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.

Oedometric compression and swelling behaviour of the Callovo-Oxfordian argillite

“…A further process of crack generation is suspected to occur during oedometric compression. Based on previous results obtained in sensitive soft clays [30][31][32] in which it appeared that compression occurred by the ordered collapse of pores, starting from the largest and progressively affecting smaller and smaller pores. This mechanism was confirmed by scanning electron microscope (SEM) observations that also showed that the elastic unloading rebound was due to the local swelling of the collapsed zones.…”

Microstructural-based approach to the interpretation of clays and transitional soils behaviour

“…For engineering analysis and design the soil mass is almost always treated as a continuum even though the soil is composed of discrete soil particles and particle groups (Mitchell & Soga, 2005). The development of the microstructure investigation of fine-grained soils started nearly five decades ago with the study of highly compressible and poorly resistant soils (Cerrolaza & Delage, 1997). From then on, many other studies and techniques on the investigation have been published and they are discussed in the following topics.…”