Study On Shallow Slide Of Loess Slope Under Acid Rainfall By Model And Numerical Method

With the development of industrialization and industry migration from the eastern developed region to the western region,industries such as acid-base chemicals,printing and dyeing,oil refining,chemical and pharmaceutical in the Loess Plateau have flourished.It has become increasingly prominent,among which loess engineering diseases caused by acid pollution are particularly notable,such as the collapse of shallow layers of loess slopes under acid pollution,foundation settlement,and instability of retaining walls.Loess has water sensitivity and special structural characteristics.The acidic contaminated fluid can easily change the chemical composition,framework structure and pore characteristics of the loess,causing changes in the physical and mechanical properties of the loess.But how do the physical and mechanical properties of acid-contaminated loess change? How to evaluate the shallow collapse of loess slope under acid pollution? There are still problems that plague the engineering community,and the thesis carries out research work on this.First,indoor direct shear tests were conducted on the contaminated and uncontaminated remolded loess samples,which revealed that acid pollution caused the shear strength of the loess to be significantly reduced.The dissolution of cement in the acid solution not only greatly reduced the cohesive force but also decreased the internal friction angle to a certain extent.The soil-water characteristic curves of the contaminated and uncontaminated loess were measured by the filter paper method.The reasons for the change of the matrix suction induced by acid pollution were analyzed.The model parameters and the permeability coefficient of the contaminated loess were obtained by fitting the VG model.Further,by constructing an artificial rainfall indoor model test system,indoor simulation test research was conducted on two rainfall conditions of normal rainfall and acid rain.The water monitoring system and slope monitoring system were used to clarify the45°slope and 60°slope in two types—the law of seepage in slope and the failure mode of slope under rainfall conditions.Slope failure under heavy rainfall is mainly due to the occurrence of several small-scale collapses on the weak side of the surface slope and expansion and connectivity to form large-scale slumps.Such landslides have the characteristics of small range,large number,shallow impact depth,and sudden occurrence.The slope failure mode under normal rainfall conditions can be summarized as the traction failure caused by the slope foot softening,the slope failure mode under acid rain conditions can be summarized as the progressive failure caused by the slope top dissolution.Finally,considering the normal rainfall infiltration and acid rain infiltration,the saturated-unsaturated soil finite element model is built to analyze the seepage and stability of the loess slope,and the difference in the water field between the polluted loess slope and the unpolluted loess slope is analyzed.It is revealed that acid pollution causes the stability of loess slopes to decrease significantly.During the process of acid rain infiltration,the change speed and amplitude of loess slope stability are greater than those of normal rainwater infiltration slopes.