THREE DIMENSIONAL SEEPAGE ANALYSIS BELOW A BARRAGE (BY FEM)

Abstract

Hydraulic structures such as weirs and barrages on pervious foundation are generally designed on the basis of Khosla's theory considering 2-D sub surface flow below the structures. The correct approach in the estimation of uplift pressure below hydraulic structures (barrages) built on previous foundation would be the one that takes into account the 3-dimensional flow conditions due to high water table behind the abutments. The subsoil water table conditions have a marked influence on the uplift pressures in the barrage floor adjacent to the abutments. It is also. important to study the variation of uplift pressures due to variation of water table. The practice is to take adhoc measures to control and,reduce the pressures on the floors due to variation in water table elevation behind the abutments such as provision of intermediate filters, pressure relief wells etc. Their efficiency is not quantifiable. The floor of the bay adjoining the abutment are designed for about 15 to 20% extra uplift pressure. In important major structures, this aspect is sometimes examined on electrical analogy model. It has several limitations and is time consuming and costly.. An attempt is made in this study to work out analytical solution to the problem. The study is carried out using 3D-FEM technique through ANSYS package program. In this study as an illustration Kanpur barrage is taken as an example.....