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Numerical assessment of the effects of end-restraints and a pre-existing fissure on the interpretation of triaxial tests on stiff clays

Title: Numerical assessment of the effects of end-restraints and a pre-existing fissure on the interpretation of triaxial tests on stiff clays
Authors: Cui, W
Potts, DM
Pedro, AMG
Zdravkovic, L
Item Type: Journal Article
Abstract: Conventional laboratory triaxial tests apply axisymmetric boundary conditions to a cylindrical sample which has an axisymmetric geometry. For a homogeneous sample this implies that the deformed shape of the sample should maintain an axisymmetric geometry during the test. Consequently, the sample should deform in a barrelling mode and if slip planes develop they should define a cup and cone-like failure surface. However, in many triaxial tests such behaviour is not observed, especially as failure is approached when a planar slip surface develops. Such a deformation mode is not axisymmetric. One reason for this behaviour is that a fissure pre-exists in the sample. Employing hydro-mechanically coupled three-dimensional finite-element analyses, this paper investigates the influence of a single fissure in a triaxial sample of stiff clay on its behaviour throughout the test, focusing on the fissure position, orientation, strength and stiffness, in conjunction with the sample's end-restraints (rough or smooth). The effects are quantified in terms of the sample's overall stiffness and strength, indicating that the presence of a fissure can affect the very small strain stiffness, and that it has a significant effect on the strength of the sample, demonstrating that the conventional methods used to interpret laboratory tests may give unconservative results. The results also show a significant effect of the conditions at the top and bottom surfaces of the sample, where in particular the lateral restraint and rough ends introduce ‘bending’ in the sample.
Issue Date: 1-Sep-2021
Date of Acceptance: 12-Jun-2020
URI: http://hdl.handle.net/10044/1/79486
DOI: 10.1680/jgeot.19.P.318
ISSN: 0016-8505
Publisher: ICE Publishing
Start Page: 765
End Page: 780
Journal / Book Title: Geotechnique: international journal of soil mechanics
Volume: 71
Issue: 9
Copyright Statement: © 2020 ICE Publishing, all rights reserved. Original article available at https://doi.org/10.1680/jgeot.19.P.318. Permission is granted by ICE Publishing to print one copy for personal use. Any other use of these PDF files is subject to reprint fees.
Sponsor/Funder: Geotechnical Consulting Group LLP
Funder's Grant Number: CISM_P60087
Keywords: Geological & Geomatics Engineering
0905 Civil Engineering
0907 Environmental Engineering
0914 Resources Engineering and Extractive Metallurgy
Publication Status: Published
Online Publication Date: 2020-12-16
Appears in Collections:Civil and Environmental Engineering
Faculty of Engineering