Successful emergency evacuation from a catastrophic loess landslide reactivated by the torrential rain in October 2021 in Tianshui, Ganusu, NW China

Abstract

Background At the beginning of October 2021, the northwest China suffered torrential rainfall and several loess landslides were induced in Northwest China. This work presents a typical case (the Zhongzhai landslide) reactivated during this period in Niangniangba town, Tianshui, Gansu, China. The retrogressive failure was triggered again in the early morning of 5 October 2021 after a succession of torrential rain, and buried 2 houses and damaged another 2 houses. In this work, the geometric feature, soil composition, evolution history and failure process were preliminary described based on field investigation, history satellite images, and unmanned aerial vehicle photogrammetry. Results The Zhongzhai landslide is mainly composed of Malan loess and the underlain silty slate, and the sliding surface is localized at their interface. The tensile cracks near the main scarp provide favorable channels for rainfall precipitation and the permeability difference between loess and silty slate enhances the liquefaction occurrence. The counter-tilt silty slate benefits water impoundment and exacerbates the flow-like slope failure. The lag effect is obvious in the Zhongzhai landslide due to the rainfall infiltration process and pore pressure generation. Conclusions Although the Zhongzhai landslide is characterized with small scar and shallow sliding surface, it provides a classic case both for evolution history investigation of loess landslide and successful emergency evacuation. Based on our preliminary study, the unstable mass at the source of the Zhongzhai landslide with an area of approximately 3600 m2 that was slightly displaced in this event and has a high possibility to slide in future. Meanwhile, the Zhongzhai landslide is a retrogressive landslide and progressive failure occurred in the 2021 case, further analysis concerning the relationship among rainfall intensity, infiltration rate and pore water generation, as well as motion feature and runout prediction will be conducted.

Extreme hourly precipitation characteristics of Mainland China from 1980 to 2019

“…Zhang et al . (2016) showed that the rate of this hourly precipitation data correctness at all stations is generally high.…”

“…The proportion of missing values at all stations was less than 7.7%, and approximately 98% of stations had less than 5% missing data (Figure S2c). Zhang et al (2016) showed that the rate of this hourly precipitation data correctness at all stations is generally high.…”

“…The hourly precipitation data over the Chinese mainland are obtained from the National Meteorological Information Centre (Zhang et al ., 2016). There are 2,157 national ground observation stations in this study from 1980 to 2019.…”

Diurnal cycle of precipitation over the southeastern Tibetan Plateau and surrounding regions: Insights from intensity–frequency structure

“…Hourly records from 303 gauge stations within the study region (96°–107°E and 21°–34°N, as shown in Figure 1) are used, to investigate the climatic characteristics of precipitation there during the period of 1995–2015 in summer (June–August). The data set is provided and quality‐controlled by the National Meteorological Information Center of the China Meteorological Administration (Zhang et al, 2016). The missing value is less than 10% of all records of each selected station during the study period.…”

Experimental study on disaster mechanism of completely weathered granite landslide induced by extreme rainfall

“…As the soil mass gradually reached saturation (Fig. 1), the anti-sliding force reduced while the sliding force increased, leading to the instability of the landslide mass (Zhang et al, 2022). Due to the vast uncertainty of natural slope materials, accurately quantifying the impact of rainfall on slope failures remains a major challenge, and physical model tests are still one of the most effective methods to study landslides.…”