潘二煤矿A组煤层底板灰岩水害微震监测

Microseismic monitoring on limestone water inrush at coal seam floor for group A coal layer of Pan’er Coal Mine

  • 摘要: 采煤工作面底板突水是我国煤矿深部开采过程中面临的重要灾害问题之一,其发生与煤层 地质条件和矿井生产活动相关。 煤层采动过程中,会对底板产生破坏,灰岩含水层上方原始导升带 在张性二次应力和承压水的共同作用下也会逐渐向上延伸,当与煤层底板破坏带形成联通时,便产 生了突水。 当煤层底板发生破坏时,岩体破裂会产生微地震,通过微地震的时空分布,可以确定底 板破坏带的时空分布。 同时,承压水向上入侵的过程中,水流可能会和周围的固体介质相互作用产 生震荡信号,并以弹性波的形式向四周传播。 利用微震监测系统在对潘二煤矿 A 组煤底板进行突 水监测时,除了监测到大量岩体破裂产生的微地震信号,还监测到该类水流震荡信号,对应波形呈 类螺钉状且持续时间超过 20 s,振幅主要在 10-5 ~ 10-4 V,频率范围为 20 ~ 40 Hz。 因此,在对煤层 底板下伏岩体微破裂信号进行微震定位确定煤层底板破坏带深度的基础上,进一步通过对水流震 荡信号进行波形分析和定位,可以得到灰岩含水层上覆岩体裂隙扩展进水的时空分布,进而确定煤 层底板破坏带和承压水导高带的空间分布及互联情况。 为此,针对煤层底板灰岩水害监测预警,提 出基于微震和水流震荡信号时空分布特征联合分析的新思路和方法,并在淮南矿业集团有限责任 公司潘二煤矿 A 组煤底板突水监测预警中得到了较好的应用。

     

    Abstract: Water inrush from the floor of the coal mining face is one of the main disasters in deep coal mining in China, and its occurrence is related to the geological conditions of the coal seam and the mining activities. In the process of coal mining, the floor can be perturbed and damaged, and the original fracture zone for fluid uplifting above the limestone aquifer can also gradually extend upwards under the joint effect of secondary tensile stress and confined water pressure. When it is connected with the failure zone of the coal floor, water inrush occurs. The rock fracturing induced by floor damage can produce microseismic events. From the spatial and temporal distributions of microseismic events, the spatiotemporal distributions of the floor damage zones can be determined. At the same time, in the process of the upward invasion of confined water, the water can interact with the surrounding solid media to produce oscillations, which can propagate outwards in the form of elastic waves. By using the microseismic monitoring system for mining group A coal layer of Pan’er Coal Mine of Huainan Mining Group, in addition to monitoring large amounts of microseismic signals related to floor rock fracturing, the oscillation signals related to the interaction between fluid and solid medium was also detected for the first time. The corresponding waveform is screw like and lasts for more than 20 s, whose amplitude is mainly in the range of 10-5-10-4 V and frequency range is 20-40 Hz. Therefore, based on microseismic locations of floor fracturing signals, the authors can further analyze and locate fluid flow induced oscillation signals, and determine the temporospatial distribution of the fluid filled fractures overlying the limestone aquifer. As a result, the floor damage depth and the spatial distribution of uplifting zone for the confined water and their connections can be determined. Therefore, based on the joint analysis of microseismic locations and fluid induced oscillation signals in time and space, a new idea and method is proposed for monitoring and early warning of water inrush from coal limestone floor. The new strategy have been applied in the monitoring and early warning of water inrush from coal floor of group A of Pan’er Coal Mine of Huainan Mining Group.

     

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