Author(s): Takahiro Koshiba, Sameh A. Kantoush, Tetsuya Sumi
Linked Author(s): Takahiro Koshiba
Keywords: Sediment Bypass Tunnels (SBTs), reservoir sedimentation, geophone, hydrophone, sediment transport
Abstract: In order to prevent reservoir sedimentation, Sediment Bypass Tunnels (SBTs) to reduce the sediment inflow by diverting sediments around a dam is an attractive solution. However, SBTs are prone to severe invert abrasion caused by high sediment flux. To estimate abrasion damage, it is important to establish a sediment transport measurement system because abrasion prediction model is basically depending on actual bedload flux in the SBT. For this purpose, impact plates, one surrogate bedload monitoring system, have been installed at the outlet of the Koshibu SBT. Field-based calibration test where 10 cases of experiments, varying grain size, water discharge, and sediment volume, were conducted with the sediment artificially damped inside the tunnel and flushed down with clean water from the inlet of SBT. Several recorded data showed that the impact plates worked well by indicating the timing of sediment passage, and showing a good correlation with the grain size. In particular, the number of waveform spikes possess the characteristics of transported particle size. In this study, the spatial distribution of transported particle size is computed by using the number of spikes. Finally, it is found that the sediment with large grain size flows faster than the smaller particles. Furthermore, another finding is that tunnel curve affects the spanwise sediment concentration of the bypassed flow is in line with the past experience observed through SBTs operation in Japan and Switzerland
Year: 2017