Shrinkage and desiccation cracking process of expansive soil and its temperature-dependent behaviour

During drying, expansive soil shrinks and induces desiccation cracks on surface due to water evaporation. The presence of cracks significantly weakens soil structure and stability, and results in various engineering problems. Better understanding the processes of shrinkage and desiccation cracking is essential in analyzing drought effects on buildings constructed on expansive soil. As temperature is one of the most important external factors that control the hydro-mechanical behaviour, desiccation tests are therefore conducted on initially saturated expansive soil slurry to investigate the temperature effects on shrinkage and cracking characteristics. Nine specimens are prepared and dried under 22°C, 60°C and 105°C respectively. Water loss and surface crack evolution are monitored during the whole drying period. The image processing technique is employed to quantitatively characterize the crack pattern, and surface crack ratio R_sc is determined to describe surface cracking extent. In addition, the filling method is used to measure the crack volume by using pure sands. It is found that the initial evaporation rate of soil water is constant and increases with increasing temperature; the drying period that needs to reach the residual water content decreases with increasing temperature; and the initial critical water content w_IC at the onset of cracking is significantly influenced by temperature as temperature increases from 22 to 105 °C, w_IC increases from 38.0 to 90.9%. After crack initiation, it is found that the ratio R_sc increases slowly at the beginning stage, and then increases quickly even when water content decreases slightly. However, as the water content reaches the final critical water content w_FC or shrinkage limit, R_sc gradually reaches stabilization, and the effect of temperature on w_FC is insignificant. The experimental results also show that the desiccation cracking behaviour of expansive soil significantly depends on environmental temperature; in general, the higher the temperature, the more the development of cracks on specimen surface.