Elasto-Viscoplastic Consolidation of a Diatomaceous Mudstone

Abstract

This paper discusses the consolidation behaviour of a diatomaceous mudstone, which is best featured as a naturally cemented material having a highly porous skeleton. Part I of the paper presents the results of isotropic consolidation tests as well as falling-head permeability tests, all of which were performed on undisturbed specimens of the mudstone by using a high-pressure triaxial cell. The principal findings include: ( 1) the mudstone exhibits distinct yielding when it straddles the pre-consolidation pressure; (2) the secondary compression is negligibly small before the initial yielding, but becomes very pronounced when loaded sensibly above the pre-consolidation pressure; and (3) the logarithm of the coefficient of permeability decreases linearly with decreasing void ratio. In part II of the paper, an associated series of coupled-stress flow analyses of the consolidation tests is performed in terms of the method of finite elements. An adapted version of the elasto-viscoplastic constitutive model (Sekiguchi, 1977) is implemented into the analysis procedure. The procedure of determining the constitutive parameters is described. It is then shown that the predicted performances compare favourably with the measured performances of consolidation in a consistent manner, thus validating the relevance of the elasto-viscoplastic formulation adopted.