| Most soil in nature is unsaturated.Rainfall infiltration will lead to the increase of soil water content.Increasing water content will lead to the reduction of shear strength parameters of unsaturated soil on the one hand,on the other hand,the negative value of pore water pressure will increase gradually,even the pore water pressure has positive pore water pressure;at the same time,the original pore is squeezed.The air in the gap leads to the increase of gas pressure in the soil slope and the decrease of the matrix suction,which leads to the reduction of the shear strength of unsaturated soil,and the unsaturated soil slope is easy to be unstable at this time.The process of rainfall infiltration is the process of water and gas two-phase flow through infiltration and replacement of air in soil slope.It is necessary to accurately analyze the influence of rainfall infiltration on the stability of unsaturated soil slope.First,the change of seepage field of soil slope caused by rainfall infiltration,that is,pore pressure,pore water pressure,and water pressure caused by rainfall infiltration,should be analyzed.The variation of matrix suction,internal friction angle,cohesion and moisture content is taken into account in the stability analysis of soil slopes.The main contents and achievements of this paper are as follows:(1)According to the experimental research of Wang et al.Combined with the stress analysis of the internal pressure in the soil,a modified formula for the gas breakthrough pressure in this paper is proposed.The formula of the modified calculation formula of the gas breakthrough pressure is verified by the experimental results of Grismer et al.(2)Grismer and others believe that the pressure of the gas is stable on this critical value after the gas breakthrough,but the infiltration time and infiltration depth of the rain water are short,and the pressure is doubtful about whether the pressure is stable when the infiltration time is long enough.In this paper,through the coupling of SEEP/W and AIR/W module,the change law of pore gas pressure and pore water pressure in rainfall infiltration is simulated and analyzed.According to the simulation results,the function relation between the wetting peak depth and the gas breakthrough pressure is fitted and the result is compared with the proposed theoretical formula.It shows that the fitting is very good with the theoretical formula,which shows that the pressure will continue to increase with the wet peak and not keep stable when the time is long enough and the infiltration depth is large enough.(3)The stability of large area shallow slope under the condition of rainfall infiltration is analyzed.The result shows that the existence of closed pressure in the same wetting depth of infiltration obviously reduces the safety factor of the slope.Combined with SEEP/W module,AIR/W module and SIOPE/W module,the influence of closed air pressure on slope stability is studied.The results show that the existence of closed pressure can impede the movement of the humid peak and postpone the occurrence of the landslide.At the same time,the existence of closed pressure can reduce the safety factor of the slope under the condition of the same depth of the wetting peak.It shows that the gas pressure in the early stage of rainfall infiltration has a hindrance to the occurrence of landslides,but when the rainfall time is long enough and the depth of the rain infiltration is very large,the existence of the pressure force will reduce the safety factor of the slope. |
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