Simulating Dam-Breach Flood Scenarios Of Yigong Rockslide Dam

On April 9th,2000, a catastrophic landslide occurred in Bomi county, Tibet, China. This landslide blocked the Yigong River and a barrier lake showed up. The maximum depth of the water was 62m. On June 8th, flood was released artificially. The roaring flood brought great damages to downstream.This thesis elucidated the characteristics of dam-breach flood scenarios of Yigong rock avalanche dam. By using the FLUENT software for computational fluid dynamics, the movement law of the flood is worked out under the both modle of full-dambreak and semi-dambreak.Main conclusions are reached as follows:(1) Under the circumstance of full-dambreak, it takes about 900 seconds for flood to reach the Tongmai Bridge, whereas under the circumstances of semi-dambreak, the flood can’t reach the Tongmai bridge until the end of the calculation about 1100s.(2) The evolution of the water body in the river is greatly influenced by the topography after the dam breaks. Mountains ahead will block the advancing water, reduce its energy and slower its speed. In the case of semi-dambreak, the peak speed of water reaches 40 m/s. In the case of full-dambreak, speed of water keeps increasing before it hits the mountain. The peak speed comes to 40m/s. After the collision with mountains, energy was lost and speed drastically reduced. When water reaches the Tongmai bridge, the velocity is about 15m/s and it will continue to grow according to the graph.(3)Mountains ahead cause an increase in depth of flood. In the case of semi-dambreak, the maximum depth of the water was 50m.While in the case of full-dambreak, the maximum depth is 62m. At Tongmai Bridge, the maximum depth of the water was 40m. The maximum depth occurred in the bending position of river.(4) The results of this simulation show that the peak outflow of breach under the circumstances of semi-dambreak is about 40400 m3/s, which happens 100 seconds after this dam broke. After that, outflow of breach keeps decreasing. Under the circumstances of full-dambreak, it takes the breach about 200 seconds to reach the peak outflow of 80000 m3/s. The peak outflow at Tongmai Bridge is 4371 m3/s.