Study On Seepage Characteristics Of Expansive Soil Slope Under Rainfall

As an important role in the infrastructure industry,the transportation industry plays an inestimable role in improving people’s living standards and enhancing my country’s comprehensive national strength.With the improvement of my country’s economic and technological level,transportation construction is proceeding in full swing.Since my country is an expansive soil widely distributed,transportation construction will inevitably be carried out in expansive soil areas,and a large number of expansive soil slopes will be built.Among them,rainfall is one of the important factors leading to instability and failure of expansive soil slopes.The infiltration of rainwater will change the state of the original seepage field inside the slope,making a transient saturation zone formed within a certain range of the slope,increasing the pore water pressure,reducing the shear strength of the soil,and accompanied by obvious expansion and deformation.,Which eventually led to the occurrence of stability damage.Therefore,studying the time-varying law of the internal seepage field of expansive soil slopes is of great significance for the future stability research and the actual protection of the project.At present,the saturated-unsaturated seepage theory is mainly used for the seepage analysis of expansive soil slopes,but the seepage process is obviously a fluid-solid coupling process,and the peculiar expansiveness of expansive soil is also a factor that cannot be ignored.Therefore,comparative research is used as the main research method to compare the differences between the two and carry out a combination of experiment,theory,and numerical simulation to systematically study the seepage characteristics of expansive soil slopes.The specific research content and results are shown below:(1)In order to obtain the hydraulic characteristics of Guangxi expansive soil,indoor pressure plate tests and outdoor double-loop permeability tests were carried out to obtain the soil-water characteristic curve and saturated permeability coefficient of expansive soil.Carry out confined unloaded swelling test,explore the law of swelling deformation of expansive soil with initial dry density and moisture content,and construct a mathematical model of swelling deformation.(2)According to the saturated-unsaturated seepage theory,different rainfall schemes are drawn up,and the time-space variation law of the seepage characteristics of expansive soil slopes under rainfall conditions is studied.The results show that:the pore pressure,volumetric water content and transient saturation area inside the slope The formation and development are not only affected by rainfall intensity and rainfall duration,but also by the geometry of the slope,the thickness of the soil layer and the soil properties.(3)Develop the FLAC3D software fluid-structure coupling analysis module to discuss the dynamic changes of negative pore water pressure,unsaturated permeability coefficient and saturation in the process of unsaturated seepage,correct the effective stress and provide solutions for the software’s deficiencies in setting boundary conditions Finally,the expansion deformation is added to the fluid-solid coupling theory to construct a suitable unsaturated fluid-solid coupling theory.(4)In the process of rainfall,the influence of swelling deformation on pore water pressure,volumetric water content,and transient saturation zone is first small and then large.However,according to the characteristics of the slope,they will eventually tend to be within a relatively stable range;after the rainfall,the swelling Deformation will inhibit the dissipation of moisture,so that it takes longer for the three to reach a stable state,and the greater the expansion and deformation,the longer the time required.