Transient slope stability in unsaturated soils by the general limit equilibrium method with analytical solution for the water infiltration
Soil slope; limit equilibrium; transient flow; unsaturated soils; shear strength; computacional modelling
Slopes are soil structures present in the landscape, whether naturally or in man-made geotechnical constructions. Slope failure is usually related to the variation in the water content within the soil during hydrological events such as intense precipitations. Thus, the global stability analysis in unsaturated soil slopes is needed. The present study models the transient factor of safety for global stability in homogeneous and unsaturated soil slopes using the Bishop and GLE (General Limit Equilibrium) limit equilibrium methods. Also, a semi-analytical solution for the transient two-dimensional water flow applied to an unsaturated shear strength model was coupled to the limit equilibrium modeling. This model was implemented in the Wolfram programming language in the Mathematica software. It allowed parametric analyses for the factor of safety varying with time during water infiltration or drying events, applying different boundary conditions for the water content and the slope geometry. This model also allowed the analyses of other state variables such as suction and shear strength. The results of the present model were compared to the results obtained by the same inputs in the commercial software package GeoStudio (Seep/W e Slope/W), presenting consistency amongst themselves for the adopted hypotheses. Some differences between the software for the formulation and the results were explained. The computational tool developed in the Mathematica can be applied in the geotechnical engineering practice for case studies in unsaturated soil slopes, and it may be improved for more complex modeling hypotheses, for both water flow and stability.