Finite Element Analysis Of The Effect Of Impervious Core Wall Inclination On The Behavior Of Steady State Phreatic Line (In Isotropic And Homogeneous Earth Dam).

摘要

Mathematically, the objective of this study is to find, by Finite Element Method (FEM), the best fit curve of the steady state phreatic line in an earth dam composed of homogeneous and isotropic bulk material, when an impervious core wall is placed in it in an inclined position, either towards the upstream or towards the downstream.;The problem involved is a scalar field problem governed by Laplace's particular form of the general quasi-harmonic equation along with specified boundary conditions of the flow domain. The flow domain considered is two-dimensional and isotropic. The flow considered is steady. The dam is assumed to be composed of homogeneous bulk material. The dam base is assumed to be impervious.;Functional approach to FEM formulation adopted. Principle of minimum of potential energy used to develop the FEM model. Natural Boundary conditions are incorporated in the model itself. Penalty approach is used to input the essential boundary conditions in the global stiffness matrix. The penalty value used is of order 104. Gauss elimination method is used to solve the set of resulting algebraic equations.;Total 42 pre-defined dam sections (6 test data sets consisting 7 dam sections each) with different core wall inclinations and core wall heights have been used to arrive at some conclusive theoretical solution. FEM solutions are also found for dam sections concerning a laboratory model and results verified experimentally. The user may also use his own set of data.;No mention could be found in existing literatures about intentionally placing a core wall in an inclined position and perhaps this study is the first attempt to introduce such a concept. The concept bears much practical significance because the possibility of using an inclined barrier to seepage can open up the prospect of using alternative core wall construction materials such as impervious geo-textile sheets which is likely to result in much savings in the time and costs of construction and supervision.;The author has improved upon the traditional FEM solution which offers solutions at discrete points by using the concept of best fit curve to make it possible to obtain the results in continuous form. Such improved continuous solution is more useful in describing the phreatic line. Legendre's Method Of Least Square is used to construct the best fit curve equation.