基于局部矿井刚度理论的煤柱冲击机理及防治

Coal pillar burst mechanism and prevention based on local mine stiffness(LMS)criterion

冲击地压频发严重威胁煤炭资源安全高效回收,冲击地压机理研究是预测预警和灾害防治的基础。针对某矿井应力环境稳定且未受到动载影响的条件下发生的冲击事件,引入局部矿井刚度(LMS)概念,并以该矿井冲击事件高发区域为工程背景,综合运用数值分析和现场实测等方法,分析复杂采掘布置条件下大空间尺度采掘作业过程中煤柱力学响应规律,并考察该过程中局部矿井刚度演化。指出采掘作业导致局部矿井刚度降低,煤层及其顶底板系统中能量快速积累,超过煤柱破坏所需能量,在失稳瞬间迅速释放造成煤柱冲击破坏,并对比分析随工作面推进局部矿井刚度演化与现场地音及微震实测数据。基于煤柱冲击破坏机理,结合该矿生产实际,采用大直径钻孔弱化煤体,降低冲击危险性,并以实测微震数据验证防冲效果。研究表明:(1)煤柱变形、载荷及弹性能量积累随采掘作业整体呈增长趋势,但LMS呈降低趋势,采出空间尺寸及其与研究区域间距离是主要影响因素,LMS对工作面回采响应程度显著大于巷道掘进,工作面回采对LMS降低显著影响范围是巷道掘进的3.67倍,单位推进距离下LMS降幅是巷道掘进的6.41倍。(2)随工作面推进LMS演化与现场地音及微震数据的良好对应关系,表明煤层回采导致LMS降低直接影响煤柱破坏方式,煤层及其顶底板系统中能量随LMS降低而快速积累,在煤柱承载能力降低时迅速释放,致使煤柱发生冲击破坏。(3)采用大直径钻孔弱化煤体后,微震能量及频次均显著降低,表明大直径钻孔破坏该区域煤体,降低煤柱峰后刚度,冲击危险性降低。

The frequent occurrence of coal burst seriously threatens the safe and efficient recovery of coal resources.The research on the mechanism of coal burst is the basis of prediction and disaster prevention.Aiming at the coal burst event under the condition that the stress environment is stable and not affected by dynamic load,the concept of local mine stiffness(LMS)is introduced.Taking the mining area with complex mining layout of the mine as the engineering background,the mechanical response of coal pillar in the process of large-scale mining is analyzed by comprehensively using numerical analysis and field measurement,The evolution of LMS in this process is investigated.It is pointed out that the mining leads to the reduction of LMS,the rapid accumulation of energy in the coal seam and its roof and floor system,and the rapid release of energy when the coal pillar is unstable,resulting in impact damage.The engineering verification is carried out by comparing the evolution of LMS with the mining and the field measured ground sound and microseismic data.The research shows that:(1)the deformation,load and elastic energy accumulation of coal pillar increase with the overall mining operation,but the LMS decreases.The mining space size and the distance between the mining space and the research area are the main influencing factors.The response degree of the two to the mining of the working face is significantly greater than that of the roadway excavation.The significant influence range of the mining of the working face on the LMS reduction is 3.67 times that of the roadway excavation,and the LMS reduction under the unit advancing distance is 6.41 times that of the roadway excavation.(2)The good correspondence between the evolution of local mine stiffness with the advancement of the working face and the on-site ground sound and microseismic data indicates that the reduction of local mine stiffness caused by coal mining directly affects the failure mode of coal pillars.The energy in the coal seams and their roof and floor systems accumulates rapidly with the reduction of local mine stiffness and is released rapidly when the bearing capacity of coal pillars decreases,resulting in impact damage.(3)After using large-diameter drilling to weaken the coal body,the microseismic energy and frequency are significantly reduced,indicating that large-diameter drilling destroys the coal body in this area,reduces its post peak stiffness,and effectively realizes the impact prevention effect.