Effect of temperature on bentonite deformation

Takayama, Yusuke  ; Sato, Daisuke*; Sugita, Yutaka 

During the initial phases after closure of a high-level radioactive waste repository, the temperature of the buffer material will increase. Therefore, fundamental properties regarding the temperature dependence of bentonite, which is the main material of the buffer material, have been tested. The number of tests for the temperature dependence of displacement behavior is less than the number of tests for the temperature dependence of swelling pressure and permeability. In this paper, two tests were conducted using a consolidation test device that can control temperature conditions. One is a cyclic loading and unloading test under temperature conditions from room temperature to 80 C. The second is a temperature rise and fall test from room temperature to 80 C under stable loading condition. It was clarified that large deformations occur in the specimen under high temperature conditions, that the deformation associated with temperature changes is affected by the past stress path, and that irreversible deformation occurs under normal consolidation conditions.