Analysis On The Slope Stability Of Expansive Soils

Slope stability of expansive soil has been researched adequately, but there are few literatures considering the influence of expansibility on slope safety factor. The slope stability of expansive soil is researched with limiting equilibrium method in this thesis. The Generalized Limit Equilibrium(GLE) method is used to deduce the safety factor Fs of expansive soil slope considering expansibility. Then the slope is analyzed with GEO-SLOPE software considering different ratio and other factors, so that the influence of expansibility on slope safety factor can be found.Because of the effect of climate, some cracks appear in the shallow layer of natural expansive soil slope, excavation expansive soil slope and filling expansive soil slope. The integrality of soil is destroyed, meanwhile the water can infiltrate expediently. When a great lot of water infiltrate into the soil, expansive force is produced. The soil intensity is reduced seriously, then the weak part aside the cracks is destroyed. The pull-type breakage appear if the cracks appear on the top slope and imbricate breakage appear if on the toe slope. Finally, the whole slope is demolished.Through routing soil mechanics test, such as expansibility test and direct shear test, the quantitative relation between the biggest expansibility and water content of compacted expansive soil is studied, and the expansibility is provided for limiting equilibrium calculation. Meanwhile, the intension decaying law of compacted expansive soil with the increasing of water content is discussed, and the intension index for stability calculation of different type expansive soil slope is provided.The safety factor formula is deduced considering expansive force based on existing limiting equilibrium formula. According to GLE method whoseboundary condition is changed, the iterative formula of safety factor is gaved. Then according to the test result, the slope stability of expansive soil is analysed using GEO-SLOPE. The influence of expansibility on slope safety factor is gaved.Finally, according to the calculating result of expansive soil slope, the stress of coast slices is analysed, which can be referenced for the calculation of expansive soil slope fence.