Characteristics and numerical runout modelling of a catastrophic rock avalanche triggered by the Wenchuan earthquake in the Wenjia valley, Mianzhu, Sichuan, China
The 2008 Wenchuan earthquake triggered more than 100 rock avalanches with volumes greater than 10 million cubic metres. The rock avalanche with the longest runout amongst these destructive landslides occurred in the Wenjia valley, Mianzhu, Sichuan, China. The landslide involved the failure of about 27.5 million cubic metres of sandstone from the source area. The displaced material travelled about 4,170 m with an elevation descent of about 1,360 m, equivalent to a fahrböschung of 16.9° and covered an area of 1.5 million square metres, with the final deposited volume of approximately 49 million cubic metres. The catastrophic event destroyed the village of Yanjing, killed 48 people and buried some houses at the mouth of the Wenjia valley. On the basis of a detailed field investigation, we introduce basic characteristics of the rock avalanche and find that the rock avalanche resulted in two run-ups and a superelevation along the runout path, and downslope enlargement due to the entrainment of path materials. A numerical model (DAN3D) is used to simulate the post-failure behaviour of the rock avalanche. By means of trial and error, a combination of the frictional model and Voellmy model is found to provide the best performance in simulating this rock avalanche. The simulation results reveal that the rock avalanche had a duration of about 240 s and an average velocity of 17.4 m/s.
KeywordsRock avalanche Post-failure behaviour Numerical modelling DAN3D model Wenchuan earthquake
This study was supported by the National Natural Science Foundation of China (nos. 41530639 and 41272382) and National Science Fund for Distinguished Young Scholars (no. 41225011). We are grateful to Prof. O. Hungr for supplying a copy of the DAN3D software.
- Boultbee N (2005) Characterization of the Zymoetz River rock avalanche. MSc thesis, Simon Fraser University, BurnabyGoogle Scholar
- Hungr O, Evans SG (1996) Rock avalanche run out prediction using a dynamic model. In: Senneset K (ed) Proceedings of the 7th International Symposium on Landslides, Trondheim 1, pp 233–238Google Scholar
- Sassa K (1988) Geotechnical model for the motion of landslides. Proceedings of the 5th International Symposium on Landslides, “Landslides”. Balkema, Rotterdam, vol 1. pp 37–56Google Scholar
- Wang YF, Cheng QG, Zhu Q (2015) Surface microscopic examinations of quartz grains from rock avalanche basal travel zones. Can Geotech J 52:67–181Google Scholar
- Zhang S, Zhang LM, Chen HX (2014a) Relationships among three repeated large-scale debris flows at the Pubugou Ravine in the Wenchuan earthquake zone. Can Geotech J 51(9):51–965Google Scholar