Abstract A deep-seated flexural toppling fracture situated on the left bank of the Lancang River, Southwest China, was used as a case study of the fracture mechanism and relations with the rapid and continuous downcutting of the Lancang River. The toppling fracture body has a maximum horizontal distance to the slope surface exceeding 150 m and a volume of approximately 6 × 106 m3. Based on surface and adit surveys, the toppled rock mass was divided into three zones: highly toppled, moderately toppled and weakly toppled zones. The formation of the deep-seated toppling failure in the steeply dipping layered rock mass was the result of the intense unloading of rock mass caused by the continuous and rapid downcutting of the Lancang River. The intense unloading caused the rock mass to be relaxed and cataclastic, and formed a deep stress relaxation zone in rock mass on both banks. The toppling failure of the steeply dipping layered rock mass occurred in the stress relaxation zone under the action of gravity, and developed inwards and downwards to the lower parts of the slope with the river further downcutting. The horizontal distance to the slope surface of highly toppled and moderately toppled rock mass was limited by the boundary of strongly unloaded rock mass.

中文翻译：

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一条深部弯曲倾覆裂缝特征及其与澜沧江下切的关系——以西南某陡倾层状岩坡为例

摘要 以西南澜沧江左岸一处深部弯曲倾覆裂缝为例，研究其断裂机理及其与澜沧江快速连续下切的关系。倾覆断裂体距坡面最大水平距离超过150 m，体积约6×106 m3。根据地表和坑道调查，将倾覆岩体划分为三个带：高度倾覆区、中倾倾覆区和弱倾覆区。陡倾层状岩体深部倾覆破坏的形成是澜沧江连续快速下切引起岩体强烈卸荷的结果。剧烈的卸载使岩体松弛并发生破裂，并在两岸岩体中形成深应力松弛带。陡倾层状岩体在重力作用下发生在应力松弛带的倾覆破坏，并随着河流进一步下切向内向下向斜坡下部发展。大倾覆和中倾倾岩体距坡面的水平距离受强卸载岩体边界的限制。