ANALYSIS OF SEEPAGE THROUGH AN EARTHDAM WITH UPSTREAM LINING

Abstract

The analysis of unconfined steady state seepage through an earth dam constructed on a pervious foundation of large depth has been carried out using inverse hodograph and conformal mapping. Three cases have been dealt : (i) seepage through an earth dam with narrow upstream impervious lining. (ii) seepage through a homogeneous earth dam without lining and (iii) seepage beneath an earth dam with wide upstream impervious apron. It has been analysed that for length of the upstream lining greater than 0.441h, where h is the height, of water in the reservoir, phreatic line does not enter the body of the dam. Thus, the earth dam will be in ideal condition if width of apron is more than 0.441h. The provision of upstream impervious apron does not reduce the seepage loss when the foundation of an earth dam is of infinite depth and water table lies at larger depth because the seepage is still infinite. Provision of upstream impervious apron reduces the saturated zone in the embankment. The hydrodynamic uplift pressure distribution should be used to analyse ti Le safety of the lining against uplift for rapid drawdown in the reservoir.