Study On Limit Equilibrium Calculation Method For The Stability Of Transient Saturated Soil Slope

For analysis the stability of transient saturated soil slope due to rainfall infiltration,the un-stability mechanism of transient saturated soil slope due to rainfall infiltration was analyzed with the consideration of the influence of unit weight,matric suction and transient water pressure.the distribution of transient saturated area and transient water pressure in the slope under the rainfall conditions were analyzed based on the literature re search.Thro ugh the coefficient for the description of the transient water pressure distribution was defined,the distribution law of transient water pressure in transient saturation area was discovered and the corresponding mathematic descrption methods for transient saturation area was proposed.According the form of the sliding surface,a modification on limite equilibrium analysis method was made with the consideration whether the slope is situated at perched transient satuated area,including the method of Fellenius?simplified Bishop Method?simplified Janbu method.A routine which could search the both circular and non-circular type slice surface was programmed for the analysis of transient saturated slope's stability.The variation law of stability factor and sliding mechanism of perched transient saturated slope was studied:1.The research results show that the stability is mainly influenced by matric suction during the beginning of rainfall period because of the depth of transient saturated area is shallow.With the increase of the depth of transient saturated area,the main factor which controls the slope stability changes to transient water pressure in the slope,which result in the safety factor keep decrease.2.The safety factor and the depth of sliding surface of non-circular type are smaller than that of circular type by the increase of transient saturated area's depth at the same calculation conditions.Besides,the potential sliding surface of non-circular sliding mode becomes more and more shallow with the decrease of the depth of transient saturated area.but the depth of the circular sliding surface is reduce first and increase later.Therefore a shallow non-circular slice mode is easier generation in perched transient saturated slope.3.The safety factor of homogeneous slope and non-homogeneous slope keep the same change rule that become smaller when the transient saturated area maintain develop.but the safey factor of non-homogeneous slope is lower.The laws of the depth of sliding surface also keep the same rule.