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
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 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