Natural Terrain Landslide Risk Mitigation

Abstract eng:
The 2008 Wenchuan earthquake in Sichuan, China, induced about 50,000 landslides. Some landslide deposits on natural terrains reactivated in wet seasons, turning into new landslides or massive debris flows. The risks posed by such landslide deposits are rather high. During the post-quake reconstruction, various measures were taken to mitigate the risks. It is preferable to quantitatively describe the risk profile and justify the effectiveness of each risk-mitigation measure by quantifying the amount of risk reduction by the specific measure. This paper looks into the natural terrain landslide risk profiles in connection with the re-construction of a highway near the epicenter. Approximately 305 fresh landslide deposits along the road are identified (Figure 1). The societal and individual risks of these fresh landslide deposits shortly after the earthquake are evaluated, which are extremely high. Next, the risk profile of the road is reevaluated after 21 high-risk roadside deposits have been removed, and after the construction of 5 flexible net barriers and 2 protection tunnels. The maximum individual risk have been decreased from 0.063 to 0.53 and 0.45, respectively. Third, the risk profile of the road is evaluated again considering the implementation of a landslide warning system. The potential casualty in a single landslide event may be decreased from 17 to 6 persons. Each of the engineering and nonengineering measures is shown effective in reducing the risk profile of the road. However, the deposits at high elevations cannot be easily stabilized or removed. Hence the residual risk levels are still too high to be acceptable. It is suggested to further decrease the risk levels to within the ALARP range by adopting long tunnels to avoid more hazardous deposits.

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