Reactivation mechanism of a large-scale ancient landslide
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Chenyang Zhang I Yueping Yin I Zhenwei Dai I Bolin Huang I Zhihua Zhang I Xiannian Jiang I Weijia Tan I Luqi Wang
Reactivation mechanism of a large-scale ancient landslide
Abstract This paper presents details of the recently reactivated landslide in Wushan Town, Chongqing, China. The landslide was reactivated on July 17, 2019, by slope cutting, and thereafter, entered a state of imminent sliding. The landslide involved 4 million m3 of rock and soil masses, thereby threatening National Road G348 and the safety of 588 residents in 136 households in Xiping Village and over 1000 residents in the Jinke Community. Field investigations, drilling, and in situ monitoring were performed to determine the landslide deformation characteristics and reactivation mechanism. The results show that the regional abundant rainfall, formation lithology, and tectonic effects were responsible for the formation of the ancient Baiyangwan landslide. Moreover, the building load on the rear and middle parts increased the sliding force. Open excavation at the toe decreased the anti-sliding force and directly promoted landslide reactivation. In particular, the groundwater table rise caused by gully filling in recent years also played a key role in the reactivation of the ancient landslide. Keywords Baiyangwan landslide . Reactivation mechanism . Human engineering activities Introduction Since the tertiary period, hundreds of large-scale ancient landslides have occurred in the Three Gorges Reservoir (TGR) area under the combined action of internal and external geological dynamics (He and Cui 1998; Cui and Li 1999). Yan (2004) reported 596 large ancient landslides with a total volume of 21.1 × 108 m3 and a total area of 78.2 km2 along the main river channel through the TGR area. With the construction of the TGR, water impoundment began in 2003, and since 2008, the water level has been annually adjusted to maintain a flood control level between 145 and 175 m (Tang et al. 2019; Wang et al. 2019). The deformation and reactivation of some of these ancient landslides have greatly impacted the safety of the reservoir area (Dai et al. 2016; Luo et al. 2019). For example, the ancient Quchi landslide has exhibited creep deformation under fluctuating reservoir water levels in recent years (Gu et al. 2017; Huang et al. 2018; Luo et al. 2019), thus threatening the safety of Quchi Town. The ancient Liangshuijing landslide reactivated in 2008, when the reservoir water level was elevated to 171.49 m (Xiao et al. 2013; Yin et al. 2016), and damaged many buildings on the landslide body. The ancient Outang landslide, a giant bedding bedrock landslide, reactivated in recent years, threatened the safety of more than 3900 people and their property (Dai et al. 2016; Yin et al. 2016). Furthermore, towns within the inundated area of the TGR had to be relocated. Generally, in the TGR region, land resources are scarce. Thus, during the construction of new urban areas, disturbances due to slope cutting, gully filling, and building loads were inevitable (Yin 2005; Yan et al
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