Microstructural evolution of remolded clay related to creep

Abstract

The aim of this study is to understand the local mechanisms related to creep behavior of a typical clay under triaxial loading. The investigation concerns both normally consolidated and overconsolidated specimens of remolded kaolin clay. The macroscopic results showed that both dilatancy and contractancy could occur during creep depending mainly on the clay behavior prior to the creep test. The magnitude of the dilatancy/contractancy was controlled by the stress level, on one hand, and by the overconsolidation ratio which governed the sign of the volumetric strain variation during triaxial loading, on the other hand. At the microscopic scale, the dilatancy/contractancy phenomena were analyzed using the scanning electron microscopy (SEM). The results indicated that the microstructural evolution of the clay along mechanical loading depended on the stress history. The structural evolution during the creep phases followed the structural pattern developed under monotonic loading. The creep dilatancy phenomenon appeared strongly related to the expansion of micro pores and micro cracks within the overconsolidated clay specimens.