Using Water-Air-Solid Three-phase Coupling Model To Analyze The Unsaturated Soil Slope Stability During Rainfall Infiltration

Generally,most soil slope failures are induced by rainfall infiltration.It often just only considers the effect of seepage field in the earlier research on slope stability under the condition of rainfall infiltration problem.While in fact,rainfall infiltration to the unsaturated soil will be accompanied by the process of the groundwater of the wetting front advance,the change of pore air pressure and stress field,meanwhile,the change of the seepage field will lead to the change of the stress field,in turn,the deformation caused by the changing stress field will also result in the change of seepage field,which is the interaction between the water-air two-phase fluid flow and solid deformation.So considering the coupled effect of seepage filed and stress field will be more tally with the actual situation when analyzing the effect of rainfall infiltration to the unsaturated soil slope stability.In this study,the loose coupling method by using TOUGH2 and FLAC3 D software is used to built the liquid-gas-solid three-phase coupling model.The specific process is as follows: Firstly,building the water-air two-phase fluid flow model by using TOUGH2,a computer code for multiphase multi component non isothermal flow in three-dimensional porous and fractured media,and setting up the deformation of solid skeleton mechanics model by using FLAC3 D,an explicit finite differences program for scientific engineering calculations in three dimensions.Finally,write the coupled program via FISH language built-in FLAC3 D.Verify the validity of the coupled model by using sand column drainage experiment results.Using water-air-solid three-phase coupling model to analyze an unsaturated soil slope stability when rainfall infiltrating.Then the safety factor of a given slip surface considering both water-air two-phase seepage and stresses field was calculated,and then studied the effects on the safety factor in detail.Meanwhile,sensitivity analysis of the slope stability was carried out primarily by analyzing the constitutive relation of mechanical behavior.