauge Selec t ion W h e n taking any type o f measurement o f a specimen dur ing testing, it is c r i t i ca l that the methods used to take the measurement disturb the sample as l i t t le as possible . In particular, for testing o f soi l -p ipel ine interaction, it is important to disturb the interface between the pipe and the so i l as lit t le as possible . Unfortunately, because the spec imen is bur ied beneath over a h a l f meter o f so i l , use o f recently developed opt ica l methods or convent ional , non-intrusive manual methods are not feasible. The instrumentation to - 3 0 -Chapter 3. Experimental Apparatus, Material Properties & Test Preparation measure strain dur ing this testing program was required to operate essentially as a remote device , and as such, the use o f strain gauges mounted direct ly to the polyethylene pipe specimen was the on ly reasonable alternative. The use o f strain gauges o n polyethylene materials provides a set o f diff icul t ies not t yp i ca l ly encountered w h e n measuring strains i n metals. Polye thylene is chosen for use as underground p i p i n g speci f ica l ly for the mechanica l and chemica l properties it possesses. In particular, the l o w elastic modulus o f polyethylene results i n characterist ical ly h igh elongat ion under an appl ied load. T h i s proves cha l lenging for strain gauge appl icat ion, par t icular ly w h e n behaviour at h igh strain is o f interest. A s the use o f plastics becomes more c o m m o n i n load bearing and structural applications (the aerospace industry be ing an example) , specia l ized gauges have become more readi ly available. Such a gauge was selected for this appl ica t ion due to the h igh w o r k i n g strain range o f the gauge. The gauge selected was a K y o w a type K F E L - 5 - 1 2 0 - C 1 strain gauge w i t h the properties l is ted i n Table 3.2. Table 3.2: S t ra in Gauge Properties Manufacturer K y o w a T y p e K F E L - 5 - 1 2 0 - C 1 Gage L e n g t h 5 m m Stra in Range ± 1 5 % Gage Resistance 120.2 ± 0.2 Q Gage Factor 2.14 ± 1.0% Temperature Coeff ic ient o f Gage Factor + 0 . 0 1 5 % / ° C A n addi t ional factor to consider w h e n mount ing strain gauges to plastics is the re inforc ing effect that the gauge i t se l f has o n the material . Th i s considerat ion has been discussed i n further detai l under the descr ipt ion o f instrumentation i n the Exper imenta l Apparatus Sect ion. - 3 1 -Chapter 3. Experimental Apparatus, Material Properties & Test Preparation A p p l i c a t i o n Procedure Cons idera t ion was g iven to faci l i tat ing mount ing the strain gauges internal ly to the pipe, a l l o w i n g the wires to run internal ly to the pipe, however , this method was considered to be imprac t ica l for several reasons. F o r gauges mounted i n the midd le portions o f the pipe, the specimen w o u l d need to be cut and re-joined us ing specia l ized heat fusion equipment. There w o u l d be a r i sk that the heat f rom the bond ing process m a y alter the o r ig ina l properties o f the pipe specimen, or worse, m a y damage the gauge. In addi t ion, the very smal l diameter pipes used for dis t r ibut ion branches w o u l d not be able to accommodate the w i r i n g for more than one or two strain gauges. W h e n the area inf luenced b y the strain gauge appl ica t ion and protective coat ing is considered i n relat ion to the overa l l length o f the sample, it can be seen that the l ong length o f the pipe specimen was benef ic ia l for reducing the relative contr ibut ion o f the strain gauges to the total pul lout force. A typ ica l array o f strain gauges w o u l d cover approximate ly 10 to 15 % o f the pipe surface. Surface Preparat ion The l o w chemica l react ivi ty o f the polyethylene to many chemicals is idea l to resist degradation w h e n bur ied be low ground. H o w e v e r , many types o f adhesive used for mount ing strain gauges require some degree o f chemica l react ion w i t h the bond ing surfaces i n order assure a strong bond. A s such, spec ia l ized surface treatments and adhesives are required w h e n mount ing gauges to plastics. F o l l o w i n g trials w i t h several surface preparation techniques, i nc lud ing exposure o f the spec imen to h i g h intensity ul t raviolet l ight , exposure to f lame, and several chemica l pr imers , a surface preparation technique was selected that p rov ided an adequate bond up to re la t ively h i g h strains. The most effective procedure was found to be the use o f i sopropanol to first remove residual chemicals f rom the manufactur ing process or other contaminants. F o l l o w i n g c leaning, sandpaper (100 to 300 grit) was used to scour the surface o f the pipe, p roduc ing a textured surface to w h i c h the adhesive can adequately - 3 2 -Chapter 3. Experimental Apparatus, Material Properties & Test Preparation bond. F i n a l l y , a surface pr imer consis t ing o f Loc t i t e 770 P r imer was used to effect a m i n o r chemica l alteration to the polyethylene surface and provide adequate react ion w i t h the adhesive. The strain gauge was mounted to the specimen w i t h i n approximately 30 minutes o f d r y i n g o f the pr imer . Gauge A p p l i c a t i o n S i m i l a r to the diff icul t ies associated w i t h selecting a strain gauge for use w i t h the h igh elongat ion behaviour o f polyethylene, the adhesive chosen to bond the gauge to the spec imen must be able to mainta in strain compat ib i l i ty w i t h the gauge and the material . The adhesive must be able to accommodate large strains i n the material , and to transfer these strains to the strain gauge wi thout debonding f rom either the spec imen or the gauge. Further, the t ime required for the adhesive to cure should be appropriate to fit w i t h i n the testing schedule. The procedure used for mount ing the strain gauge to the specimen is nearly ident ica l to that used for moun t ing gauges to metals. The gauge is first a l igned w i t h the axis o f the spec imen and he ld i n place us ing cel lophane tape. The tape is then pealed back to a l l o w a sma l l amount o f Loc t i t e 414 cyanoacrylate adhesive to be p laced a long the base o f the strain gauge. F i n a l l y , the strain gauge is transferred to the specimen us ing thumb pressure to squeeze the gauge d o w n to the specimen, expe l l ing any excess adhesive. T h u m b pressure is mainta ined for one minute, then the adhesive is a l l o w e d to cure for 24 hours p r io r to comple t ing the strain gauge connections. The connect ion o f the strain gauge to the data acquis i t ion system is accompl i shed b y solder ing lead wires f rom the strain gauge to external terminals mounted adjacent to the strain gauge. The instrumentation cables leading to the data acquis i t ion system are then also soldered to the terminals, comple t ing the circui t . Gauge Protect ion Protect ion o f the strain gauge was required to withstand the considerable abrasion f rom the sand that occurred dur ing the pul lout tests. A s noted above, because the gauge and - 3 3 -Chapter 3. Experimental Apparatus, Material Properties & Test Preparation protective coatings were at the interface between the so i l and the pipe, it was vi ta l that the protective coat ing interfere as litt le as possible w i t h the natural so i l behaviour at the interface. It was found dur ing ini t ia l trials us ing convent ional protection consis t ing o f a metal l ic fo i l w i t h an adhesive back ing that the thickness o f the adhesive and fo i l protruded excess ively from the pipe, result ing in the foi l anchoring in the sand and being pu l l ed away from the strain gauge. Th i s appears to have contributed to s ignif icant ly higher pul lout resistances in pre l iminary tests. A s an alternative means o f protecting the gauge from abrasion and damage from the sand, a single layer o f electrical tape was found to provide sufficient protection for the strain gauge, w i th the advantage o f maintaining the approximate surface texture o f the polyethylene. The tape was scaled w i t h adhesive at the edges to prevent peal ing dur ing pullout . Figure 3.6: O r i g i n a l and Modi f i ed Strain Gauge Installation and Protection Technique The thrcc-strand wires connect ing the strain gauge to the data acquis i t ion system s imi l a r ly required protection in order to prevent, or at least delay for a significant per iod - 3 4 -Chapter 3. Experimental Apparatus, Material Properties & Test Preparation o f t ime, detachment o f the wires dur ing the test. The wires were thus t ied f i rmly to the pipe and p rov ided w i t h a stress-relief loop, as shown i n F igure 3.6 i n order to prevent the resistance f rom the sand f rom detaching the wires . The wires were addi t ional ly bonded to the pipe w i t h adhesive to prevent detachment. 3.3.3 S a n d P l a c e m e n t In order to protect the p ipel ine and instrumentation f rom disturbance dur ing the in i t i a l placement o f so i l above the pipe, sand was manua l ly p laced on the m a i n trunk l ine and any branch pipes to a depth o f approximately 100 m m . The first layer o f sand was then s lumped f rom the storage bags onto the c r o w n o f the pipe, as the bag was m o v e d a long the axis o f the pipe. Preparat ion o f loose sand specimens was accompl i shed by a l l o w i n g the sand to s lump f rom the b u l k bags as the bag traveled above the surface o f the preceding layer. B y main ta in ing consistent heights and bag movement veloci t ies , a re la t ively un i fo rm sample c o u l d be prepared i n 4 to 6 hours. The sand was not disturbed dur ing placement b y smoothing or r ak ing each surface, rather on ly the f inal s o i l layer was smoothed i n order to a l l o w a survey o f the so i l surface to be made. Preparat ion o f dense s o i l samples was achieved us ing increased drop heights o f sand f rom the bags, and b y e m p l o y i n g a plate tamper to compact each s o i l layer. S o i l was p laced f rom the bags i n 150 m m lifts, l eve led w i t h a rake, and compacted w i t h two passes o f the plate tamper, i n alternating patterns. The plate tamper used was a gasoline powered B a r t e l l m o d e l B 1 3 1 8 . Because the sand was dry, moderate amounts o f dust were generated, requi r ing the use o f exhaust fans and respirators and occas ional ly causing w o r k stoppages to a l l o w the air qual i ty to improve for others w o r k i n g i n the laboratory. F o l l o w i n g placement o f each sand layer, s o i l density measurements were taken us ing a nuclear densometer. The nuclear densometer a l l owed rap id testing o f a significant number o f locations w i t h i n each s o i l layer. In i t ia l ly , placement o f density pans i n the s o i l layer was also attempted i n order to conf i rm the accuracy o f the nuclear density testing. - 3 5 -Chapter 3. Experimental Apparatus, Material Properties & Test Preparation H o w e v e r , these attempts were unsuccessful i n obtaining reasonable or consistent density measurements. The f inal s o i l surface was surveyed after be ing leve led w i t h a rake and straight edge. The laser range finder o n the survey equipment a l l owed a significant number o f points to be surveyed across the sand surface wi thout in t roducing any disturbance to the specimen. The in i t i a l s o i l surface was prof i led us ing survey points at a g r id spacing o f approximately 300 m m . Once a test was completed, r emova l o f the sand f rom the test chamber was accompl i shed v i a the two access holes i n the test chamber. The p l y w o o d panel was removed , and the sand was a l l owed to fa l l b y gravi ty onto a conveyor beneath the opening. A d d i t i o n a l manual r emova l o f the sand was required for s o i l further f rom the access holes. The sand was l if ted b y the conveyor and re-deposited into the bulk-storage bags, w h i c h were then stored next to the test chamber pr ior to the next test. - 3 6 -CHAPTER 4 STRAIGHT PIPELINE PULLOUT TESTING 4.1 Introduction A x i a l p ipe l ine pul lout testing was conducted o n straight polyethylene pipe specimens i n order to observe the soi l -pipel ine interaction behaviour o f these pipel ines w h e n subjected to permanent lateral ground deformations. The purpose o f this series o f tests was to establish an understanding o f the mechanisms and magnitudes o f deformation o f the polyethylene specimens w h e n tested i n an idea l ized configurat ion. In particular, this w o r k was performed to provide some basis upon w h i c h comparisons to t radit ional steel p ipel ine networks c o u l d be made, and for w h i c h tradit ional des ign methods c o u l d be ver i f ied . T h i s chapter describes the results o f the tests performed, and compares the results to predict ions based on theoretical and analyt ical methods avai lable i n the literature. A summary o f the series o f tests undertaken is indicated i n Table 4 .1 . Table 4.1: Straight Pipeline Test Matrix Test No. Pipe Size (mm) Configuration Soil Density Test ID 1 115 Straight M e d i u m - L o o s e 1 1 5 a L - S G 2,3 115 Straight M e d i u m - L o o s e 115aL 1 1 5 a L - R T 4 115 Straight Compac t 115aD 5 115 Straight M e d i u m - L o o s e 115aL-Retest 6 60 Straight M e d i u m - L o o s e 6 0 a L 7 60 Straight Compac t 6 0 a D 8 15 Straight Compac t 15aD - 3 7 -Chapter 4. Straight Pipeline Pullout Testing The test identifications (Test ID) use a shortened notat ion that refers to pipe diameter, d i rect ion o f displacement, s o i l density, and m a y include an addi t ional identifier. F o r example , 1 1 5 a L - S G refers to a 115 m m diameter pipe pu l l ed a x i a l l y through m e d i u m -L o o s e s o i l that has several addi t ional strain gauges (SG) mounted to it. Comple te test results are contained i n A p p e n d i x B , w h i l e on ly informat ion relevant to the current d iscuss ion is inc luded i n the sections f o l l o w i n g . 4.2 Results of Straight Section Pullout A x i a l pul lout tests (Tests number 1 through 8) were performed o n straight sections o f polyethylene pipe, and were general ly s imi la r i n configurat ion to those performed at other facil i t ies such as C o r n e l l U n i v e r s i t y (Traughtman et a l . , 1983), and C - C O R E (Pau l in et a l . , 1998). The test specimens were prepared w i t h 0.75 m s o i l cover above the pipe, w h i c h is t yp ica l o f field installations for dis t r ibut ion p i p i n g o f this size. D u e to the constant bu r i a l depth but va ry ing pipe diameters, the resul t ing H / D ratios differ between the different sizes o f pipe. Because the intent o f the testing was to characterize the behaviour o f typ ica l field installations, it was deemed acceptable that the H / D ratio w o u l d differ, w h i l e the bur ia l depth was maintained. In order to provide some measure o f the effect o f displacement rate o n pul lout resistance, tests were performed (Tests number 3 and 6) i n w h i c h the rate o f displacement was increased i n increments o f 100%. Tests were performed o n both 115 m m pipe sections and o n 60 m m pipe sections. The results indicated that for displacement rates up to 100 m m per hour, there was no appreciable difference i n measured pul lout resistance. B a s e d o n the observed response dur ing increases i n rates, a rate o f displacement o f 10 m m / h r was selected for the in i t i a l load ing o f the p ipe specimen. T h i s displacement rate was considered adequate i n order to a v o i d a dynamic response f rom the pipe specimen and/or the so i l , and also to reasonably represent the s l o w displacements associated w i t h - 3 8 -Chapter 4. Straight Pipeline Pullout Testing landsl ide creep movements . Once the peak load was obtained, the rate was often increased to 20 m m / h r i n order to facilitate cont inuing the test to greater displacements w i t h i n a reasonable t ime frame. Furthermore, since the load ing system c o u l d not be operated cont inuously for the durat ion o f the ve ry l ong testing per iod, the requirement to shut d o w n overnight presented an opportunity to perform unload-reload tests o n the pipe and to observe nay potential re laxat ion effects o f the p ipe overnight. Th i s also p rov ided an opportunity to observe the ax ia l re loading response o f pipe that has been prev ious ly subjected to large ax i a l displacements. B a s e d on the results o f pul lout tests performed at other facil i t ies (Traughtman and O ' R o u r k e , 1982), the Equa t ion 4.1 b e l o w has been developed for determining the m a x i m u m pul lout force for straight sections o f pipe ( A S C E , 1984). where: T» = ult imate ax ia l force on pipe (soi l resistance) D = external p ipe l ine diameter L = embedded pipel ine length y = effective unit weight o f s o i l H = depth f rom ground surface to center o f the p ipel ine K o = coefficient o f s o i l pressure at rest 6 = interface angle o f f r ic t ion between so i l and pipel ine U s i n g Equa t ion 4 .1 , values for interface f r ic t ion angle corresponding to each o f the tests conducted herein were back-calculated. In order to estimate the interface angle o f f r ic t ion, 8, it is generally assumed that 8 is s imp ly some percentage o f the internal angle o f f r ic t ion o f the so i l . T h i s ratio o f interface f r ic t ion angle to the s o i l internal angle o f - 3 9 -Chapter 4. Straight Pipeline Pullout Testing f r ic t ion is typ ica l ly referred to a s / , w h e r e / = 8/(|). F o r polyethylene pipes, it is general ly assumed t h a t / = 0.6 (Traughtman et a l . , 1983). 4.2.1 Tests in Medium Loose Sand A series o f ax ia l pul lout tests were performed i n uncompacted sand, and are referred to as " m e d i u m loose" samples herein. These density ranges were intended to represent s o i l condit ions i n locations where pipel ines are instal led wi thout trench excavat ion (i.e. " p l o w i n g " ) , or where trench b a c k f i l l is purposely left uncompacted i n order to reduce stresses o n the pipe. The test parameters for p ipel ine specimens prepared i n loose sand are contained i n Table 4.2. In total, 5 tests were run w i t h two sizes o f pipe, 115 m m and 60 m m diameter. The first test performed, 1 1 5 a L - S G was the first test w i t h the load ing system, and as such, s ignificant deviations f rom a smooth displacement rate were achieved. D u e to these diff icul t ies , the data obtained from this first test are largely disregarded, w i t h the except ion o f the strain gauge data w i t h i n the first 50 m m , w h i c h were considered for discussion. Table 4.2: Test Parameters for Straight Sections in Medium-Loose Sand Test ID Pipe Diameter, D (mm) Soil Unit Weight, (kN/m 3) Void Ratio, e Relative Density, D r (%) Burial Depth, H (mm) 1 1 5 a L - S G 115 Not Available (equipment check) 115aL 115 14.7 0.80 63 0.75 1 1 5 a L - R T 115 14.7 0.80 63 0.75 115aL-Retest 115 14.9 0.78 70 0.74 6 0 a L 60 14.2 0.86 43 0.72 The var iab i l i ty o f the density o f the so i l w i t h i n each test specimen, as tested dur ing sand placement, is presented graphica l ly i n Figure 4 .1 , be low. It can be seen that the placement o f sand f rom the large bu lk bags results i n a re la t ively non-uni form "as-p laced" sample. The placement o f sand us ing the "bag-dropped" method, however , c o u l d - 4 0 -Chapter 4. Straight Pipeline Pullout Testing be considered to correspond to typica l trench back f i l l methods where material is dropped into the trench us ing the bucket o f an excavator. The density test results indicate that regardless o f h o w carefully the operator controls the sand placement us ing the excavator bucket, or in this case the storage bag, significant density variations w i l l l i k e ly occur. A s such, it should be considered un l ike ly that loose trench back f i l l w i t h a relat ively uni form density cou ld be accompl ished, even in field installations. 10 o c o 3 a-24 • 115aL-Retest H 6 0 a L 1350 1400 1450 1500 1550 1600 1650 1700 Density (kg/m ) Figure 4.1: Density Testing Summary for Straight Tests in Medium-Loose Sand F o r tests performed on straight specimens, the resistance to displacement generated by interface fr ict ion can be presented using traditional T - x curves, as shown in Figures 4.2 and 4.3, for 115 m m and 60 m m pipe specimens, respectively. B o t h the load response curves presented include mul t ip le unload/reload loops, where each unload/reload cyc le corresponds to an increase in displacement rate conducted to observe rate effects, as discussed in Sect ion 4.2. The load response curves indicate that the resistance to pul lout for polyethylene pipe sections i n medium-loose sand is relat ively non-l inear up to the peak value, after w h i c h - 4 1 -Chapter 4. Straight Pipeline Pullout Testing the resistance decreases. The values o f peak ax ia l pullout force, T m a x , residual ax ia l force, T r , and associated displacements are p rov ided in Table 4.3. Th i s strain-softening effect is more c o m m o n l y observed in the shear response o f re la t ively dense sands, however, this response can also be observed i n samples w i t h i n the range o f so i l densities o f the samples tested herein. In these tests w i t h dry sand, the strain-softening response o f axia l pul lout load can be attributed to a combinat ion effect ar is ing from the variat ion o f the m o b i l i z e d fr ict ion angle at the sand/pipe interface and possible changes i n the interfacial normal effective stress resulting from a decrease in diameter due to pipe elongation. 100 200 300 400 500 S P Displacement, x (mm) 600 700 Figure 4.2: Pullout Resistance for Test on 115 mm Straight Section in Medium-Loose Sand (115aL-RT) Changes to the normal effective stress act ing at the p ipe/soi l interface, par t icular ly i n instances where the diameter is potential ly decreasing due to elongation o f the pipe, are considered to be a direct result o f the effect o f so i l arching above the c r o w n o f the pipe. - 4 2 -Chapter 4. Straight Pipeline Pullout Testing 5.0 Figure 4.3: Pullout Resistance for Tests on 60 mm Straight Sections in Medium-Loose Sand (60aL) Table 4.3: Pullout Force Results for Straight Sections in Medium-Loose Sand Forces Displacements Normalized Forces Normalized Displacements Test ID T 1 max (kN) T r (kN) ^max (mm) xr (mm) T' 1 max T ' r Xmax/D x r/D 115aL-SG 115aL 4.45 (3.52)* 2.67 (2.17) 6.8 N / A 0.55 0.34 0.059 N / A 115aL-RT 3.76 (2.83) 2.47 (1.97) 11.5 N / A 0.44 0.31 0.10 N / A 115aL-Retest N / A 4.41 (3.91) N / A N / A N / A N / A N /A N /A 60aL 1.87 (1.12) 1.02 (0.40) 11.8 170 0.36 0.13 0.20 2.8 note: ( ) indicates value corrected for gasket fr ict ion - 4 3 -Chapter 4. Straight Pipeline Pullout Testing It can be seen i n both figures that the reducing trend i n the noted ax ia l force noted seems to continue i n spite o f the increase i n the rate o f displacement. H o w e v e r , at higher rates o f displacement ( -300 mm/hr) it appears that there is a tendency for the ax ia l force to s l ight ly increase w i t h further displacement. W i t h a subsequent decrease i n displacement rate, the m a x i m u m ax ia l force is seen to again decrease to previous values. T h i s sl ight recovery i n ax i a l force w i t h increasing displacement rates can potent ia l ly be interpreted as result o f a disturbance to this arched so i l zone (above the pipe crown) surrounding the p ipel ine . W i t h increasing displacement rates, it cou ld be expected that the movement o f the p ipe c o u l d result i n mino r vibrat ions o f the arched zone causing the arching to collapse, again potential ly increasing the so i l pressures on the pipe. Th i s , i n turn, w o u l d translate into the observed increase i n ax ia l forces. In order to compare results between differ ing geometries and configurations o f pipe, and to be able to predict the response o f installations under design, the test results are no rma l i zed to dimensionless units. Test results are no rma l i zed for pipe diameter, depth o f bur ia l , s o i l density, pipe specimen length and in-s i tu lateral earth pressure. N o r m a l i z e d plots are presented i n F igure 4.4 for 115 m m and 60 m m diameter pipe specimens. It should be noted that the values for normal ized peak and residual ax i a l forces contained i n Table 4.3 have been corrected for the end gasket f r ic t ion, w h i l e the curves presented i n F igure 4.4 have not. Because gasket f r ic t ion is dependent on the displacement o f the pipe, it is more convenient to correct the peak and residual pul lout forces, where it is k n o w n that the gasket f r ic t ion is fu l ly m o b i l i z e d . A s can be seen i n the normal ized plots, except for the interference f rom the effects o f the rate testing, the no rma l i zed pu l lou t resistance for the t w o p ipe sizes are i n very g o o d agreement w i t h each other. A l s o presented i n the figure us ing dashed l ines is the predicted m a x i m u m pul lout force based on Equa t ion 4 .1 , f o r / e q u a l to 0.6 and ko equal to 0.5, w h i c h are the typ ica l ly assumed values. The predicted pul lout force is c lear ly far greater, and the predicted displacement required to mob i l i z e the peak ax i a l force ( x m a x ) is s ignif icant ly less than the experimental results. - 4 4 -Chapter 4. Straight Pipeline Pullout Testing 2.0 3.0 4.0 5.0 Normal ized S P Displacement , x/D 6.0 •115aL-RT -60aL 7.0 Note: Dashed line indicates predicted maximum pullout force using Equation 4.1 Figure 4.4: Normalized Pullout Resistance for Tests on 115 mm and 60 mm Straight Sections in Medium-Loose Sand (115al-RT and 60aL) (without correction for gasket fiction) The discrepancy between predicted and actual p ipel ine displacement to achieve m a x i m u m axia l resistance can be attributed to the capacity for the polyethylene pipe to elongate w i t h appl ied stress. A s the co l la r o f the pipe is d isplaced, the movement is accommodated by a combina t ion o f the pipel ine s l id ing through the so i l and elongat ion o f the pipe. The elongation o f a 115 m m pipe based on point strains at several locations a long the pipe is presented i n Figure 4.5, for several increments o f appl ied displacement. Th i s elongation o f the pipe adds to the displacement o f the pipe col lar , result ing in a larger required displacement to achieve the m a x i m u m pullout force. - 4 5 -Chapter 4. Straight Pipeline Pullout Testing -3500 -3000 -2500 c ' r o g -2000 £ c 'ro >_ *-> CO -1500 -1000 -500 Leading E n d Disp lacement o * x " - • - 1 mm - • - 2 mm a 5 mm 10 mm 20 mm 50 mm 75 mm * * * X 1000 2000 3000 4000 Distance From Clamp (mm) 5000 6000 Figure 4.5: Observed Point Strains, 115 mm Diameter Pipeline Specimen Exper imenta l values for peak and residual interface friction angle have been back-calculated us ing a constant k 0 value o f 0.5, and arc contained in Tab ic 4.4. It is noted that Equat ion 4.1 has been developed to compute the m a x i m u m axia l force corresponding to the peak friction angle, al though herein it has been considered for the interpretation o f forces even under strain-softening condit ions o f the so i l . The interpreted peak interface friction angle, 8 P , was found to be w i th in a narrow range o f 11° to 13° for both 115 m m and 60 m m pipe specimens in medium-loose sand. T h i s corresponds to an interface friction angle ratio, fp, o f 0.4. The residual angles o f interface friction were found to differ, w i th 115 m m pipe having a 5 r value o f 8 ° , and 60 m m pipe having a 8 r value o f 3 ° . These correspond to fr values o f 0.2 and 0.1, respectively. - 4 6 -Chapter 4. Straight Pipeline Pullout Testing Table 4.4: Interpreted Interface Friction Angles for Straight Sections in medium-Loose Sand Test ID Assumed k« Peak Interface Friction Angle, 8P(degrees) Residual Interface Friction Angle, 8 r (degrees) Peak Interface Friction Angle Ratio, /p Residual Interface Friction Angle Ratio, / r 1 1 5 a L - S G 115aL 0.5 13 8 0.41 0.26 1 1 5 a L - R T 0.5 11 8 0.33 0.22 115aL-Retest 0.5 N / A N / A N / A N / A 6 0 a L 0.5 12 3 0.37 0.10 The discrepancy between the predicted and actual peak and residual ax ia l resistances is probably a result o f two mechanisms impac t ing the interface fr ic t ion. Firs t , arching o f the so i l , as p rev ious ly discussed is l i k e l y occurr ing as the zone o f sheared s o i l around the pipe is shedding load onto the surrounding s o i l mass. A s the load is shed onto the surrounding s o i l mass, the no rma l effective s o i l stress act ing o n the surface o f the pipe w o u l d be reduced, i n turn l ower ing the overa l l resistance to pul lout . In larger diameter pipes, such as those tested i n previous studies, it is l i k e l y that the degree o f s o i l arching over the pipe diameter w o u l d be less. Secondly , due to the elongat ion o f the pipe, points o n the pipe closer to the appl ied displacement are subjected to larger movements relative to points o n the pipe further f rom the appl ied displacement. A s such, by the t ime points near the t ra i l ing end o f the pipe reach displacement sufficient to m o b i l i z e peak resistance, points nearer to the appl ied displacement have reached residual shear strength values. The resul t ing cumulat ive (or mob i l i zed ) resistance w o u l d be considerably less than the predicted resistance. T h i s phenomenon o f var ia t ion o f m o b i l i z e d strength a long a failure plane is t yp i ca l ly termed progressive failure. - 4 7 -Chapter 4. Straight Pipeline Pullout Testing 4.2.2 Tests in Dense Sand The second series o f straight specimen tests were performed i n compacted sand backf i l l s , w i t h relative densities near 100%. S o i l compac t ion was conducted us ing equipment typ ica l ly used i n the field, namely a vibratory plate tamper. The compacted so i l condit ions were considered to represent typ ica l trench installations, and i n particular, installations beneath or near compacted road fills where s ignif icant ly elevated s o i l densities are often encountered, either by design or as a result o f construct ion and operating condi t ions . Test parameters for p ipe l ine specimens prepared i n compacted sand are contained i n Table 4.5. Three tests were performed, one on each size o f pipe used i n the testing, w h i c h is 15 m m , 60 m m and 115 m m diameter. Strain gauges were attached on ly to the largest size o f pipe, 115 m m , because it was felt that the influence due to the phys i ca l presence o f the strain gauge instal lat ion "patches" w o u l d be too great on smaller diameter s ized pipes, par t icular ly i n compacted sand were the anchor ing effect w o u l d be magni f ied b y the dense sand. Because o f the abi l i ty to control density, the achieved densities o f the so i l w i t h i n each test specimen were m u c h more un i fo rm than i n the medium-loose sand samples. The dis t r ibut ion o f density test results is shown i n F igure 4.5. A s can be seen i n the figure, densif icat ion o f the samples provides a re la t ively un i fo rm density dis t r ibut ion throughout the sample. St ra in and displacement measurements were recorded dur ing sample preparation and so i l compact ion , w i t h litt le to no disturbance o f the p ipe specimens observed dur ing so i l compact ion . M o v e m e n t s o f the pipe ends were typ i ca l ly less than 1 m m , and strains i n the 115 m m diameter pipe were less than 100 microst ra in . T h e resistance to displacement generated by interface f r ic t ion has been presented i n T - x curves i n Figures 4.7 through 4.9, for 115 m m , 60 m m , and 15 m m diameter p ipe specimens, respectively. The load response curves again include several unload/reload loops, however , addi t ional rate effect testing was not conducted o n the dense samples. A thorough invest igat ion o f the effects o f displacement rate on the load response was considered beyond the scope o f the current research. The rate tests p rev ious ly performed - 4 8 -Chapter 4. Straight Pipeline Pullout Testing on the loose samples was intended only to determine a suitable displacement rate i n order to represent creep displacement. Table 4.5: Test Parameters for Straight Sections in Dense Sand Test ID Pipe Diameter, D (mm) Soil Unit Weight, Y (kN/m3) Void Ratio, e Relative Density, D r (%) Burial Depth, H (mm) U S a D 115 15.5 0.71 91 0.52 6 0 a D 60 15.8 0.67 102 0.48 15aD 15 15.7 0.68 99 0.48 2 I • 115aD • 15aD • 60aD 1350 1400 1450 1500 1550 1600 1650 1700 Density (kg/m 3) Figure 4.6: Density Testing Summary for Straight Tests in Dense Sand - 4 9 -Chapter 4. Straight Pipeline Pullout Testing 14 „ o M - 4 • ' v i • — • • 1 0 100 200 300 400 500 600 700 SP Displacement (mm) Figure 4.7: Pullout Resistance for Tests on 115 mm Straight Sections in Dense Sand 14 -I 12 ^ 10 Z l~_ 8 of u L. o LJ- 6 5 450 SP Displacement (mm) Figure 4.8: Pullout Resistance for Tests on 60 mm Straight Sections in Dense Sand - 5 0 -Chapter 4. Straight Pipeline Pullout Testing 3.0 2.5 0 100 200 300 400 500 600 700 SP Displacement (mm) Figure 4.9: Pullout Resistance for Tests on 15 mm Straight Sections in Dense Sand The load response curves for dense sand tend to be even more non-l inear than loose sands in the ini t ia l loading port ion o f the curve, and the peak load is sustained for a larger displacement increment pr ior to exhib i t ing a strain softening response. The observed load-displacement response can be expla ined us ing the strain response plot shown in Figure 4.10. The very non-l inear behaviour o f the load response curve for the 115 m m diameter specimen occurs at displacements beginning in the range o f 5 to 10 m m up unti l 50 m m . A s can be seen in Figure 4.10, this corresponds to the development o f a very non-linear strain distr ibution a long the pipe. In the in i t ia l part o f the pul lout tests only a relat ively smal l length o f the pipe is m o b i l i z e d i n resisting the appl ied load. It can be argued that this should be the case since the pipe is embedded i n a dense so i l that w o u l d provide a relat ively large pullout resistance in compar ison to a medium-loose bedding. W i t h increasing load, this m o b i l i z e d length w o u l d increase, as can be noted from Figure 4.10. Once the axia l pipe displacement is approximately 50 m m , the variat ion o f ax ia l strain is linear, indicat ing a un i form mob i l i za t ion o f shear strength a long the pipe. It can be noted that this commencement o f l inear strain distr ibution along the pipe is also - 5 1 -Chapter 4. Straight Pipeline Pullout Testing coincident w i th the flat peak in the load response curve. Th i s observation essentially indicates the dependence o f the shape o f the load response curve on the axia l stiffness o f the p ipel ine material as w e l l as the magnitude o f interface frict ion. N o r m a l i z e d plots for 115 m m , 60 m m , and 15 m m diameter pipe specimens in loose sand are presented in Figure 4.11 and 4.12, w i t h tabulated results p rov ided in T a b i c 4.6. The results indicate relat ively consistent behaviour for 60 m m and 115 m m specimens, but a considerably different response for the 15 m m specimen. In terms o f the normal ized force, it is observed that the peak norma l i zed pul lout force for the 15 m m pipe is comparable to those computed for the larger diameter pipes. However , the normal ized displacement at w h i c h the peak pul lout force occurs is more than and order o f magnitude greater for the 15 m m specimen than for the 60 m m and 15 m m specimens. The curve for the 15 m m specimen is plot ted separately due to this magnitude difference in normal ized displacements. -3500 -3000 -2500 -I " ro b tj -2000 o o E c 'ro C/3 -1500 -1000 -I -500 Leading End * Displacement • * - • - 1 mm - • - 2 mm - a - 5 mm - • - 10 mm - * - 20 mm hamber - • - 50 mm - - - 100 mm hamber u uS ai I -3 0J O) T3 LU • * * idge of Test C * •> * idge of Test C * m • : : : : 1 • - • • * * 0 1000 2000 3000 4000 5000 6000 Distance From Front Edge of Test Chamber (mm) Figure 4.10: Observed Point Strains, 115 m m Diameter Pipel ine Specimen - 5 2 -Chapter 4. Straight Pipeline Pullout Testing 3.0 2.5 + 0.0 +1 l—Ji ' I • « 1 • , . * l ( 0.0 2.0 4.0 6.0 8.0 Normalized SP Displacement, x/D — 115aD — 6 0 a D | Figure 4.11: Normalized Pullout Resistance for Tests on 115 mm and 60 mm Straight Sections in Dense Sand (without correction for gasket fiction) 3.0 -j 1 2.5 • O X o.o -M——, — — . '—i .— - | 0 5 10 15 20 25 30 35 40 45 Normalized SP Displacement, x/D | — l 6 a D I Figure 4.12: Normalized Pullout Resistance for Tests on 15 mm Straight Section in Dense Sand (without correction for gasket fiction) - 5 3 -Chapter 4. Straight Pipeline Pullout Testing The peak ax i a l pul lout force for the 15 m m specimen is reached after a ve ry long , non-linear por t ion o f the load response curve. A s discussed previous ly , e longat ion o f the pipe and progressive failure tend to draw-out the approach to a peak force, and flatten the peak. The peak ax ia l strain w i t h i n the 15 m m pipe, based on the measured elongat ion prof i le shown i n F igure 4.13, is approximately 12.8% (128,000 microstrain) . In compar ison , the peak ax ia l strain measured w i t h i n the 115 m m specimen was 0 .3% (3000 microstrain) . Th i s indicates that pipe elongat ion accounts for a s ignif icant ly higher percentage o f the measured displacement i n the smaller diameter p ipe than i n the larger diameter pipe. Consequent ly , the observed load response curves are s ignif icant ly different due to the unequal f r ic t ional contributions resul t ing f rom elongat ion o f the pipe. Table 4.6: Pullout Force Results for Straight Sections in Dense Sand Forces Displacements Normalized Forces Normalized Displacements Test ID T x max (kN) T r (kN) Xmax (mm) X r (mm) T ' *• max T ' r Xmax/D x r/D 115aD 11.9 (10.9) 7.8 (7.3) 84.4 692.7 2.4 1.6 0.73 6.02 60aD 4.7 (3.9) 3.5 (2.9) 44.4 421.8 1.7 1.3 0.74 7.03 15aD 1.2 (0.7) 0.9 (0-4) 399.0 711.2 1.1 0.7 26.6 47.4 A s shown i n Figures 4.11 and 4.12, the exper imental ly obtained peak ax ia l pul lout resistances for tests i n dense sand are higher than predict ions based on Equa t ion 4 .1 , w i t h an assumed coefficient o f lateral earth pressure o f 1.0 and fr ic t ion ratio, / , equal to 0.6. Res idua l values for pul lout resistance beg in to approach the predicted value at larger displacements, however , a stable res idual pul lout force was not obtained b y the end o f the test. T h i s discrepancy m a y be expla ined i n part by observations b y F i l z and D u n c a n (1996), indica t ing that f o l l o w i n g compac t ion o f p laced soils the in-s i tu coefficient o f lateral earth pressure, ko, m a y be considerably higher than 1.0 due to induced lateral s o i l stresses. - 5 4 -Chapter 4. Straight Pipeline Pullout Testing 700 Leading End Disp lacement 350 mm - • - 4 0 0 mm 200 mm — 300 mm 500 mm —A— 600 mm - X - 1 0 0 mm -1000 0 1000 2000 3000 4000 5000 6000 Distance Along Pipe (mm) Figure 4.13: Inferred Elongation from E n d Displacements, 15 mm Diameter Pipeline Specimen A d d i t i o n a l l y , due to the relat ively soft p ipel ine material , the so i l grains may gouge the polyethylene surface, causing an in ter locking between the pipe and so i l , e levating the apparent interface fr ict ion ratio, / above 0.6. A l t h o u g h significant gouging o f the pipe surface was not readily apparent f o l l o w i n g testing, there was some indicat ion o f increased abrasion o f the pipe surface f o l l o w i n g tests in dense sand. A s s u m i n g a constant coefficient o f lateral earth pressure o f 1.0, values o f interface fr ict ion angle, 5, and interface fr ict ion angle r a t i o , / have been back-calculated for peak and residual values, as contained in Table 4.7. A s can be seen in Figure 4.14, the value o f apparent interface fr ict ion angle ratio appears to vary w i t h pipe diameter, w i t h values o f 5 m a x increasing wi th increasing pipe diameter. Th i s trend is consistent w i th the observed behaviour o f increased pipe elongation i n smaller pipe diameters. A s previous ly discussed, the increased elongation results i n a decrease i n diameter and subsequently a potential decrease in normal stresses act ing at the interface, w h i c h this - 5 5 -Chapter 4. Straight Pipeline Pullout Testing s impl i f i ed analysis w o u l d manifest as a lower apparent interface f r ic t ion angle ratio. In the larger diameter pipes, the diameter decrease due to pipe elongat ion w o u l d be less, and the effect o f in ter locking and stress increase due to d i la t ion w o u l d be more prevalent, w h i c h w o u l d manifest as an increase i n the apparent interface f r ic t ion angle ratio. The no rma l i zed displacement to achieve peak pul lout resistance, x / D , is again s ignif icant ly larger than that suggested b y the A S C E (1984) guidel ines. A s was noted i n the loose tests, progressive failure a long the soi l -p ipel ine interface, augmented by pipe elongation, w i l l result i n the larger requisite displacements for peak ax ia l force response. Table 4.7: Interpreted Interface Friction Angles for Straight Sections in Dense Sand Test ID Assumed ko Peak Interface Friction Angle, 8 P (degrees) Residual Interface Friction Angle, 8 r (degrees) Peak Interface Friction Angle Ratio, / p Residual Interface Friction Angle Ratio, / r 115aD 1.0 37 32 0.97 0.70 2.0 27 19 0.70 0.49 6 0 a D 1.0 29 26 0.76 0.58 2.0 20 15 0.53 0.40 15aD 1.0 20 16 0.52 0.33 2.0 14 8 0.36 0.22 - 5 6 -Chapter 4. Straight Pipeline Pullout Testing 40 60 80 100 P i p e Diameter , D (mm) 120 140 160 • Loose Peak O Loose Residual l Dense Peak • Dense Residual Figure 4.14: Variation of Apparent Interface Friction Angle Ratio,/, With Diameter, D - 5 7 -CHAPTER 5 BRANCHED PIPELINE PULLOUT TESTING 5.1 Introduction Branched polyethylene pipe specimens were tested b y app ly ing an ax ia l displacement to the trunk l ine i n order to observe the so i l -p ipel ine interaction behaviour o f pipel ines w i t h complex geometries. The purpose o f this series o f tests was to establish an understanding o f the patterns o f deformation that result f rom permanent ground deformations impac t ing such p ipe l ine configurations. Th i s chapter describes the results o f the tests performed, and identifies several significant behavioura l characteristics o f branched pipel ine sections. The series o f tests is indicated i n Tab le 5.1, be low. Table 5.1: Branched Pipeline Test M a t r i x Test No. Pipe Size (mm) Configuration Soil Density Test ID 8 15 Straight Compac t 15aD 9 115 Branched M e d i u m - L o o s e 115baL 10 115 Branched Compac t 115baD 11 60 Branched M e d i u m - L o o s e 6 0 b a L 12 60 Branched Compac t 6 0 b a D - 5 8 -Chapter 5. Branched Pipeline Pullout Testing 5.2 Results of Branched Section Pullout Branched specimens w i t h configurations typ ica l o f loca l dis t r ibut ion networks were tested b y app ly ing an ax ia l load to the m a i n (or trunk) l ine , and moni to r ing the deformation and displacements occurr ing i n the branched sections. A s indicated earlier, the objective o f the branched specimen tests was to provide contro l led observations o f h o w branched polyethylene pipel ines deform beneath a s o i l cover, and to determine whether a failure c o u l d be induced dur ing s imple pul lout tests. The tests were performed at displacement rates matching those used for pul lout tests on straight specimens. Termina t ion o f the branched tests was not determined on the basis o f accompl i sh ing a g iven displacement, but rather, on the condi t ion o f the strain gauges. Since the intent o f the tests was to moni tor deformation o f the pipel ine , tests were terminated w h e n the strain gauges measurements were no longer rel iable due to degradation o f the strain gauge installations f rom sand abrasion. In most instances, a complete loss o f s ignal f rom 50 to 6 0 % o f the strain gauges occurred pr ior to test cessation. U p o n terminat ion o f a test, the specimens were then exhumed and surveyed to provide a correlat ion between strain gauge data and actual phys i ca l pos i t ion . 5.2.1 Tests in Medium-Loose Sand Pul lou t tests on branched sections i n medium-loose sand were conducted i n order to represent t yp ica l f ie ld installations i n w h i c h the pipel ines are "p loughed" into re la t ively loose so i l , or locations where trench b a c k f i l l is intent ional ly left loose to reduce stresses i n the pipe. Test parameters for pul lout testing performed on branched p ipe l ine sections i n medium-loose sand are contained i n Table 5.2. Tests were performed us ing two configurations: i ) a 115 m m trunk l ine w i t h two 15 m m branches, and i i ) a 60 m m trunk l ine w i t h two 15 m m branches. Strain gauges were attached to several points a long both the trunk and branch l ines, w i t h a typ ica l instrumentation layout shown i n F igure 5.1. - 5 9 -Chapter 5. Branched Pipeline Pullout Testing Table 5.2: Test Parameters for Branched Sections in Loose Sand Test ID Pipe Soil Unit Void Relative Burial Diameter, Weight, Ratio, Density, Depth, D Y e D r H (mm) (kN /m 3 ) (%) (mm) 115baL 115 14.7 0.80 62 0.74 6 0 b a L 60 14.9 0.77 71 0.54 A s was observed dur ing sample preparation o f straight section specimens, the s o i l density achieved w h e n preparing medium-loose sand samples for branched sections was rela t ively var iable , as shown i n F igure 5.2. The average s o i l density o f the s o i l samples was 14.8 k N / m 3 . A s discussed above, the method o f sample preparation adequately reproduces typ ica l construct ion practices i n w h i c h a un i fo rm, loose trench b a c k f i l l w o u l d not l i k e l y be achieved. R Lood Cell - ht LVDT- • * * = # SPI • 1 n-£Gl 1 n SG2 0:75n -SD6 d.75r> - 1 n — » i &G7 S • SP? 0.09 n 7 " SC3 5G5 L SGI SG8 0.5 n SG10 SGI1 SPt SP5 note: SG - Strain Gauge; SP/LVDT - String Potentiometer/Linear Variable Displacement Transducer Figure 5.1: Typical Instrumentation Layout for Branched Pipeline Specimen in Medium-Loose Sand - 6 0 -Chapter 5. Branched Pipeline Pullout Testing • 115baL • 60baL >» 3 O c o 3 er o U. 2 1350 1400 1450 1500 1550 1600 1650 1700 Density (kg/m ) Figure 5.2: Density Testing Summary for Branched Tests in Medium-Loose Sand The resistance to displacement generated by interface friction and the anchoring effect o f the branches has been presented us ing a T - x curve, as for straight sections, as shown in Figures 5.3 and 5.4 for 115 m m and 60 m m diameter pipe specimens, respectively. A l t h o u g h not a true representation o f the pul lout behaviour, the T -x curves provide a pre l iminary comparison between s imple and more complex configurations, as w e l l as offering a gateway in extrapolating analyt ical techniques developed for s imple configurations to more complex problems. - 6 1 -Chapter 5. Branched Pipeline Pullout Testing 12 10 0 50 100 150 200 250 300 350 400 450 500 S P Displacement, x (mm) Figure 5.3: Pul lout Resistance for Tests on 115 mm Branched Section in Med ium-Loose Sand The load response curves for branched sections i n loose sand show gradual and cont inual increase in pullout resistance w i t h cont inued displacement. A s noted above, tests were stopped when the majority o f strain gauge readings were lost, in order to survey the final posi t ion o f the pipe. Otherwise , it is expected that a strain-softening behaviour s imi lar to that observed in straight specimen tests w o u l d have occurred, the start o f w h i c h can be seen to be occurr ing in the 115 m m diameter sample in Figure 5.3. A s indicated in the figures, however , the approach to the peak axia l pul lout force, and subsequent decrease to a residual value w o u l d l i k e l y be a very prolonged response. Va lues o f peak ax ia l pul lout force and associated displacement for the two pipel ine configurations tested are contained in Table 5.3 for comparat ive purposes. - 6 2 -Chapter 5. Branched Pipeline Pullout Testing 0 50 100 150 200 250 300 350 400 S P Displacement, x (mm) Figure 5.4: Pullout Resistance for Tests on 60 mm Branched Section in Medium-Loose Sand Table 5.3: Pullout Force Results for Branched Sections in Medium-Loose Sand F o r c e s D i sp l acemen t s Tes t I D Tmax ( k N ) * T r ( k N ) Xmax ( m m ) x r ( m m ) 115baL 9.6 (8.7) N / A 305.0 N / A 60baL 7.7 (7.0) N / A 402.0 N / A * note: Backets indicate values corrected for gasket fr ict ion It was noted that a more adequate analysis and predict ion can be made i f the contr ibut ion to the pul lout resistance from the branches is estimated by isolat ing resistance from ind iv idua l components. It can be reasonably approximated that the contribution from the 15 m m branches is equivalent to the difference i n pul lout forces between the tests on branched specimens and those on the corresponding tests on straight specimens. Table 5.4 provides the approximated contributions o f the branches and trunk l ine. It can be - 6 3 -Chapter 5. Branched Pipeline Pullout Testing noted that the contr ibut ion f rom branched sections to the ax ia l pul lout force estimated f rom 115 m m diameter pipe tests are essentially ident ica l to those estimated f rom 60 m m diameter trunk l ine tests. T h i s not on ly show the sui tabi l i ty o f the above approximat ion to the difference i n pul lout forces between branched and non-branched tests, but also suggests that the performance o f the branch is not s ignif icant ly affected by the diameter o f the trunk l ine . Table 5.4: Approximate Branch Contributions to Peak Pullout Resistance Test ID Branched Tmax (kN) Straight Tmax (kN)* Estimated Total Branch Contribution (kN) Estimated Branch Contribution (kN) 115baL 8.7 2.8 5.9 2.95 6 0 b a L 7.0 1.1 5.9 2.95 *note: F r o m Table 4.3 Figures 5.5 and 5.6 present the var ia t ion o f string potentiometer readings at the exposed ends o f the trunk l ine and branch pipes dur ing the tests. A s can be seen, there is a delayed displacement response i n the branches dur ing the test. T h i s indicates that considerable bending and elongat ion o f the branch pipe occurs dur ing in i t i a l t runk l ine displacements, f o l l owed b y ax ia l movement o f the branch. It can also be noted f rom the figure that the slope o f the branch displacement curve does not reach para l le l w i t h the displacement curve o f the trunk l ine , indicat ing that e longat ion o f the branch pipe was cont inuing at the t ime o f terminat ion o f the test. The contr ibut ion to the observed ax ia l resistance by the branches thus appears to be governed by a p ipe-so i l mechanism that invo lves transverse ax i a l pu l lout and transverse lateral pul lout responses. The surveyed displacements o f the 115 m m and 60 m m branched pipe specimens f o l l o w i n g the test is presented i n F igure 5.9 and 5.10. The deformed sections indicate re la t ively s imi la r patterns o f deformation for the two sizes o f trunk l ine i n medium-loose sand. The survey results and measured end displacements indicate that the translation o f the trunk l ine imposes both bending and s l id ing o f the branch l ine . Th i s deformed shape - 6 4 -Chapter 5. Branched Pipeline Pullout Testing supports the theory that the contr ibut ion to pul lout resistance generated by the branches is a combinat ion o f lateral bearing capacity and axia l fr ict ional resistance. 500 SP1 Displacement, x (mm) Figure 5.5: Relative Displacements of Pipe Ends, Test 115baL (see Figure 4.15 for Instument Locations) 400 i . SP1 Displacement, x (mm) Figure 5.6: Relative Displacements of Pipe Ends, Test 60baL (see Figure 4.15 for Instument Locations) - 6 5 -Chapter 5. Branched Pipeline Pullout Testing Figures 5.7 and 5.8 d isplay the measured strains at several locations a long the trunk l ine for 115 m m and 60 m m diameter pipes, respectively. The figures indicate that at the base o f the first tee j o i n i n g the branch to the trunk l ine, a significant increase in measured tensile strain occurs. S i m i l a r l y , the strain gauge located behind the second tee, relative to pipe translation (i.e. in the "shadow") , tec experiences significant compressive stresses. It appears that substantial rotation o f the tec induced by lateral so i l forces dur ing translation o f the pipe causes these compressive stresses. -4000 -3000 C -2000 <5 i— •*—* in O M -1000 E TO 1000 2000 LU » - » - X - - X . SG ahead of Tee *6 -Leading End Displacement - * - 1 mm - m - 2 mm • ^ * 5 mm - K - 10 mm - K - 20 mm 50 mm 100 mm 200 mm - * - 300 mm SG behind Tee 500 1000 1500 2000 2500 3000 3500 4000 4500 Distance From Front Edge of Test Chamber (mm) E Oj O o ffi 5000 Figure 5.7: Loca l Strain Readings A l o n g T r u n k L ine for Test on 115 m m Branched Section in Medium-Loose Sand - 6 6 -Chapter 5. Branched Pipeline Pullout Testing -25000 -20000 C -15000 .a -10000 -5000 5000 + * - -ill SG ahead of Tee I Leading End Displacement * \ »• SG behind \ » ' » Tee • - ^ - - - • • - 5 = 111 i t • i i m*£l - * - 1 mm - * - 2 mm - * - 5 mm - K - 10 mm - *- 20 mm - •m -50 mm - + - 75 mm - -- 100 mm - - - 200 mm - * - 300 T i m 500 1000 1500 2000 2500 3000 3500 4000 4500 Distance From Front Edge of Test Chamber (mm) 5000 Figure 5.8: Local Strain Readings Along Trunk Line for Test on 60 mm Branched Section in Medium-Loose Sand 459 mm Surveyed 444 mm 217 mm Surveyed 438 mm N 421 mm 206 mm Initial Location •Maximum Displacement Figure 5.9: Surveyed Locations Before and After Testing (115baL) - 6 7 -Chapter 5. Branched Pipeline Pullout Testing 365 mm Surveyed 242 mm 107 mm Surveyed 233 mm 250 mm 97 mm - Initial Location •Maximum Displacement Figure 5.10: Surveyed Locations Before and After Testing (60baL) 5.2.2 Tes ts i n Dense S a n d Pul lout tests performed on branched sections i n dense sand w o u l d also represent typica l field installations, where pipel ine networks arc often placed i n open cut trenches and backf i l l ed w i t h a compacted so i l . The tests in dense sand were performed on configurations ident ical to those used for test i n medium-loose sand, namely: i) 115 m m trunk l ine w i t h two 15 m m branches, and i i ) 60 m m trunk l ine w i t h two 15 m m branches. The instrumentation layout was also ident ical to previous tests, the locations and labels for w h i c h are show in Figure 5.11. The test parameters for pul lout testing performed on branched pipel ine sections in compacted sand are presented in Table 5.5. - 6 8 -Chapter 5. Branched Pipeline Pullout Testing V 1 Lood Celt LVDT SPl.T ] n SGI 1 rr SG2 0.75ft: -» 0.75m SG7 0.12 n J SG3 SGS I SG4 0.5 n J SG8 1 n SG10 SG1I — . 1 I SP4 SP5 Figure 5.11: Typical Instrumentation Layout for Branched Pipeline Specimen in Dense Sand Table 5.5: Test Parameters for Branched Sections in Dense Sand Test ID Pipe Soil Unit Void Relative Burial Diameter, Weight, Ratio, Density, Depth, D Y e D r H (mm) (kN/m3) (%) (mm) 115baD 115 15.6 0.69 96 0.49 60baD 60 15.7 0.68 99 0.47 S o i l densities achieved dur ing the preparation o f dense samples us ing the vibratory plate tamper were re la t ively un i fo rm, w i t h an average achieved so i l density o f 15.6 k N / m 3 . The dis t r ibut ion o f density testing results is shown i n F igure 5.12, ind ica t ing a re la t ively un i fo rm sample. Strain and displacement measurements were recorded dur ing sample preparation and s o i l compact ion . In general, there was litt le disturbance o f the pipe specimens observed dur ing s o i l placement and compact ion . M o v e m e n t s o f the p ipe ends were typ i ca l ly less than 0.5 m m , and strains were observed to be less than 500 micros t ra in dur ing s o i l compact ion . The one except ion was an observed spike i n strain readings f rom the second branch o f test 115baD. Howeve r , the strain levels decrease dur ing subsequent passes o f the plate tamper, result ing i n no net displacement o f the - 6 9 -Chapter 5. Branched Pipeline Pullout Testing branch. Th i s spike was interpreted to be a lateral shifting o f the soi l due to the influence o f the vibratory plate tamper dur ing sand compact ion. 12 10 o c 3 6 w 2 H115baD H60baD 1350 1400 1450 1500 1550 1600 1650 1700 Density (kg/m ) Figure 5.12: Density Testing Summary for Branched Tests in Dense Sand Pul lout force versus axia l displacements o f the trunk lines have been plotted on T - x curves and arc presented in Figures 5.13 and 5.14 for 115 m m and 60 m m diameter trunk l ine configurations, respectively. The same l imitat ions as noted above for medium-loose specimens apply when observing branched configuration pul lout resistance on a T -x curve, namely that T - x curves arc meant to represent s imple ax ia l pul lout displacement, and do not exp l i c i t l y a l l ow isolat ing the effects from the branches. The T -x plot, nonetheless, is a convenient method by w h i c h to observe the pipel ine response to appl ied pul lout forces. - 7 0 -Chapter 5. Branched Pipeline Pullout Testing The load response curve for the 115 m m trunk l ine shows a relat ively steep, non-linear increase to a peak pul lout resistance, w h i c h is then maintained for the remainder o f the test. The curve, unfortunately, displays significant load fluctuations and several episodes o f unloading resulting from a recurrence o f the loading system instabili t ies. It is apparent, however , that the in i t ia l pul lout resistance response is steeper than in the loose tests, and that the pul lout force remains relat ively constant throughout the larger displacement portions o f the curve. Va lues o f peak axia l pullout force and associated displacement arc contained in Table 5.6. The pullout resistance curve for the 60 m m pipel ine, Figure 5.14, displays a response s l ight ly more s imi la r to the tests i n loose so i l , however , there appears to be a significant difference in pul lout resistance behaviour occurr ing in the middle port ion o f the curve. F o l l o w i n g the ini t ia l softening o f the response after approximately 10 m m displacement, there is a sharp change in slope o f the curve, fo l lowed by a near-linear increase in pul lout -71 -Chapter 5. Branched Pipeline Pullout Testing resistance, once again becoming non-l inear at approximately 125 m m displacement, as the curve begins to approach a m a x i m u m pullout resistance. Th i s behaviour is markedly different from the gradually increasing, re lat ively smooth T - x curve observed i n loose samples. A s discussed i n the latter part o f this section, the above observed response can be expla ined based on measured strain gauge readings. 20 r 1 18 16 -j „ 14 -• z JC 12 0 50 100 150 200 250 300 350 400 SP Displacement, x (mm) Figure 5.14: Pullout Resistance for Tests on 60 mm Branched Section in Dense Sand Table 5.6: Pullout Force Results for Branched Sections in Dense Sand Forces Displacements Test ID Tmax (kN) T (kN) ^max (mm) (mm) 115baD 17.0(16.1) 16.3 (15.8) 58.4 551.2 60baD 10.8(10.1) N / A 277.4 N / A note: values in brackets are corrected for gasket fr ict ion A s previous ly discussed in section 5.2.1 for medium-loose tests, it is reasonable to estimate the contr ibut ion due to the branches based on the pul lout resistance o f the - 7 2 -Chapter 5. Branched Pipeline Pullout Testing straight specimens, the results o f w h i c h are p rov ided i n Table 5.7. The estimated contributions f rom the branches are again very s imi lar , w h i c h indicates that the performance o f the branches are not impacted b y the size o f the trunk l ine . It is also interesting to note that the branch contributions are not s ignif icant ly inf luenced by the density o f the so i l (compare Table 5.4 and 5.7). It is possible that ach iev ing w e l l compacted s o i l condi t ions around a sma l l 15 m m diameter branch is imprac t ica l , and as a result the s o i l effectively is i n the cond i t ion o f medium-loose density for both the medium-loose and dense specimens tested. Table 5.7: Approximate Branch Contributions to Peak Pullout Resistance Test I D Branched Tmax (kN) Straight Tmax (kN) Total Branch Contribution (kN) Branch Contribution (kN) 115baD 16.1 10.9 5.2 2.6 60baD 10.1 3.9 6.2 3.1 note: values are corrected for gasket f r ic t ion Figures 5.15 and 5.16 present the displacement measurements for the trunk l ine and branch l ine pipe ends dur ing the tests. A s w i t h tests i n medium-loose sand, there is a delayed response before the branch ends beg in to displace. In the case o f the 115 m m pipe, the required leading pipe end displacement to initiate movement at the branch ends is nearly double i n the dense sand compared to medium-loose sand (200 m m i n F igure 5.15 versus 100 m m i n F igure 5.6). S i m i l a r l y , for the 60 m m diameter tn ink l ine , 150 m m displacement is required to initiate movement o f the branch ends i n medium-loose sand (Figure 5.6), whereas essentially no displacement o f the branch ends is observed dur ing tests i n dense sand (Figure 5.16). The absence o f movement o f the branch l ines dur ing tests o f 60 m m trunk lines i n dense sand indicates that the entire imposed displacement is be ing accommodated by elastic and/or plastic deformation o f the trunk pipel ine . - 7 3 -Chapter 5. Branched Pipeline Pullout Testing 600 0 100 200 300 400 500 600 SP1 Displacement, x (mm) Figure 5.15: Relative Displacement of Pipe Ends, test 115baD (see Figure 5.1 for Instrument Locations) Figure 5.16: Relative Displacement of Pipe Ends, test 115baD (see Figure 5.1 for Instrument Locations) - 7 4 -Chapter 5. Branched Pipeline Pullout Testing Figures 5.17 and 5.18 d isplay the measured strains at several locations a long the trunk l ine for 115 m m and 60 m m diameter pipes, respectively. O f part icular interest is the strain gauge located just in front o f the base o f the first tec, located 2000 m m from the front edge o f the test chamber. A s can be seen in the figure, not on ly arc the loca l strains s ignif icant ly higher in the 60 m m trunk l ine, especial ly at displacements greater than 50 m m , but the strain distr ibution i n the 60 m m diameter pipe appears to have very steep gradients a long the pipe. The strain in the pipe behind the first tec is at very l o w values in both specimens, indicat ing that the majority o f the pul lout resistance is generated by an anchor ing effect caused by the tec. The force generated by this anchoring effect w o u l d be conveyed direct ly to the trunk l ine at the point o f attachment, result ing in the significant strain concentration observed in the strain gauge measurements. A s noted earlier, the ini t iat ion o f the near l inear port ion o f the T -x curve appears to correspond wi th the strong strain response in the strain gauge mounted at the base o f the tee connection. -10000 -8000 C -6000 'to o .y -4000 c 'ro in -2000 o 2000 SG ahead of Tee I X - - A -SG behind Tee - « „ Leading End Disp lacement - * - 1 mm - • - 2 mm - * - 5 mm X 10 mm - * - 20 mm - « - 50 mm - +- 75 mm - - 100 mm 200 mm 500 1000 1500 2000 2500 3000 3500 4000 Distance From Front Edge of Test Chamber (mm) 4500 5000 Figure 5.17: Local Strain Readings Along Trunk Line for Test on 115 m m Branched Section in Dense Sand - 7 5 -Chapter 5. Branched Pipeline Pullout Testing -25000 -20000 -15000 o . r -10000 c ' ro •*-» CO -5000 5000 o a 111 X Leading End Displacement - •» - 1 m m - * - 2 m m - * - 5 mm - X 10 m m - 20 m m - » - 50 m m - + - 75 m m - -- 100 mm - - - 200 m m - • - 275 mm (max disp.) »• * * SG behind » » » _ » % T * Tee * • . » * - . » t ' I::: SG ahead of Tee 500 1000 1500 2000 2500 3000 3500 4000 Distance From Front Edge of Test Chamber (mm) 4500 it-'s <D o> "O U J 5000 Figure 5.18: Loca l Stra in Readings A long T r u n k L ine for Test on 60 m m Branched Section in Dense Sand The magnitude o f the strain difference between the 115 m m and 60 m m pipe indicates that the 115 m m trunk l ine is able to accommodate the stress concentration caused by the tee, wh i l e the 60 m m pipe is undergoing significant deformation in front o f and in the v i c in i ty o f the tec. The surveyed displacements o f the two pipe specimens fo l lowing the tests arc shown in Figures 5.19 and 5.20. The survey results indicate that the 115 m m trunk l ine caused the 15 m m branches to essentially fo l l ow the trunk l ine movement, causing significant bending o f the branched pipe. T h i s can also be noted i n the surface expression o f the so i l disturbance caused by the tec, as shown i n Figure 5.21. The results shown in Figure 5.20 support the observation that the majority o f the displacement o f the 60 m m trunk l ine was accommodated by i t ' s o w n deformation. The surveyed displacements o f the 60 m m diameter branched specimen indicate that the branches and the trunk l ine beh ind the first tee have experienced very li t t le displacement although the front o f the pipe was displaced nearly 300 m m . These measurements indicate that the trunk l ine between the point o f attachment to the actuator and the first tee was exper iencing the majority o f the deformation, as observed in the strain response. - 7 6 -Chapter 5. Branched Pipeline Pullout Testing 527 mm Surveyed 514 mm 224 mm Surveyed 511 mm 509 mm 250 mm Initial Location Maximum Displacement Figure 5.19: Surveyed Locations Before and After Testing for 115 m m Branched Section in Dense Sand 276 mm Surveyed 25 mm -4.5 r Surveyed 4 mm 2 mm -0.7 mm Initial Location • Maximum Displacement Figure 5.20: Surveyed Locations Before and After Testing for 60 m m Branched Section in Dense Sand - 7 7 -Chapter 5. Branched Pipeline Pullout Testing - 7 8 -CHAPTER 6 ANALYSIS AND DISCUSSION OF RESULTS 6.1 Introduction In this section, the results f rom the full-scale tests o f polyethylene dis t r ibut ion configurations are compared to publ i shed studies and guidel ines that have been developed for steel t ransmission pipel ines , w i t h specif ic focus on mechanisms o f s o i l resistance to imposed displacement, compar i son to exis t ing analyt ica l models and operational guidel ines, and fundamental " so i l - sp r ing" representations. 6.2 Mechanisms of Soil Resistance on Polyethylene Pipelines F o r so i l displacements occur r ing longi tud ina l ly to the pipe axis o f a straight section o f pipe, the currently accepted analyt ica l models emp loy a f r ic t ion based peak ax i a l pul lout resistance per unit length o f pipe, t u, w h i c h is reached at some specif ied displacement, t yp ica l ly 2.5 m m (0.1 inch) . The f r ic t ional resistance act ing at the interface between the so i l and pipel ine is general ly based on some f r a c t i o n , / o f the internal f r ic t ion angle, <|), o f the so i l . Further, the normal forces act ing at the interface are an average between the ver t ica l and hor izonta l effective stresses. Thus , the standard equation for ax ia l pul lout can be wri t ten i n a s l ight ly different fo rm than i n Equa t ion 4 .1 , as is shown i n Equa t ion 6.1: [6.1] -79-Chapter 6. Analysis and Discussion of Results Observat ions dur ing tests on polyethylene pipe specimens indicate that the c o m m o n l y assumed constants / and ko i n the above equation change as a p ipe l ine pul lout test progresses. D i rec t measurements made o f the pipe dur ing the test indicated that pipe e longat ion occurred throughout the course o f the test, and based on observations made o f the pipe specimens dur ing mechanica l testing, reduct ion o f the pipe diameter w o u l d l i k e l y have resulted. It is reasonable to assume that any reduct ion i n p ipe diameter w o u l d result i n a macroscopic vo lume change i n the zone o f so i l immedia te ly adjacent to the pipe . T h i s v o l u m e change w o u l d subsequently lead to arching, or " load-shedding" o f s o i l no rmal stresses f rom the pipe to the surrounding so i l . Th i s decrease i n so i l no rma l stresses o n the pipe w o u l d essentially result i n an apparent, or "effective", decrease i n either ko, o r / Further, l oca l i zed changes i n so i l density w i t h i n a zone o f s o i l immedia te ly adjacent to the pipe c o u l d occur due to shear-volume coupl ing . Because internal f r ic t ion angle o f the so i l , § , is related to so i l density, it is possible that the m o b i l i z e d soi l -polyethylene interface f r ic t ion angle i n the annular space around the pipe w o u l d be affected b y these changes i n s o i l density. D u e to the significant differences i n extensibi l i ty between polyethylene and steel, the pul lout resistance behaviours noted above w o u l d not l i k e l y be evident dur ing testing o f steel pipel ines . A s a result, the parameters i n Equa t ion 6.1 that are he ld reasonably invar iable dur ing relative displacements between s o i l and steel p ipel ines , m a y be variable dur ing relative displacements between s o i l and polyethylene p ipel ines . F o r appl ica t ion o f s imple analy t ica l models such as Equa t ion 6.1 to more c o m p l e x p ipe l ine geometries, such as the branched junct ions tested i n this study, there is l imi t ed cri ter ia or informat ion o n w h i c h to base an analysis. The branches are subjected to a complex disturbance due to so i l movement , beg inn ing as a lateral movement and transi t ioning to a nearly exc lus ive ly ax ia l p u l l out f rom the so i l . Further, the branch j unc t i on j o i n i n g the branches to the trunk l ine impart a geometric anomaly attracting signif icant l oca l i zed stresses and strains, numer ica l models for w h i c h are not i n state o f practice. - 8 0 -Chapter 6. Analysis and Discussion of Results F o r exis t ing analyt ica l models , and for future attempts to numer ica l ly m o d e l so i l -p ipel ine interaction, adjustments m a y be required i n order to incorporate interface behaviours resul t ing f rom the s o i l vo lume change and polyethylene pipe extension and subsequent diametr ic reduction. In particular, ver t ica l and lateral s o i l forces act ing o n the p ipe m a y require a reduct ion propor t ional to p ipe strain and so i l vo lumet r ic change. Current analyt ica l and numer ica l models lack such capabil i t ies. 6.3 Review of Experimental Observations with Respect to Existing Approaches In the presentation o f the no rma l i zed pul lout resistance i n Sections 4.2.1 and 4.2.2, comparisons were made to predict ions made us ing current analyt ica l models that were developed us ing test data f rom steel pipel ines ( A S C E , 1984; A L A , 2001). The comparisons are reproduced i n F igure 6.1, for pul lout tests on straight specimens i n loose and dense sand. B a s e d o n the results o f fu l l scale testing o f polyethylene pipel ines , it appears that the theoretical predict ions made us ing convent ional analyt ical equations developed for steel pipel ines , shown as dashed l ines i n F igure 6.1, vary s ignif icant ly f rom the experimental results. T h e ax ia l pul lout response estimated f rom the equations over-predicts the forces act ing o n polyethylene pipes i n uncompacted sand, w h i l e at the same t ime, s igni f icant ly underestimates pul lout resistance i n dense sand. A s p rev ious ly discussed, the most reasonable sources o f the discrepancies appear to l ie i n account ing for the angle o f m o b i l i z e d interface f r ic t ion and n o r m a l stress dis t r ibut ion around the p ipe i n pul lout tests. These effects are essentially absent i n steel p ipel ine lengths typ i ca l ly used for laboratory testing. Because o f their re la t ively h i g h r ig id i ty , the entire steel p ipe l ine w o u l d move as a single element, and also w o u l d not experience a change i n diameter w h e n subjected to an ax ia l tensile force. A s such, w h e n extending the analyt ical methods for steel pipes to polyethylene pipes, it is important to systematical ly account for the effects ar is ing due to the f l ex ib i l i t y o f the pipe. - 8 1 -Chapter 6. Analysis and Discussion of Results 3.0 0.0 2.0 4.0 6.0 8.0 Normalized SP Displacement, x/D - 1 1 5 a D 60aD 115aL 60aL | Figure 6.1: Compar i son of Normal ized Exper imental Pullout Resistance to Predictions The accurate est imation o f k 0 i n both laboratory testing and field applications deserves particular attention. A s can be seen in Figure 6.2, the predicted value o f pul lout resistance is very sensitive to the variat ion o f the assumed value o f ko. Va lues for lateral earth pressure in the range o f 0.5 to 1.0 arc c o m m o n l y assumed for native or l ight ly compacted soi ls , however , there is evidence that in compacted soils , ko m a y be s ignif icant ly elevated f o l l o w i n g compact ion ( F i l z and Duncan , 1996). The value o f ko may also depend on the potential dcformabi l i ty o f the pipe dur ing compact ion. In the case o f polyethylene pipes, because o f re la t ively l o w material stiffness ( in comparison to steel), the value o f ko may be subject to change due to changes in diameter dur ing compact ion . O v e r a l l , the select ion o f a ko value for use i n these equations should be undertaken w i t h careful attention to the as-built so i l condi t ions, and preferably w o u l d be refined through further research. - 8 2 -Chapter 6. Analysis and Discussion of Results Figure 6.2: Comparison of Predictions Based on Different k„ conditions, Test 60aD In addi t ion to the discrepancies noted between the magnitude o f experimental and predicted peak pul lout resistance, the shape o f the graph o f pul lout resistance versus displacement response is also an important considerat ion. The predict ions shown in Figure 6.2 arc based on the assumption that peak axia l pul lout resistance occurs at 0.25 m m (0.1 in), as recommend in the A S C E guidel ines. A s can be noted from the figure, this is much earlier than the displacement required to m o b i l i z e axia l resistance in the current pipe tests. A s ment ioned earlier, the experimental results contain a progressive failure response, w h i c h reflects the full-scale nature o f the test, rather than the response o f a smaller clement. 6.4 C o r r e s p o n d e n c e o f M e a s u r e d S t r a i n s a n d D i s p l a c e m e n t s A n attempt was made to compare the measured point strains (from the strain gauges), w h i c h reflect the influence o f strain concentrations and variations a long the pipe, w i th those back calculated from pipe elongation measurements observed dur ing the tests. In - 8 3 -Chapter 6. Analysis and Discussion of Results pipel ine dis t r ibut ion networks, s imi la r p ipe elongat ion estimates w o u l d typ ica l ly be avai lable f rom f ie ld survey measurements. E las t ic strain, £ a , i n the p ipe l ine due to the appl ied ax ia l load , T u , can be s imp ly computed us ing Equa t ion 6.2: Where : s a = peak ax ia l strain i n p ipe T u = ul t imate ax i a l force o n pipe ( so i l resistance) A = cross sectional area o f pipe E = modulus o f elast ici ty o f pipe material A compar i son o f measured strain and pipe e longat ion to predicted strain and pipe elongat ion are contained i n Table 6.1. Predic ted peak ax ia l strains have been calculated based on the measured peak ax i a l force, T u , and the relat ion p rov ided by Equa t ion 6.2. P ipe e longat ion is then calculated based on integration o f the estimated strain, assuming a l inear var ia t ion o f strain a long the pipe. The predicted elongations agree ve ry c lose ly w i t h the measured elongations i n a l l o f the tests, w i t h the except ion o f the 15 m m diameter pipe. T h i s indicates that w i t h the except ion o f the ve ry sma l l diameter pipe, the s imple relat ionship p rov ided i n Equa t ion 6.2, w i t h the assumption o f a l inear dis t r ibut ion o f strain a long the pipe at peak ax ia l force, provides a reasonable methodology for estimating p ipe l ine strains based o n measured elongations, or vice-versa . - 8 4 -Chapter 6. Analysis and Discussion of Results Table 6.1: Measured versus Predicted Strains Pipe Diameter (mm) Test ID Measured Peak Axial Force,* T„ (kN) Measured Pipe Elongation (mm) Calculated Peak Axial Strain, Sa (%) Calculated Pipe Elongation4 (mm) 115 115aL 3.8 4.9 0.3 % 9 115aD 11.9 34.0 1.1 % 27 60 60aL 1.9 11.2 0.6 % 15 60aD 4.7 41.0 1.5 % 38 15 15aD 1.2 276.8 4.0 % 99 notes: * values are uncorrected for gasket f r ic t ion + f rom Equa t ion 6.2 and assuming linear var ia t ion o f strain a long pipe at peak ax ia l force The discrepancy between the measured and calculated pipe e longat ion for the 15 m m diameter p ipe can be accounted for by consider ing the difference i n magnitude o f the pipe strain. B y assuming a l inear strain dis t r ibut ion for the 15 m m diameter pipe, the measured elongat ion (277 m m ) results i n a back-calcula ted peak strain o f 11%. B a s e d on mechanica l testing o f the pipe specimens, a peak strain o f 11% w o u l d occur o n l y after the y i e l d stress had been exceeded and the pipe is deforming plas t ica l ly . A s noted above, Equa t ion 6.2 is v a l i d on ly for deformations i n the elastic range, and as such, the discrepancy between measured and predicted e longat ion i n the sma l l diameter pipe is accounted for i n the plast ic strain contr ibut ion. 6.5 Strain Distributions in Branched Pipeline Configurations There have been no attempts i n the literature to apply s imple analyt ica l models and equations to the determination o f strains and deformations associated w i t h a bur ied pipel ine exper iencing an imposed curvature. It appears that such analyses m a y be possible us ing detai led three d imens iona l finite element analysis for p ipe l ine segments i n an elastic cont inuum. Such detailed analysis is beyond the scope o f the current work , - 8 5 -Chapter 6. Analysis and Discussion of Results however , some comments are p rov ided for branched sections exper iencing induced curvature. A s observed in the survey results, the branched sections o f the tested specimens experience displacement induced S-shaped curvatures adjacent to the point o f attachment to the trunk l ine. A l t h o u g h the strain response behaviour in the branches was h igh ly variable between tests, peak measured strains in the branched specimens i n excess o f 2 . 5 % were typ ica l ly observed. A typica l strain response i n a branched section is presented in Figure 6.3. A s noted in the straight specimen tests above, these strain levels are approaching the y i e l d strain o f the pipe and onset o f plastic deformation. Unfortunately, the displacements required to achieve these h igh strain levels also corresponded to degradation o f the signal from the strain gauge, and as such, measurements o f the branched sections at the larger strain levels are unavailable. In terms o f an operable or safe l imi t , however , the plastic pipel ine deformations w o u l d constitute the l imi t for serviceabi l i ty , at w h i c h point repair w o u l d be required. 5 0 0 0 T - 3 0 0 0 0 I • • • • 1 . • • 1 , 1 . , . . 1 1 0 1 0 0 2 0 0 3 0 0 4 0 0 5 0 0 6 0 0 Trunk Line Displacement, x (mm) Figure 6.3: Typ ica l St ra in Response in Branch , Test 115aD 8 6 -Chapter 6. Analysis and Discussion of Results The strain and survey measurements avai lable , i n addi t ion to v i sua l observations, indicate that plast ic deformation o f the branched specimens typ ica l ly occurs w i t h i n a re la t ively l im i t ed zone adjacent to the point o f attachment to the trunk l ine, as shown i n F igure 6.4. Further, it appears that the onset o f plast ic deformation for sma l l diameter branches i n un i fo rm sand occurs at re la t ively h igh trunk l ine displacements, on the order o f 200 m m or more. B a s e d o n v i sua l observations, this displacement m a y correspond to the amount o f movement required to expose the branch sect ion f rom w i t h i n the protective cover ing that is c o m m o n l y used i n polyethylene p ipe l ine installations. The large strain and apparent onset o f plastic deformation o f the smal l diameter branches occurs at trunk l ine displacements that also correspond reasonably w e l l w i t h the m a x i m u m pul lout force. B a s e d on mechanica l testing o f pipe specimens, the onset o f plast ic deformation is characterized by a strain softening response o f the pipe specimen. A s such, the ax ia l pul lout response o f branched sections appears to reflect the structural response o f the branches, i n that the p ipe l ine configurat ion suffers a reduct ion i n the abi l i ty to transfer load a long the pipe beyond the point o f plastic y i e ld . Therefore, the s o i l beyond the point o f plastic y i e l d contributes fr ic t ional resistance to pul lout at a reduced eff ic iency, and hence, the plateau on the load-displacement curve. - 8 7 -Chapter 6. Analysis and Discussion of Results CHAPTER 7 SUMMARY AND CONCLUSIONS 7.1 S u m m a r y The m a i n objective o f this thesis was to study the contr ibut ing factors, and k e y parameters in f luenc ing the behaviour o f bur ied polyethylene ( P E ) natural gas dis t r ibut ion pipel ines dur ing ground displacements. The w o r k undertaken m a i n l y i n v o l v e d full-scale experimental testing (phys ica l model ing) under control led condi t ions. The research stems f rom potential concerns i n natural gas dis t r ibut ion areas where s low, cont inual ground movements such as "perpetual" slope creep are anticipated. The research f indings were intended to provide input for the development o f guidelines and cri teria to determine the so i l displacement magnitudes associated w i t h the safe operational stress l imi ts o f typ ica l P E gas dis t r ibut ion p i p i n g configurations (i.e. fitness evaluations o f P E gas dis t r ibut ion p i p i n g systems i n general. The research has generated several key findings related to the behaviour o f P E pipel ines dur ing ground displacements, the effects o f t yp ica l d is t r ibut ion branches on p ipe l ine performance, and the appl icab i l i ty o f exis t ing analyt ica l models and methods to P E p i p i n g systems. It is also judged that the f indings w i l l p rovide useful new data to assist often sought sui tabi l i ty comparisons between steel and P E mater ial options i n the design o f bur ied dis t r ibut ion p i p i n g systems to withstand ground movements . The research w o r k undertaken w i t h i n the scope o f this thesis i n v o l v e d three m a i n areas: (a) Deve lopment o f a full-scale testing faci l i ty ; (b) Pu l lou t (axia l load) testing o f straight pipel ines; and (c) Pu l lou t (axia l load) testing o f branched configurations. The pertinent informat ion, f indings, and conclusions related to each o f the above areas are summar ized be low. - 8 9 -Chapter 7. Summary and Conclusions 7.2 Full Scale Testing Facility The development o f a new full-scale testing faci l i ty to investigate the performance o f bur ied p i p i n g configurations subjected to ground deformations formed a key component o f this thesis. The new faci l i ty essentially comprises a 3 m x 5 m so i l box , w i t h the capacity to test p ipe l ine segments w i t h up to one meter displacement i n order to investigate the h igh ly f lex ib le behaviour o f polyethylene pipel ines . The s o i l b o x has a modula r construct ion to provide the abi l i ty to change the p lan area so that the response o f a variety o f typ ica l pipe configurations subjected to ax i a l and transverse s o i l loadings corresponding to mul t ip le applications can be accommodated. A program o f instrumentation was developed for the moni to r ing o f loads, displacements, and pipel ine strains dur ing the testing o f various pipe configurations. F o r the measurement o f p ipel ine strains, specif ic methods and configurations had to be developed i n the mount ing o f strain gauges to obtain rel iable readings w h i l e m i n i m i z i n g addi t ional drag forces due to the strain-gauge inc lus ions that w o u l d increase the apparent interface fr ic t ion between the s o i l and pipel ine . W i t h regard to the preparation o f s o i l specimens, density test measurements indicated that b a c k f i l l i n g above the p ipel ine w i t h medium-loose sand results i n significant non-uni formi ty o f s o i l density throughout the b a c k f i l l . H o w e v e r , i n the case o f dense samples, where densif icat ion was achieved us ing vibratory tamping, a re la t ively un i fo rm density dis t r ibut ion was achieved throughout the sample. 7.3 Pullout Testing of Straight Pipe Configurations The observed load-response curves indicate the resistance to ax ia l pul lout for polyethylene pipe sections is re la t ively non-l inear up to a peak value, after w h i c h the pul lout resistance decays i n a strain-softening manner. T h i s behaviour can be attributed to the f o l l o w i n g : 1) the typ ica l changes i n interface f r ic t ion angle that occur i n the shearing zone adjacent to the pipe due to a w e l l - k n o w n shear-volume coup l ing response o f soi ls ; 2) arching o f the s o i l outside the shearing zone and associated reduct ion o f normal stress due to this " load shedding"; and 3) tensile strain-induced reduct ion o f the - 9 0 -Chapter 7. Summary and Conclusions diameter o f the pipel ine . The inferred arching act ion is l i k e l y not a factor i n larger diameter pipel ines due to the l i k e l y inab i l i ty o f the s o i l to arch over large rad i i . Measurements o f relative pipe displacements indicate that polyethylene pipes experience significant e longat ion dur ing testing, result ing i n a non-uni form m o b i l i z a t i o n o f s o i l f r ic t ional resistance a long the pipe and leading to "progressive fa i lure" at the soi l -pipe interface, again, a w e l l - k n o w n phenomenon i n relat ion to behaviour o f soi ls . It is also observed that the peak ax ia l pul lout resistance o f a straight pipel ine section, T m a x , estimated f rom currently avai lable design equations developed based on data f rom steel pipel ines , over-predicts the required pul lout force for polyethylene pipes i n uncompacted sand, and s ignif icant ly underestimates pul lout resistances i n dense sand. The measured ax i a l displacement, x m a x , required to m o b i l i z e the peak ax i a l force for straight polyethylene p ipe l ine sections is s ignif icant ly larger than the displacements suggested i n exis t ing design guidel ines. Further, the value o f x m a x was observed to be larger for dense sand than for medium-loose sand. In essence, the research f indings indicate that there are significant l imitat ions i n the appl icabi l i ty o f the currently avai lable equations (developed for steel pipel ines) for the predic t ion o f ax ia l pul lout resistance o f polyethylene pipel ines . Test results indicated that for displacement rates up to approximately 100 m m per hour, there was no appreciable difference i n measured pul lout resistance. A t higher rates o f displacement (> 300 mm/hr) it appears that there is a tendency for the ax ia l pul lout resistance to increase by as m u c h as 8%. Th i s m a y be a result o f collapse o f the arched zone above the pipe c r o w n due to some disturbance at the higher rates o f displacement, w h i c h w o u l d re-establish so i l pressures act ing o n the pipe. T h i s , i n turn, w o u l d translate into the observed increase i n ax ia l forces. 7.4 Pullout Testing of Branched Pipeline Configurations The research w o r k also p rov ided several pertinent observations related to the behaviour o f branched polyethylene pipelines dur ing ground displacements. The load response curves for branched sections i n medium-loose sand show gradual and cont inual increase o f pu l lout resistance w i t h cont inued displacement. A n y strain-softening response o f - 9 1 -Chapter 7. Summary and Conclusions branched sections l i k e l y occurs on ly at very large displacements. The contr ibut ion by the branches to the measured pul lout resistance appears to be p rov ided b y a p ipe - so i l interaction mechan i sm that invo lves both transverse ax ia l pu l lout and transverse lateral movement . Considerable bending and elongat ion o f the branch pipe occurs dur ing in i t i a l trunk l ine displacements, f o l l owed b y ax ia l displacement o f the branch. The rate o f ax ia l displacement o f the branches does not match the rate o f displacement o f the trunk l ine , indica t ing that the branches continue to elongate as displacement continues. The measured strain profi les i n the pipel ines indicate that significant l oca l i zed strains were imparted on the trunk l ine due to the force generated b y the anchor ing effect o f the tee-joint and branch pipe. The contributions f rom the branches to the pul lout resistance o f a trunk l ine c o u l d be approximated b y the difference i n pul lout forces between the tests o n branched specimens and those on the corresponding tests o n straight specimens. The results also suggested that the response o f the branch was not s ignif icant ly affected by the diameter o f the trunk l ine . S imple analyt ica l models are unavai lable for predic t ing pul lout resistance o f compound geometries such as the branched junct ions tested i n this study. The experimental observations indicate that these branched pipes are subjected to a complex interaction w i t h so i l , beg inn ing as a lateral movement and transi t ioning to a nearly exc lus ive ly ax ia l p u l l out f rom the so i l . It is observed that the presence o f branched sections attached to smaller diameter trunk pipes c o u l d cause the trunk l ine to be more vulnerable to damage than the branch. In contrast, w i t h large diameter trunk pipes the higher vu lnerab i l i ty was observed i n the branched pipe. The strain and survey measurements avai lable , i n addi t ion to v i sua l observations, indicate that plast ic deformation o f the branch l ine t yp i ca l ly occurs w i t h i n a re la t ively l im i t ed zone, w i t h i n approximately 300 m m o f the point o f attachment to the trunk l ine . Peak strains i n the branch were typ ica l ly measured to be i n excess o f 2 .5%. Plas t ic deformation for smal l diameter branches i n un i fo rm sand occurs at re la t ively h i g h trunk l ine displacements, on the order o f 200 m m or more, w h i c h appears to correspond to the peak pul lout force. B a s e d on observations, this displacement m a y also correspond to the - 9 2 -Chapter 7. Summary and Conclusions amount o f movement required to expose the branch section from w i t h i n the protective cover ing . 7.5 R e c o m m e n d a t i o n s f o r F u t u r e R e s e a r c h The outcomes f rom the research presented i n this thesis have c lear ly demonstrated the performance o f re la t ively f lex ib le bur ied polyethylene pipes subjected to g round movements is a complex soi l -pipe interaction prob lem, and phys i ca l m o d e l i n g has a k e y role to p lay i n understanding some o f these behaviours i n a fundamental manner. It is j udged that further research i n the f o l l o w i n g areas w i l l complement the current f indings, and also w o u l d lead to the development o f necessary fundamental input for the development o f guidel ines to determine the s o i l displacement magnitudes associated w i t h the safe operational stress l imi t s o f typ ica l polyethylene gas dis t r ibut ion pipel ine configurations. 1. A d d i t i o n a l fu l l scale testing to quantify the contr ibut ion to pul lout resistance and failure modes o f each o f the addi t ional p ipel ine geometries (i.e. e lbows, tees, etc.) typ ica l ly found i n bur ied pipel ine networks; 2. Tes t ing o f pipel ines w i t h compound geometry and an appl ied internal pressure to provide measurements o f p ipel ine displacement and strain at the occurrence o f rupture or pressure loss; 3 . D e v e l o p numer ica l models o f structural and geotechnical components, and calibrate to measured laboratory test results, w h i c h w i l l then provide predict ive capabil i t ies o f p ipel ine displacement and r i sk o f failure relative to s o i l displacement; 4. Per form f ie ld based moni to r ing o f typ ica l installations us ing strain gauges and survey data to measure induced strains i n the pipel ines relative to observed surface displacement. - 9 3 -Chapter 7. Summary and Conclusions A l t h o u g h this outline m a y be subject to modi f i ca t ion as informat ion becomes avai lable f rom addi t ional studies, it is envis ioned that the above components w o u l d beg in to fo rm a re la t ively comprehensive basis for deve lop ing a methodology for r i sk assessment and performance predic t ion o f regional natural gas p ipel ine networks. The areal extent and complex configurations o f p ipe l ine dis t r ibut ion networks for l oca l service compl ica te the appl ica t ion o f s imple design methods and analyses that have typ ica l ly been developed for larger diameter, l inear, t ransmission pipel ines . A n a l y s i s o f the system w o u l d generally be more easi ly facil i tated w i t h a computer based m o d e l that c o u l d accommodate s o i l parameter, p ipe l ine geometry, and displacement data that varies across the area o f the p ipel ine network. A GIS-based (Geographic Information System) approach w o u l d be suitable for the development o f a spatial mode l that w o u l d combine results f rom numer ica l mode l i ng o f p ipe l ine structural integrity w i t h results f rom s o i l deformation models . - 9 4 -REFERENCES A L A , 2001 , "Gu ide l ines for the D e s i g n o f B u r i e d Steel P ipe" , A m e r i c a n L i f e l ines A l l i a n c e . A S C E , 1984, Guide l ines for the Se i smic D e s i g n o f O i l and Gas P ipe l ine Systems. Commi t tee on Gas and L i q u i d F u e l L i f e l ines . A S C E , N e w Y o r k . Br iassou l i s , D . , and Schet t ini , E . , " M e a s u r i n g strains o f L D P E films: the strain p rob lem" , P o l y m e r Tes t ing 21 (2002), pp. 507-512. B r u s c h i , R . , G l a v i n a , S., Spinazze , M . , Tomass in i , D . , B o n a n n i , S., and Cuscuna , S., 1996, "P ipe l ines Subjected to S l o w Lands l ides Movemen t s : Structural M o d e l l i n g vs . F i e l d Measurement" , Proceedings of the 15th International Conference on Offshore Mechanics and Arctic Engineering, A S M E , pp 343-354. B u k o v a n s k y , M . , Greenwood , J . H . , and M a j o r , G . , 1985, " M a i n t a i n i n g a Na tu ra l Gas P ipe l ine i n A c t i v e Lands l ides" , Proceedings of the International Conference on Advances in Underground Pipeline Engineering, A S C E P ipe l ine D i v i s i o n , M a d i s o n , pp 438-448. B u g h i , S., A l e o t t i , P . , B r u s c h i , R . , A n d r e i , G . , M i l a n i , G . , Scarpe l l i , G . , and Sakel la r iad i , E . , 1996, " S l o w M o v e m e n t s o f Slopes Interfering w i t h P ipe l ines : M o d e l l i n g and M o n i t o r i n g " , Proceedings of the 15th International Conference on Offshore Mechanics and Arctic Engineering, A S M E , pp 363-372. - 9 5 -Cappellet to , A . , Tagl ia fer r i , R . , G i u r l a n i , G . , A n d r e i , G . , Fu r l an i , G . , and Scarpe l l i , G . , 1998, " F i e l d F u l l Scale Tests on L o n g i t u d i n a l P i p e l i n e - S o i l Interaction", Proc. International Pipeline Conf., A S M E , pp 771-778, Ca lgary , A B . Chambers , R . E . , and M c G r a t h , T . J . , 1981, "Structural D e s i g n o f B u r i e d Plast ic P ipe" , Proceedings of the International Conference on Underground Plastic Pipe, A S C E , N e w Orleans, pp 10-25. D a u b y , F . A . , L e e , C . H . , and Vo l lb r ech t , G . M . , 1993, " G a s P ipe l ine Fi tness-For-Service Investigation", Proceedings of the International Conference on Pipeline Infrastructure II, A S C E , San A n t o n i o , pp 468-491 . Dinov i t ze r , A . S . , and Smi th , R . J . , 1998, "S t ra in -Based P ipe l ine D e s i g n Cr i t e r i a" , Proc. International Pipeline Conf, A S M E , pp 763-770, Ca lga ry , A B . F i l z , G . M . , and Duncan , J . M . , 1996, "Ear th Pressures D u e to C o m p a c t i o n : C o m p a r i s o n o f Theory w i t h Labora tory and F i e l d Behav iou r " , Transportat ion Research R e c o r d 1526, Transportat ion Research B o a r d , Wash ing ton , D . C . , pp. 28-37. Flores-Berrones , R . , and O ' R o u r k e , M . , 1992, " S e i s m i c Effects o n Underg round Pipel ines D u e to Permanent L o n g i t u d i n a l G r o u n d Deformat ion" , Proceedings, 4th Japan-US Workshop on Earthquake Resistant Design of Lifeline Facilities and Countermeasures for Soil Liquefaction, Technical Report NCEER-92-0019, N a t i o n a l Center for Earthquake Engineer ing Research, Buf fa lo , N . Y . , pp 465-479. Gerbault , M . , 1995, " A Soil-Structure Interactive M o d e l " , 2 n d International Conference on Advances i n Underground P ipe l ine Engineer ing , A S C E P ipe l ine D i v i s i o n , B e l l e v u e , Wash ing ton , pp 42-53. Hibbi t t , H . D . , K a r l s s o n , B . I . , and Sorensen, P . , 2000 , " A B A Q U S Theore t ica l M a n u a l " , V e r s i o n 4.5, M a r c h 1984. - 9 6 -H s u , T . W . , 1993, "Rate Effect o n Latera l S o i l Restraint o f P ipe l ines" , Soils and Foundations, Japanese Society o f S o i l M e c h a n i c s and Foundat ion Engineer ing , V o l . 33 , N o . 4, D e c 1993, pp 159-169. Janson, L . E . , 1985, "Invest igat ion o f the L o n g - T e r m Creep M o d u l u s for B u r i e d Polye thylene Pipes Subjected to Constant Def lec t ion" , Proceedings of the International Conference on Advances in Underground Pipeline Engineering, A S C E P ipe l ine D i v i s i o n , M a d i s o n , pp 253-262. K e n n e d y , R . , C h o w , A . , and W i l l i a m s o n , R . , 1977, "Faul t M o v e m e n t Effects on B u r i e d O i l P ipe l ines" . Journal of Transportation Engineering, A S C E , V o l . 103, N o . 5, pp 617-633. K o b a y a s h i , T . , Nakane , H . , S u z u k i , N . , and Ishikawa, M . , 1989, "Parametric Study o n F l e x i b i l i t y o f B u r i e d P ipe l ine Subject to Large G r o u n d Disp lacement" , Proceedings, 2nd Japan-US Workshop on Liquefaction, Large Ground Deformation and Their Effects on Lifelines, Technical Report NCEER-89-0032, N a t i o n a l Center for Earthquake Eng inee r ing Research, Buf fa lo , N . Y . , pp 348-362. K o n u k , I., P h i l l i p s , R . , H u r l e y , S., and Pau l in , M . J . , 1999, "P re l im ina ry Ova l i sa t ion Measurements o f B u r i e d Pipe l ines Subject to La te ra l L o a d i n g " , 18th International Conference o n Offshore M e c h a n i c s & A r c t i c Engineer ing , St. John ' s , Ju ly 1999, paper 99-5023. L a m b e , T . W . (1991) S o i l Tes t ing for Engineers , B i t e c h Publishers L t d . , V a n c o u v e r , B C , Canada. L i u , X . , and O 'Rourke , M . J . , 1997, " B e h a v i o u r o f continuous p ipe l ine subject to transverse P G D " , Earthquake Engineering and Structural Dynamics, V o l . 26, N o . 10, pp 989-1003. M u t h u , R . , 1991, "Large Scale Pu l lou t Tes t ing o f Geosynthet ics" , Masters Thesis submitted to the Department o f C i v i l Eng ineer ing , Un ive r s i t y o f B r i t i s h C o l u m b i a , V a n c o u v e r , Canada. - 9 7 -Negussey , D . , W i j e w i c k r e m e , D . , and V a i d , Y . P . , 1989, "Geomembrane Interface F r i c t i o n " , Canad ian Geotechnica l Journal , V o l . 26, N o . 1, pp. 165-169. N e w m a r k , N . , and H a l l , W . , 1975, "P ipe l ine D e s i g n to Resis t La rge Faul t Disp lacement" , Proceedings, US National Conference on Earthquake Engineering, Earthquake Engineer ing Research Institute, Oak land , Ca l i fo rn i a , pp 416-425. N i s h i o , N . , 1995, " M e c h a n i s m o f Gas P ipe l ine Fai lures on B a l b o a B o u l e v a r d dur ing the 1994 Nor thr idge Ear thquake" Proceedings, 4th U.S. Conference on Lifeline Earthquake Engineering, San Franc isco , A u g u s t 22-23, pp 216-223. O ' R o u r k e , T . , 1988, " C r i t i c a l Aspec ts o f So i l -P ipe l i ne interaction for La rge G r o u n d Deformat ion" , Proceedings, 1st Japan-US Workshop on Liquefaction, Large Ground Deformation and Their Effects on Lifelines, A s s o c i a t i o n for Deve lopment o f Earthquake Pred ic t ion , Japan., pp 118-126. O ' R o u r k e , M . J . , 1989, " A p p r o x i m a t e A n a l y s i s Procedures for Permanent G r o u n d Deformat ion Effects o n B u r i e d P ipe l ines" , Proceedings, 2nd Japan-US Workshop on Liquefaction, Large Ground Deformation and Their Effects on Lifelines, Technical Report NCEER-89-0032, N a t i o n a l Center for Earthquake Eng inee r ing Research, Buf fa lo , N . Y . , pp 336-347. O ' R o u r k e , M . J . , and L i u , J . , 1998, " S e i s m i c L o a d i n g and B e h a v i o u r o f B u r i e d P ipe l ines" , PVP-Vol. 360, Pressure Vessel and Pipeing Codes and Standards, ASME, pp 513-519. O ' R o u r k e , M . J . , and Nordbe rg , C , 1990, " A n a l y s i s Procedures for B u r i e d Pipel ines Subject to L o n g i t u d i n a l and Transverse Permanent G r o u n d Deformat ion" , Proceedings, 3rd Japan-US Workshop on Earthquake Resistant Design of Lifeline Facilities and Countermeasures for Soil Liquefaction, Technical Report NCEER-91-0001, N a t i o n a l Center for Earthquake Engineer ing Research, Buf fa lo , N . Y . O ' R o u r k e , M . J . , L i u , X . , and Flores-Berrones , R . , 1995, "Steel P ipe W r i n k l i n g D u e to L o n g i t u d i n a l Permanent G r o u n d Deformat ion" , Journal of Transportation Engineering, V o l . 121, N o . 5, pp 443-451 . - 9 8 -O ' R o u r k e , T . D . , and O ' R o u r k e , M . J . , 1995, "P ipe l ine Response to Permanent G r o u n d Deformat ion : A Benchmark Case" , Proceedings, 4th US Conference on Lifeline Earthquake Engineering, TCLEE, ASCE, San Franc isco , Ca l i fo rn i a , A u g u s t 1995, pp 288-295. O ' R o u r k e , T . D . , and Palmer , M . C . , 1996, "Earthquake Performance o f Gas Transmiss ion P ipe l ines" , Earthquake Spectra, V o l . 20, N o . 3, pp 493-527. O ' R o u r k e , T . , and T a w f i k , M . , 1983, "Effects o f La tera l Spreading o n B u r i e d Pipe l ines D u r i n g the 1971 San Fernando Earthquake", Earthquake Behaviour and Safety of Oil and gas Storage Facilities, Buried Pipelines and Equipment, P V P V o l . 7 7 , A S M E , N e w Y o r k , N . Y . , pp 124-132. P a u l i n , M . J . , P h i l l i p s , R . , C l a r k , J.I., H u r l e y , S., and T r i g g , A . , 1997, "Establ ishment o f a full-scale p ip l ine / so i l interaction test fac i l i ty and results f rom lateral and ax i a l investigations i n sand", V o l . V , 16th International Conference Offshore Mechanics and Arctic Engineering '97, Y o k o h a m a , pp. 139-146. P a u l i n , M . J . , P h i l l i p s , R . , C l a r k , J.I., T r i g g , A . , and K o n u k , I., 1998, " A fu l l scale invest igat ion into p ipe l ine / so i l interaction". Proc. International Pipeline Conf, A S M E , pp 779-788, Ca lgary , A B . Petroff, L . J . , 1990, "Stress Re laxa t ion Characterist ics o f the H D P E P i p e - S o i l Sys tem" , Proceedings of the International Conference on Pipeline Design and Installation, A S C E P ipe l ine D i v i s i o n , L a s Vegas , 1990, pp280-294. Petroff, L . J . , 1990, " R e v i e w o f the Rela t ionship Be tween Internal Shear Resistance and A r c h i n g i n Plas t ic P ipe Installations", Symposium on Buried Plastic Pipe Technology, A S T M S T P 1093, George S. B u c z a l a and M i c h a e l J . Cassady, Eds . , A m e r i c a n Socie ty for testing and Mater ia l s , Ph i lade lphia , pp 266-280. Plast ics P ipe Institute, Inc., 1998 "Eng inee r ing Properties o f Polye thy lene" , P P I H a n d b o o k o f Polyethylene P ipe , Techn ica l Report . - 9 9 -Popescu, R . , P h i l l i p s , R . , K o n u k , I., G u o , P . , and Nobahar , A . , 2002, " P i p e - S o i l Interaction: La rge Scale Tests and N u m e r i c a l M o d e l l i n g " , Popescu , R . , P h i l l i p s , R . , K o n u k , I., and Deacu , D . , 1999, " N u m e r i c a l and P h y s i c a l m o d e l i n g o f p ipe-so i l interaction", Proc. 52nd Canadian Geotech. Conf, Reg ina , S K , pp 437-444. Se l ig , E . T . , 1988, " S o i l Parameters for D e s i g n o f B u r i e d P ipe l ines" , Proceedings of the Conference Pipeline Infrastructure, A S C E P ipe l ine D i v i s i o n , Bos ton , pp 99-117. Structural Software Deve lopment Inc., 1981, " P I P L I N - I I I Compute r P rog ram for Stress and Deformat ion A n a l y s i s o f P ipe l ines" , Structural Software Deve lopment Inc., Berke ley , Ca l i fo rn i a . S u z u k i , N . , K o b a y a s h i , T . , Nakane , H . , and Ishikawa, M . , 1989, " M o d e l l i n g o f Permanent G r o u n d Deformat ion for B u r i e d P iep l ines" , Proceedings, 2nd Japan-US Workshop on Liquefaction, Large Ground Deformation and Their Effects on Lifelines, Technical Report NCEER-89-0032, N a t i o n a l Center for Earthquake Engineer ing Research, Buf fa lo , N . Y . , pp 413-425. Swanson A n a l y s i s Systems Inc., 1992, " A n s y s User 's M a n u a l " , Swanson A n a l y s i s Systems, Inc., 1992 Trautmann, C . H . , and O ' R o u r k e , T . D . , 1983, " B e h a v i o u r o f P ipe i n D r y Sand U n d e r Latera l and U p l i f t L o a d i n g " , Geotechnica l Eng inee r ing Repor t 83-7, C o r n e l l Un ive r s i t y , Ithaca, N e w Y o r k . Trautmann, C . H . , and O ' R o u r k e , T . D . , 1985, "La te ra l Force-Disp lacement Response o f B u r i e d P ipe" , Journal of Geotechnical Engineering, V o l . I l l , N o . 9, September 1985, pp 1077-1093. Tseng , W . S . , and L e e , C . H . , 1995, "Structural Performance Cr i t e r ia for Fitness-for-Service Evalua t ions o f Underg round Na tu ra l Gas P ipe l ines" , 2nd International - 1 0 0 -Conference on Advances in Underground Pipeline Engineering, A S C E P ipe l ine D i v i s i o n , B e l l e v u e , Wash ing ton , pp 536-547. V a i d , Y . P . , and Thomas , J . , 1995, "L ique fac t ion and Post l iquefact ion B e h a v i o r o f Sand ," Journal o f Geotechnica l Engineer ing , v o l . 121. N o . 2, A S C E . W a n g , L . , and W a n g , L . R . L . , 1995, " B u r i e d Pipe l ines i n Large Faul t M o v e m e n t s " , Proceedings, 4th U.S. Conference on Lifeline Earthquake Engineering, San Franc isco , A u g u s t 22-23 , pp 152-159. Y o s h i z a k i , K . , O ' R o u r k e , T . D . , B o n d , T . , M a s o n , J . , and Hamada , M . , 2001 , "La rge Scale Exper iments o f Permanent G r o u n d Deformat ion Effects on Steel P ipe l ines" , Research progress Report , M C E E R , pp 21-28. - 101 -APPENDIX A PIPE SPECIMEN COMPRESSION TESTING This appendix contains the data obtained dur ing compress ion testing o f 60 m m and 115 m m polyethylene p ipe specimens. T h i s data was obtained to p rov ide guidance o n the select ion o f engineering parameters, i n part icular the elastic modulus , for use i n the analyses o f the forgoing sections. The results f rom the fu l l series o f tests are contained herein for the interests o f the reader. - 1 0 2 -Appendix A. Pipe Specimen Compression Testing Stress-Strain Curve 60 mm PE Pipe - 103 -Appendix A. Pipe Specimen Compression Testing Stress-Strain Curve 60 mm PE Pipe 25 5 15 5 60-sa10-A 60-sa11-A 60-sa12-A 60-sa13-A -60-sa14-A \ V 0 5 10 15 20 25 30 Strain (%) - 1 0 4 -Appendix A. Pipe Specimen Compression Testing Stress-Strain Curve 115 mm PE Pipe Axial Displacement (mm) Stress-Strain Curve 115 mm PE Pipe Strain (%) - 105 -Appendix A. Pipe Specimen Compression Testing Comparison of Pipe Size 25 20 5 Typical Response, 60-sa5-A ^ " T y p i c a l Response, 115-sa2-A 0 5 10 15 20 25 30 Displacement (%) - 1 0 6 -APPENDIX B P U L L O U T TEST RESULTS Conta ined w i t h i n this appendix are the data col lected f rom the set up and testing o f each specimen, i nc lud ing tests not spec i f ica l ly referenced or presented i n the preceding discussions. The data contained herein includes the f o l l o w i n g , i n order: • Instrumentation layout part icular to each test, • Statist ical dis t r ibut ion and tabulated results o f density testing, • Measu red and norma l i zed load response relative to pipe displacement. P ipe displacement was measured at the first string potentiometer (SP1) , w h i c h for each test was mounted di rect ly to the pipe, just outside the front edge o f the box , • Displacements o f specif ic points a long the pipe, relative to pipe displacement, • Measu red response o f the strain gauges, relative to pipe displacement, and • Prof i le o f strain dis tr ibut ion w i t h i n the pipe at consecutive intervals dur ing pipe displacement. - 1 0 7 -Appendix B. Pullout Test Results TEST 115AL-SG (TEST#1) - 1 0 8 -Appendix B. Pullout Test Results m T f 3 Instrumentation Layout. Test 115aL-SG - 1 0 9 -Appendix B. Pullout Test Results - 1 1 0 -Appendix B. Pullout Test Results 450 450 SP1 Displacement, x (mm) ) SG1 SP2 SP3 SG4 SG5~| D i s p l a c e m e n t s o f Po in t s A l o n g P i p e R e l a t i v e to P i p e D i s p l a c e m e n t , Tes t 1 1 5 a L - S G -3500 -3000 ^ -2500 C~ ' r o g -2000 o 1 c CD L. w -1500 -1000 -500 O ' X . + - 4 , o * X *» x Leading End Displacement • • • 1 mm - • - 2 mm 5 mm 10 mm 20 mm 50 mm 75 mm 1000 2000 3000 4000 5000 Distance From Front Edge of Test Chamber (mm) 6000 P i p e S t r a i n P r o f i l e , Tes t 1 1 5 a L - S G - I l l -Appendix B. Pullout Test Results TEST 115AL (TEST #2) - 1 1 2 -Appendix B. Pullout Test Results OJ Instrumentation Layout, Test 115aL - 113 -Appendix B. Pullout Test Results 1 \ 1 r . J — i — , — , 1 — ^ ^ 5 0 25 50 75 100 125 150 SP Displacement, x (mm) A x i a l Pullout Resistance, Test 115aL r— O o O 0.6 Predicted 1 J I i 1 1 1 1— ^ 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Normalized S P Displacement, x/D Normal ized A x i a l Pullout Resistance, Test 115aL - 1 1 4 -Appendix B. Pullout Test Results 140 0 20 40 60 80 100 120 140 SP1 Displacement, x (mm) SP1 SP3 SP4 SP5 Disp l acemen t s o f Po in t s A l o n g P i p e R e l a t i v e to P i p e D i s p l a c e m e n t , Tes t 1 1 5 a L - S G - 115 -Appendix B. Pullout Test Results TEST 115AL-RT (TEST #3) - 1 1 6 -Appendix B. Pullout Test Results OJ Instrumentation Layout. Test 115aL-RT - 1 1 7 -Appendix B. Pullout Test Results 2 100 200 300 400 500 SP Displacement, x (mm) 600 700 A x i a l Pul lout Resistance, Test 115aL-RT 1.0 2.0 3.0 4.0 5.0 Normalized S P Displacement, x/D 5.0 Normal ized A x i a l Pullout Resistance, Test 115aL-RT -118-Appendix B. Pullout Test Results 700 0 100 200 300 400 500 600 700 SP1 Displacement, x (mm) SP5 — S P 1 D i s p l a c e m e n t s o f Po in t s A l o n g P i p e R e l a t i v e to P i p e D i s p l a c e m e n t , Tes t 1 1 5 a L - S G -119-Appendix B. Pullout Test Results TEST 115AL-RETEST - 1 2 0 -Appendix B. Pullout Test Results OJ D_ ID € •sr z n Instrumentation Layout, Test 115aL-Retest - 121 -Appendix B. Pullout Test Results 8 + 0 I I ! I 1 1 : 1 1 1 I | « , H | H | f f l . « | H | H , H 1 i I 1350 1400 1450 1500 1550 1600 1650 Densi ty (kg/m 3 ) Sta t i s t i c a l D i s t r i b u t i o n o f Dens i t y Tes t Resu l t s , Tes t 1 1 5 a L - R e t e s t Den s i t y Tes t Resu l t s , Tes t 1 1 5 a L - R e t e s t Probe Dry Relative Depth Elevation % Density, Void Density, Test No. (mm) (mm) Test Location Moisture pd, kg/m3 Ratio, e Dr,% 1 300 700 D1 0.0 1497 0.80 61.4 2 300 800 D2 0.2 1516 0.78 68.4 3 300 750 C2 0.3 1515 0.78 68.1 4 300 750 B2 0.2 1498 0.80 61.7 5 300 800 A2 0.2 1507 0.79 65.1 6 300 800 A1 0.6 1490 0.81 58.7 7 300 800 B1 0.1 1530 0.76 73.5 8 300 800 C1 0.1 1544 0.75 78.5 9 300 1050 D2 0.0 1517 0.78 68.8 10 300 1050 C2 0.1 1514 0.78 67.7 11 300 1050 B/C 1/2 Middle of Box 0.0 1498 0.80 61.7 12 300 1050 B2 -0.1 1524 0.77 71.4 13 300 1050 A2 0.1 1537 0.76 76.0 14 300 1050 A1 0.3 1551 0.74 81.0 15 300 1050 B1 0.0 1542 0.75 77.8 16 300 1000 C1 0.0 1540 0.75 77.1 17 300 1000 D1 0.2 1540 0.75 77.1 Average 1521 0.78 70.2 Minimum 1490 0.74 58.7 Maximum 1551 0.81 81.0 Std Dev 19.1 0.02 7.0 - 122 -Appendix B. Pullout Test Results 0 50 100 150 200 250 300 SP Displacement, x (mm) A x i a l P u l l o u t Res i s tance , Tes t 1 1 5 a L - R e t e s t 1 in N o r m a l i z e d A x i a l P u l l o u t Res i s tance , Tes t 1 1 5 a L - R e t e s t - 123 -Appendix B. Pullout Test Results 0 50 100 150 200 250 300 SP1 Displacement, x (mm) I — SP1 — S P 2 Disp l acemen t s o f Po in t s A l o n g P i p e R e l a t i v e to P i p e D i s p l a c e m e n t , Tes t 1 1 5 a L -Retest -800 -600 C -400 re O .a -2oo £ ' r a CO 200 400 . 50 mm • 9 • X Leading End Displacement - * - 1 mm a 2 mm - • - 5 mm - K - 10 mm - € - 20 mm - - - 50 mm - + - 75 mm - 100 mm - Compression £ o UJ Compression 500 1000 1500 2000 2500 3000 3500 4000 Distance From Front Edge of Test Chamber (mm) 4500 5000 P i p e S t r a i n p ro f i l e , Tes t 1 1 5 a L - R e t e s t - 1 2 4 -Appendix B. Pullout Test Results TEST 60AL - 1 2 5 -Appendix B. Pullout Test Results 9 > Instrumentation Layout , Test 60aL - 1 2 6 -Appendix B. Pullout Test Results 11 11 1350 1400 1450 1500 1550 1600 1650 1700 Density (kg/m ) Statistical Distr ibution of Density Test Results, Test 60aL Density Test Results, Test 60aL Probe Dry Relative Depth Elevation % Density, Void Density, Test No. (mm) (mm) Test Location Moisture pd, kg/m3 Ratio, e D r % 1 250 500 C1 2.1 1500 0.80 62.5 2 250 500 B2 -40cm from wall 2.0 1433 0.88 36.2 3 300 900 D1 -80cm from wall 1.0 1407 0.92 25.3 4 300 900 C2 -60cm from wall 0.8 1423 0.90 32.1 5 300 800 A/B1 80 cm from wall 0.4 1424 0.90 32.5 6 300 800 B2 middle 1.4 1390 0.94 18.0 7 300 1050 B/C 112 Center of box 0.4 1430 0.89 35.0 8 300 1050 D1 middle 0.5 1431 0.89 35.4 9 300 1000 D2 middle 0.5 1455 0.86 45.1 10 300 1050 C2 middle 0.3 1465 0.84 49.1 11 300 1100 C1 middle 0.4 1491 0.81 59.1 12 300 1100 B1 middle 0.4 1506 0.79 64.7 13 300 1100 B2 middle 0.4 1434 0.88 36.6 14 300 120 A2 middle 0.4 1438 0.88 38.2 15 300 1150 A1 middle 1.0 1501 0.80 62.9 Average 0.8 1449 0.87 42.2 Minimum 0.3 1390 0.79 18.0 Maximum 2.1 1506 0.94 64.7 St Dev 0.6 36.3 0.05 14.5 - 1 2 7 -Appendix B. Pullout Test Results 150 200 250 300 S P Displacement, x (mm) 350 400 A x i a l P u l l o u t Res is tance , Tes t 6 0 a L 2.0 3.0 4.0 Normalized S P Displacement, x/D 6.C 7.0 N o r m a l i z e d A x i a l P u l l o u t Res i s tance , Tes t 6 0 a L - 128 -Appendix B. Pullout Test Results 500 j 450 400 0 50 100 150 200 250 300 350 400 450 500 SP1 Displacement, x (mm) — SP2 — S P 1 I Displacements of Points Along Pipe Relative to Pipe Displacement, Test 60aL - 1 2 9 -Appendix B. Pullout Test Results TEST 115AD - 1 3 0 -Appendix B. Pullout Test Results O f OJ Instrumentation Layout, Test 115aD - 131 -Appendix B. Pullout Test Results 10 8 1350 1400 1450 1500 1550 1600 1650 1700 Density (kg/m3) Statistical Distr ibution of Density Test Results, Test 115aD Density Test Results, Test 115aD Probe Dry Relative Depth Elevation Density, Void Density, Test No. (mm) (mm) Test Location % Moisture pd, kg/m3 Ratio, e D r . * 1 200 550 C/D 1 1.4 1565 0.73 85.9 2 200 550 C2 0.8 1600 0.69 97.7 3 250 500 A/B 1 1.7 1545 0.75 78.9 4 200 500 A2 1.0 1585 0.70 92.7 5 200 650 D1 0.4 1604 0.68 99.0 6 200 700 D2 1.1 1565 0.73 85.9 7 200 700 C2 0.4 1574 0.72 88.9 8 200 700 CI 0.4 1623 0.66 105.1 9 200 700 B1 0.3 1542 0.75 77.8 10 200 650 B2 0.9 1581 0.71 91.3 11 200 650 A2 0.6 1577 0.71 90.0 12 200 700 A1 0.8 1566 0.72 86.2 14 200 800 A/B 2 0.4 1604 0.68 99.0 15 200 850 A/B 1 0.6 1607 0.68 100.0 16 200 850 B/C 1/2 Middle of Box 0.5 1586 0.70 93.0 17 200 850 C/D 1 0.5 1568 0.72 86.9 18 200 850 C/D2 1.1 1588 0.70 93.7 Average 1581 0.71 91.3 Minimum 1542 0.66 77.8 Maximum 1623 0.75 105.1 St Dev 22.0 0.02 7.4 - 1 3 2 -Appendix B. Pullout Test Results 14 0 100 200 300 400 500 600 SP Displacement, x (mm) A x i a l P u l l o u t Res i s tance , Tes t 115aD 1.0 2.0 3.0 4.0 Normalized S P Displacement, x/D 5.0 6.0 N o r m a l i z e d A x i a l P u l l o u t Res i s tance , Tes t 115aD - 133 -Appendix B. Pullout Test Results 800 700 4 0 100 2 0 0 3 0 0 4 0 0 500 6 0 0 700 8 0 0 SP1 Displacement, x (mm) I — SP1 S P 2 | Displacements of Points Along Pipe Relative to Pipe Displacement, Test 115aD Leading End Displacement - • - 1 mm - m - 2 mm - * - 5 mm - a - 10 mm - * - 20 mm - * - 50 mm 100 mm * v * * • -o w I-o a 03 1000 2000 3000 4000 5000 Distance From Front Edge of Test Chamber (mm) 6000 Pipe Strain Profile, Test 115aD - 134-Appendix B. Pullout Test Results TEST 60AD - 135 -Appendix B. Pullout Test Results in o_ lA I > Instrumentation Layout, Test 60aD - 1 3 6 -Appendix B. Pullout Test Results 10 >. u c o 3 a-2 1350 1400 1450 1500 1550 Density (kg/m3) 1600 1650 1700 Sta t i s t i ca l D i s t r i b u t i o n o f D e n s i t y Tes t Resu l t s , Tes t 6 0 a D Tes t D e n s i t y Tes t Resu l t s , Tes t 6 0 a D Probe Dry Relative Depth Elevation % Density, Void Density, Test No. (mm) (mm) Test Location Moisture pd, kg/m3 Ratio, e Dr % 1 200 700 A2 0.7 1609 0.68 100.6 2 200 700 A1 0.9 1583 0.71 92.0 3 200 700 B1 0.4 1606 0.68 99.6 4 200 700 B2 0.5 1609 0.68 100.6 5 200 650 C2 0.6 1600 0.69 97.7 6 200 650 C1 0.8 1603 0.68 98.6 7 200 600 D1 0.7 1620 0.67 104.2 8 200 650 D2 0.8 1596 0.69 96.3 9 200 700 D2 0.6 1595 0.69 96.0 10 200 750 D1 0.4 1619 0.67 103.8 11 200 750 CI 0.6 1611 0.68 101.3 12 200 750 C2 08 1599 0.69 97.3 13 200 800 B2 0.7 1619 0.67 103.8 14 200 800 B1 0.2 1620 0.67 104.2 15 200 750 A1 0.3 1626 0.66 106.1 16 200 750 A2 0.5 1618 0.67 103.5 17 200 800 B/C 1/2 MIDDLE OF BOX 0.3 1610 0.68 100.9 18 200 800 D1 0 5 1634 0.65 108.6 19 200 900 C2 0.5 1605 0.68 99.3 20 200 850 B1 0.4 1623 0.66 105.1 21 200 850 A2 0.6 1623 0.66 105.1 22 200 950 D2 05 1621 0.67 104.5 23 200 1000 C1 0.4 1620 0.67 104.2 24 200 1000 B2 0.5 1625 0.66 105.8 25 200 950 A1 05 1604 0.68 99.0 Average 0.5 1612 0.68 101.5 Minimum 0.2 1583 0.65 92.0 Maximum 0.9 1634 0.71 108.6 St Dev 0.2 12.0 0.01 3.9 - 1 3 7 -Appendix B. Pullout Test Results 150 200 250 300 SP Displacement, x (mm) A x i a l P u l l o u t Res i s tance , Tes t 6 0 a D 350 400 450 Normalized SP Displacement, x/D N o r m a l i z e d A x i a l P u l l o u t Res is tance , Tes t 6 0 a D - 138 -Appendix B. Pullout Test Results 450 450 SP1 Displacement, x (mm) SP2 SP1 Disp l acemen t s o f Po in t s A l o n g P i p e R e l a t i v e to P i p e D i s p l a c e m e n t , Tes t 6 0 a D - 1 3 9 -Appendix B. Pullout Test Results TEST 15 AD - 1 4 0 -Appendix B. Pullout Test Results m Q. Instrumentation Layout , Test 15aD - 141 -Appendix B. Pullout Test Results 1350 1400 1450 1500 1550 1600 1650 1700 Dens i ty (kg/m ) Statistical Distribution of Density Test Results, Test 15aD Density Test Results, Test 15aD Probe Dry Relative Depth Elevation % Density, Void Density, Test No. (mm) (mm) Test Location Moisture pd, kg/m3 Ratio, e D r % 1 250 350 D1 0.7 1576 0.71 89.6 2 200 700 D2 0.5 1612 0.67 101.6 3 200 350 C1 0.1 1620 0.67 104.2 4 200 700 C2 0.4 1615 0.67 102.6 5 200 750 B2 0.3 1604 0.68 99.0 6 200 700 B1 0.2 1606 0.68 99.6 7 200 750 A1 0.4 1594 0.69 95.7 8 200 750 A2 0.4 1610 0.68 100.9 9 200 800 D1 0.6 1589 0.70 94.0 10 200 800 D2 0.5 1605 0.68 99.3 11 200 850 C2 0.1 1596 0.69 96.3 12 200 850 C1 0.4 1599 0.69 97.3 14 200 900 B2 0.4 1598 0.69 97.0 15 250 900 B1 0.3 1602 0.69 98.3 16 200 900 A2 0.3 1624 0.66 105.4 17 200 850 A1 0.6 1598 0.69 97.0 18 200 850 B/C 1/2 Middle of Box 0.2 1596 0.69 96.3 Average 0.4 1603 0.68 98.5 Minimum 0.1 1576 0.66 89.6 Maximum 0.7 1624 0.71 105.4 StDev 0.2 11.7 0.01 3.8 - 1 4 2 -Appendix B. Pullout Test Results - 143 -Appendix B. Pullout Test Results 700 0 100 200 300 400 500 600 700 SP1 Displacement, x (mm) ~ SP1 SP2~ Displacements of Points Along Pipe Relative to Pipe Displacement, Test 15aD - 1 4 4 -Appendix B. Pullout Test Results TEST 115BAL - 145 -Appendix B. Pullout Test Results Instrumentation Layout, Test 115baL - 1 4 6 -Appendix B. Pullout Test Results 5 4 >. 3 O c a 3 CT 0) 1 + 0 - I — I — • — • — I — I — n n n 1350 1400 1450 1500 1550 1600 1650 1700 Density (kg/m ) Statistical Distr ibution of Density Test Results, Test 115baL Density Test Results, Test 115baL Probe Dry Relative Depth Elevation % Density, Void Density, Test No. (mm) (mm) Test Location Moisture P d , kg/m3 Ratio, e D r % 1 300 800 D2 0.4 1492 0.81 59.5 2 300 850 CI 0.9 1528 0.77 72.8 3 300 1100 D1 0.3 1503 0.80 63.6 4 300 1050 C2 0.0 1555 0.74 82.4 5 300 1050 B1 0.1 1568 0.72 86.9 6 300 1050 A2 0.0 1511 0.79 66.6 7 300 800 A/B1 - during excavation 1.0 1451 0.86 43.5 8 300 800 B2- during excavation 1.1 1463 0.85 48.3 9 300 800 D2 - during excavation 1.0 1429 0.89 34.6 10 300 800 C1 - during excavation 1.3 1485 0 82 56.8 Average 0.6 1499 0.80 61.5 Minimum 0.0 1429 0.72 34.6 Maximum 1.3 1568 0.89 86.9 St Dev 0.5 44.3 0.05 16.6 - 147-Appendix B. Pullout Test Results A x i a l Pullout Resistance, Test 115baL Normal ized A x i a l Pullout Resistance, Test 115baL - 1 4 8 -Appendix B. Pullout Test Results 500 0 50 100 150 200 250 300 350 400 450 500 SP1 Displacement, x (mm) D i sp l acemen t s o f Po in t s A l o n g P i p e R e l a t i v e to P i p e D i s p l a c e m e n t , Tes t 1 1 5 b a L X a E z JZ O To H "5 ra -X- -SG ahead of Tee • * • - •- 9 z ;* Leading End Displacement J» " X SG behind Tee - • - 1 mm - « - 2 mm - •* - 5 mm - X - 10 mm - *- 20 mm to m - « - 50 mm harr 100 mm u 200 mm of Tes - * - 300 mm CD O) •o u 500 1000 1500 2000 2500 3000 3500 4000 4500 Distance From Front Edge of Test Chamber (mm) 5000 P i p e S t r a i n P r o f i l e , Tes t 1 1 5 b a L - 1 4 9 -Appendix B. Pullout Test Results 459 mm Surveyed 444 mm 217 mm Surveyed 438 mm 206 mm 421 mm - Initial Location •Maximum Displacement S u r v e y e d L o c a t i o n s Be fo re a n d A f t e r T e s t i n g , Tes t 1 1 5 b a L - 1 5 0 -Appendix B. Pullout Test Results TEST 60BAL - 151 -Appendix B. Pullout Test Results a. Instrumentation Layout , Test 60baL - 1 5 2 -Appendix B. Pullout Test Results 1350 1400 1450 1500 1550 1600 1650 1700 Density (kg/m3) Statistical Distr ibution of Density Test Results, Test 60baL Density Test Results, Test 60baL Test No. Probe Depth (mm) Elevation (mm) Test Location % Moisture Dry Density, pd, kg/m3 Void Ratio, e Relative Density, D,,% 1 300 950 B2 0.1 1495 0.81 60.6 2 300 900 A/B1 0.1 1497 0.80 61.4 3 300 800 C1 (walked-on area ) 0.3 1525 0.77 71.7 4 300 900 D2 0.0 1509 0.79 65.9 5 300 1100 D2 0.3 1532 0.76 74.2 6 300 1050 CI 0.0 1539 0.75 76.8 7 300 1050 B2 0.0 1557 0.73 83.1 8 300 1050 A1 0.2 1530 0.76 73.5 Average 0.1 1523 0.77 70.9 Minimum 0.0 1495 0.73 60.6 Maximum 0.3 1557 0.81 83.1 St Dev 0.1 21.4 0.02 7.8 - 153 -Appendix B. Pullout Test Results o u i -o u. S P Displacement, x (mm) A x i a l P u l l o u t Res i s tance , Tes t 6 0 b a L = o.o IS E < o z -0.5 | -1.0 0 0.5 f « ,— 1.0 1.5 2.0 - 1 — ' — i — ' — > — 3.0 3 I y Normalized S P Displacement, x/D N o r m a l i z e d A x i a l P u l l o u t Res i s tance , Tes t 6 0 b a L - 154-Appendix B. Pullout Test Results 400 SP1 Displacement, x (mm) Displacements of Points Along Pipe Relative to Pipe Displacement, Test 60baL -25000 -20000 4. C -15000 ' « S— *-» o .y -10000 E CO -5000 041 SG ahead of Tee SG behind Tee x I - * -Leading End Displacement * - 1 mm « - 2 mm A - 5 mm K- 10 mm K - 20 mm • - 50 mm + -75 mm - - 100 mm 200 mm • - 300 mm 1 • • • • • t s ^ t - - -5000 500 1000 1500 2000 2500 3000 3500 4000 4500 Distance From Front Edge of Test Chamber (mm) 5000 Pipe Strain Profile, Test 60baL - 155-Appendix B. Pullout Test Results 365 mm Surveyed 242 mm 107 mm Surveyed 233 mm 250 mm V 97 mm - - Initial Location • Maximum Displacement S u r v e y e d L o c a t i o n s Be fo re a n d A f t e r T e s t i n g , Tes t 6 0 b a L - 1 5 6 -Appendix B. Pullout Test Results TEST 115BAD - 1 5 7 -Appendix B. Pullout Test Results Instrumentation Layout , Test 115baD - 1 5 8 -Appendix B. Pullout Test Results 8 1350 1400 1600 1650 1700 Density (kg/m ) Statistical Distr ibution of Density Test Results, Test 115baD Density Test Results, Test 115baD Probe Dry Relative Depth Elevation Density, Void Density, Test No. (mm) (mm) Test Location % Moisture pd, kg/m3 Ratio, e Dr % 1 250 500 D1 1.0 1593 0.69 95.3 2 250 500 C2 0.9 1552 0.74 81.3 3 250 500 A/B 1/2 0.7 1596 0.69 96.3 4 200 600 C/D2 0.9 1588 0.70 93.7 5 250 600 A/B1 0.5 1588 0.70 93.7 6 200 650 B2 0.5 1605 0.68 99.3 7 200 700 D2 0.9 1583 0.71 92.0 8 200 700 D1 0.5 1612 0.67 101.6 9 200 750 C1 0.4 1591 0.70 94.7 10 200 750 C2 0.2 1613 0.67 101.9 11 200 750 B2 0.5 1611 0.68 101.3 12 200 750 31 0.5 1568 0.72 86.9 13 200 800 A1 0.8 1581 0.71 91.3 14 200 800 A2 0.4 1606 0.68 99.6 15 200 800 D1/2 0.7 1607 0.68 100.0 16 200 800 B/C1 0.6 1606 0.68 99.6 17 200 850 0.6 1613 0.67 101.9 18 250 1000 D1 0.4 1579 0.71 90.6 19 200 1000 D2 0.8 1593 0.69 95.3 20 200 1000 C2 0.5 1597 0.69 96.7 21 250 1050 CI 0.2 1580 0.71 91.0 22 200 1000 B1 0.2 1599 0.69 97.3 23 200 1000 B2 0.5 1592 0.70 95.0 24 200 1000 A2 0.5 1602 0.69 98.3 25 200 1000 A1 0.6 1594 0.69 95.7 Average 0.6 1594 0.69 95.6 Minimum 0.2 1552 0.67 81.3 Maximum 1.0 1613 0.74 101.9 Standard Deviation 0.2 14.8 0.02 5.0 - 159 -Appendix B. Pullout Test Results 20 r 18 : 0 100 200 300 400 500 600 SP Displacement, x (mm) A x i a l P u l l o u t Res i s tance , Tes t 1 1 5 b a D 4.0 , _ 0.0 H • • • • , . 1 1 1 , , , u _ 0.0 1.0 2.0 3.0 4.0 Normalized S P Displacement, x/D N o r m a l i z e d A x i a l P u l l o u t Res i s tance , Tes t 1 1 5 b a D - 1 6 0 -Appendix B. Pullout Test Results 600 0 100 200 300 400 500 600 SP1 Displacement, x (mm) Displacements of Points Along Pipe Relative to Pipe Displacement, Test 115baD SG ahead of Tee - -* SG behind Tee 0 41 X X - A - • . * • Leading End Displacement * - 1 mm • • 2mm •* - 5 mm X 10 mm X - 20 mm • - 50 mm + • 75 mm • - 100 mm 200 mm 2000 1 , , , | , , 1—i 1 i i • 1 1 1 1 M 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 Distance From Front Edge of Test Chamber (mm) Pipe Strain Profile, Test 115baD - 161 -Appendix B. Pullout Test Results 527 mm Surveyed 514 mm N 224 mm Surveyed 511 mm 509 mm 250 mm Initial Location • Maximum Displacement S u r v e y e d L o c a t i o n s Be fo re a n d A f t e r T e s t i n g , Tes t 115baD - 1 6 2 -Appendix B. Pullout Test Results TEST 60BAD - 163 -Appendix B. Pullout Test Results Ckl 0 -Instrumentation Layout , Test 60baD - 1 6 4 -Appendix B. Pullout Test Results 1400 Density (kg/m ) Statistical Distr ibution of Density Test Results, Test 60baD Density Test Results, Test 60baD Probe Dry Relative Depth Elevation Density, p d , Void Density, est No. (mm) (mm) Test Location % Moisture kg/m1 Ratio, e 1 250 450 D2 1.4 1556 0.74 82.7 2 250 500 C.1 0.9 1577 0.71 90.0 3 250 500 B2 0.4 1601 0.69 98.0 4 250 450 A1 0.8 1603 0.68 98.6 5 250 550 D1 0.5 1619 0.67 103.8 6 250 500 D2 0.7 1611 0 63 101.3 7 200 600 C1 0 6 1623 0.66 105.1 8 200 550 C2 0.1 1604 0 63 99.0 9 200 600 B2 0.2 1609 0.68 100.6 10 200 600 A2 0.6 1578 0.71 90.3 11 250 600 A1 0.0 1572 0.72 88.3 12 200 550 B1 0 3 1603 0.68 98.6 13 250 650 D1 0.7 1585 0 70 92.7 14 200 700 D2 0.5 1609 0.68 100.6 15 200 750 C2 0 7 1621 0.67 104.5 16 200 700 C1 0.6 1613 0.67 101.9 17 200 700 E1 05 1624 0.66 105.4 18 200 750 B2 0 6 1578 0.71 90.3 19 200 750 A2 0.7 1614 0.67 102.2 20 200 700 A1 0.6 1628 0 66 106.7 21 200 850 D1 0.5 1607 0.68 100.0 22 200 900 C2 0 4 1610 0.68 100.9 23 200 900 B1 06 1598 0.69 97.0 24 200 900 A2 05 1614 0.67 102.2 25 200 950 D1 0.4 1614 067 102.2 26 200 950 D2 0.2 1614 067 102.2 27 200 950 C2 0.4 1612 0.67 101.6 28 200 1000 C1 0.3 1608 0.68 100.3 29 250 1000 B1 03 1612 0.67 101.6 30 200 1000 B2 0.5 1617 0.67 103.2 31 200 1000 A2 0.5 1624 0.66 105.4 32 200 1000 A1 0.5 1607 0.68 100.0 Average 0.5 1605 0.68 99 3 Minimum 0.0 1556 0.66 82.7 Maximum 1.4 1628 0.74 106.7 Standard Deviation 0.3 17.0 0.02 5.6 - 165 -Appendix B. Pullout Test Results 20 j 18 - : 16 -• _ 14 300 350 400 S P Displacement, x (mm) A x i a l P u l l o u t Res i s tance , Tes t 6 0 b a D 3.0 2.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Normalized SP Displacement, x/D N o r m a l i z e d A x i a l P u l l o u t Res i s tance , Tes t 6 0 b a D - 1 6 6 -Appendix B. Pullout Test Results 30C 250 £ 200 E •*-« c o 150 -E u ra a. t/> 100 -Q CL 50 -<n -50 Trunk Line Leading End Trunk Line Trailing End Branch 1 Axial Displ. Branch 2 Axial Displ. I 50 100 150 200 250 300 SP1 Displacement (mm) Disp l acemen t s o f Po in t s A l o n g P i p e R e l a t i v e to P i p e D i s p l a c e m e n t , Tes t 6 0 b a D -25000 -20000 c ' ro 10 o o J . c ' r o 55 •15000 H -10000 -5000 o 5000 E ra sz a to CD I -O X Leading End Displacement - •• - 1 mm - « - 2 mm - * - 5 mm X 10 mm - * - 20 mm - • - 50 mm - +- 75 mm - - - 100 mm - - - 200 mm - • • - 275 mm (max disp. • - * SG behind » . , » Tee * * • * - . * » v * 1 • t SG ahead of Tee 500 1000 1500 2000 2500 3000 3500 4000 Distance From Front Edge of Test Chamber (mm) 4500 o CD — U 5000 P i p e S t r a i n P r o f i l e , Tes t 6 0 b a D - 1 6 7 -Appendix B. Pullout Test Results 276 mm Surveyed 25 mm Surveyed 4 mm 2 mm -4.5 mm -0.7 mm Initial Location • Maximum Displacement S u r v e y e d L o c a t i o n s Be fo re a n d A f t e r T e s t i n g , Tes t 6 0 b a D - 168 -APPENDIX C PHOTOGRAPHS This appendix contains photographs o f the test chamber construction, test specimen preparation, mater ia l hand l ing procedures, and addi t ional details o f var ious components and aspects o f the research performed for this thesis. - 1 6 9 -Appendix C. Photographs Appendix C. Photographs Photo 3: Conveyor for Removing Sand V i a Access Panel Photo 4: Data Acquis i t ion System - 171 -Appendix C. Photographs Appendix C. Photographs Appendix C. Photographs Appendix C. Photographs Appendix C. Photographs Appendix C. Photographs Photo 15: Preliminary Strain Gauge Protection Technique (before test) and Modified Strain Gauge Protection Technique (after test) f' - y \ '&JfilhL*?~ •' V \ v * ! '. ;' * ,'',41 * > Jt •' '• f ^ ' ^ f • ~~-~*t Photo 16: Exposed Strain Gauge Following Failure of Strain Gauge Protection in Test in Medium-Loose Sand - 177-Appendix C. Photographs Appendix C. Photographs Appendix C. Photographs Photo 21: A e r i a l V iew of Tee Deformation in Direction of Pullout Fol lowing Test in Medium-Loose Sand Photo 22: Rotation of Branch Pipe Fol lowing Test in Medium-Loose Sand Indicated by Or ig ina l ly Ver t i ca l P in - 1 8 0 -Appendix C. Photographs Photo 24: Depressions Above and Behind Tees following Test of 115 m m T r u n k L i n e Branched Section in Dense Sand - 181 -Appendix C. Photographs Photo 25: Surface Deformation Above and In Front of First Branch Following Test of 115 mm Trunk Line Branched Section in Dense Sand Photo 26: Arial View of Surface Deformation Following Test of 115 mm Trunk Line Branched Section in Dense Sand - 182 -Appendix C. Photographs Photo 27: Branch Position Following Test of 115 mm Trunk Line Branched Section in Dense Sand Photo 28: Deformation of Branch Relative to Trunk Line Following est of 115 mm Trunk Line Branched Section in Dense Sand - 183 -Appendix C. Photographs Photo 30: Deformation of Tee Junct ion Fol lowing Test of 115 m m T r u n k L i n e Branched Section in Dense Sand - 1 8 4 -Appendix C. Photographs Photo 31: A r i a l V iew of Excavat ion of Fi rs t and Second Branches Fol lowing Test of Test of 115 m m T r u n k L ine Branched Section in Dense Sand Photo 32: Deformation of Second Tee Junct ion Fol lowing Test of 115 m m T r u n k L ine Branched Section in Dense Sand - 185 -Appendix C. Photographs Photo 33: Defromation of Second Branch Relative to T r u n k L ine Fol lowing Test of 115 m m T r u n k L ine Branched Section in Dense Sand Photo 34: A i r i a l V iew of F i r s t and Second Branch Positions Fol lowing Test of 115 m m T r u n k L i n e Branched Section in Dense Sand - 1 8 6 -Appendix C. Photographs Photo 35: Rotation of Tee Junction Relative to Soil Surface Following Test of 60 mm Trunk Line Branched Section in Medium-Loose Sand Photo 36: Rotation of Tee Following Test of 60 mm Trunk Line Branched Section in Medium-Loose Sand - 187-Appendix C. Photographs Photo 37: Deformation of Tee Fol lowing Test of 60 m m T r u n k L ine Branched Section in Medium-Loose Sand Photo 38: Rotation of Tee and Deformation of Branch Fol lowing Test of 60 m m T r u n k L i n e Branched Section in Medium-Loose Sand - 188 -
Thesis/Dissertation
eng
Civil Engineering
Vancouver : University of British Columbia Library
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
Graduate
Response of buried polyethylene natural gas pipelines subjected to lateral ground displacement
Text