抽采钻孔孔周煤岩体水-瓦斯耦合裂隙扩展机理及其超声波特征研究

Gas in high gas content mines is extracted by drilling wells to ensure mine safety. Since the extension mechanism, before and after the borehole is sealed, of cracks in coal rock mass around a borehole is unknown it is impossible to ensure a good result of gas extraction.To achieve this result, damage fracture mechanics, multi-field coupling theory and other theories, as well as image processing, waveform analysis and other methods are used to establish evolution models of cracks in coal rock mass around a borehole and to find out the changing rule of ultrasonic characteristics of the cracks. First, mechanical property tests are carried out for coal rock masses under water-gas coupling action, and the multi-field coupling theory is employed to analyze the creepage damage of coal rock masses under multi-field coupling and build damage models. Second, compression and creepage tests are done for coal rock masses with a borehole, non-contact full-field strain observation system is utilized to obtain test images, and multi-field coupling evolution models of cracks in coal rock masses with a borehole are built based on image processing and theories of damage fracture mechanics.Finally, the three-dimensional gas drainage simulation system and RSM-SY7 ultrasonic detection system are used to carry out the detection of cracks around a borehole, including both the laboratory tests and the field tests in a coal mine. By using Fast Fourier Transform and Hilbert Transform and other methods, ultrasonic characteristic parameters are obtained, a data base of crack samples is established, and a neural network model for identifying cracks is set up.Through the above-mentioned study, the extension mechanism of cracks in coal rock masses around a borehole is expounded, and thus new theories and methods could be provided for quality test of the sealing of the boreholes.

高瓦斯矿井钻孔预抽瓦斯过程中，抽采钻孔封孔前后孔周煤岩体裂隙扩展机理仍不明确，导致瓦斯抽采效果无法得到保证。为此，协同运用损伤断裂力学、多场耦合等理论，结合图像处理、波形分析等方法，建立抽采钻孔孔周煤岩体裂隙演化模型，并分析其超声波特征变化规律。首先，开展水-瓦斯耦合作用下煤岩体力学特性试验，运用多场耦合理论分析并建立多场耦合下煤岩体蠕变损伤破坏模型；其次，进行含钻孔煤岩体试样压缩及蠕变试验，利用非接触式全场应变观测系统获取试验图像，结合图像处理及损伤断裂力学理论建立多场耦合作用下含钻孔煤岩体孔周裂隙演化模型；最后，利用瓦斯抽采三维相似模拟与RSM-SY7超声波检测系统开展钻孔孔周裂隙检测的实验室及煤矿井下现场试验，采用快速傅立叶变换、希尔伯特变换等方法获取超声波特征参数，建立裂隙样本数据库及其识别神经网络模型。通过以上研究阐明孔周煤岩体裂隙扩展机理，为钻孔封孔质量检测提供新的理论和方法。

本项目针对瓦斯抽采中抽采钻孔变形与抽采效果之间的关系，以瓦斯抽采钻孔在水-瓦斯耦合作用下的裂隙扩展机理及其超声检测特征为研究主线，综合运用损伤断裂力学，渗流力学，蠕变力学，超声学，信号处理与分析等理论，采用数值模拟计算，室内试验及现场测试分析相结合的方法，开展了不同含水率条件下试样破坏的非接触式全场应变观测与三轴渗流试验，不同含水率的含钻孔试样单轴压缩及蠕变试验，含裂隙煤岩体孔周超声波检测试验等主要工作，取得了如下的主要成果：建立多场耦合条件下煤岩体蠕变损伤破坏模型，表征了瓦斯与水共同作用下的煤岩体破坏规律，建立了多场耦合条件下含钻孔煤岩体孔周裂隙演化模型。获得了钻孔变形过程中中得超声波特征参数，得到了裂纹扩展的状态与含钻孔煤岩体孔周裂隙扩展演化过程中的超声波特征参数变化关系。最后，结合钻孔破坏过程中的裂隙演化规律与超声波特征参数关系，利用LR回归模型结合超声裂隙特征形成一种瓦斯抽采钻孔孔周裂隙检测方法。为煤层瓦斯抽采效果测定提供了一种现场检测方法，为矿井安全、高效生产提供了科学依据与研究基础。