THREE DIMENSIONAL ANALYSIS OF UPLIFT IN GRAVITY DAMS BY FEM

Abstract

Uplift pressures developed by water seeping through a gravity dam and its foundation play an important role in the stability of the dam. To reduce these pressures, formed drains in the dam body -and drainage holes in the foundation are provided. The extent of the relief depends on diameter, location and spacing of drains and on relative perviousness of the dam and the foundation. The rational solution of this problem, capable of simulating realistically all these parameters is still not available. However, with the advent of highpower computers and latest advances in numerical techniques like finite element methods, it is now possible to arrive at rational and reliable solution of this complex problem. In this work, an attempt has been made to evaluate the uplift pressures within the dam body and also in the foundation using finite element method. The method of analysis duly accounts for the three dimensional seepage based on Darcy's law. The effect of relative permeability of the dam and the foundation, location and spacing of drains, and seeping discharge under different drainage conditions have been studied. Average pressure distribution from upstream face to downstream face, average pressure intensity at drains for different drain location and spacings have been evaluated and plotted. The results of the analysis have been compared with two dimensional analysis by seepage theory and with current design practice.....