Abstract:
Objective Influenced by reservoir regulation and rainfall in the Three Gorges Reservoir area, the monitored displacement-time curves of many landslides show step-like deformation that is strongly affected by hydrodynamic pressure. To investigate the deformation mechanism of hydrodynamic-pressure-induced landslides, this study takes the Xiangxi Seed Station landslide as an example and reveals its deformation response and formation mechanism under the effects of reservoir water and rainfall.
Methods Geological investigation, monitoring-data analysis, and numerical simulation were combined to systematically examine the landslide deformation process.
Results The results indicate that reservoir-water drawdown is the primary factor inducing landslide deformation. In particular, when the water level continuously declines within the 145～160 meters range, outward-directed hydrodynamic pressure triggers deformation at the front of the slope and pulls the rear part to form tensile cracks. A single displacement step ranges from 30 to 100 mm and is mainly completed within 20～50 days. By contrast, reservoir-water-level rise has little influence on slope deformation.
Conclusions Data analysis shows that step-like landslide deformation lags behind reservoir-water drawdown and that the drawdown rate is positively correlated with deformation intensity: a higher drawdown rate corresponds to a shorter lag time and a larger step displacement. Rainfall promotes landslide deformation only during reservoir drawdown and low-water-level operation, and it has almost no effect during water-level rise or high-water-level operation. These findings provide a theoretical basis and engineering reference for monitoring, early warning, and prevention of similar hydrodynamic-pressure-induced landslides in the Three Gorges Reservoir area.
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