The Experimental Researches About Properties Of Unsaturated Soils In Gushubao Landslide And Building Of Finite Element Method

The researches about the fundamental properties of unsaturated soils such as the permeability,shear strength and constitutive model are the basis and starting points of analyzing unsaturated soils mechanical characters as well as developing numerical simulations, and they are also the key to study the landslides with unsaturated soils. As far as unsaturated soils are concerned, there are very important realistic senses to gain abundant experimental data for the foundation and development of theory frame, so significance must be attached to the situation that current information and data are very scarce due to the complexities of the testing instrument and experimental method. Firstly, this paper summarizes the main background of experimental researches and relates the research history and current status of the field concerned unsaturated soils, then narrates the essential theory about every experimental research and present the formulas general used and their comment.Secondly, experiment should be commenced from three aspects followed, with the experimental principles recounting and testing instrument introducing, then the experimental data are listed and analyzed to draw the conclusion.No.1: the soil-water characteristic curve can be educed through the soils drying test in the Temp Pressure Plate Cell and the Volumetric Pressure Plate Cell. Then the permeability coefficients of unsaturated soils are fitted on the basis of above data.No.2: the test parameters of shear strength of unsaturated soils, can be got through the triaxial test and direct shear test, 25 specimens are completed with compression and shear courses, and the test parameters are listed. Then the merits and faults of two methods are analyzed and compared.No.3: the constitutive model tests on unsaturated soils are developing on the basis of model tests on saturated soils, from the load and unload of net normal stress,suction and deviate stress, 12 parameters of model are listed and model equation are established.Finally, according to the yield criterion,flow principle and hardening rule, the stiffness matrix and its finite element method are bring forth as the same with Cam model of saturated soils and Alonso model of unsaturated soils in order to provide foundation for further numerical simulations.