Author(s): Wenxue Chen; Jiguang Liu; Jun Guo; Di Hong; Sicun Shi
Keywords: Horizontal vortex spillway tunnel; Prototype observation; Dissipator; Aeration
Abstract: Gongboxia Hydropower Project locates on the upstream of Yellow River. The dam is the concrete faced rockfill dam with 139m high. The shaft horizontal vortex spillway tunnel is on the right bank, which has been reconstructed by utilizing the existing diversion tunnel. The maximum head and discharge flow of this vortex spillway tunnel are 110m and 1090m3/s respectively. The prototype observations were carried out at nearly design flood in August 2006 to evaluate properties and safeness of the vortex spillway tunnel and to verify model results. During the prototype observations, the water level in the shaft and near the outlet of the tunnel, pressure distribution and air concentration distribution in the shaft and the swirling flow generator, air flowrate of the vent systems, structure vibration and structure dynamic response etc. were measured. The observed results show that: the flow pattern in the inlet and in the diversion tunnel are quite steady; the discharge capacity of the spillway tunnel satisfies design demand; the aerator in the shaft works well and do protect the structure from cavitation damage; the mean velocity in the outlet of the spillway tunnel is about 14. 4m/s and the energy dissipation rate of the spillway tunnel is about 84. 5% ; while structure vibration and structure dynamic response of the spillway are very small. The prototype observation results indicate that the shaft horizontal vortex spillway tunnel can operate safely.