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An elasto‐viscoplastic model for diatomaceous mudstone and numerical simulation of compaction bands

It is well known that highly porous rocks under relatively high confining pressure succumb to volumetric compression with the emergence of the so‐called compaction bands. These normally occur as perpendicular or very slightly inclined deformation bands with respect to the direction of the most compressive principal stress. An experimental study of diatomaceous mudstone, a highly structured and porous soft rock, was conducted to demonstrate the existence of compaction bands in laboratory tests. In these tests, the local strain field on the specimen's face is determined by means of image analysis. The main objective of this paper is the numerical simulation of compaction bands in diatomaceous mudstone. First, an elasto‐viscoplastic model considering microstructural degradation is used to simulate the behavior of diatomaceous mudstone at the element test level. It has been found that such a model can accurately reproduce the stress–strain and dilatancy responses of diatomaceous mudstone. Then, a numerical analysis of a series of triaxial compression tests under drained conditions was carried out using the elasto‐viscoplastic model within the framework of Biot's theory for a two‐phase mixture. As a boundary problem, the triaxial tests were analyzed via finite elements with an updated Lagrangian formulation to simulate strain localization behavior under large deformations. The present study demonstrates that it is indeed possible to successfully simulate the experimentally observed compaction bands in diatomaceous mudstone. Copyright © 2010 John Wiley & Sons, Ltd.