Experiments on the internal stability of widely graded cohesionless soils
department or school: Applied Science, Faculty of
department or school: Civil Engineering, Department of
data provider: DSpace
degree campus: UBCV
creator: Moffat, Ricardo
issued: 2009-12-23T17:26:45Z
issued: 2005
related degree: Doctor of Philosophy - PhD
degree grantor: University of British Columbia
description: Internal instability of widely-graded cohesionless soils results from an inability to prevent loss of the finer particles in the presence of forces induced by seepage flow and, on occasion, vibration. Instability is governed by a combination of geometrical and hydromechanical constraints, and therefore largely controlled by soil type and seepage regime. Performance monitoring of embankment dams suggests the phenomenon is an important factor in the overall stability of these structures. A large permeameter test device was designed and commissioned to perform unidirectional seepage flow tests on four widely-graded cohesionless soils, all of which are potentially unstable. The objective was to assess the main hydromechanical factors that influence the onset of instability. A modified slurry mixing technique, with discrete deposition, was found satisfactory for reconstitution of homogeneous saturated test specimens. Test variables examined include hydraulic gradient, rate of increase in hydraulic gradient, flow direction, and vertical effective stress. The onset of internal instability was found to be triggered either by an increase in hydraulic gradient, or by a decrease in vertical effective stress. The relation between effective stress and hydraulic gradient, where the onset of instability occurs, is used to characterise a hydromechanical constraint to internal stability. Each soil yielded a hydromechanical boundary, and the difference between them is attributed to the shape of the grain size distribution of the soil and to the variation of vertical effective stress in the direction of flow where suffosion initiated. A limit-equilibrium approach is used to explain the experimental findings on hydromechanical constraints, based on a geometrical characterization of the gradation curve and for an assumed distribution of effective stress between coarser and finer fraction particles of the soil. Analysis of the experimental data established that the hydromechanical bounda…
aggregated CHO: https://circle.library.ubc.ca/rest/handle/2429/17146
note: EXPERIMENTS ON THE INTERNAL STABILITY OF WIDELY GRADED COHESIONLESS SOILS by RICARDO MOFFAT B.Sc, University de Chile, 1996 Civil Engineering, University of Chile, 1998 M.So, The University of British Columbia, 2002 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE STUDIES Civil Engineering THE UNIVERSITY OF BRITISH COLUMBIA June 2005 ©Ricardo Moffat, 2005. ABSTRACT Internal instability of widely-graded cohesionless soils results from an inability to prevent loss of the finer particles in the presence of forces induced by seepage flow and, on occasion, vibration. Instability is governed by a combination of geometrical and hydromechanical constraints, and therefore largely controlled by soil type and seepage regime. Performance monitoring of embankment dams suggests the phenomenon is an important factor in the overall stability of these structures. A large permeameter test device was designed and commissioned to perform unidirectional seepage flow tests on four widely-graded cohesionless soils, all of which are potentially unstable. The objective was to assess the main hydromechanical factors that influence the onset of instability. A modified slurry mixing technique, with discrete deposition, was found satisfactory for reconstitution of homogeneous saturated test specimens. Test variables examined include hydraulic gradient, rate of increase in hydraulic gradient, flow direction, and vertical effective stress. The onset of internal instability was found to be triggered either by an increase in hydraulic gradient, or by a decrease in vertical effective stress. The relation between effective stress and hydraulic gradient, where the onset of instability occurs, is used to characterise a hydromechanical constraint to internal stability. Each soil yielded a hydromechanical boundary, and the difference between them is attributed to the shape of the grain size distribution of the soil and to the v…
has type: Thesis/Dissertation
date issued: 2005-11
is shown at: 10.14288/1.0063322
language: eng
degree discipline: Civil Engineering
provider: Vancouver : University of British Columbia Library
publisher: University of British Columbia
rights: 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.
scholar level: Graduate
type: Text
identifier URI: http://hdl.handle.net/2429/17146