Research On Instability Characteristics Of Root Soil Composite Slope Caused By Rainfall

The vegetation slope protection technology reinforces the soil through the additional cohesion produced by the root system to the soil,reduces the pore water pressure of the slope,and enhances the slope resistance to damage.To this end,this thesis aims at the current deficiencies in the research on the effect of vegetation roots on soil slope reinforcement,proposes a research plan for the instability characteristics of root-soil composite slopes under rainfall events,and carries out physical model tests and numerical simulations of rainfall-induced root-soil composite slope instability The simulation study compares the instability of the root-soil composite slope under different working conditions,and quantitatively analyzes the effect of the root reinforcement of the soil slope,which provides a scientific basis for the design of vegetation slope protection.The paper has mainly achieved the following results:(1)Combining root soil laboratory tests and theoretical models to select dominant slope protection vegetationAccording to the studied mechanical performance parameters of single roots of herbaceous vegetation and the basic physical and mechanical parameters of the experimental soil,and based on the classic WU model theory,the increase in shear strength of the root system to the soil is obtained.The test results show that: for the same vegetation type,the deformation characteristics of a single root are not significantly related to the root diameter,but the tensile performance of a single root is affected by the root diameter.The root diameter-tensile strength/tensile strength has a power function relationship,and the tensile strength varies with The root diameter increases,the tensile strength decreases with the increase of root diameter,and the root system of Zoysia japonica increases the soil shear strength the most,providing accurate parameters for physical model tests and numerical simulation studies.(2)Reveal the instability mechanism and infiltration process analysis of the root-soil composite slope under continuous rainfall eventsAccording to the test parameters obtained above,a physical model of plain soil slope and root-soil composite slope was prepared,and the physical model test of rainfall-induced soil slope instability was carried out.Use the corresponding test equipment to analyze the changes of the slope under continuous rainfall,and collect the internal volumetric water content of the slope,matrix suction and pore water pressure data,and reveal the slope instability characteristics from the slope characterization and the slope infiltration process analysis.The test results show that from the slope instability mode and the movement distance of the landslide,it is found that the anti-damage ability of the root-soil composite slope is better than that of the plain soil slope,and the thick-root-fine-root mixed reinforced slope has the strongest anti-damage ability.(3)Verify the effect of root system on slope reinforcement through numerical simulationFirst,a numerical model slope is constructed based on the physical model test slope 1:1,and the results of the physical model test and the numerical simulation are compared to verify the accuracy of the numerical simulation.Numerical simulation is used to study the instability characteristics of root-soil composite slopes under different root density during the instability process.Further analyze the reinforcement effect of the root system on the slope of the actual slope in the K53+200 section of the Longyang section of the Daguang Expressway,so as to provide technical support for the vegetation slope protection project.The test results show that the numerical model is consistent with the physical model test results,and the influence of vegetation roots on the slope stability coefficient is related to the root density.In the numerical simulation results of the actual slope,it is confirmed that the vegetation root system can strengthen the slope.