Abstract
On 4 April 2013, a 1.5 million cubic meter landslide occurred in Sunjia Town, Wanzhou County, Three Gorges Reservoir, China. After initiation, the Sunjia landslide traveled about 30 m toward the northeast and destroyed most of the infrastructure in its path. The landslide was triggered by heavy rainfall and previous slope excavations, but this slope also displayed a complicated failure process: the overlying earth slope first deformed and then induced sliding along underlying rock surfaces. Surface displacements that resulted from continuous creeping of the post-event slope were observed by an emergency monitoring system that revealed the disequilibrium state of the slope. To discuss the stability and future movements of the remaining unstable debris deposits, we developed a geotechnical model of the post-slide slope, calculated how it can slide again in an extreme rainfall scenario, and estimated the potential runout distance using the Tsunami Squares method. We then estimated the number of people and the value of the infrastructure threatened by this potential landslide. Lastly, we analyzed the vulnerability of elements at risk and quantitatively evaluated the hazard risk associated with the most dangerous scenario. This quantitative risk analysis provides a better understanding of, and technical routes for, hazard mitigation of rainfall-induced complex landslides.
Highlights
Rainfall-induced complex landslides often exhibit characteristics of progressive deformation and failure, and threaten people’s lives and properties all over the world (Baum and Godt 2010; Martha et al 2015; Bignami et al 2018; Conte et al 2018)
The Sunjia landslide occurred in Wanzhou County, in the Three Gorges Reservoir region, an area considered one of the most landslide-prone in China
We evaluate landslide hazard as a joint probability of temporal and spatial probabilities under the conditions of extreme rainfall outlined in scenario D (100-year return period rainfall for 10 days) that would trigger the slope failure with a magnitude simulated by the Tsunami Squares method
Summary
Rainfall-induced complex landslides often exhibit characteristics of progressive deformation and failure, and threaten people’s lives and properties all over the world (Baum and Godt 2010; Martha et al 2015; Bignami et al 2018; Conte et al 2018). Many numerical methods for landslide runout modeling have been proposed in recent decades, such as DAN3D (Hungr and McDougall 2009), LS-RAPID (Sassa et al 2010), MassFlow (Ouyang et al 2013), and Tsunami Squares (Wang et al 2015, 2019; Xiao et al 2015; Xiao et al 2018) In view of these considerations, landslide hazard analysis needs to take into account the intensity of each landslide, which can be defined in terms of its volume and sliding velocity (Fell 1994). To discuss the potential risk, we develop a geotechnical model of the landslide, calculate its failure probability, and simulate the potential run out distance using the Tsunami Squares method (Wang et al 2015; Xiao et al 2015) Combining these results, we evaluate the potential risk of this slope based on a detailed investigation of the endangered elements
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