急倾斜巨厚煤层矿震诱冲机制及时-空特征

Mechanism of rock burst induced by mine earthquake and the time-space characteristics of in steep and extremely thick coal seam

  • 摘要: 针对急倾斜巨厚煤层赋存环境复杂,开采过程矿震频发,冲击危险性高的问题,通过构建岩柱力学模型及数值模型、统计分析现场矿震事件,掌握急倾斜巨厚煤层开采的煤岩灾变规律,形成基于动静载理论的急倾斜巨厚煤层矿震诱冲机制。选取5个微震指标深入分析矿震发生的异常前兆及时间跨度特征,预警冲击危险并把握补强卸压时机;通过微震事件定位掌握矿震发生的空间特征,明确卸压关键区域,基于矿震发生的时空特征提出防冲策略。研究结果表明:急倾斜巨厚煤层岩柱在直立极限长度范围内其弯曲变形效应随采深增大愈加明显,岩柱内部能量积聚随采深增加也愈高,岩柱及煤层内高能量积聚区域受开采扰动发生大尺度破裂产生矿震,形成动载震动波,动静载叠加易诱发冲击;矿震发生前日总能量-频次、Ab)、S均出现低值异常,bPb)均出现高值异常,异常跨度即表示矿震孕育过程。矿震发生时日总能量-频次、Ab)、S均快速跃升至高值,b值、Pb)值均快速降低至低值;矿震事件发生前在空间上某区域出现明显的缺震现象,缺震程度越高矿震能量越大,据此可对缺震区域采取补强卸压措施,从源头降低冲击危险性。防冲策略包括对岩柱及煤层充分卸压,弱化冲击源头及路径,加强采场与巷道支护,使其具有一定的抗冲能力。但不能保障开采时没有冲击危险,因此需对开采过程煤岩活动密切监测,识别高能矿震发生的时空异常前兆,以便及时精准的采取补强卸压及支护、撤人等安全防护措施。

     

    Abstract: Aiming at the problems of complex occurrence environment, frequent mine earthquakes and high impact risk in steep and extremely thick coal seams, through the construction of rock pillar mechanical model and numerical model, the statistical analysis of on-site mine-induced earthquake events, the law of coal-rock catastrophe in steep and extremely thick coal seam mining is obtained, and the mechanism of mine-induced shock in steep and extremely thick coal seam based on dynamic and static load theory is formed. Five microseismic indicators are selected to deeply analyze the abnormal precursors and time span characteristics of mine earthquakes, to show the impact danger and grasp the opportunity of reinforcement and pressure relief. Through the location of microseismic events, the spatial characteristics of mine earthquakes are got, and the key areas of pressure relief are clearly defined. Based on the temporal and spatial characteristics of mine earthquakes, the anti-scour strategy is put forward. The results show that the bending deformation effect of rock pillar in steep and extremely thick coal seam becomes more and more obvious with the increase of mining depth, and the energy accumulation in rock pillar increases with the increase of mining depth. Rock pillar and high-energy accumulation area in coal seam are broken on a large scale by mining disturbance, resulting in dynamic load vibration wave, and the superposition of dynamic and static loads is easy to induce impact. The total energy-frequency, A(b) value and S value all appear low-value anomalies, while B value and P(b) value all appear high-value anomalies, and the abnormal span indicates the process of mine earthquake preparation. The total energy-frequency, A(b) value and S value all jump to high values, while B value and P(b) value all drop to low values. Before the mine earthquake, there is an obvious lack of earthquake in a certain area in space. The higher the degree of lack of earthquake, the greater the energy of mine earthquake. According to this, reinforcement and pressure relief measures can be taken to reduce the impact risk from the source. Anti-scour strategies include fully relieving the pressure of rock pillars and coal seams, weakening the source and path of impact, and strengthening the support of stope and roadway to make them have certain anti-scour ability. However, there is no guarantee that there will be no impact danger during mining. It is necessary to closely monitor the coal and rock activities in the mining process and identify the spatio-temporal abnormal precursors of high-energy mine earthquakes, so as to take some timely and accurate safety protection measures such as reinforcement and pressure relief, support and evacuation.

     

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