Abstract

AbdelHameed M. AlTahan
Effect of Upstream Cutoff Position on both Uplift and Efficiency underneath Hydraulic Structures
Two main problems face the stability of hydraulic structures, piping and uplift. Cutoffs are used to increase the horizontal length of seepage under the apron of the hydraulic structures to overcome the effect of both uplift and piping under these aprons. The position of each cutoff is critical for decreasing the effect of both. In this study, an electrical analogue model was used to investigate the effect of the position of the upstream cutoff L1 and the distance of the downstream cutoff Lt both measured from the upstream edge of the apron and the depth of the upstream and downstream cutoff D1 and D2 respectively on the uplift forces along the hydraulic structure and the rear and front faces head of both upstream and downstream cutoff. Each of the previous parameters were measured, unit head were calculated and compared for all of the cases understudy, the lowest values for piping and uplift were determined and the highest effect of downstream and upstream cutoff were determined for the cases understudy. The ratio between the distances of the upstream cutoff L1 the total length of the apron Lt (L1/Lt) ranged from 0 to 1. The ratio between depths of the upstream cutoff D1 and the downstream cutoff D2 (D1/D2) ranged from 0.75 to 1.25. 16 models were tested with total number of 64 runs.