Damming The Soil Properties Of Water Conservancy Projects

Currently, there is a big waste of phenomenon of the dam process of water conservancy and hydropower engineering earth-rock dams in China,it has resulted in great economic burden and loss of the country and the people, it was mainly due to lack of awareness of the hydraulic property and general safety factor value was higher.It was historic mission of water conservancy and hydropower and geotechnical workers that to accelerate the pace of research and awareness of the property of hydro project of dam soil material and to construct the engineering of safe,reliable,economical and reasonable of water conservancy and hydropower and to promote social development and to save money for the state.It was of great guiding significance to the theory and actual production of meaning that to carry out in-depth study of the property of water conservancy and hydropower of dam soil material, it was not only rich in scientific theory in the water conservancy and hydropower and geotechnical engineering,but also directly alleviated the burden on the national economy of the infrastructure.In order to more comprehensive and thorough understanding of the property of water conservancy and hydropower of dam soil material and to provide theoretical and experimental basis for the future water conservancy and hydropower projects, this paper main relying on the actual water conservancy project of Xi'an Heihe, it was main line to the property of water conservancy projects of dam soil material and it was kind of focus on the compaction of soil material, permeability, seepage deformation characteristics and tensile properties of cohesive soil,and the author had carried out laboratory study on thematic issues of some properties of water conservancy projects of dam soil material.Study was divided into three parts, namely, the maximum dry density of soil, soil hydraulic properties and tensile strength of unsaturated clay.(1) In the study of maximum dry density, the author discussed some of the major problems on the clay.They were the main factors of the maximum dry density of clay, water content to maximum dry density of clay controlling, determine the maximum dry density of clay simple method, the oversized coarse grained soil maximum dry density of test handling and construction control program.(2) In the study of mechanical properties of soil water, the author discussed some of the major problems on the soil permeability coefficient of variation They were coarse-grained soil permeability coefficient and the relationship between the graded index, correlation of coarse-grained soil infiltration parameters of slope and particle size distribution and clay and gravelly soil in various degrees of crack slotted changes of erosion.(3) In the study of the tensile strength of unsaturated cohesive soil, the author tested the tensile strength of unsaturated cohesive soil using two methods of the uniaxial and triaxial tension, a comparison of the same traits unsaturated cohesive tensile and shear strength of the law and analysis of the intrinsic link between them.The author summed up the following conclusions through experimental analysis.The first, the dam of the soil maximum dry density mainly affected by two factors of the compaction function and moisture, in some cases,moisture content,dry density increases with the increase of compaction features. Compaction features in certain circumstances, the soil dry density and moisture content would showing the relationship between normal curve, soil dry density was the greatest at a certain moisture content under one medium,in other words there was an optimum moisture content and maximum dry density. The maximum dry density of soil limited by the moisture content, it would not exceed the soil water content under the restricted by compaction to achieve saturation of maximum dry density.The second, remove method used to gradually remove large-size coarse-grained soil material,study materials maximum dry density of the remaining, following an analysis of the law that was a strong linear correlation rules between the maximum dry density and eliminate the amount of residual of the coarse-grained soil. Pointed out the idea that indirect found the maximum dry density of the original grade ingredients of super-size coarse-grained soil after the law of extrapolation.The density of super-size coarse-grained soil compacted was continues to show non-uniform,analysis of compaction process changes in soil dry density, obtained results that fine material was the last to be compacted in the super-size coarse-grained soil compaction process and the various parts of the soil compacted was still very uneven density, pointed out that the view was fine materials maximum dry density test as the standard for compaction quality construction control of minimum dry density of fine materials after the discounting giant grain groups.The third, the coarse-grained soil permeability coefficient and void ratio were closely related to,under the conditions of gradation determined, there was showing a linear positive correlation between them,the greater the void ratio, the permeability coefficient the greater; there was a linear positive correlation between the permeability coefficient and the non-uniform coefficient of the square root of the coarse-grained soil, the greater the non-uniform coefficient,the permeability coefficient the greater; There was a positive correlation between the permeability coefficient and the curvature coefficient of the square root, the greater the curvature coefficient,the permeability coefficient the smaller, The author established a model of related factors of coarse-grained soil permeability and size distribution index based on the correlation and regression analysis.The fourth, there was a link with the coarse-grained soil seepage deformation gradient and the particle size distribution, in certain areas there were some changes in the law, and the asymmetry coefficient, curvature coefficient in the different areas related to memory in different forms.With 5% of the group and the level of fine granular soil with good infiltration and sabotage was generally flow of soil type damage, destruction of large slope, generally up to about 4.5, and more literature that the seepage failure slope was generally not more than 1.5 higher than the results.Crack in clay and gravel soil erosion would change the original filter layer structure, their mechanism was the same as changing the original filter layer structure,as the gravel soil than in clay cohesive force was weak,and it easily dispersed by water erosion, it could form the finer secondary filter with layer structure than the clay when erosion crack.Two kinds of erosion cracks could form a secondary filter layer, This allowed the original filter with thinner layer structure,and soil conservation performance enhancement.Crack had a self-healing function as hydraulic scour.The fifth, there was a kind of relationship between the triaxial tensile strength and confining pressure of the unsaturated cohesive soil, it expressed as tensile failure when confining pressure was low,it expressed as necking damage when confining pressure was high.There were several conclusions after doing the triaxial elongation test of the unsaturated cohesive soil, Mohr circle satisfied the coulomb criterion as drawing with different confining pressures for the major principal stress and axis of stress for the minor principal stress; There was a linear correlation between the tensile and shear strength of the same physical shape of unsaturated cohesive soil; it could be calculated tensile strength of unsaturated cohesive soil that to reduce shear strength parameters of the same characteristics of unsaturated clay, if there was no tensile conditions on the soil to tensile test.The author established a correlation model of the coarse-grained soil permeability coefficient and its coefficient of uniformity and curvature. Solved maximum dry density of the super-size coarse-grained soil by the extension removed method. Pointed out the compaction test of fine-grained soil by the single compaction test method, can overcome the conventional five-point compaction test the shortcomings of time-consuming. These are the innovation of this thesis.