Stress-strain Behaviour of Remoulded Lias Clay

Abstract

This work is concerned with laboratory investigations of the
behaviour of remoulded Lias clay under different stress paths, Basic
mechanical properties of the soil were determined and were used in a
theoretical study of its stress-strain behaviour based on the strain-hardening
plasticity concept and time-dependent strains. Remoulded
samples of Lias clay were prepared in a specially developed 100 mm
diameter tall oedometer; triaxial and oedometer tests were carried
out on 70 mm diameter specimens. Stress-controlled tests were carried
out using a specially developed dead loading system in which corrections
could be made for change in cross-sectional area of the samples.

The results indicated that the initial mixing (preparation) water
content and the one-dimensional consolidation stress-history of the
soil affect its subsequent stress-strain behaviour: an increase of the
effective mean stress of the order of four times the original consolidation
stress is needed to eliminate the stress-history of the soil. The
void ratio - mean effective stress plots for isotropic and anisotropic
consolidation cases are parallel, and in the latter case approach the
state-of-failure line (C.V.R.) as the value of q/p increases. A linear
relationship between shear strains from drained and undrained compression
tests was obtained which, in conjunction with shear strains from constant
stress ratio tests could be used to predict shear strains for any stress
increment resulting in plastic strains. It was also found that plastic
strain increments and undrained stress paths (for isotropic and
anisotropic cases) were not predicted well by the Modified Cam-clay Model,
It was confirmed also that the plastic strain increment vector is
stress-path dependent; this implies that there is no unique plastic
potential surface for a given soil, but its shape is stress-path or
stress-history dependent.

Date of Award	1976
Original language	English
Awarding Institution	Aston University