Study On The Stability Of Slope In Unsaturated Soil Affected By Rainfall Infiltration Based On Catastrophe Theory

A new method is proposed in this paper for analysis of the stability of slope in unsaturated soil affected by rain infiltration based on catastrophe theory, take into account that rainfall infiltration is one of the major factor causing the slope failure of unsaturated soil and the failure is usually abrupt. The unsaturated soil water movement formula is adopted for calculated the transient water content within the slope. With equilibrium method the stability of soil-nail bracing structure of unsaturated soil slope is analyzed considering the connection between the shear strength of unsaturated soil and water content. Genetic algorithm is introduced for searching the minimum factor of safety of natural slope and soil-nail bracing in unsaturated soil. The optimal course is automatically implemented with MATLAB. The cusp catastrophe model is established by means of the upper bound theorem of plastic limit theory. The characteristic formula of the failure of slope is also deduced. At last an engineering example is calculated with the two methods above-mentioned and the calculated results are approximate. This demonstrates that the methods adopted in this paper are valid and feasible. It also can be concluded that the environmental variations, for example rainfall infiltration that decreases the shear strength of unsaturated soil, are determinants for the failure of slope.