Numerical Simulation Of Expansive Soil Cutting Slope With Geogrid Reinforcement Considering Fluid-solid Interaction

Expansive soil is a kind of special clay which tends to expand and shrink when it meets water.Because of its unique engineering characteristics,it will bring great hidden danger to the slope engineering exposed under natural conditions.In the meantime,many methods have been sought for treatment of expansive soil problem.At present,the treatment means of expansive soil problem can be roughly divided into rigid reinforcement and flexible support according to the form.Flexible support is widely used in highway engineering because of its simple structure and strong ability to adapt to terrain.Geotechnical workers have gained rich experience in treating expansive soil problems with flexible support.However,the research on the grid reinforcement range and grid layout mode is a little insufficient.Therefore,this paper,based on a project in Guangxi,simulated the stress-strain change process of the reinforced expansive soil slope under the condition of rainfall infiltration,analyzed the slope stability under different grid reinforcement modes,and provided theoretical basis for the slope reinforcement design in the future.The specific contents and achievements are as follows:(1)According to the engineering characteristics of expansive soil in Guangxi,the hydraulic characteristics parameters of expansive soil were obtained through pressure plate test and outdoor double-ring permeability test;With the help of expansion deformation test,stragiht shear test and triaxial test,the strength and deformation parameters of soil were obtained,and the change law of the strength parameters of the geogrid interface was obtained through the pull-out test.At the same time,in order to reflect the strength attenuation of soil and geogrid caused by rainwater,the relationship between the above parameters and water content was obtained,which provided data support for subsequent numerical simulation.(2)Since the saturation of FLAC3D unsaturated seepage module defaults to 1,it does not consider the variation of unsaturated soil permeability coefficient with water content,and cannot realize the true meaning of unsaturated seepage.Therefore,in this paper,the generation of the initial seepage field and the effective stress in the unsaturated seepage module are corrected,and the rainfall boundary setting is also improved.With the help of Visual Studio programming software,the expansion property is introduced into the constitutive model in the form of additional strain,and finally the expansion soil constitutive model is improved.By invoking the improved constitutive model,the multi-field coupling analysis method for unsaturated soils can be realized.(3)Through the finite difference software FLAC3D,the numerical simulation of the reinforced expansive soil slope under rainfall conditions,it is found that the geogrid can effectively limit the deformation of the slope,but also promote the drainage of water from the slope soil,reduce the moisture absorption and softening effect of the soil to a certain extent,and then enhance the stability of the slope.On this basis,the influence of different spacing and length of gratings reinforcement and interface parameters on slope deformation and stability is further studied,which provides a basis for the reinforcement design of expansive soil slope.