Study On Three Dimensional Numerical Simulation Of Yigong Rock Avalanche And It's Dam Breach

The widespread distribution of geological hazards in China is a serious threat to people's life and property safety.On April 9,2000,a catastrophic landslide was occurred in Yigong,Tibet,China.Based on the detailed report of post-disaster survey and physical test,a three dimensional numerical simulation was adopted to simulate the movement of Yigong landslide and the flowing process of flood after the dam collapsed.And the main results are summarized as follows:(1)Through a detailed study of Yigong landslide,we introduce the basic feature of landslide,and analyze the characteristics of Yigong dam break,establish the three numerical simulation of Yigong landslide and dam breach.(2)Based on the mechanics parameters of the soil obtained by the ring shear test,the investigation report and the movement characteristics of the Yigong landslide,the F-V model of DAN3D was used to simulate the movement process of Yigong landslide.The results showed that the maximum speed of the landslide is 90m/s at elevation from 3200m to3800m;the maximum scraping depth of the slide body to the barn groove is 80m at elevation from 2500m to 3200m;the maximum accumulation thickness of the landslide debris is 100m,located at elevation of 2200~2300m.The avalanche moved from the collapse zone to Yigong Zangbo River only costs about 3minutes.(3)After the collapsing of Yigong dam,the peak flow at the breach location reaches 126000m~3/s,which is close to the measured peak flow of124000m~3/s.The flood reached Tongmai Bridge in 2400s.At the end of the simulation,the flood flow at Tongmai Bridge reached 13000 m ~3/s.(4)During the whole evolution of the flood,the flow characteristics of the flood are affected by the topography of the river.The energy of the water flow is lossed after encountering with the mountain sides of the river,which reduces the flow velocity of the flood.In the simulation,the maximum flood velocity is about 40m/s,and the velocity in the middle of the river channel is quicker than the sides of the river.