煤柱稳定性分析评价的高频电磁波CT技术研究

Study on high frequency electromagnetic wave CT technology for stability analysis and evaluation of coal pillar

针对回采工作面内区段煤柱稳定性分析定量计算难度大、直观超前预评价难实施问题,应用JW-6型地下高频电磁波CT系统,研究电磁波衰减与煤柱稳定性评价因子(煤层裂隙发育和围岩应力集中程度)相关性,并以灵东煤矿及古山煤矿为工程背景,利用高频电磁波CT技术探测分析大、小煤柱的稳定性。在此基础上,总结了基于电磁波CT技术的煤柱稳定性评价的多参量指标,建立了基于电磁波衰减特征参数指标的煤柱稳定性评价方法。研究结果表明:1)电磁波衰减系数随煤层裂隙的扩展不断增大;2)在采场围岩应力环境中,电磁波衰减系数值呈现应力集中区>应力降低区域>未采动影响区;3)对于同一性质的煤层,当煤体未发生异常破碎时,电磁波衰减系数越大,表明其所受载荷越高;4)电磁波CT技术可以较准确地实现煤柱稳定性的预测评价,煤柱稳定性预测评价因子反映在电磁波衰减特征图像上,表现为电磁波衰减异常区数目、衰减异常区的分布位置及范围、衰减异常集中系数;5)根据指数分析法确定了煤柱稳定性危险指数W,并对煤柱稳定性进行了等级划分:W≥0.75,较不稳定;0.45≤W<0.75,中等稳定;W<0.45,比较稳定。该研究结论对煤柱稳定性的超前预评价、煤柱宽度的优化具有重要参考意义。

In view of the difficulty in quantitative calculation and pre-evaluation of the stability of coal pillar in the working face,JW-6underground high-frequency electromagnetic CT system was used to study the relationship between electromagnetic wave attenuation and coal pillar stability evaluation factors,i.e.,coal seam fracture development and stress concentration degree of surrounding rock.The high frequency electromagnetic wave CT technology was used to detect and analyze the stability of large and small coal pillars in Lingdong coal mine and Gushan coal mine.The multi-parameter indexes of coal pillar stability evaluation employing electromagnetic CT technology were summarized,and the coal pillar stability evaluation method based on the characteristic parameter of electromagnetic wave attenuation was established.The results are as follows:1)The attenuation coefficient of electromagnetic wave increases with the expansion of coal seam fracture;2)In the stress environment of the surrounding rock, the attenuation coefficient of electromagnetic wave is the largest in the stress concentration area,followed by the decreased stress area,while the area not affected by mining is the smallest;3)For the coal seam with the same properties,when the coal body is not broken abnormally,greater attenuation coefficient of electromagnetic waves indicates higher load on the coal body;4)The electromagnetic wave CT can accurately predict and evaluate the stability of the coal pillar.The coal pillar stability prediction and evaluation factors can be achieved from characteristics of electromagnetic wave attenuation image,such as the number of the abnormal area of electromagnetic wave attenuation,the location and extent of attenuation area,the attenuation abnormal concentration coefficient;5)According to the exponential analysis method,the stability risk index (W)of coal pillar is determined and the stability of coal pillar is classified as follows:W≥0.75,unstable;0.45≤W<0.75,moderately stable;W<0.45,relatively stable. The conclusions of the study provide significant reference for the pre-evaluation of coal pillar stability and the optimization of coal pillar width.