Author(s): Jun Guo; Zhiping Liu; Jiguang Liu
Keywords: High dam; Flow discharge; Spray; Field observation
Abstract: The flow discharging on a high dam often causes strong spray and it quite different from the heavy rain. It can cause the bank slope unstable, interrupt the access to the power plant and influence the operation of switchyard or transmission line. The paper introduces three different situations causing by discharging sprays and field measurement results and studies based on these problems. Lijiaxia arch gravity dam is located on the upstream of the Yellow River, the first operation by middle outlets and bottom outlet during the reservoir filling in the winter in 1996 caused serious spray and banks slides. The observation on spray helps the designer to make proper protection measures. Ertan is the highest arch dam under the operation in China with a height of 240m. The discharge facilities are 7 surface spillways, 6 middle outlets and 2 tunnel spillways, there was no experiences on spray protection for such high dam and large discharge flow. The field observations between 1998 to 1999 on spray give clear indication on the distribution of spray by different operations. Such observation results are also very valuable for the research and protection of banks on the spray of the other project under the design or construction. Dachaoshan Project is a gravity dam with 5 spillways and 3 bottom outlets. The access tunnels of underground power plant, transformer tunnel in the project are on the right bank of the dissipation zone by the bottom outlets. The design of the protection gallery and its length are verified by the observation. The field observation of the spray is the best way to understand the mechanism of spray and safety of banks and structures, as there is scale similarity on the physical model test. The proper measures can be taken through the measured results. The measured results in prototype on sprays from the different projects are very valuable. These can be applied for calibrating the mathematic model for predicting the spray situations, affected areas, spray intensities and distributions for a new design project. The research work on spray prediction and simulation is under going on.