三峡库区杉树槽滑坡成因及视向滑动机制分析

Analysis on the Formation and Apparent⁃dip Lateral Sliding Mecha⁃nism of Shanshucao Landslide in the Three Gorges Reservoir Area

三峡库区杉树槽滑坡属于典型的顺层岩质滑坡,但其失稳模式不同于常见顺层岩质滑坡,由于真倾向受阻,属于真倾向滑移变形转为视向滑动的特殊失稳模式。在滑坡发生后对其追踪调查的基础上,从地层岩性、岩体结构、泥化夹层、纵向裂缝等地质特征分析杉树槽滑坡形成的原因;通过对滑坡区的滑坡发生前几年降雨数据进行对比分析,研究降雨类型对滑坡的影响;基于极限平衡法,考虑滑坡的失稳模式,对主滑体进行稳定性计算。分析结果表明,杉树槽滑坡是在后缘静水压力、底滑面扬压力、侧向静水压力和滑带土软化综合作用下发生的失稳破坏;多日持续降雨之后的暴雨是杉树槽滑坡发生的必要条件;将主滑体从纵横两个方向分别进行力的解析,当纵向裂缝内水头高度达到滑坡启动的临界高度时,确实可以依靠纵向裂缝的静水压力将主滑体侧向推出。结论可为此类滑坡早期识别、稳定性评价和防治工程提供参考。

Shanshucao landslide in the Three Gorges Reservoir area is a typical bedding rock land⁃slide,but its failure mode is different from that of the common bedding rock landslide due to the block in the true dip direction.Shanshucao landslide exhibited a special failure mode of sliding from the true dip direction to the apparent dip direction.On the basis of the follow-up investigation after the occur⁃rence of Shashucao landslide,the formation was analyzed from the geological characteristics such as stratum lithology,rock mass structure,muddy interlayer,lateral structural fracture and so on.Through the comparative analysis of the rainfall data in the landslide area a few years before the occur⁃rence of the landslide,the influence of rainfall type on the development of the landslide was studied.Based on the limit equilibrium method,the failure mode of the landslide is considered,and the stabili⁃ty of the main landslide is calculated.Results show that Shanshucao landslide was caused by the com⁃bined action of hydrostatic pressure on the trailing edge,uplift pressure on the bottom sliding surface,lateral hydrostatic pressure and soil softening in the sliding zone.The heavy rainstorm after days of consecutive rainfalls was a necessary condition for the occurrence of the Shanshucao landslide.The force of the main sliding body was analyzed from both vertical and horizontal directions.It is true that the main landslide can be pushed sideways by the hydrostatic pressure of the lateral crack when the wa⁃ter head reaches the critical height for slope failure.The conclusion can provide references for early identification,stability evaluation and prevention of this kind of landslide.