American Society of Civil Engineers

Research on Deformation and Instability Characteristic of Expansive Soil Slope in Rainy Season

by Bingxu Wei, (Teacher, Changsha University of Science & Technology School of Highway Engineering E-mail: and Jianlong Zheng, (Teacher, Changsha University of Science & Technology School of Highway Engineering)
Section: Earth Retaining Walls and Slope Stability, pp. 226-236, (doi:

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Document type: Conference Proceeding Paper
Part of: Slope Stability, Retaining Walls, and Foundations: Selected Papers from the 2009 GeoHunan International Conference
Abstract: The analysis of the deformation and instability characteristic for the cutting slope in expansive soil during a rainy season by FLAC software is presented in this paper. The main conclusions are as follows: if the moisture content is increasing, Poisson ratio decreases with the increase of the depth in atmosphere influence zone, while elastic modulus, internal friction angle and cohesion increase on the contrary. However, the changing zone does not extend the atmosphere influence zone. By the moisture increment, horizontal displacement mainly concentrates on the surface because there is no constraint in horizontal direction on free face of the slope. The soil mass located at the toe of the slope reaches saturation state first, as the rainwater filtering into the slope aggregate, and further, to the toe-slope under gravity load, which on the one hand increase the soil bulk density, on the other hand reduce the soil strength after absorbing water. In addition, the shear stress is concentrated on the toe-slope. So slumps occur at the toe-slope first. When it happens, the support for upper slope decreased and the resistance of lateral swelling become weakened, which will cause sliding upwards again, finally engenders the imbricated surface shape.

ASCE Subject Headings:
Expansive soils
Slope stability
Computer software