Shear behaviour and stiffness of naturally cemented sands
type: CreativeWork
description: The behaviour of natural soils is highly influenced by structural features arising from their geological history and was recognised to lie outside current frameworks which account only for the stress-volume state of the soil. The objective of the research was to compare the shear behaviour and stiffness of two naturally cemented sands: a calcarenite with relatively low densities, weak particles and strong bonding and a silica sandstone with high densities, strong particles and weak bonding. Comparative studies were also undertaken on their corresponding reconstituted soils and on an artificially cemented carbonate sand. Testing was performed in stress path controlled triaxial systems over a wide range of confining pressures. Identification of the yield surface was found to be an essential feature to describe the shear behaviour of the soils examined. The determination of the yield points of such stiff soils required internal measurements of stresses and strains, with an accuracy higher than currently achieved in soil testing. For reliable determinations of stiffness and yielding the uniformity of strains in the samples had to be guaranteed. Therefore several parts of the equipment were redesigned or modified and new sample preparation and setting up procedures were developed. Comparison of results from natural and reconstituted soils showed that bonding increased the stiffness and the stress-strain linearity. For the naturally cemented sands the maximum shear modulus was found to vary with state only when the soils were sheared after isotropic yielding. Undrained loading-unloading probes showed that the linear behaviour was reversible and that plastic strains were accompanied by a progressive deterioration of bonding resulting initially in a reduction of the yield stresses and finally, after sufficient cycling in a decrease of the maximum shear modulus. The combined influence of bond strength and specific volume on yielding could be accounted for when normalizing th…
abstract: The behaviour of natural soils is highly influenced by structural features arising from their geological history and was recognised to lie outside current frameworks which account only for the stress-volume state of the soil. The objective of the research was to compare the shear behaviour and stiffness of two naturally cemented sands: a calcarenite with relatively low densities, weak particles and strong bonding and a silica sandstone with high densities, strong particles and weak bonding. Comparative studies were also undertaken on their corresponding reconstituted soils and on an artificially cemented carbonate sand. Testing was performed in stress path controlled triaxial systems over a wide range of confining pressures. Identification of the yield surface was found to be an essential feature to describe the shear behaviour of the soils examined. The determination of the yield points of such stiff soils required internal measurements of stresses and strains, with an accuracy higher than currently achieved in soil testing. For reliable determinations of stiffness and yielding the uniformity of strains in the samples had to be guaranteed. Therefore several parts of the equipment were redesigned or modified and new sample preparation and setting up procedures were developed. Comparison of results from natural and reconstituted soils showed that bonding increased the stiffness and the stress-strain linearity. For the naturally cemented sands the maximum shear modulus was found to vary with state only when the soils were sheared after isotropic yielding. Undrained loading-unloading probes showed that the linear behaviour was reversible and that plastic strains were accompanied by a progressive deterioration of bonding resulting initially in a reduction of the yield stresses and finally, after sufficient cycling in a decrease of the maximum shear modulus. The combined influence of bond strength and specific volume on yielding could be accounted for when normalizing th…
author: Cuccovillo, T.
keywords: TA Engineering (General). Civil engineering (General)
date published: 1995-12
date modified: 2026-07-24T01:39:04Z
provider: City University of London
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: City University London