Experimental Study On The Soil-water Characteristic Curve And Permeability Coefficient Of Unsaturated Soil

In the existing theory system of soil mechanics, most of the theories are based on the assumption that the soil is saturated, and the view of this is that there are only soil particles and pore water in soil. But most soil in actual project is three-phase. In addition to the presence of soil particles and pore water, there is pore air. Such three-phase soil is called unsaturated soil. Research on various aspects of the characteristics of unsaturated soil is an important subject in geotechnical engineering. Based on previous theory results on the existing of unsaturated soil permeability characteristics were studied by the mean of testing in this paper.Soil-water characteristic curve and permeability coefficient are very important in the seepage study of unsaturated soil. In this paper, the significance, characteristics and applications of soil-water characteristic curve and permeability coefficient are introduced. And previous Experimental and theoretical methods of obtaining water characteristic curve and permeability of unsaturated soil are summarized. The soil-water characteristic curve and permeability coefficient testing instrument has been developed by the geotechnical and environmental mechanics laboratory of DUT. Using this instrument, the permeability characteristics of unsaturated loess and silica powder have been researched. According to the test results, the soil-water characteristic curves are fitted by VG model. Also, the variation relationships between permeability coefficient and soil matric suction, saturation of unsaturated soil are described. By comparison of the two kinds of test results, combined with their basic physical properties, particularly the composition of the particles, effects of different particle size on permeability characteristics are discussed.This article also derived equations of motion of pore water seepage flow and theoretical formula of permeability coefficient from the balance equation of pore water and theoretical interaction force between soil and water. Based on the test data, the rationality of theoretical formula of permeability coefficient has been verified.