Study On Seepage Control Calculation Method And Anti-seepage Measures Of Earth-rock Dam On The Infinite Deep Pervious Foundation

The dam locations with the good geologic condition gradually are decreasing in our country, many dams which will be developed have to be seated on the infinite deep foundation. But there is not a suit of seepage control calculation theoretic effectively by far. The paper aims at the seepage calculation of the infinite deep pervious foundation to do a deeply and systemic analysis using the numeric calculation approbatory method and mathematics method, finally to validate by the experimentation.The theoretic analysis part of the paper is that author uses the conformal transformation to establish a mathematics model of infinite deep pervious foundation, the model makes the complex subterranean contour to transform a plane and to study and ratiocinates a series of seepage calculation formulas. According to the characteristic of foundation soil, we can confirm the scope of filtrate layer. The numerical method part of the paper includes FEM and BEM. First, author uses the FEM establish a model of infinite deep pervious foundation; we can get the seepage discharge, seepage gradient and location of paretic line. Besides, author uses the BEM to establish models of horizontal blanket and vertical cut-off wall respectively and to calculate. Based on the theoretic analysis and numerical method, author uses seepage sand groove experiment to validate the above conclusions by collecting the dates when the foundation took the different anti-seepage. At the same time, this paper build a model of"preventing of the up and drainage the down", find out the relations of anti-seepage measures and ground water level of the downstream, seek after a right size of anti-seepage measures to prevent the solid sanitization of downstream.Based on the validating of each method, to calculate the actual project and find that the horizontal blanket has a effective length, the size is 22-30 times than water-head of upstream; the vertical cut-off wall exist a effective depth is 11-15times than water-head of upstream, when the size of anti-seepage measures reaches to the effective scope, we prolong the size of anti-seepage measures is not significance. Through studying the anti-seepage effect of the both measures, we find that there is a given relation between them, the anti-seepage effect of vertical cut-off wall is 1.5-3.5 times than horizontal blanket's. Besides that author find that it will affect the seepage discharge and average seepage gradient of dam foundation when the position of vertical cut-off wall is changed under the dam foundation, the best position should be located the forefront of dam base and the worst position is located the middle of dam base.The scope of filtrate layer is count for much with the pervious or not of dam. When the dam is impervious, the worst point of seepage escape gradient is located on the corner of downstream dam slope, the number goes to infinity, so we can letdown the seepage escape gradient of the corner. The filtrate layer should be set from the point. When the dam is pervious, the worst point is the joint of vertical cut-off wall and dam base, the number is H/Ï€s (H is the water-head of upstream, s is the depth of cut-off wall). The filtrate layer should be set from the joint.On the premise confirm of the horizontal blanket effective length, author bring forward the calculation method of economical length about horizontal blanket. Through actual project analyzing, we find that the economical length is longer much than the length of common horizontal blanket which is on the limited deep pervious foundation (6-8 times water-head of upstream). It shows that the length of horizontal blanket is not economy but also is not in reason. Aims at the soil sanitization problem of actual engineering (plain reservoir based on the infinite deep pervious foundation), author brings forward the concept of ecotypes length of horizontal blanket, and constitutes a integrality calculation formulas when the downstream located a drainage well.Finally, according to difference of the geology, author takes the infinite deep pervious to divide into three types: monolayer configuration, double deck configuration and complex configuration. Integrative analyze from anti-seepage effect, project cost, construction, etc, suggests that the best anti-seepage measures is horizontal blanket when the foundation is belong to the monolayer configuration or double deck configuration, but to the complex configuration, the choice of anti-seepage should be all-round, whether takes vertical cut-off wall or not, we should pay attention to the distributing and place of weak pervious layer.