Experimental Study On Water Retention And Mechanical Behaviors Of Saline Soil

Landfill,nuclear waste disposal and infrastructure construction in saline soil area are the environmental geotechnical problems that need to be solved urgently.These engineering problems are closely related to the water retention capacity and mechanical behavior of saline soil.Therefore,in this study,the water rentention capacity and mechanical properties of saline soil were studied by laboratory tests.The research results can provide some reference for related engineering problems.The main research contents of this paper are as follows:(1)The water-retention behavior of unsaturated silty clay with different salt solution concentration and initial void ratio has been studied by pressure plate method and vapour equilibrium technique,and the soil-water characteristic curve in full suction range have been obtained.The experimental results show that the concentration of salt solution has obvious influence on the matrix suction in the low suction stage.The water rentention capacity of soil increases with the increasing of salt solution concentration.The initial void ratio has influence on saturated volume water content and air entry value of soil.Saturated volume moisture content and air entry value decrease with the increasing of initial void ratio.In the stage of high suction,the influence of salt solution concentration and initial void ratio on soil water retention capacity decreases with the increasing of matrix suction.This is because capillary action and adsorption action in soil matrix potential have different influence mechanisms on soil water retention behavior.(2)Based on the mechanism of water retention,a soil-water characteristic curve model considering the influence of salt solution and initial pore ratio has been established.Firstly,according to the existing models,the matrix suction model and residual water content model consisdering the influence of salt have been proposed.Secondly,the relationships between parameters related air entry value and curvature of SWCC and the initial void ratio has been established.Finally,based on VG model,a soil-water characteristic curve model of saline soil considering the influence of initial void ratio has been established,which is suitable for full suction range,and the model is verified by the experimental results.(3)The mechanical behavior of saline silty clay in saturated state has been studied by TSZ-1 automatic triaxial apparatus,including isotropic consolidation test and drained consolidation shear test.The test results show that salt solution concentration and initial dry density affect the mechanical properties of silty clay.In terms of consolidation characteristics,the increasing of salt solution reduces the slope of normal consolidation line and rebound line and the intercept of normal consolidation line for saturated clay,and increases the initial consolidation yield stress.In terms of strength characteristics,saturated saline clay is prone to strain softening failure at low confining pressure and high dry density,and shows dilatancy.Strain hardening failure is easy to occur at high confining pressure and low dry density,and shows shrinkage.The increase of salt solution concentration can inhibit the dilatancy potential of soil.With the increase of salt solution concentration,the peak strength,cohesion,internal friction angle and critical stress ratio of saturated clay are improved.(4)The unconsolidated undrained shear test of saline silty clay under high matric suction has been carried out by TSZ-1 automatic triaxial apparatus.The test results show that unsaturated saline silty clay under high matric suction is usually subjected to strain softening failure.Salt content has an influence on its peak strength and post-peak residual strength.Generally,the increasing of salt content will reduce the peak strength.Its influence level is affected by the matrix suction.When the matrix suction is dominated by capillary action,the cohesion and internal friction angle decrease with the increase of salt content.In the stage of extremely high suction,the internal friction angle gradually tends to a stable value.The influence of salt on the mechanical properties of clay depends on the content of clay minerals.Compared with saline solution,the initial dry density has a greater influence on the mechanical properties of saline silty clay...