Abstract
Since the impoundment of the Three Gorges Reservoir (TGR) in June 2003, the fluctuation of the reservoir water level coupled with rainfall has resulted in more than 2500 landslides in this region. Among these instability problems, most colluvial landslides exhibit slow-moving patterns and pose a significant threat to local people and channel navigation. Advanced monitoring techniques are therefore implemented to investigate landslide deformation and provide insights for the subsequent countermeasures. In this study, the development pattern of a large colluvial landslide, locally named the Ganjingzi landslide, is analyzed on the basis of long-term monitoring. To understand the kinematic characteristics of the landslide, an integrated analysis based on real-time and multi-source monitoring, including the global navigation satellite system (GNSS), crackmeters, inclinometers, and piezometers, was conducted. The results indicate that the Ganjingzi landslide exhibits a time-variable response to the reservoir water fluctuation and rainfall. According to the supplement of community-based monitoring, the evolution of the landslide consists of three stages, namely the stable stage before reservoir impoundment, the initial movement stage of retrogressive failure, and the shallow movement stage with stepwise acceleration. The latter two stages are sensitive to the drawdown of reservoir water level and rainfall infiltration, respectively. All of the monitoring approaches used in this study are significant for understanding the time-variable pattern of colluvial landslides and are essential for landslide mechanism analysis and early warning for risk mitigation.
Highlights
According to a previous study, more than 2500 landslides are caused by the fluctuation of reservoir water levels in the Three Gorges Reservoir (TGR) area, and many of these are colluvial landslides [6,7,8]
We studied the development pattern of a large colluvial landslide in the Wu Gorge of the TGR area
Surface deformation obtained by the global navigation satellite system (GNSS) network and crack measurements reveals the spatial variations and time evolution of the Ganjingzi landslide
Summary
The Ganjingzi landslide is located on the right bank of the Yangtze river in the Gongjiafang–Goddess peak section. Due to tectonic activity and landcover changes, the steep-sided valley, especially the exposed colluvial and eluvium deposits of the Holocene (Q4 col+el ) on the south bank of the Yangtze River, are prone to landslides (Figure 2). According to a field survey carried out by the China Geological Survey in 2016, there are 13 unstable slopes along the Yangtze River (Figure 3). In this regard, geological hazards commonly occur, especially in the bank region of the study area, which is vulnerable to the state of the river and operation of the reservoir. The reservoir water level fluctuates with scheduled velocities
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