Research On The Unsaturated Engieering Properties Of Granite Residual Soil With Consideration Of Seepage

The distribution of unsaturated soil on the land is very extensive, the area they covered is far greater than saturated soil. Unsaturated soil is different from saturated soil, and its engineering properties also has great difference between the saturated soil. With the expansion of people's engineering behavior and the development of scientific and economic, more and more engineering problems from unsaturated soil to solve. This thesis mainly research is the unsaturated granite residual soil. Granite is widely distributed in our country, particularly the coastal areas of Minyue.The grante residual on this area has a very thick covering layer as the area in subtropical monsoon climate zone with the weathering is very intense, Granite residual soil is a kind of special soil, has its unique composition and structure characteristics and special engineering properties, such as inhomogeneity and anisotropy, soften and disintegration, perturbation etc. And these special properties have not attracted great attention in many occasions, leading to general cohesive soil engineering accident or investment waste. In the natural state granite residual soil underlying has lower compressibility, high bearing capacity and large shear strength, but under water, particularly saturated state after mechanical properties significantly reduced. So research on unsaturated granite residual soil engineering properties under the influence of seepage which is of great practical significance.Based on scanning electron microscopy(SEM), unsaturated soil quad scissors apparatus, unsaturated soil direct shear apparatus and unsaturated soil triaxial apparatus to study the engineering properties of unsaturated granite residual soil. Analysis the safety stability of embankment under the influence seepage combining with actual engineering.The research work mainly in the following aspects:1 Research the microstructure of granite residual soil. This paper firstly analyzes the microstructure characteristics of granite residual soil(Research on the similarity),then discussed the microstructure characteristics in different matrix suction respectively, probe into the microstructure characteristics of unsaturated soil from the microcosmic angle, and try to explain the special engineering properties of granite residual in the view of microcosmic mechanism.2 Determine the soil-water characteristic curve(SWCC) of granite residual soil, and get the relevant parameters S s, S r, g a, g n through the nonlinear fitting of VG model.The moisture content of unsaturated soil is not only relate to the matrix suction,but also to depent on the overlying pressure, then there is a determination of SWCC under the defferent vertical pressure and fitting them.3 Calculate the unsaturated permeability coefficient by the measured SWCC of granite residual soil, and obtain the related experience parameter g l from VG function.4 Research the shear strength of unsaturated granite residual soil. Get the direct shearing strength and triaxial shearing strength by unsaturated soil direct shear apparatus and unsaturated soil triaxial apparatus respectively. Discusses the characteristic value of shear strength and its extended M-C failure envelope of 3d.5 The shearing-infiltration text of unsaturated granite residual soil, by bringing about seepage into shear tests of unsaturated soil, discuss the shear strength changes of the granite residual soil under the situation of seepage.6 Analyzing the actual engineering example in numerical analysis with the test results. With Plaxis 2d analysis function and submodule of PlaxFlow. Analysis in Shantou Dawei reinforcement stable seepage and unsteady seepage situation seepage situation and safety of the stability analysis, the analysis of the reinforced areas get meet the design requirements.