工作面过废弃巷顶板微震时空演化机制及危险性分区

Temporal and spatial evolution mechanism and risk zoning ofmicroseisms in working face passing through the roof of old roadway

  • 摘要: 研究过废弃巷期间顶板微震响应的时空演化,对于掌握顶板岩层的损伤程度与运移特征具有重要意义。以东庞煤矿9212工作面过废弃巷为例,首先通过理论分析和微震监测对研究阶段进行划分,然后对不同阶段微震事件的平面、剖面分布以及空间位置关系进行分析,并通过能量离散系数(AE)和空间双因子(S,α)研究了顶板微震事件的能量差异与聚集特征;之后应用主成分分析与熵权法确定综合权重,并基于脆弱性指数法建立了危险性评价模型;最后使用GIS技术绘制3个阶段的危险性等级分区图。研究表明:① 工作面过废弃巷期间共划分为3个研究阶段,分别为正常开采阶段、废弃巷超前影响阶段和过废弃巷阶段,各阶段分别以“低频次、低能量”、“低频次、高能量”、“高频次、高能量”为主要微震响应特征;② 顶板关键层破断前,存在前后2个AE异常区,前异常区以应力异常作为主要诱发因素,导致AE值突增到7以上,后异常区以周期来压作为直接诱因,引发连续性的大规模强震,其重要征兆为前异常区结束并出现AE值骤降的突变;③ 角度因子α一般集中在30°~60°,但在周期来压时α<30°,且关键层破断前的α会以>60°的高角度向上孕育,然后以α<30°的小角度发生破断;面积因子S在高位关键层破断以及周期来压时会出现瞬时突增,而低位关键层超前断裂所导致的S较小,但煤岩体破碎程度较大;④ 3个研究阶段共划分为6个危险性等级,其中红色“Ⅰ级”危险区域发生顶板整体垮落以及大面积来压的可能性最大,其主要集中在过废弃巷阶段煤层上方0~60 m以及废弃巷超前影响阶段的顶板0~30 m内,并呈现上小、下大的分布形态。

     

    Abstract: Studying the temporal and spatial evolution of the roof microseismic response during passing through the old roadway is of great significance for mastering the damage degree and migration characteristics of the roof strata. The paper takes the 9212 working face of Dongpang Coal Mine as an example. First, the division of the research stage is based on theoretical analysis and microseismic monitoring. Then the plane, section distribution and spatial position relationship of microseismic events in different stages are analyzed. The energy dispersion coefficient (AE) and spatial double factors (S, α) are used to study the energy difference and accumulation characteristics of microseismic events on the roof; Then, the comprehensive weight is determined by principal component analysis and entropy weight method, and the risk assessment model is established based on vulnerability index method; Finally, GIS technology is used to draw the risk level zoning map of three stages. The research shows that:① The period when the working face passes through the old roadway is divided into three research stages, namely the normal mining stage, the advanced influence stage of the old roadway, and the old roadway passing stage. Each stage is divided into “low frequency, low energy” and “ Low frequency, high energy”,“high frequency, high energy” are the main microseismic response characteristics;② There are two AE abnormal areas before and after the roof key layer breaking. The former abnormal area takes the stress anomaly as the main inducing factor, which leads to the AE value suddenly increasing to more than 7; The latter abnormal area takes the periodic weighting as the direct inducement, which leads to continuous large-scale strong earthquakes. The important sign is that the former abnormal area ends and the A E value suddenly drops.③ The angle factor α is generally concentrated in the range of 30° to 60° but it is less than 30° during periodic weighting. And the α before the fracture of the key layer will be inoculated upward at a high angle of>60° and then fracture at a small angle of <30° . The area factor S will increase suddenly when the high-level key layer is broken and periodic weighting occurs. Although the S caused by the advanced fracture of low key stratum is small, the degree of coal and rock fragmentation is large;④ The three research stages are divided into six risk levels, in which the red “grade I” risk area is the most likely to occur roof collapse and large-area weighting, which mainly concentrated in the range of 0-60 m above the coal seam in the old roadway stage and 0-30 m above the roof in the advanced influence stage of the old roadway, and presented the distribution pattern of upper small and lower large.

     

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