Quantifying soil characteristics using state of the art equipments is a necessary step in
introducing comprehensive constitutive models which can be used in engineering
design. Large areas of the Southern UK are covered by Triassic to Eocene mudrocks
that were deposited in dissimilar geological environments, and have experienced
diverse post depositional histories leading to a range of current natural structures. The
aim of this study was to investigate different aspects of the mudrock’s structure and
their implication on the mechanical behaviour of these soils.
Three mudrocks were chosen and sampled; Oxford, Kimmeridge and Gault Clays.
These were to be compared with London Clay which was previously studied at
Imperial College by Gasparre (2005), Nishimura (2006) and Minh (2007). High
quality block and rotary core samples obtained for these soils were used in two
experimental studies carried out by the author and Brosse (2011) as well as for a
micro-structure analysis performed by Wilkinson (2011). The author carried out series
of tests using triaxial apparatus equipped with bender elements and high resolution
displacement transducers. These tests provided the strength envelopes of each soil,
undrained stiffness and drained elastic parameters. Oedometer cells were also used to
investigate the 1-D compression of each material. These were complimented by ring
shear tests and index tests performed on all four mudrocks.
Findings of this study highlighted the highly anisotropic behaviour of these soils. No
clear correlation was found to relate the anisotropy or any other characteristics of
these materials to their geological age or their depth of burial. For Gault Clay, the
effects of weathering and root action were investigated and the importance of highly
fissured macro-structure of the soils was noted. The results from this study are in
good agreement with those from tests carried out by Brosse (2011) using a hollow
cylinder apparatus and the micro-analysis carried out by Wilkinson (2011).