为研究滑坡在库水位变动下的变形演化机制,以车邑坪滑坡为原型,建立了1∶70滑坡概化模型,设计了一套库水位升降系统,开展了一次水位抬升及两次不同速率水位连续骤降的离心模型试验。研究结果表明:水位抬升阶段滑坡变形不明显;当水位首次骤降时,滑坡前缘拉裂缝迅速发展贯通形成断裂带,随后断裂带下错滑塌,中后部产生张拉裂缝;当水位二次骤降时,滑坡沿原断裂带继续下滑,但滑动程度明显减弱,中后部竖向压密行为导致裂缝扩展趋稳。水位抬升阶段孔压滞后性明显,随后各阶段逐渐减弱,前缘滑体土压各阶段变幅剧烈,而中后部在首次骤降时最剧烈。总体上来看,导致滑坡失稳的水位骤降速率区间为0.7~1.5 m/d,滑坡深部动水压力效应较浅层强烈,滑坡变形受库水位首次骤降影响强于二次骤降,变形破坏呈现由前缘到后部逐渐减弱的牵引式特征,各阶段依次呈现初始变形、加速变形及减速变形特征。

To investigate the deformation and evolution mechanism of landslides under changing reservoir water levels, a 1∶70 scale model of the Cheyiping landslide was established, and a reservoir water level rising and falling system was designed. Centrifugal model tests were conducted with one water level rise and two consecutive water level plummets at different rates. The findings reveal that during the water level rising stage, the landslide deformation is not significant. However, during the initial water level drop, tension cracks in the front edge of the landslide develop rapidly and form a fracture zone. Subsequently, the fault zone collapses and tension cracks appear in the middle and rear part of the landslide. During the second water level drop, the landslide continues to slide along the original fracture zone, but the sliding noticeably attenuates. The vertical compaction in the middle and rear parts of the landslide leads to the stabilization of fracture propagation. During the water level rising stage, the pore pressure exhibits noticeable lag and gradually diminishes in subsequent stages. The soil pressure in the leading edge of the sliding mass varies significantly in each stage, while in the middle and rear changes most severely during the first rapid water level drop. Overall, the water level drop rates that lead to landslide instability range from 0.7 to 1.5 m/day. The dynamic water pressure effect is stronger in the deeper parts of the landslide compared to that in the shallower layers. The deformation of the landslide is more influenced by the initial water level plummet than the second. The deformation and failure gradually decrease from the front to the rear, resembling traction characteristics.The water level rising, the first plummeting and the second plummeting stages demonstrate initial deformation, accelerated deformation, and decelerated deformation characteristics, respectively.