Application Of Strength Theory Of Unsaturated Expansive Soil To The Limit Analysis

The engineering properties and stability of unsaturated expansive soils are the important projects in the area of geotechnical engineering. The expansive soils not only have generality of clayey soils, but also have its special characteristics. The essential reason that the engineering properties of unsaturated soils are different from saturated soils is that unsaturated soils are under matrix suction. Matrix suction plays an important role in the controlling mechanics properties of unsaturated soils. But the tradictional saturated soil mechanics is unfit for unsaturated soil. The unsaturated soil strength theory should be applied to study expansive soils, but the acquired achievement of saturated soil theory isn't abandoned. This paper is based on the theory of unsaturated soils shear strength, the summation of the strength which is lead by matrix suction and effective cohesion intercept is total cohesion and this way is similar to the strength theory of saturated soils. Then the saturated soil stability analysis—slope stability analysis, ultimate bearing capacity, earth pressure already researched achievement is applied to deduce the basic formula of unsaturated soil stability analysis that think over the matrix suction. As the same time, hypothesing the matrix suction reduced to the ground-water table. The matrix suction influencing soil stability is related to the ground-water table. When the ground-water table is rather shallow, matrix suction light influence the analysis result, and saturated soils theory is able to analysis it. When the ground-water table is rather deep, matrix suction influence greatly the result, saturated soils theory is not applicable. Then the unsaturated soils theory must be adopted.