Soil-water Characteristic Curve Test And Slope Stability Of Unsaturated Loess Under Dry-wet Cycle Conditions

The dry-wet cycle makes the water-gas state in the shallow soil of the loess slope change dynamically.The change of water-gas causes the change of suction in the soil,which affects the mechanics and permeability of the soil and even jeopardizes the stability of the slope.In order to explore the evolution mechanism of mechanical properties and slope stability analysis of unsaturated loess under dry-wet cycle conditions,this project intends to pass the soil-water characteristic curve test and analyze the data obtained from the test to study the unsaturated loess after many times of drying.Under the condition of wet circulation,the law of water and gas migration of soil and the evolution mechanism of soil strength change,the function related to the number of dry and wet cycles is introduced,and the soil-water characteristic curve of unsaturated loess under dry and wet circulation water and gas migration conditions is established.Predicting the model of the permeability coefficient and obtains the relationship between the permeability coefficient and the matrix suction or water content.Based on the limit equilibrium analysis method,the rainfall evaporation-water vapor migration-slope stability analysis is established.The model studies the stability of the slope,and the research results can provide the basis for the design and reinforcement of the slope engineering in the loess area.In order to study the above problems,this paper mainly does the following work:(1)Dry-wet cycle unsaturated loess soil-water characteristic curve test: The reshaped loess samples with undisturbed loess and different initial dry densities were studied,and the samples were subjected to 0,1,2 and 5 respectively.The dry-wet cycle of the second time was carried out by GCTS SWC-150 Fredlund soil-water characteristic curve meter.The soil-water characteristic curve test was carried out on the samples with different wet and dry cycle times,and the corresponding soils of each sample under different matrix suction were obtained.The soil water-water characteristic curves of different samples were plotted for the volumetric water content.It can be found that both the undisturbed soil sample and the remolded soil sample have two different soil-water characteristic curves in the process of dehumidification and moisture absorption,which produces a hysteresis effect,and the hysteresis loops with the increase of the number of dry and wet cycles.It gradually decreases and tends to be stable;the initial dry density has a great influence on the soil-water characteristic curve.Under the same matrix suction condition,if the initial dry density of the unsaturated soil sample is larger,then the volumetric water content will be The smaller,the effect on the soil-water characteristic curve.(2)Establish a soil-water characteristic curve prediction model considering the effect of dry-wet cycle: SWCC curve of unsaturated loess under different conditions of dry and wet cycles,based on Gardner,Brooks and Corey,Van Genuchten and Fredlund and Xing models By contrast,the Gardner model with the highest fitting accuracy was selected as the analytical model of this experiment.The parameters of Gardner model fitting were analyzed.It was found that the parameters x0 and p increased with the increase of the number of dry and wet cycles,and the fitting parameters x0 and p of the remolded soil samples with different initial dry densities were obtained.The change in the number of times can be expressed by an exponential function.(3)Based on the soil-water characteristic curve obtained by the experiment,the soil-water characteristic curve method is used to predict the permeability coefficient model.Through the calculation of the model,the change of the permeability coefficient with the matric suction or water content is obtained,and the wet and dry is analyzed.The effect of the number of cycles on the permeability coefficient.After research,it is found that the unsaturated permeability coefficient of the sample will change with the change of matrix suction or water content;the dry-wet cycle will also cause the value of the permeability coefficient to change.The more the dry-wet cycle,the unsaturated permeability coefficient Will get bigger.(4)Establishing the model of rainfall evaporation-slope stability analysis: Using Geo-studio software,the variation of the stress field and seepage field of the slope with the increase of rainfall-evaporation times is calculated,and then the calculated pore pressure will be calculated.The distribution field and the suction field were substituted into the SLOPE/W software based on the limit equilibrium analysis method to study the slope stability considering the number of dry and wet cycles.