Infiltration Evolution Model And Dynamic Stability For Bedding Rock Slope With Soft Interlayer Under Rainfall

Rainfall-induced landslides exist widely in nature,and bedding rock landslide with weak interlayer is typical.The driving effect of rainfall seriously restricts its stability and is the key factor in inducing its instability.In the rainfall infiltration process,the soil water content in the moist area increases,which leads to the decrease of matric suction in the moist area,and then reduces the anti-sliding force of the slope.In addition,continuous and intense rainfall increases the hydrostatic pressure at trailing edges and sliding surfaces by rapidly elevating the water head in the crack.These two adverse effects reduce the stability of the slope.The infiltration of the soft interlayer involves inclined seepage,variable head seepage,and other seepage characteristics,such as seepage at the front edge and nonlinear layered distribution of water content in the moist zone.It is impossible to predict the rainfall infiltration process considering these infiltration characteristics based on the classical GA model and related modified models.However,the seepage evolution law and dynamic stability evolution process of bedding rock slope with soft interlayer under rainfall have always been a hot topic in geotechnical engineering and become a fundamental scientific problem to be solved urgently in the evaluation,prediction,and prevention of landslide stability.This thesis takes bedding rock slope with weak interlayer as the research object,takes rainfall infiltration evolution model and dynamic stability evolution mechanism as the core scientific issues,and adopts a comprehensive research method combining numerical simulation,theoretical analysis,and laboratory test.The spatial and temporal distribution law of water content in the soft interlayer of the slope,the variation law of water head in fracture,and the evolution mechanism of dynamic stability of slope are studied.The main innovative achievements are as follows:(1)The critical rainfall intensity indexes corresponding to different infiltration modes were proposed,and three kinds of rainfall infiltration models were established to accurately predict the length of the wetting zone,water pressure,and the spatial and temporal distribution of fracture heads in different infiltration modes.The classical GA and related modified models are widely used to analyze the seepage law of vertical soil or inclined soil slope.However,no infiltration model has been found for bedding rock slope with soft interlayer,and the dynamic stability analysis method based on the infiltration model has not been established.In this thesis,three typical infiltration models are established by means of numerical tests and theoretical analysis.The unsaturated steady-state infiltration analytical model can accurately predict the matric suction and volumetric water content of soft interlayer at any position.The length of the layered wetting zone and the spatial and temporal evolution of the water head of the fissure in slope can be predicted by the semi-analytical model of unsaturated and saturated infiltration.The saturated infiltration analytical model can accurately predict the spatial and temporal evolution characteristics of water head height in fractures under different rainfall-driven conditions.(2)The stability calculation method based on the dynamic hydraulic model was established to calculate the dynamic stability coefficient of bedding slope with soft interlayer in the whole rainfall infiltration process.Based on the derived analytical and semi-analytical models,the relevant dynamic hydraulic models were established,and based on the dynamic hydraulic action models,two kinds of dynamic stability calculation methods for bedding slopes with soft interlayers were developed.Based on the proposed calculation method,the dynamic stability coefficient of slope in the whole process of rainfall infiltration was accurately predicted.(3)Two landslide types of bedding rock slope with soft interlayer under the action of rainfall are proposed,the mechanical of landslide instability was revealed,and the critical rainfall index under the condition of critical slope instability was proposed.Two types of landslides are found in the evolution process of slope dynamic stability coefficient under rainfall.The matric suction of the soft interlayer decreases gradually during unsaturated infiltration.When the overall sliding force of the sliding surface is greater than the anti-sliding force,the slope will fail.In the process of unsaturated and saturated infiltration or saturated infiltration,the matric suction decreases while the hydrostatic pressure increases on the fissure and sliding surface.Under the combined action of these two aspects,the slope will cause failure when the overall sliding force of the sliding surface is greater than the anti-sliding force.