The stress-strain behaviour of Bothkennar clay
This thesis describes the findings of an experimental and numerical investigation into the mechanical behaviour of a soft clay. Chapter 1 outlines the need for continued research on soft clay behaviour. The aims and objectives of the work are set out, as well as the structure of the research. The mechanical behaviour of soft clays has been reported by a large number of researchers and the findings of thee are considered in Chapter 2. A review of Bothkennar clay is given. Chapter 3 sets out the details of two constitutive models, whose purpose is to model the efforts of plastic anisotropy and destructuration. In Chapter 4 the experimental apparatus and procedures used in the testing programme are described. The majority of testing was carried out in triaxial cells and the arrangement of this equipment is detailed. In Chapter 5, the main experimental programme is described. Chapter 6 contains results from triaxial tests on vertically oriented samples. These tests include multi-stage stress path tests and standard drained shearing tests to failure. Triaxial tests on horizontally oriented samples are presented in Chapter 7. These provide a more generalized assessment of the role of anisotropy and destructuration, aided by the use of local strain measuring devices. In Chapter 8 tests results on both vertical and horizontal samples are compared with simulations from the constitutive model S-CLAY1 in order to assess how well this constitutive model predicts the stress-strain response of the soil, with particular respect to plastic anisotropy. Chapter 9 is concerned with the constitutive modelling of both plastic anisotropy and destructuration. In Chapter 10, it is concluded that the constitutive models introduced in Chapter 4 have provided considerably improved predictions of the mechanical behaviour of natural soft clays when compared to commonly used modelling techniques.