Preliminary study on engineering behaviors and water retention characteristics of expansive soil under influence of drying rate

Through adjusting the working parameters of temperature and humidity in the constant temperature and humidity equipments,the state variation of saturated expansive soil under different drying rates is achieved.The influences of the drying rates on shrinkage,strength and water retention characteristics of expensive soil are investigated,in which the shrinkage tests and the unsaturated triaxial tests are employed.The experimental results indicate that the coefficient of shrinkage increases as the drying rate decreases,and that the drying process is linear at the beginning and then becomes nonlinear.Moreover,the suction strength of unsaturated expansive soil increases as the drying rate decreases under the same water content,which is more prominent especially under the condition of low moisture content and confined pressure.Based on the expression of power function relationship between suction strength and suction,a bi-linear water retention curve is back-calculated from the coefficient of shrinkage and suction strength.It is found that the drop part of water retention characteristic curve tends to approximate parallel under various drying rates.The smaller the drying rates,the greater the air-entry value and suction.