Influence of sand content on the non-linear creep and swelling behavior of bentonite in oedometric condition

The time-dependent feature of clayey soils has gained concern worldwide. Due to its highly absorbent nature, the bentonite obviously demonstrates both creep and swelling phenomena. This paper presents experimental results from one-dimensional oedometer consolidation tests on undisturbed sand mixed bentonite (SMB) specimens. These specimens had sand proportion of 50%, 60% and 70%, respectively. Multistage oedometer tests with loading, unloading and reloading were done on these specimens with a long duration in order to investigate the time-dependent creep and swelling behavior. The prime objective of this paper is to examine the influence of the sand content on the time-dependent creep and swelling behavior of the SMB under 1-D consolidation and to gain a better understanding of the behavior of the natural undisturbed bentonite. In the 1-D creep and swelling tests, the non-linear creep behavior as well as the swelling behavior has been investigated. Distinct non-linear creep behavior has been observed for the undisturbed SMB during the oedometer tests. Results and related analysis are presented in this paper. The ratio of secondary compression index over compression index, C α/C c, is found to vary with vertical effective stresses and time. Moreover, sand content exerts an indispensible impact on creep behavior. Finally, the non-linear creep function proposed by Yin (1999) originally for the remoulded HKMD has been adopted and modified to simulate the non-linear creep behavior of the SMB. Influences of sand content on parameters in an Elastic Visco-Plastic (EVP) model are also investigated. The EVP model is used to simulate the time-dependent behavior. It is found that the modeling results are in excellent agreement with data of tests on SMB.