Soil And Water Conservation Characteristics Of Soil-rock Mixture Based On Resistivity Tests

Soil-water characteristic curve(SWCC)is usually used to describe the relationship between the moisture content of unsaturated soil and its matric suction.Currently,studies on soil-water characteristics mainly focus on fine granular soil such as clay and silt,as well as sand and silt mixture,but there are few studies on soil-water characteristics of soil-rock mixture.For the soil-rock mixture with the same property,its resistivity mainly depends on the water content,and the matric suction also depends on the water content,so there must be a certain internal relationship between the resistivity of soil-rock mixture and its matric suction.In view of this,the research on soil-water characteristics of soil-rock mixture based on resistivity test was carried out by the National Natural Science Foundation of China.The main research contents and results are as follows:(1)Study on SWCC surface model for soil-rock mixture.Based on the classicalSWCC model and the two-step cross model of unsaturated soil,the parameters of each model and the applicability of the model are analyzed.The SWCC surface model of soil-rock mixture was established through equivalent substitution,formula superposition and parameter optimization.The model was coupled with the compaction degree,and the quantitative relationship among matric suction,mass moisture content and compaction degree was established.Through the sensitivity analysis of the model parameters,it is found that the variation of parameters reflects the variation of pore drainage process in the soil-rock body.(2)Experimental study on soil water retention characteristics and resistivity of soil-rock mixture.Combining filter paper method and Vanderbilt method,a kind of matric suction and resistivity collaborative testing device was designed.Using this device,the resistivity,water content and matric suction tests of common weathered mudstone mixture in Chongqing area were carried out.The SWCC surface model was used to analyze the test data.The results show that the shape of the fitted surface with different soil and rock ratios is similar,and the mass moisture content decreases with the increase of matric suction.In the process of the decrease,arc will be generated,and there is a significant difference between the decreasing speed of mass moisture content before and after the arc.(3)Study on soil-water characteristics of soil-rock mixture.The SWCC curve of soil-rock mixture is a two-step shape of two "S" shaped combination,which describes the drainage process of the large pores and small pores in the boundary effect section,the transition section and the unsaturated residual section respectively.When the soilrock ratio is 5:5 and 6:4,the curve as a whole moves towards the direction of mass moisture content decreases with the increase of compaction degree,while when the soil-rock ratio is 7:3,the curve as a whole moves towards the direction of mass moisture content increases with the increase of compaction degree.(4)Study on matrix suction evaluation of soil-rock mixture based on resistivity test.The mass moisture content,resistivity and matric suction of soil-rock mixture specimens are analyzed,and the comprehensive resistivity parameters of soil-rock mixture are calculated.To the parameter represents the resistivity characteristics of earth-rock aggregate,based on the comprehensive parameter matrix suction and resistivity of correlation analysis,obtained the bits ?-R_e integrated parameters(the matrix suction-resistivity)mathematical model,established a quantitative relationship between the two,the results show that the resistivity of rock body and decreases as the water mass fraction,a simple power function relationship between,and the matrix suction increases with the increase of resistivity;Through the sensitivity analysis of the parameters of the ?-R_e model,it is found that the variation of the model parameters reflects the variation of the pore drainage process in the soil-rock body.