Sediment removal from dam reservoirs using syphon suction action

Abstract

Dam reservoir siltation is a worldwide problem that results in loss of storage capacity and blockage of drainage outlets. Previous sediment removal techniques include flushing, excavation, dredging, and sluicing. In this study, sediment removal is investigated experimentally using image processing techniques, to assess the suction action of a syphon pipe. The syphon results in a scour hole that depends on several factors including the sediment mean diameter (d₅₀), the applied suction head (H_w), the pipe diameter (d_p), and the penetration depth (Z_o). One soil type was used, poorly graded sand (d₅₀ of 1 mm), to examine the interdependence of the other factors on the developed scour hole at equilibrium. Three heads (H_w) of 0.82 m, 1.04 m, and 1.22 m were applied and three pipe diameters (d_p) of 6 mm, 9.5 mm, and 13.8 mm were used. Various Z_o values that ranged between 0.0 and 7.0 cm were used. Measurements of the hole depth (h_d), the hole diameter (D), and the removed soil mass were recorded. Non-dimensional characteristic relationships between the different factors were developed and a new non-dimensional design parameter (ϕ) is proposed to be used for estimating the scour hole dimensions. The design parameter ϕ depends on (Z_o/H_w) and Reynolds number as input parameters. The results indicate a linear relation between (D/d_p) and (h_d/d_p) with a regression coefficient (R²) ≈ 0.98, and a power-law relation between the normalized weight of the removed sediments (W_s/F_p) and (h_d/d_p) with R² ≈ 0.95, where F_p is the suction pressure force.