瓦斯治理视角下原煤破裂演化及瓦斯渗流-微震耦合特性研究

    Study on gas seepage and microseismic characteristics of raw coal under triaxial compression

    • 摘要: 瓦斯治理是煤矿安全生产的关键环节,其核心在于精准掌握煤体破裂演化规律及瓦斯渗流特性,并结合微震监测技术,实现动力灾害的超前预警。基于此,本文采用原煤试样,利用三轴伺服渗流装置,在不同瓦斯压力梯度下开展抗压强度测试,系统探讨瓦斯压力对煤体力学响应的影响,确定瓦斯压力阈值,并揭示瓦斯渗流演化规律。研究结果表明:在初始压密阶段,煤体原生裂隙逐渐闭合,渗流通道受限;进入弹性变形后期,煤样内部孔隙进一步压实,瓦斯渗流流量降至最低;至屈服点附近,渗流流量达到最小值,而微震事件开始显著增加;煤样承受载荷达到峰值后,瓦斯渗流通道瞬时贯通,流量突跃式增大,微震频带能量急剧增强,事件数量达到峰值。通过计算微震信号不同小波基函数的熵值,确定Db6为最优基函数,并进行4层小波包分解,获得16个频带的归一化能量分布。研究表明,煤样破坏的特征频带主要集中在第6~8频带,对应的频率范围为625~1000 Hz。本研究可为煤矿瓦斯治理及动力灾害监测预警提供理论支撑和技术参考。

       

      Abstract: Gas control is a critical aspect of coal mine safety, fundamentally relying on the precise understanding of coal fracture evolution and gas seepage characteristics, combined with microseismic monitoring technology to achieve early warning of dynamic disasters. Based on this principle, this study employs raw coal specimens and utilizes a triaxial servo-controlled seepage apparatus to conduct compressive strength tests under different gas pressure gradients. The research systematically investigates the influence of gas pressure on the mechanical response of coal, determines the gas pressure threshold, and reveals the evolution characteristics of gas seepage. The results indicate that, during the initial compaction stage, the primary fractures in the coal gradually close, restricting seepage channels. In the late stage of elastic deformation, the internal pores of the coal sample are further compacted, causing the gas seepage flow rate to drop to its minimum. Near the yield point, the seepage flow rate reaches its lowest value, while the frequency of microseismic events significantly increases. When the coal sample reaches the peak load, the gas seepage channels become instantaneously connected, leading to a sudden surge in flow rate, a sharp increase in microseismic frequency band energy, and the highest number of recorded events. By calculating the entropy values of different wavelet basis functions for microseismic signals, the optimal function (Db6) was selected, and a four-layer wavelet packet decomposition was performed to obtain the normalized energy distribution across 16 frequency bands. The findings indicate that the characteristic frequency bands associated with coal sample failure are primarily concentrated in the 6th to 8th bands, corresponding to a frequency range of 625 Hz to 1000 Hz. This study provides theoretical support and technical guidance for gas control in coal mines and early warning of dynamic disasters.

       

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