地下采动作用下超高陡中缓倾逆向坡变形破坏过程研究

PROCESS OF DEFORMATION AND DESTRUCTION WITH SUPER-HIGH-STEEP AND MEDIUM-GENTLE ANTI-DIP SLOPE BY UNDERGROUND MINING

我国西南地区地质环境条件复杂,多发育上硬下软、上陡下缓的二元山体结构。频繁的地下开采活动,极易导致崩滑灾害,因此对此类崩滑灾害的研究迫在眉睫。本文以攀枝花煤矿崩塌为例,总结崩塌体变形破坏特征,同时基于PFC^(2D)软件模拟地下开采作用下坡面和上覆岩体的变形趋势、力学行为、裂隙演化过程以及地质破坏模式。研究表明:在地下开采作用下,采空区边界应力集中效应显著,导致裂隙最先发育,应力调整下呈现拱形应力分布。坡脚处向坡外剪应力集中显著并具有明显的鼓胀现象,坡顶位移和接触力增量均较坡脚慢,变形和应力的传递具有明显的时间滞后效应。位移和裂隙范围随地下开采区域增加而增大,并始终向坡面临空方向偏转,对于坡脚至永宁镇组第二段软硬互层岩体变形方式表现为软岩的塑性挤出、硬岩的折断破坏以及整体弯曲下沉和向临空方向的倾覆,坡顶主要表现为悬臂弯曲和断裂。该斜坡地质力学模式可分为:“表生”改造、塑流-拉裂、弯曲-拉裂以及溃屈崩塌4个阶段。

The geological environment conditions in Southwest of China are complex,and most of there develop binary mountain structures which are top hard-bottom soft and top steep-bottom gentle.Frequent underground mining activities can easily lead to collapse and landslide disaster,so the research on such collapse and landslide disasters is imminent.This paper took Panzhihua coal mine collapse as an example as well as summarized the deformation and destruction characteristics of the collapse body.Meanwhile,simulated the deformation trend,mechanical behavior,fracture evolution process and geological destruction mode of the slope and overlying rock mass under the action of underground mining based on PFC^(2D) software.The results of research suggest that the stress concentration effect of goaf boundary is significant under the action of underground mining,which leads to the first development for fractures,and the stress adjustment shows arch stress distribution.The shear stress at the slope toe is concentrated and has obvious swell phenomenon.The displacement and contact force increment of the slope top are slower than the slope toe,the deformation and stress transfer have obvious time lag effect.The displacement and fracture range increase with the augment of underground mining area,in addition,always deflect towards the slope surface.For the soft-hard interbedded rock mass between the slope toe to the second section of the Yongningzhen Formation,the deformation modes are plastic extrusion of soft rock,fracture destruction of hard rock,overall bend and sink as well as topple to the free direction,the slope top is mainly cantilever bend and fracture.The geomechanical model of the slope can generalize four stages:“supergene”transformation,plastic flow-tensile,bend-tensile and collapse.