Study On Soil-water Characteristic Curve And Pore Characteristic Of Intact Loess

Engineering activities in the loess area are increasing.Geological disasters such as landslides and collapsing induced by engineering activities have caused serious economic losses and even endanger life safety.The occurrence of these disasters is closely related to the unsaturated characteristics of loess.The soil-water characteristic curve(SWCC)is an important constitutive relationship in unsaturated soils and is the key content of unsaturated soil research.In this paper,8 layers of intact loess in Jingyang,including L1,L2,L3,L4,L5,L6,L7 and L9,were taken as the research objects.The contact filter paper method is used to measure the soil water characteristic curve of 8 layers of loess and the soil water characteristic curve of L1 and L5 layers,the pressure plate instrument is used to measure the soil water characteristic curve of L1 loess,and the mercury pressure method is used to measure the pore distribution curve of 8 layers of loess.The results are as follows.According to the result of mercury intrusion method,the pore of undisturbed loess presents a typical "double peak" pore distribution,which is the weak peak and the dominant peak respectively.The weak peak has nothing to do with deposition time,while the dominant peak has a significant correlation with deposition time.According to the characteristics of pore evolution,the pores of loess are divided into five types: ultra-micro pores,micro pores,small pores,medium pores and large pores.The pore size of 5?m can be used as the boundary of the transition from unstable pore to stable pore.With the aging of sedimentary age,the medium pores and large pores of loess gradually disappear,and the dominant pore structure evolves to the uniform pore structure.In addition,the pore diameter of the upper side of the dominant pore peak is selected as the characteristic parameter to establish the correlation between the sedimentary age and the characteristic parameter.According to the test results of pressure plate apparatus and filter paper method,the filter paper method is suitable for testing soil water characteristic curve.The soil water characteristic curve of 8 layers of loess measured by filter paper method shows that the evolution process of soil water characteristic curve of loess shows that the transition area is a straight-line transition of steep reverse "S" syncline,and the soil water characteristic curves of residual area basically coincide.The soil water characteristic curve is controlled by pore distribution in the transition area and mineral composition in the residual area.Taking 3000 k Pa as the suction boundary,the SWCC of loess is divided into capillary section and adsorption section.Campbell and Shiozawa model is used to fit the SWCC of adsorption section.Gardner,van Genuchten and Fredlund & Xing model are used to fit the SWCC of capillary section.The relationship between the slope parameter SL of Campbell and Shiozawa model and the clay content in loess,and the relationship between the parameters a,m,n of van Genuchten model and deposition time are established.Therefore,the SWCC of loess can be predicted by the age of loess deposition and clay content.