The object of this research programme was to investigate
the stability of a silty clay under undrained repeated loading.
Equipment has been designed and developed for the application of
a quasi-sinusoidal compressive load form to triaxial samples.
A series of monotonic strain controlled triaxial tests
with pore pressure measurement was performed on normally
consolidated and overconsolidated samples of saturated
reconstituted Keuper Marl. These tests defined the critical
state parameters, and hence the stable state boundary surface
for this soil, and provided a basis for a comparison with the
results of cyclic stress controlled triaxial tests.
Two series of cyclic triaxial compression tests were
performed: firstly, single stage tests using a constant level of
repeated stress; and secondly, multistage tests. These aimed to
investigate: a) stress conditions at failure under cyclic
loading; b) strength of non-failed samples after cyclic loading;
and c) strain and pore pressure behaviour under repeated
Criteria for the stability of a soil under cyclic loading are presented
and a model is developed based on the pore pressure behaviour of the soil under repeated loading. This model can be used to predict pore pressures and failure for normally consolidated and lightly overconsolidated soils.
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.