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Landslides often occur within the reservoir area behind dams. In China, a common strategy for stabilizing these landslides is to install large piles through the landslide and into the stable ground below. The piles interact with the landslide and constitute a landslide-stabilizing pile system. The deformation of this system under the reservoir operation is more complicated than the deformation of the landslide itself. Understanding the behaviour of this system is very important to the long-term safety of landslides stabilized with piles in reservoirs. The Majiagou landslide, which was selected as a case study, was triggered by the first impoundment of the reservoir behind the Three Gorges dam. A row of anti-slide piles was installed in the landslide in 2007, but monitoring results found these were ineffective at stabilizing the landslide. Subsequently, in 2011, two longer test piles and an integrated monitoring system were installed in the landslide to better understand the failure mode of the landslide and to measure the deformation characteristics of the landslide-stabilizing pile system. Monitoring results show that the Majiagou landslide is a translational landslide with three slip surfaces. The test piles provided local resistance and partially slowed down the sliding mass behind the piles, and the landslide deformation response to external factors decreased for a time. However, after 2 years, the deformation of the landslide-stabilizing pile system reverted to seasonal stepwise cumulative displacements influenced by cycles of reservoir drawdown and rainfall. The monitoring results provide fundamental data for evaluating the long-term performance of anti-slide piles and for assessing long-term stability of the stabilized landslide under the reservoir operation. [ABSTRACT FROM AUTHOR]

Water level fluctuations and rainfall, as external factors, are typically the two dominant causal factors of landslide deformation in the Three Gorges Reservoir Area. A quantitative model capable of evaluating landslide deformation processes is critical for early warning of landslide. The primary purpose of this paper is to take the Zhujiadian landslide as an example to determine the main control factors for different deformation stages of landslide. Original field date collected from the Zhujiadian landslide was examined using the grey relational grade analysis (GRGA). The approach consists of three steps: determination of landslide type, data processing, and identifying the main control factors of landslide deformation. The results obtained suggest that the Zhujiadian landslide is typical retrogressive landslide, and its deformation occurred first at the front part of the landslide and progressed upslope due to drawdown of reservoir water level and heavy rainfall. In the whole deformation process, the main control factors of different parts of landslide changed with the landslide development. Thus, the findings of the study are useful for rapidly predicting landslide deformation relating to water level fluctuations and rainfall, and the GRGA is useful for interpreting the main control factors of landslide deformation from a quantitative point of view. [ABSTRACT FROM AUTHOR]