浅埋深坚硬顶板工作面冲击地压微震时空前兆信息特征

Characteristics of microseismic spatio-temporal precursory information of rockburst in a shallow working face with hard roof

为提高冲击地压矿井现场防冲措施实施的针对性,以宽沟煤矿B2煤层I010203工作面为工程背景,研究其历次矿压显现事件发生前后的微震监测信息时空演化规律。结果表明:I010203工作面矿压显现事件震源位置受上层"刀把型"采空区边界影响,具有阶段性特征,且主要集中于工作面中下部、区段煤柱和侧向采空区围岩,垂向上大多位于煤体和顶板岩层中,坚硬顶板破裂是该矿发生冲击地压的主要诱导因素;在矿压显现事件发生前7d内微震前兆预警指标b值、断层总面积A(t)值和微震活动度S值分别出现突降或突增现象并保持低值或高值异常,表明煤岩体内部弹性能积聚、破裂程度增大,冲击危险性增高;结合高斯空间光滑法绘制的微震指标云图在矿压显现事件发生前呈现一定规律性,可进一步量化确定局部冲击危险区域。研究结果揭示了在坚硬顶板条件下工作面冲击地压微震时空前兆信息特征,可指导现场人员采取针对性防冲措施,有助于冲击地压的精准防治。

In order to improve the pertinence of the implementation of on-site prevention and control measures in rock burst mines,taking I010203 working face of B2 coal seam in Kuangou Coal Mine as the engineering background,the temporal and spatial evolution law of microseismic monitoring information before and after the occurrence of mine pressure behaviors. The results show that: the focal position of mine pressure behaviors in I010203 working face are affected by the upper “knife handle”goaf boundary,which has stage characteristics,and mainly concentrates in the middle and lower part of the working face,section coal pillar and surrounding rock of lateral goaf. Vertically,it is mostly located in coal and roof rock,and the fracture of hard roof is the main inducing factor of rock burst;within 7 days before the occurrence of mine pressure behaviors,the b value of the microseismic precursor warning factor,the A( t) value of the total fault area and the S value of the microseismic activity suddenly decreases or increases,respectively,and keeps the low value or high value anomaly,indicating that the elastic energy accumulation and fracture degree increase in the coal and rock mass,and the rockburst risk increases;the microseismic factor contour drawn with spatially smoothed seismicity method presents certain regularity before the occurrence of large energy tremors,which can further quantify the local rockburst risk area. The research results reveal the spatio-temporal precursory information characteristics of rock burst under hard roof conditions,which can guide the field personnel to take targeted measures for rockburst risk,and contribute to the accurate prevention and control of rock burst in coal mine.