Abstract
The stability analysis of damaged landslides and unstable debris is important for rescue work and emergency operations. This paper investigates a predisposed geological emergence, inducing the factors and deformation processes of the Zhongbao landslide, which happened on July 25, 2020. The stability of the landslide debris was evaluated by an integrated monitoring system consisting of ground-based radar, unmanned aerial vehicles, airborne Lidar, thermal infrared temperature monitoring, GNSS displacement monitoring, deep displacement monitoring, and rainfall monitoring. The strata and weak layer controlled the landslide failure, and topography defined the boundary of the failed rock mass. A continually intensive rainfall caused the deformation and accelerated failure of the landslide. The shallow and steep deposit (Part I) firstly slid at a high velocity, and then pushed the rear part of the landslide (Part II) to deform, forming numerous cracks, which accelerated the rainfall infiltrating into the rock mass. The moisture content increase could decrease the strength of the shale rock within the bedding planes. Finally, with the rock and soil mass sliding along the weak layer, a barrier dam and a barrier lake were formed. The monitoring and numerical simulation results showed that after the landslide failure, there was still local collapse and deformation occurrences which threatened rescue work and barrier lake excavation, and the stability of the accumulation area gradually decreased as the rainfall increased. Therefore, the barrier dam was not excavated until the accumulation rate gradually stabilized on July 28. Moreover, most of the reactivated deposits still accumulated in the transportation and source areas. Thus, in August, the displacement of the landslide debris gradually accelerated in a stepwise manner, and responded strongly to rainfall, especially in the accumulation area, so that it was inferred that the damaged landslide could slide again and cause a more threatening and severe failure. The analysis results of the study area can provide references for the failure mechanism of a rainfall-induced landslide and the stability evaluation of a damaged landslide.
Highlights
Rainfall-induced landslides are widely distributed in the world, for example, over 2,500 landslide events were reported between 1950 and 2005 (Tohari, 2018)
Rainfall increases the weight of the sliding mass, decreases the shear strength of the soil, and groundwater level change could cause dynamic and static pore pressure inside landslide (Tsai, 2008; Li et al, 2018a)
It is necessary to study the deformation characteristics and failure mechanism of affected bedding rock slopes triggered by rainfall
Summary
Rainfall-induced landslides are widely distributed in the world, for example, over 2,500 landslide events were reported between 1950 and 2005 (Tohari, 2018). Some new technologies have been developed to monitor landslide deformation, such as GB-InSAR, TLS, IRT, digital photogrammetry (DP), and so on (Nicola et al, 2010; Del Ventisette et al, 2011; Bardi et al, 2014; Crosetto et al, 2016; Zin et al, 2016; Casagli et al, 2017; Li et al, 2020; Zhou et al, 2020), and have achieved remarkable achievements in monitoring, prediction, and early warning of the landslides (Xu et al, 2016; Piciullo et al, 2018; Ouyang et al, 2019) Those technologies are characterized by more efficient operation and higher accuracy of monitoring data, compared with traditional monitoring sensors: offering high-resolution image data acquisition, data diversity, device portability, and easy and fast data processing (Casagli et al, 2017). There are few reports about using these technologies to monitor damaged landslide debris, where local deformations or further collapse can still occur and threaten rescue and emergency work
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