Study On Soil Water Characteristic Surface And Strength Model Construction Of Unsaturated Loess In Xining Area

The soil-water characteristic curve of unsaturated soil and the prediction model of shear strength are important contents in the study of unsaturated soil mechanics.Through the literature review,the author has learned that there are few researches on the relevant models of loess in Xining.Therefore,the author obtained the SWCC of remolded loess at different dry densities through the filter paper test.The strength parameters of Xining unsaturated loess under different water contents were studied by triaxial shear test.Based on the study of the suction and strength of unsaturated loess in Xining,the author combines the experiment with the theory of unsaturated soil to obtain the following results:(1)Improve the filter paper test,and propose to test the soil water characteristic curve of the soil by the continuous filter paper method.In order to reduce the error,the author used the same soil sample for continuous suction test.The complete process of soil dehumidification was simulated.First,the test soil sample is saturated by capillary saturation method.After each suction measurement is completed,the test is placed in the same environment for dehydration;after the dehydration is completed,the next suction test is performed.Finally,the complete curve of unsaturated loess in Xining area at different dry densities is obtained.(2)Through the study of SWCC of unsaturated loess in Xining area,it is concluded that the Fredlund-xing model can well fit the soil-water characteristic curve of loess in the area.Based on the Fredlund-xing curve model and previous studies,the relationship between dry density and the parameter a of the model is derived theoretically,and the Fredlund-xing model is modified.The soil water feature surface model under different dry density effects is established.That is,the initial dry density-saturation(water content)-matrix suction multidimensional model.The feasibility of using the surface model to predict the soil water characteristic curve of loess under different dry densities is verified.(3)Based on the theory of unsaturated soil strength,the empirical formulas of relative water content and matrix suction are explored,and the model formula for predicting the shear strength of unsaturated loess in Xining is established.The strength calculation of unsaturated loess is carried out by using the formula.The calculated values of the Coulomd formula are compared.It is concluded that the calculated intensity value of the modified formula can reflect the collapsibility of loess and the strength of the soil.The characteristics of the reduction reflect the importance of the theoretical study of unsaturated strength on the construction of unsaturated loess.