基于“应力场-震动波场”的深部工作面合理终采线位置确定

Reasonable determination of terminal mining line using technology of stress field with seismic wave in deep coalfaces

大量的现场实践表明,深部工作面终采线和下(上)山煤柱区冲击显现频发。受巷道布局影响,此段煤体容易形成"准煤柱",在高静载作用下易于诱发冲击地压,其与回采速度关系不大,主要与高位覆岩结构及支撑围岩的状态有关。以山东曲阜星村煤矿3302工作面"7·26"冲击地压为例,通过理论分析和现场监测数据,构建了基于"应力场-震动波场"联合评价的合理终采线位置确定的方法。首先,基于掘进期间揭露的静态地质资料计算分析工作面超前应力场分布规律,对工作面终采线附近的冲击危险性进行静态评价。根据工作面采空区上覆主关键层破断与否,将其顶板结构划分为全空间OX结构和半空间OX结构。通过理论分析2种顶板结构的应力传递机制,建立了工作面超前支承压力估算模型,提出了超前支承压力估算方法。其次,根据微震和应力在线监测系统对工作面回采期间的矿震和应力动态信息进行监测,基于震动场监测识别应力异常区域,进而动态的确定工作面终采线位置。钻孔应力监测通过工作面推进过程中应力的变化,推断超前支承压力的影响范围;微震监测对于终采线位置的确定,主要考虑回采时引起的各能量级震动的超前范围;震动波CT反演技术建立以波速异常系数An和波速梯度异常系数VG为主要因子的冲击地压危险评估模型,根据波速分区特征确定工作面的超前支承压力带。采用本文提出的静态估算模型及动态评估方法,对3302工作面终采线位置进行了优化。结合理论分析(255 m)、应力在线监测(200 m)、微震监测(262 m)和震动波CT反演(220~250 m)结果,最终可确定3302工作面终采线保护煤柱宽度应不小于262 m。

A large number of field observations have shown that rockbursts occur frequently near the terminal mining line and dip coal pillar area in deep coal mining.Influenced by roadway layout,the"quasi coal pillar"is easily formed,and it is easy to induce rock burst hazard under high static load,which is independent of mining rate and mainly related to the state of high overburden structure and supporting surrounding rock.Taking the"7·26"rock burst in the coalface 3302 in the Xingcun Coal Mine as an example,based on theoretical analysis and filed observation,the rockburst mechanism was investigated,and a combined evaluation method using the technology of stress field with seismic wave was established to determine a reasonable terminal mining line of coalface.First of all,the static geological data revealed during roadway excavation were used for pre-evaluation of rockburst risk at working face.The spatial structures of overburden above the panel were classified into two categories based on whether the key stratum was broken or not:the overall OX spatial structure and the half OX spatial structure.By theoretically analyzing the stress transfer mechanism of the two types of roof structure,the computational model of abutment pressure was set up and the calculation method of abutment pressure was proposed.Subsequently,a dynamic evaluation method,adopting micro-seismic and stress online monitoring system to monitor dynamic information such as mine tremors and stress during coalface mining,was presented to define stress anomaly areas,and then dynamically determine the terminal mining line.Through the change of borehole stress values with the advance of coalface,the influence range of abutment stress was inferred.For the determination of terminal mining line by micro-seismic monitoring,the advance range of mine tremors of each level was mainly considered.The passive seismic velocity technology established a risk assessment model of rock burst with the velocity anomaly coefficient An and velocity gradient anomaly coefficient VG,the abutment stress zone was determined by the characteristics of wave velocity division.Finally,the proposed model was applied to optimize the position of terminal mining line of 3302 in the Xingcun Coal Mine.The findings obtained in this study provide a theoretical guidance for safe coal mining.Combined with the results of theoretical analysis(255 m),stress online monitoring(200 m),micro-seismic monitoring(262 m)and passive seismic velocity tomography(220-250 m),it can be finally determined that the width of the protective coal pillar for the terminal mining line of the coalface 3302 should be at least 262 m.