The Effect of Bottom Holes’S Spacing and Diameter of Suction Pipe on the Efficiency of Burrowing-Type Sediment Removal Method

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Wednesday 1 july 2015

12:39 - 12:42h at Oceania (level 0)

Themes: (ST) Sediment transport mechanisms and modelling, (T) Sediment management and morphodynamics, Poster pitches

Parallel session: Poster pitches: 8A. Sediment - Erosion

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Reservoir sedimentation declines the reservoir storage and water conservation, also, can arise many problems such as reduction in capacity for flow regulation, reservoir lifetime and flood control volume, and many other types of sediment-related problems. Several techniques have been proposed to prevent entrance of sediment to the reservoirs and/or removing deposited sediment from reservoirs. However, actual observations of world reservoirs sedimentation rates have revealed that the problem still remains. The "burrowing-type sediment removal suction pipe method" is widely considered among the new methods introduced in the last decade. This study investigates the influence of geometrical and mechanical properties of suction pipe on mean sediment discharge concentration as a measure for evaluating the burrowing-type method efficiency using laboratory experiments. This research, also, study the time series of sediment discharge, and suction pipe piezometric head. A series of experiments are conducted to find out the effect of bottom holes diameter and spacing, and weighted bent part of the pipe on the performance of the method. A flexible spiral duct pipe with internal diameter of 61 mm was used as suction pipe, and the values of bottom holes diameter to pipe diameter varied from 0.25 to 0.5. The distance between bottom holes changed from 2 to 4 times of holes diameter. The results showed that the buoyant weight of pipe bends part has a remarkable effect on method performance. With the increase of bend part weight from 3.47 to 9.36 N the performance increases and it decreases just the buoyancy weight were more than 9.36 N. Also, results showed that the decrease of the bottom holes spacing ratio from 4 to 2 increases the efficiency and the suction flow has its maximum average concentration (performance) at spacing ratio 2, with an amount of 1.58 %. The results of diameter ratio of 0.25 has less fluctuations and more efficiency than diameter ratio of 0.5. Finally, the sediment discharge time series showed that after the beginning of the test, the suction flow concentration has a rapidly increasing trend till the pipe reaches to reservoir bottom, and then the concentration decreases gradually.