Abstract
A subsidiary weir is proposed to be constructed downstream of each of the existing barrages on the Nile river in Egypt to secure its stability, which might have been affected after the construction of the Aswan High Dam. The present paper is intended to investigate the characteristics of seepage flow beneath two structures with an intermediate filter. The downstream structure (the proposed weir) has a slopping middle apron and two flat aprons in the upstream and downstream sides and is also provided with upstream and downstream cutoffs. The upstream structure (the existing barrage) has upstream and downstream cutoffs. A conformal mapping technique is used to solve the problem. Equations to calculate the uplift pressure distribution acting on both the existing barrage and the suggested weir are obtained; also equations to calculate the values of exit gradient along the intermediate filter and the downstream bed are derived. The seepage flows which seep into and/or drained from the intermediate filter are estimated. The analytical results are verified using experimental measurements performed on electrical analogue model and a very good agreement is noticed. A computer program is designed to compute the seepage flow, the uplift pressure and the exit gradients.