Research On Shear Strength And Matrix Suction Field Measurement Of Unsaturated Soils

With the continuous exposition of many unsaturated soil problems, such as expensive soils, loess and so on, the mechanics and engineering characteristics of unsaturated soils are the intense studying interest in circles of the international geotechnical engineering. The testing work concerned with unsaturated soils, especially the shear strength and soil matrix suction measurement, is the essential problems of studies for unsaturated soils, which determines the development of this subject. In this paper, the author tries to do some research works in the field of shear strength and matrix suction field measurement of unsaturated soils based on experiments.Firstly, a critical review of research on the air phase patterns and regularities of air/water movement , soil-water characteristic curve(SWCC) , the shear strength properties and matrix suction measurement of unsaturated soils was given.Secondly, Luojiashan soil samples were selected for the unsaturated triaxial tests and the shear strength parameters were obtained. Soil-water characteristic curve was obtained from the experimental date measured in the tests. And the practical equation of SWCC and shear strength for the soil sample was proposed. Relevant formulas with shear strength were compared based on the results of tests. At the same time, the shear strength contributed from matrix suction was analyzed, and the differences between the linear failure envelope with the nonlinear failure envelope were compared.Finally, matrix suction in situ was measured by filter paper method andtensiometer method for four months. Curves of suction variation with depth and time were obtained, and the measurements of the two methods were compared.