Numerical Analysis for Shallow Landslides of Expansive Soil Slopes Based on Three Fields Coupling

To revealing the reasons for shallow landslides of expansive soil slopes, in reference to the existing calculation ways of multifield-coupling numerical analysis, the seepage processes from unsaturation to saturation in expansive soil slopes and hygroscopic expansion processes were simulated by the two-phase flow module and thermal module of the finite difference software FLAC^2D;based on the transformation relations for saturation degrees, temperatures and thermal expansion coefficients of expansive soil and integrating and extracting the information from both of the modules simultaneously, the hygroscopic expansion effect of expansive soil was simulated in time;the three fields involving the seepage field, displacement field and stress field were coupled under consideration for the changes of groundwater levels and permeability coefficients and intensity attenuation. And then, the numerical model with or without expansive deformation was constructed. The seepage processes from unsaturation to saturation in slopes considered and not considered the hygroscopic expansion during rainfall and the stability of slopes were simulated individually;the difference of seepage fields and slopes stability between considering and not considering the hygroscopic expansion effect in the same rainfall intensities but different rainfall duration was contrasted and analyzed. The important reason caused shallow landslides of expansive soil slopes was revealed, it was hygroscopic expansion of expansive soil. Furthermore, the stability of expansive soil slopes under different rainfall intensities and durations was further studied, the variation and distribution of the seepage field and stress field in slopes were compared and analyzed at the same time, and the effects of different rainfall conditions on shallow landslides were obtained.