Combined effects of strain rate and temperature on consolidation behavior of clayey soils

It is considered that the long term settlement of clay deposits, known as secondary consolidation, is caused by clay viscosity. In this paper, the viscous property of clayey soils is examined from two viewpoints: one is temperature and the other is the effect of the strain rate. To investigate these effects, a special constant rate of strain (CRS) loading test, in which the strain rate is changed during the test, was carried out at temperatures of 10 and 50 °C on reconstituted clay samples. Under the normal strain rate, such as the order of 10⁻⁶ s⁻¹, well-known temperature effects on the consolidation behavior were confirmed. That is, the high temperature condition leads to increased hydraulic conductivity due to the reduction in the viscosity of pore water at higher temperatures. It is also observed that the yield consolidation stress decreases with increasing temperature due to the viscous properties of soil skeletons. However, it is found that with higher temperature and smaller strain rates, the clay specimen does not follow conventional viscous behavior, like the Isotache model, but the gradient of stress–strain curve considerably decreases. The reason for different behavior from the Isotache model may be attributed to the creation of a new structure to resist the external deformation, under high temperature and a slow strain rate.