深部矩形底煤巷围岩破坏失稳全过程宏细观演化特征研究

Macroscopic and mesoscopic evolution characteristics of surrounding rock of rectangular bottom coal roadway in deep during failure

为研究深部矩形煤巷围岩破坏失稳全过程宏细观演化特征,以山东龙郓煤矿深部矩形底煤巷为背景,采用自主研制的深部地下工程结构失稳全过程模拟试验系统,从宏观尺度研究矩形底煤巷锚固围岩承载全过程的应力、变形和电磁辐射特征,获得锚杆支护和锚杆索支护模型的峰值强度比无支护模型分别增强31.49%和45.56%,其峰值位移同样增长76.00%和113.71%才破坏失稳的结论。在此基础上,通过颗粒流软件PFC2D建立锚杆索加固巷道围岩的“两介质-四界面”模型,并实现模型承载全过程不同位置测点的实时应力监测;从细观层面揭示不同支护方式下巷道围岩破坏失稳全过程内部的应力演化和裂纹发育规律,建立以锚固围岩的裂纹分布表征结构损伤程度的巷道失稳风险模型。结果表明,裂纹分布分形维数在无支护和锚杆支护模型达到其峰值强度的30%和70%前即已达1.3以上,具有巷道失稳风险。而锚杆索支护模型在整个承载过程中的裂纹分布分形维数始终低于1.3,表明巷道是稳定的。巷道锚固围岩破坏失稳的根本原因是首先始于锚固端岩体围岩的力链断裂和内部应力跌落,并逐渐向深部岩体和表层围岩2个方向发展。为此,提出阻断力链断裂和内部应力跌落的深部底煤巷“强帮护顶”支护原则,为深部煤巷防治片帮冒顶提供了新思路。

In order to study macroscopic and mesoscopic evolution characteristics of surrounding rock of deep rectangular bottom coal roadway during failure and instability,with deep rectangular bottom coal roadway in Shandong Longyun Coal Mine as research background,stress,deformation and electromagnetic radiation characteristics of anchoring surrounding rock of rectangular bottom coal roadway were investigated from the macro scale with a self-developed simulation test system for failure process of deep underground engineering structure.It was found that peak strengths of bolt support and bolt-cable support models increase by 31.49%and 45.56%,respectively,compared with unsupported model,and peak displacements also increase by 76.00%and 113.71%,respectively.On this basis,particle flow software PFC^(2D) was used to construct a“two media-four interfaces”model of roadway surrounding rock reinforced by bolt and cable,and real-time stress monitoring of measuring points at different positions in the whole loading process was realized.The internal stress evolution and crack development of roadway surrounding rocks under different support methods in the whole failure process were revealed from mesoscopic level,and a roadway instability risk model based on crack distribution of anchored surrounding rock was established to characterize damage degree of structure.Results have shown that fractal dimensions of crack distribution are more than 1.3 before unsupported and bolt-supporting models reach 30%and 70%of their peak strengths,which indicates that there is a risk of roadway instability.Fractal dimension of crack distribution is always lower than 1.3 in the whole loading process of bolt-cable support model,which indicates that the roadway is stable.The fundamental reason for failure and instability of anchored roadway surrounding rock is that fracture of force chain and internal stress drop of surrounding rock firstly begins at anchoring ends and then gradually develops in the two directions of deep rock mass and surface surrounding rock.A“strengthening sides and protecting top”support principle of deep bottom coal roadway to prevent force chain fracture and internal stress drop was proposed to prevent spalling and roof fall.