A New Concept of Residual-State Creep Test to Understand the Creeping Behavior of Clayey Soils

Abstract

Many researchers have studied creeping behaviour of clayey soils in the laboratory using both oedometer and triaxial tests; however in most cases, they have only concentrated on the pre-peak creep behaviour of soil, which does not adequately explain the creep movement that undergo large displacements at close-to-residual state of shear. This necessitates the importance of further studying creep behaviour of clayey soils in residual-state of shear. In order to investigate creep behaviour of clayey soils, a new concept of residual-state creep test in a modified torsional ring shear machine is developed in laboratory, which can simulate the creeping displacement behaviour of clayey soils. Representative clayey soils, which have higher percentage of Smectite, Chlorite, Mica and commercially available Kaolin clay, are taken in this study. A series of residual-state creep test (i.e. seven tests) with varying applied constant shear stress for each sample were conducted, the results thus obtained are interpreted in terms of Residual-State Creep Stress Ratio (RCSR), at which the soil samples fail at their residual-state of shear. The term RCSR is the ratio of applied constant shear stress with residual strength. The test results show that when RCSR ≤1, the clayey soil does not show creeping behavior where as the soil undergo creeping behavior when RCSR>1. This paper mainly focus on the methods of residual-state creep test, its implications for the study of creeping displacement behavior of clayey soils.