卸荷扰动下窄煤柱巷道底板破坏力学行为分析

Mechanical behavior analysis of floor failure of narrow coal pillar roadway under unloading disturbance

基于弹性力学和经典矿压理论,以FLAC^(3D)软件模拟矿井窄煤柱巷道开挖后底板的稳定特征,得到了窄煤柱回采巷道开挖前和开挖后底板的应力演化规律和损伤特性.研究结果表明:巷道开挖后,巷道和煤柱底板的球应力值低于原岩应力,实体煤底板则相反,导致巷道底板处于一侧膨胀一侧压缩的非均压状态.开挖后煤柱和巷道底板处于卸轴压和卸围压状态,实体煤底板处于双向加载状态.巷道底板呈非对称破坏特征,并且浅部底板以卸荷张拉破坏为主.煤柱和巷道底板以卸荷膨胀变形为主,裂隙密度较大,底板超声波速较低;实体煤底板以压缩变形为主,裂隙密度较小,超声波速较高.

Based on elastic mechanics and classical mine pressure theory,FLAC^(3D)software was used to simulate the stability characteristics of the floor after the excavation of narrow coal pillar roadway,the stress evolution law and damage characteristics of the mining roadway floor were studied.Research indicates that after the excavation of the roadway,the spherical stress value of the roadway and coal pillar floor is lower than the original rock stress,while that of solid coal floor is opposite,resulting in a nonuniform pressure state where the roadway floor is expanded on one side and compressed on the other side.After excavation,the coal pillar and the roadway floor are in a state of unloading axial pressure and confining pressure,while the solid coal floor is in a twoway loading state.The floor of the narrow coal pillar roadway shows obvious asymmetric failure characteristics,and the shallow floor is mainly damaged by unloading and tensioning.The coal pillar floor and the roadway floor are mainly deformed by unloading expansion,the crack density is relatively large,the ultrasonic velocity in the floor is low,and the solid coal floor is mainly compressed and deformed,the crack density is lower,and the ultrasonic velocity is higher.