Microstructure and volume change behaviour of soft clays: a boundary element simulation

Abstract

The relationship between the microstructure and the volume change behaviour of fine-grained soft soils is analysed by using a model derived from the experimental observation of the microstructure of soft clays, and the Boundary Element Method (BEM). The soil is modelled as a bidimensional porous matrix containing circular pores. The matrix is linear elastic and obeys a Tresca failure criterion, and the pore size distribution follows a Gaussian normal law. The pores are randomly located, with a minimum distance between them. Volume decrease during compression is due to the collapse of the pores. The collapse of a pore is activated once the stress state at the pore boundary calculated by the BEM is reaching the Tresca failure criterion, thus leading to a non-linear analysis process. An isotropic incremental loading test as well as a loading–unloading test are presented and discussed, showing that the model is able to reproduce properly the experimental volume change behaviour of soft clays and other porous geomaterials like chalk. Numerical results show that a macroscopic hardening elastoplastic behaviour could be obtained from a model elaborated from microstructure observation. © 1997 by John Wiley & Sons, Ltd.