Articles written in Sadhana

    • Sediment management of run-of-river hydroelectric power project in the Himalayan region using hydraulic model studies


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      Storage capacity of hydropower reservoirs is lost due to sediment deposition. The problem is severe in projects located on rivers with high sediment concentration during the flood season. Removing the sediment deposition hydraulically by drawdown flushing is one of the most effective methods for restoring the storagecapacity. Effectiveness of the flushing depends on various factors, as most of them are site specific. Physical/mathematical models can be effectively used to simulate the flushing operation, and based on the results of the simulation, the layout design and operation schedule of such projects can be modified for better sediment management. This paper presents the drawdown flushing studies of the reservoir of a Himalayan River Hydroelectric Project called Kotlibhel in Uttarakhand, India. For the hydraulic model studies, a 1:100 scale geometrically similar model was constructed. Simulation studies in the model indicated that drawdown flushing for duration of 12 h with a discharge of 500 m3/s or more is effective in removing the annual sediment deposition in the reservoir. The model studies show that the sedimentation problem of the reservoir can be effectively managed through hydraulic flushing.

    • Effectiveness of combinations of raft foundation with aprons as a protection measure against bridge pier scour


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      Scour around bridge pier is the main reason for the failure of bridges. The local scour around the pier causes exposure of the foundation and may lead to undermining of the structure. Different types of protection measures such as the provision of raft, apron, sheet piles, etc. can be used as scour protectionmeasures. One of the possible effective bridge scour protection measures is to provide a raft foundation with cutoff walls and provision of flexible stone aprons towards upstream (u/s) and downstream (d/s) sides of the pier. In this study, the effectiveness of various bridge pier scour protection measures using raft and aprons is investigated through hydraulic model studies in the laboratory. The results are compared for various cases, such as a simple pier, pier with raft and extended raft, pier resting on a raft with stone aprons at u/s and d/s of the raft and pier resting on an extended raft with stone aprons on u/s and d/s of it. The comparison of various cases showed that rigid raft with stone aprons on u/s and d/s and extended raft with apron are found to be more effective in reducing immediate scour beyond the rigid raft, thereby giving protection to the bridge piers.

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