Study On The Mechanism Of Infiltration Failure Of Double-slip Zone Landslides Under The Combined Action Of Rainfall And Reservoir Water Level

After the completion of large-scale water conservancy projects,landslide disasters are particularly serious,and previous studies mostly focus on simple landslides with single-layer slip belts,and less research on complex landslides with double-layer slip belts.Taking Majiagou,a typical landslide in the Three Gorges Reservoir area,as the research object,this paper constructs a landslide calculation model with shallow slip belt,deep slip belt and double-layer slide belt,and uses the SEEP/W module in GEO-STUDIO software to analyze the seepage field change law of landslide under the combined action of rainfall,rainfall and reservoir water level drop,and then imports the results of the seepage field into SLOPE/W and SIGMA/W to study and analyze the seepage field of the double-layer slip zone landslide under the action of rainfall and reservoir water level.The variation law of safety factor and its relationship with rainfall intensity and reservoir water level decline rate,as well as the deformation law of displacement field.The study found that:The numerical simulation results of typical landslides under the combined effects of rainfall,rainfall and reservoir water level can find the following rules:(1)Under rainfall conditions:(1)The seepage line of the landslide model with only shallow slide zone keeps rising,and the pore water pressure keeps increasing,while the soak line of the model with only deep slide zone keeps falling;(2)With the occurrence of rainfall,the slope surfaces of the three landslide models all have a sliding tendency,and the front of the slip belt at the foot of the slope has a downward sliding trend.The front of the slip zone at the foot of the slope has a downward sliding trend,and the deformation area of the landslide model with only the shallow slip zone is the largest,while the deformation area of the model with the deep slip zone is the smallest;(3)The change range of safety factor of the landslide model with only shallow slide zone is the most obvious,and the change range of safety factor of the model with only deep slide zone is the smallest.(2)Under the combined effect of rainfall and reservoir water level:(1)The seepage line of the upper slide mass in the landslide model with only shallow slide zone has been decreasing,and the seepage line of the middle slide mass has risen first and then declined,while the seepage line of the landslide model with only deep slide zone has been falling;(2)With the change of rainfall and water level,reservoir water has a greater impact on the landslide.The displacement of the front edge of the three landslide models is greater than that of the rear edge;(3)The landslide model with shallow slip zone is more likely to be unstable,the safety factor of the landslide model with shallow slide zone has the largest variation range,and the model with deep slide zone has the smallest variation range of safety factor.Taking Majiagou landslide as the research object,comparative analysis can find the interaction law between the shallow slide zone and the deep slide zone,and at the same time,At the same time,a detailed study and analysis of the seepage field,safety factor and displacement field of the double-layer sliding belt landslide under different reservoir water level drop rates(0.5m/d,0.8m/d,1.2m/d)and different rainfall conditions(0.03m/d、0.05m/d、0.08m/d):(1)Since the shallow slip zone is closer to the surface,the influence of rainfall and reservoir water level changes on the shallow slip zone is greater than that of the deep slip zone,the model with shallow slip zone has a relatively fast rainfall infiltration speed,pore water pressure and infiltration line change are more obvious,the safety factor changes are large,and the shallow slip belt is unstable under each simulated working condition,and the deformation area is large.(2)The deep slip belt weakens the infiltration velocity of rainwater,which makes the wetting line of the landslide body lag,and the pore water pressure and wetting line change amplitude of the landslide model with double slip belt are weaker than those of the model containing shallow slip belt alone,which weakens the safety factor reduction range of shallow slip belt.After the end of the working condition,the safety factor of the model with a single deep slip belt is 1.148,and the deformation area is the smallest,while the safety factor of the deep slip belt model of the double-layer slip belt slide is 1.067,which can be concluded that the shallow slip belt accelerates the slippage of the deep slip belt.(3)The stability of landslide is related to the rainfall intensity and the decline rate of reservoir water level,the greater the rainfall intensity,the greater the decline rate of reservoir water level,the more obvious the hysteresis of the infiltration line,the increase in the amplitude of safety factor,and the more prone to landslides.