Numerical investigation of the air blast generated by the Wenjia valley rock avalanche in Mianzhu, Sichuan, China

摘要

On 12 May 2008, a catastrophic rock avalanche was triggered by an earthquake in Mianyang, Sichuan, China. This catastrophic event killed 48 people and destroyed some houses at the mouth of Wenjia valley. The sliding mass caused a powerful air blast that blew down the trees on both sides and front margin. To better understand the possible mechanism of the air blast generated by the Wenjia valley rock avalanche and provide information for the assessment of this type of disasters in southwestern China, a numerical simulation was performed through a computational fluid dynamics software (Fluent) to simulate the runout behavior of the sliding mass and dynamic characteristics of the air blast. The frictional rheology is used for the source area and the Voellmy model is selected for the erosion and deposition areas. Simulated results indicate that the movement process of Wenjia valley rock avalanche lasted approximately 210 s with a maximum velocity of 65 m/s. The maximum velocity and relative pressure of the air blast are 35 m/s and 2.25 kPa, respectively. Furthermore, the variation of topography has a significant effect on the distribution of relative pressure for the air blast. The work conducted in this study is expected to make people deeply realize the disaster caused by the air blast and establish a risk assessment system in the southwestern China.