武隆鸡尾山滑坡发生机制与裂缝成因分析

Sliding mechanisms and fracture genesis of Jiweishan landslide in Wulong

由于鸡尾山向山体内斜倾岩体发生滑坡有其特殊性,必须搞清楚滑坡发生岩体的地质环境、地质结构与几何形态的特殊性、以及岩体与滑面的力学性质,进行滑体的稳定性与裂缝成因分析。在考虑滑体几何形态特征、地质结构与构造特征、岩体的岩溶裂隙发育性质、具有较大压缩性条件下,推导新的稳定性分析与岩体蠕滑压缩的弹性模型公式,计算弱层滑面与前侧壁面的等抗剪强度参数,估算滑动岩体的压缩量(即T0裂缝的内外侧宽度),从而证明T0裂缝是由滑体压缩发生的扩张裂缝,而不是有些研究中主张的拉裂缝,也证明蠕滑是由滑动岩体压缩而发生。根据滑体的几何重心靠外,产生偏心压与外侧压缩量大等原因,分析T1裂缝属拉张裂缝。分析计算结果表明,由于蠕滑导致滑体前部应力、应变最大,达到岩体压缩破坏强度,发生滑体前部岩体压碎并剪断前侧壁,从而解释了滑坡失稳原因。利用岩体蠕滑的弹性压缩模型公式,估算该岩溶裂隙灰岩滑体不同地段的压缩应力、前部岩体破坏应力、压缩量以及压缩模量和方向裂隙率。

Because of the unique characteristics of Jiweishan landslide,it is necessary to make clear special geological environment,geological structure and geometry of failure rock masses,and mechanical properties of both rock masses and sliding plane for studying the failure mechanism of Jiweishan landslide and distinguishing from other types of rock landslides. In this paper,the stability of the sliding body and crack causes were analyzed based on detail analyses of engineering geological environment and conditions of Jiweishan landslide as well as physical and mechanical properties of rock masses. New elastic mechanics formulas for evaluating slope stability and creep compression behaviors of rock masses were derived based on geometry,geological structure and tectonic characteristics of the sliding body,distribution of karst fractures of rock masses as well as the large compression stress condition. The shear strengths of the weak sliding plane and the front side wall were calculated,and the compression amount of the sliding rock mass,i.e.,the opening width of the crack T0,was also estimated. It is revealed that T0 is an extension fissure caused by the compression of the sliding body rather than a tensile crack suggested by other literatures and that the creep sliding results from the compression of the sliding body. It is also pointed out that T1 is a tensile fissure based on the side-aligned geometric weight center of the sliding body,center-tilted compression and large lateral compression amount. Calculations by the developed formulas show that the stress and strain of the front sliding body are the highest and reach the compression strength of the rock mass,and hence,the front rock masses are broken by compression and the front side wall is also sheared off,which explains the failure cause of the sliding body. Moreover,the compression stress within different segments of the karst fractured limestone,failure stress of the front rock masses,compression amount and compression modulus and directional fracture ratio were assessed based on the formula of the elastic compression model.