Large deformation mechanisms of the Xiaochatou landslide reactivated by the impoundment of the Wudongde reservoir based on multisource data and the material point method (MPM)
摘要
Landslides triggered by reservoir impoundment, particularly those resulting in considerable deformation, have increasingly become important concerns in the Wudongde Reservoir area. This study focuses on the characteristics of the deformation and reactivation mechanism of the Xiaochatou (XCT) landslide reactivated by the third-phase impoundment of the Wudongde Reservoir, which underwent large deformation of up to 9 m after five periods of reservoir fluctuations. Multisource data from satellite images, optical images, uncrewed aerial vehicle (UAV) field surveys, crack extensometers, inclinometer, global navigation satellite systems (GNSSs), rainfall gauge and reservoir level, along with wavelet coherence, were utilized to investigate the deformation characteristics and explore the main causes of reactivated landslide deformation. In addition, the reactivation mechanism was revealed via the material point method (MPM) in combination with the cross-correlation function (CCF). The results indicate that the XCT, an old landslide, continuously deformed after the third-phase impoundment of the Wudongde Reservoir. Large displacement magnitudes exhibit progressive attenuation from 8‒9 m at the toe to 1‒2 m at the crown. Wavelet coherence revealed that the XCT landslide was reactivated mainly by reservoir impoundment. During the third-phase impoundment at Wudongde Reservoir, rising groundwater weakened the landslide material, increasing the pore pressure and reducing the effective stress, which led to deformation at the front edge. This outcome provided space for deformation at the rear edge, forming shoulder cracks and exerting loading toward the center. Consequently, the landslide underwent composite reactivation characterized by traction and thrust.