| Due to the complexity of the material composition of the soil-rock mixture in the Qinba Mountain area,the high heterogeneity of the structure and the limitation of the experimental conditions,it has always been difficult to study the unsaturated soil-water characteristics and infiltration mechanism.The occurrence of soil-rock mixture landslides is closely related to rainfall infiltration.Therefore,it is urgent to carry out the study of unsaturated soil-water characteristics of soil-rock mixture in Qinba Mountain area.In addition,the unsaturated soil-water characteristics of soil-rock mixture are analyzed from the perspective of microstructure,which lays a foundation for the prediction of unsaturated seepage characteristics of soil-rock mixture in Qinba Mountain area.In view of the above research status,this paper takes the remolded soil-rock mixture samples with different void ratios（0.7,0.8,0.9）and different stone contents（0,10%,30%,50%）as the research object,and uses the water potential and moisture sensor as the test instrument to monitor the matrix suction and volume water content of the samples at different times.The natural air-drying method is used to test the soil-water characteristic curve and residual water content of the samples.The unsaturated permeability coefficient of the sample was tested by transient section method.The pore distribution characteristics of samples with different structural characteristics were tested by mercury intrusion method to study the correlation between unsaturated soil water characteristics and microscopic mechanism.The main innovations of this paper are as follows:（1）The soil-water characteristic curve of soil-rock mixture under high compaction and low stone content is obviously higher than that under low compaction and high stone content.The pore size of soil-water characteristic pore of soil-rock mixture is less than 200μm.When the stone content is low,increasing the compaction degree causes the pores to decrease.（2）When the confidence level is greater than 99.5%,there is a negative correlation between void ratio,stone content and residual water content of soil-rock mixture.The residual water rate of the soil-rock mixture is related to the pores（<2μm）in the aggregate,and the residual water occurs in pores less than 0.5μm.Under the condition of the same stone content,reducing the void ratio makes the pore distribution shift to the direction of small pores,thus increasing the content of small pores and increasing the residual water content.The stone content affects the internal pores of the aggregate of the soil-rock mixture by affecting the matrix content of the soil-rock mixture and the compression degree of the matrix,thereby affecting the residual water content.Based on the analysis of the influence mechanism of porosity and stone content on the residual moisture content of soil-rock mixture,a model based on stone content and void ratio is proposed to predict the residual moisture content of soil-rock mixture in Qinba mountain area.The model can better describe the residual moisture content of soil-rock mixture with specific structure in Qinba mountain area.（3）The unsaturated permeability coefficient of soil-rock mixture has a nonlinear relationship with saturation.The unsaturated permeability coefficient has a large span(10-6～10-2cm/s)and low saturation.The permeability coefficient increases slightly with the increase of saturation.When the saturation reaches a certain value,the permeability coefficient increases sharply.The unsaturated permeability coefficient of soil-rock mixture is closely related to void ratio and stone content.The unsaturated permeability coefficient of high void ratio and high stone content samples is significantly higher than that of low void ratio and low stone content samples.In addition,there is a certain threshold pore size value for each sample of soil-rock mixture.When the pore size is less than this value,the seepage is small and the unsaturated permeability coefficient is small.When the pore diameter is greater than this value,the unsaturated permeability coefficient is larger;and this threshold pore size decreases with the increase of void ratio and stone content. |
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