Study On Approximate Approach For Calculating Seepage Flow Into A Drain By Finite Element Method

With the acceleration of urbanization process,underground space development has become one of the effective ways to achieve sustainable urban development.As the scale and depth of the development further expand,the anti-floating engineering problem is becoming increasingly severe.The active anti-floating method with cut-off wall and pressure-relief drainage at its core is one of the valid means to solve the problem,in which drain represented by drainage gallery and french drain,etc.,is one of the common tools to realize the goal of relieving pressure by drainage.The main content of this dissertation is the research on approximate equivalent method for calculating seepage flow into a drain by Finite Element Method(FEM).Around this topic,three aspects of the author's work can be reduced to the following:1.Study on simplified method for 2D seepage calculation of drain node by FEM.The Analytical solution for the problem of seepage flow to a drain in a homogeneous,isotropic confined aquifer is derived first by Conformal Transformation Method(CTM),then based on Cao et al.'s work of the modified formula for well node with common mesh generation,the modified formula for drain node with common mesh generation is presented.2.Study on approximate equivalent method for pressure flow and free flow of a drain.The simplified methods for calculating inflow into a drain under normal conditions at home and abroad are summarized and compared.Moreover,for the case of free flow of a drain under submerged state,the approximate equivalent method for pressure flow and free flow of a drain by calculating the average head of drain wall and translating the 'centroid' of drain flow is proposed.3.Study on approximate equivalent method for the shape of drain's cross section.The analytical solutions for the problem of seepage flow to a drain with the shape of circle and rectangular under infinite boundary condition are derived by CTM,and the mapping relationship between them is obtained.Further,with the assumption of equal perimeter of inflow and outflow,the approximate equivalent method for rectangular drain and circle drain by calculating the equivalent radius is introduced.