Saturated cohesive soil contracts due to heating and due to the secondary compression without any change in temperature: thermal and time effects. In order to quantitatively assess an interrelationship between these two effects through experiments on a highly plastic bentonitic clay, one-dimensional consolidation tests were conducted with the temperature varied and held constant under a vertical pressure, and the thermal rate of compression and the rate of secondary compression were determined. One of conclusions is that heating the sample from 20 to 80°C may cause the decrease in void ratio corresponding to that to be caused by the secondary compression for about three hundred years at 20°C.
We encounter environments, which had never been experienced in the past, where the temperature in the subsoil is elevated. It is planned to emplace high or low level radioactive wastes below several tens of meters below the sediment surface in the deep sea oceans. Temperatures surrounding the waste canisters are expected to rise temporarily to 200°C, which will produce the deformation, leading to movements of canisters (Houston and Lin, 1987). In the on- or nearshore areas wastes have been disposed in many countries. Some wastes generate heat. Chemical piles used for the ground improvement also generate heat.
The volume of saturated cohesive soil under a constant load tends to decrease under elevated temperature. This phenomenon may be used for accelerating the consolidation process of soft soils. However, we have not developed methods or principles that predict how much change in temperature will reduce how long period of consolidation. With the objective to quantitatively interrelate thermal and time effects on the consolidation behavior of saturated soils, several kinds of cohesive soils were investigated (Shimizu and Kambe, 1997; Shimizu, 2003).