Study On The Influence Of Contact Characteristics Of Soil-rock Interface On Its Layered Seepage

Under the conditions of rainfall and groundwater level changes,the landslide moundbedrock contact surface will produce large shear deformation,making the mound-bedrock contact surface the dominant seepage channel for water movement and intensifying the landslide disaster process.As a typical soil-rock interface,the mound-bedrock contact surface needs further research on the evolution mechanism of the seepage characteristics of the soilrock interface under shear due to its complex interface contact characteristics and many factors influencing the dominant seepage characteristics.In this paper,based on the analysis of the soil-rock interface seepage characteristics and soil-rock contact seepage test methods at home and abroad,a new full set of soil-rock interface shear-flow test system is developed and constructed;the experimental study of soil-rock interface seepage characteristics is carried out,and the evolution of soil-rock interface non-linear seepage characteristics under the conditions of shear action and soil porosity change is analyzed;the finite element analysis method of soil-rock interface seepage stress coupling is adopted to investigate the evolution of soil-rock interface seepage characteristics under the conditions of shear action and soil porosity change.The main research works are as follows:(1)A new full set of soil-rock interface shear-percolation test system was constructed independently,including shear loading system,shear box and its sealing system,and seepage control and data acquisition system.And a new full set of sealed shear box was designed independently to solve the problem of sealing of the shear box when the line source unidirectional inflow seepage method is used;a shear-percolation test study of smooth rock interface was conducted to verify the reliability and applicability of this test system.(2)The soil-rock interface seepage characteristics were tested under the different shear displacement conditions,and the effect of shear on the nonlinear seepage characteristics of the soil-rock interface was analyzed based on the Izbash equation.The test results show that the relationship curve between hydraulic gradient and seepage volume at the soil-rock interface has an upward convex shape with obvious deviation from linearity;with the increase of shear displacement,the larger the overflow capacity of the interface,the more significant the nonlinear characteristics of seepage,and the equivalent hydraulic openness and apparent permeability increase nonlinearly.(3)An experimental study on the effect of soil porosity on the seepage characteristics of soil-rock interface was conducted to analyze the correlation between the hydraulic gradient of seepage at the soil-rock interface and the seepage volume under different soil porosity conditions.The experimental results show that the smaller the soil porosity,the lower the interface overflow capacity and the weaker the nonlinear characteristics of seepage,and the equivalent hydraulic openness and apparent permeability are decreasing nonlinearly with the decrease of soil porosity.(4)The finite element analysis method of soil-rock interface seepage stress coupling is used to study the change of soil-rock interface seepage characteristics under shear effect,and the mechanism of shear expansion effect and soil porosity on soil-rock interface seepage characteristics is analyzed.The results show that the shear action causes large shear expansion deformation near the soil-rock interface,the larger the shear displacement,the more significant the shear expansion effect,the larger the soil pore channel,and the shear action increases the hydraulic passability of the soil-rock interface,which in turn affects the nonlinear seepage characteristics of the soil-rock interface.