Study On The Stability Of Unsaturated Soil Slope With Porous Gas Effect Under Precipitation

Most slope soil mass is in unsaturated state,and the occurrence frequency of slope instability landslide induced by rainfall is the highest within practical engineering field worldwide.Unsaturated state is transformed into saturated for soil slope after precipitation,and the attraction force in matric of soil is decreased,thus reducing the shear strength for slope soil,eventually lead to the failure of unsaturated soil slope,the failure is serious.Therefore,study the unsaturated soil slope stability problem after the rainfall infiltration is of great significance.(1)The moisture content,cohesion and internal friction angle of the unsaturated soil sample collected directly from site were measured without any disturbing force.It is significant to look deep into the mechanism of the soil-slope stability in unsaturated-saturated after infiltration of rain.(2)It provides parameters for simulation about soil slope in the changing state of unsaturated-saturated under precipitation.The matric attraction and total-cohesion are substituted into the Mohr-Coulomb model based on the effective stress equation and shear strength equation of unsaturated soil,while the van Genuchten model was utilized to fit the soil-water characteristic curve(SWCC).The relation between unsaturated seepage coefficient and matric suction is established in the state of unsaturated-saturated seepage.The real-time update of unsaturated seepage coefficient in the unsaturated zone under the process of rain was realized with Fish language.Furthermore,numerical coupling analysis for unsaturated-saturated seepage and stability of unsaturated soil slope are finished.(3)According to gas escape of unsaturated soil slopes after rainfall and air cushion formation,counting pore gas escape location and air cushion formation location using Weibull distribution statistical analysis method to establish unsaturated-saturated seepage field in a soil slope with pore gas escape and seepage field with air cushion formation conditions respectively.Consequently,the seepage and stability of numerical coupling analysis considering gas influence on unsaturated soil slope can be executed.(4)The changes of parameters such as pore water pressure,shear strain increment,plastic zone and safety coefficient were summarized after coMParing the simulation results of the unsaturated soil slope without gas influence and that with gas(escape,air cushion)influence after rainfall,and the influence of the gas in the unsaturated soil slope affected by rainfall on the stability is analyzed quantitatively,so that the analysis results are clear and the results can provide references for the actual unsaturated soil slope engineering body.