Characteristics of Shear Strength of Unsaturated Weak Expansive Soil

Abstract

The strength properties of unsaturated soil are far more complicated than those of saturated soil. As a kind of typical and widely spread unsaturated soil, expansive clay shows a very close relationship between its shear strength and water content, for its high content of hydrophile, such as montmorillonite, illite and etc. The shear strength of soil is of much significance in the design of foundation and slope in expensive soil area. The determination of shear strength for expensive soil is always an important issue in this aspect. Based on the investigation of expansive clay in a slope along Han-Shi highway, Hubei Provence, some unsaturated shear tests with suction control have been conducted, and then, unsaturated mechanical parameters have been obtained using double-variables strength theory, and characteristics of the unsaturated shear strength of the specimen have been explored. Results indicate that slight shear dilatation appeared during the unsaturated shearing course and its value decreases with the increase of confining pressure and suction. For lower suction, the cohesion of the tested soil specimen linearly increases with suction increases. The shear coefficient for testing specimen is 10.7°.