受载含瓦斯煤岩破裂过程次声波前兆特征实验研究

Coal and rock dynamic disasters like coal and gas outburst, rock instantaneous outburst pose great threats to mining operations. Its reliable prediction, however, is still a world-wide mystery. The projective result captured by infrasound wave emitted by coal and rock indicated precursory infrasound in extremely low frequency can be monitored a few days before a strong seism while infrasound in comparatively high frequency becomes evident just ahead of or during seism. It is safe to conclude the application of infrasound provides new direction to the prediction of geological hazards and coal and rock dynamic disasters. An infrasound analyzing system incorporated improved denoising technique and optimized frequency spectrum analyzing method will be constructed to observe infrasound emission during loading gassy coal and rock. The infrasound response will be recorded in various loading conditions including uniaxialcompression, triaxialcompression, impact and shearloading. Meanwhile the time-frequency characteristics of infrasound to all the loading scenarios described above will be critically studied as well. In addition the influence of adsorption and migration of gas to the emission of infrasound will be investigated. Induced coal and gas outburst will be experimentally simulated and transitional and precursory features of infrasound response during the entire process will be studied as well. Through assistive analysis of rock and coal acoustic emission system and low frequency seismic signal testing system, combining mechanical parameters of loaded coal and rock and propagation characteristics of ruptures and cleats within coal, conjugating corresponding correlation of abnormal infrasound signal to various degrees of breakage of coal and rock and to critical conditions of occurrence of outburst, the precursory law of infrasound frequency and intensity for damage of gassy coal and rock will be revealed and theoretical foundation for infrasound prediction of gassy coal and rock dynamic hazard will be forged.

我国煤与瓦斯突出和冲击地压等煤岩动力灾害严重，对其可靠预测是世界性难题。地震次声波监测结果表明，大震前几天监测到极低频次声前兆，临震或震发过程较高频率的次声波信号显著，低频次声波对地质灾害的超前监测，为煤岩瓦斯动力灾害预测提供了新的技术途径。课题搭建含瓦斯煤岩受载破坏次声波测试分析系统，优化次声波滤噪和动态谱分析方法；测试煤岩试样在单轴、三轴及冲击和剪切等不同加载方式下次声波响应特征，研究煤岩破坏过程次声波的时-频规律及对加载应力的响应；测试分析吸附及运移瓦斯对煤岩次声波的影响，实验研究高应力或高瓦斯压力诱导的突出模拟过程中次声波的阶段特征和前兆规律；通过配套煤岩声发射和低频微震信号测试分析，结合受载煤岩力学参数及裂纹、孔隙扩展规律，综合研究异常次声波信号与煤岩破裂程度及临界致灾条件的对应关系，揭示含瓦斯煤岩破坏的次声波频率及强度前兆特征，为含瓦斯煤岩动力灾害次声波监测提供理论支撑。

我国矿井煤岩瓦斯动力灾害严重，对其可靠预测是世界性难题。煤岩破裂振动声波是动力灾害的主要能量释放形式和前兆信息，低频的次声波可以实现远程、非接触监测。地震和地质灾害的次声波超前监测研究成果，为煤岩瓦斯动力灾害预测提供了新的技术途径，但含瓦斯煤岩破裂过程次声波信号的演化规律及其破坏前兆特征缺乏深入研究，制约着该技术在煤岩瓦斯动力灾害预测的应用。.项目搭建了受载煤岩次声波测试分析系统，研究了适合于受载煤岩次声波信号的去噪和频谱分析方法，对比分析了煤岩单轴加载过程的次声波和声发射信号，重点研究受载煤岩破裂过程中次声波信号的阶段性特征；借助小波包变换信号分析方法研究了受载煤岩加载过程中次声波信号能量分布特征，分析煤样破裂次声信号的频率分布范围。设计了含瓦斯煤岩三轴受载过程次声波信号测试方法，进行常规三轴和含瓦斯煤岩受载破坏次声波信号的实验研究，次声波的累计计数与累积能量可作为预测含瓦斯煤岩破坏失稳的指标。基于应力-应变法的低频岩石测试系统，测试煤岩在不同频率条件下的次声波波速及衰减参数，建立煤岩层的粘弹介质波动方程，采用交错网格有限差分法和COMSOL模拟软件，研究了煤岩破裂次声波在不同煤岩层、不同采掘空间和不同采集方式下的传播特性及其衰减规律。发表学术论文17篇，其中SCI、EI收录9篇；申请发明专利5项（授权4项）；获得省部级科技奖5项；培养毕业硕博研究生6名；参加国内外学术交流17人次。超额完成项目计划任务。.项目创新性实现了煤岩次声波加载油路监测途径，为含瓦斯煤岩三轴加载次声波屏蔽干扰监测提供新的技术手段。通过模拟和实验分析，提出适合煤岩次声波时-频分析的小波包变换和希尔伯特变换、改进的EMD小波阈值滤波去噪。实验结果表明，受载煤岩破裂过程次声波信号与应力-应变曲线具有较好的对应关系，煤岩破坏次声频率范围主要集中在0.5-16Hz，破坏前后集中在0.5-5Hz；试样破坏前，次声波超前声发射信号显现；在瓦斯气体的影响下，次声波计数值和频次均有所增多，提出次声波的计数与能量可作为预测含瓦斯煤岩破坏失稳的指标。数值模拟结果表明，次声波在煤层中的衰减与传播距离呈幂函数的关系，得出巷道内的噪声可以通过接触及非接触耦合方式的合理布置进行有效的识别，为煤岩瓦斯动力灾害次声波监测提供重要理论支撑。