Measurement and analysis of shrinkage stress of expansive soils during drying process

During the expansion process, the expansive soils will produce expansion stress and vice versa. Therefore, it is very significant to explore the change of the shrinkage stress of the expansive soils during drying. In order to investigate the relationship among internal shrinkage stress of expansive soils, water content and suction during the drying shrinkage process, a series of desiccation tests are conducted under different relative humidity conditions. In the tests, three slurry samples of the initial saturation are prepared and respectively placed in humidifiers with different over-saturated salt solutions and then dried at a constant temperature of 20℃. The change of water content is recorded in real-time. Additionally, the micropressure sensors are embedded in these samples to measure the change of the internal shrinkage stress during drying. The results show that: (1) The evaporation characteristics of soil water are different under different relative humidity conditions. For example, the smaller the relative humidity, the faster the soil water evaporates, and the lower the residual water content of the soils. (2) During the process of drying, the internal shrinkage stress in the soils shows obviously phasic variation. The shrinkage stress increase slowly in the early drying and then begins to increase sharply with drying when the time or soil water content reaches the critical value w_s or t_s, which decreases with the increase of evaporation rate. (3) After the evaporation, the shrinkage stress has a negative correlation with the environment relative humidity and has a positive correlation with the corresponding suction.