Thermomechanical Creep in Sensitive Clays

Abstract

A systematic series of temperature-controlled oedometer tests on intact and remolded samples of sensitive clay from two depths has been performed. The focus is on studying the temperature effects on the emerging creep rate for a relatively small temperature range, that is, 5°C–25°C, during incremental heating and decremental cooling tests with steps of 5°C. An efficient testing scheme has been developed that exploits the simultaneous testing of several samples. Furthermore, the testing scheme is designed such that no excess pore pressures are generated in the samples during temperature change. The creep rate for intact samples proved to be very sensitive to a temperature change, with the largest effects found for stress levels above the apparent preconsolidation pressure. Heating increments showed larger increases in creep rate than cooling decrements. Both, however, led to a significant change of creep rate in the intact clay samples. In contrast, the reference tests on remolded samples of the same clay that were reconstituted to the in-situ stress state did not show much sensitivity to temperature change. The latter leads to the conclusion that the significant thermal creep triggered in sensitive clays is primarily an effect of the apparent bonding of the natural clay.