重庆武隆鸡尾山滑坡视向滑动机制分析

Mechanism analysis of apparent dip landslide of Jiweishan in Wulong,Chongqing

重庆武隆鸡尾山山体为典型的斜倾厚层灰岩山体,其破坏模式不同于常见侧向崩塌-堆积层滑坡,属于真倾向滑移变形转为视向整体滑动的特殊失稳模式。在现场地质调查的基础上,从地层岩性、岩体结构、岩溶及地下水作用、软弱夹层等影响因素分析重庆武隆鸡尾山滑坡形成原因;根据滑坡破坏机制,基于关键块体控制理论,对鸡尾山滑坡进行三维稳定性极限平衡分析;利用三维离散元软件模拟鸡尾山滑坡的初始变形破坏过程,分析了鸡尾山滑坡不同影响因素条件下的视向滑动形成机制和变形破坏特征,并探讨了节理化和溶蚀岩体的参数取值。结果分析认为,在重力的长期作用下,鸡尾山山体初始沿真倾向方向滑移,沿岩溶发育的陡倾节理裂隙逐渐产生后缘及侧向裂缝,形成块状后部驱动块体,由于地下水等因素使软弱夹层软化,驱动块体下滑力增大,前缘阻滑关键块体内部应力积累,并最终沿强度较低的岩溶发育带发生剪切破坏,从而导致整体滑动;在进行滑坡稳定性极限平衡分析时,考虑实际的滑坡机制,将滑体分为驱动块体和关键块体分别进行力的解析,并以关键块体的安全系数代表滑坡的安全系数更加合理。数值模拟显示,软弱夹层强度降低、岩溶发育带剪切破坏后,滑体进入大变形阶段,表明关键块体控制和阻滑作用明显,软弱夹层强度降低是滑坡发生的关键因素。采矿形成的采空区对山体的影响主要是使上覆岩体压应力增大,但对滑体的变形无影响。

As a typical oblique inclined bedding carbon slope,Jiweishan slope does not collapse laterally and results in a deposit landslide,but creeps down the dip at initial stage and then turns into an overwhelming apparent-dip rockslide.On the basis of field investigation,several causes of Jiweishan landslide are discussed in terms of lithology,structure,karstification and underground water,weak intercalation.According to failure mechanism,three dimensional stability of limited equilibrium analysis has been done based on key block theory.3DEC software is brought in to study the apparent dip-sliding mechanism and deformation character by simulating the initial failure process.Parameters value of discontinuous and corroded rock mass for numerical analysis are also discussed.Conclusions could be drawn via analysis that the slope creeps down the dip initially under gravity and tension crack and lateral crack are generated along karstification steep-crossing joints forming independent driving blocks in the rear.Underground water continuously softens weak intercalation and that leads to rising of residual sliding force of driving blocks and stress accumulation in the key block.Finally,the intensive karstification zone is sheared,and it causes overwhelming apparent-dip rockslide.Numerical simulation results demonstrate that after shear strength reduction of weak layer the karstifiction zone is sheared and sliding masses enter into large-scale deformation stage.This shows controlling and hindering effect of the key block and the key factor of Jiweishan landslide＇s occurrence is weak intercalation softening.It also indicates that mining goaf mostly leads to increment of compression stress in rock mass over the roof and does not affect displacement of sliding mass.