Uniqueness of rate-dependency, creep and stress relaxation behaviors for soft clays

ZHU Qi-yin(朱启银)^{1, 2}, YIN Zhen-yu(尹振宇)^{1, 3}, XU Chang-jie(徐长节)⁴, YIN Jian-hua(殷建华)⁵, XIA Xiao-he(夏小和)¹

(1. Department of Civil Engineering, Shanghai Jiao Tong University, Shanghai 200240, China;
2. State Key Laboratory for Geomechanics and Deep Underground Engineering
(China University of Mining and Technology), Xuzhou 221116, China;
3. Lunan University, Ecole Centrale de Nantes, UMR CNRS GeM, Nantes, France;
4. School of Civil Engineering and Architecture Departments,
East China Jiaotong University, Nanchang 330013, China;
5. Department of Civil and Environmental Engineering, Hong Kong Polytechnic University, Hong Kong, China)

Abstract:This work focuses on the uniqueness of rate-dependency, creep and stress relaxation behaviors for soft clays under one-dimensional condition. An elasto-viscoplastic model is briefly introduced based on the rate-dependency of preconsolidation pressure. By comparing the rate-dependency formulation with the creep based formulation, the relationship between rate-dependency and creep behaviors is firstly described. The rate-dependency based formulation is then extended to derive an analytical solution for the stress relaxation behavior with defining a stress relaxation coefficient. Based on this, the relationship between the rate-dependency coefficient and the stress relaxation coefficient is derived. Therefore, the uniqueness between behaviors of rate-dependency, creep and stress relaxation with their key parameters is obtained. The uniqueness is finally validated by comparing the simulated rate-dependency of preconsolidation pressure, the estimated values of secondary compression coefficient and simulations of stress relaxation tests with test results on both reconstituted Illite and Berthierville clay.

Key words:soft clays; creep; rate-dependency; stress relaxation; oedometer test