EVALUATION OF SHEAR STRENGTH OF UNSATURATED LOESS USING CONVENTIONAL DIRECT SHEAR TEST

In order to investigate the simplified method for evaluating the shear strength of unsaturated loess, we conduct a series of conventional consolidated quick shear test and the suction test before consolidation as well as after shearing using filter paper method. The data is validated by unsaturated direct shear test. Then we discuss the variation of initial suction and shear suction under normal stress. The research shows that air entry value and residual value of the soil-water characteristic curve control the change of dry density and water content within consolidating. Based on the Vanapalli's model, a simple method to predict the shear strength of loess is gained. The proposed model using the initial soil-water characteristic curve, effective cohesion and effective internal friction angle of soil simplifies the procedure and time of shear strength measurement for unsaturated soil. The model provides a novel technique for the application of unsaturated shear strength theory in engineering practice.