UBC Theses and Dissertations
In-situ testing of soil with emphasis on its application to liquefaction assessment Robertson, Peter Kay
The major objective of this research was to advance the state of the art in interpretation and application of results from in-situ testing of soil, in particular the Cone Penetration Test (CPT), the Self-boring Pressuremeter Test (SBPMT) and the Flat Plate Dilatometer Test (DMT). This study critically examines the equipment, field procedures and methods of test interpretation so that improvements can be made in their application to field liquefaction assessment. Improvements to in-situ test equipment and procedures are proposed. Improvements for the interpretation of CPT data in sands for evaluating relative density, friction angle and modulus are made. A method for prediction of deformation characteristics of clay from CPT data is proposed by incorporating the influence of soil stiffness. A correlation between cyclic stress ratio to cause liquefaction (10 percent double amplitude shear strain) and cone penetration resistance is proposed for sands and silty sands. The proposed CPT liquefaction correlation is substantiated using data from B.C., Japan, China and U.S.A. and appears to represent a good lower bound. The addition of continuous pore pressure measurements during cone penetration is shown to significantly improve the interpretation of the CPT. Data is also presented that clarifies the correlation between the Standard Penetration Test (SPT) and the CPT. Improvements are suggested for the interpretation of SBPMT data in sands for friction angle and modulus. These improvements are applied to the assessment of liquefaction resistance using the SBPMT. New correlations are proposed for estimating the relative density and liquefaction resistance of sand using the results from DMT. A field and laboratory study is carried out to evaluate existing and proposed methods of interpretation of in-situ tests and their application to the assessment of liquefaction resistance. In general the proposed new correlations produce good results, although further field verification is required.
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