含瓦斯水合物突出煤体变形破坏过程声发射特征试验研究

The characteristics of acoustic emission of gas hydrate bearing coal in the deformation and failure process are vitally important to evaluate the effect of coal and gas outburst prevention based on hydration solidification technique. Firstly, the physical parameters(hydrate crystal type, hydrate saturation and distribution) are measured using Raman spectrometer, resistance and ultrasonic detection method; then, the experimental researches are conducted to investigate the effects of the physical parameters and different stress paths(uniaxial compression, triaxial compression, triaxial unloading confining pressure and triaxial cyclic loading) on the acoustic emission characteristics using the integrated experiment device for gas hydrate formation, triaxial compression and acoustic emission monitoring. Finally, the characteristics of the acoustic emission and space-time evolution mechanism are revealed， based on the variations of such target parameters as count, energy, amplitude, Kaiser effect and positioning of acoustic emission of gas hydrate bearing coal . The effect of the hydrate solidification effects are discussed by comparing the variation law of acoustic emission during the deformation and failure process of in the aspects of strength, time and space . Therefore, the distinguish criterion is established for discuss the effect of coal and gas outburst prevention based on the hydration solidification technique. This research has scientific significance and engineering value in driving the development of coal and gas outburst prevention.

含瓦斯水合物突出煤体变形破坏过程声发射特征是评价水合固化防突效果的重要依据。首先，利用拉曼光谱仪、电阻监测和超声波探测等设备，测定水合物晶体类型、水合物饱和度及分布等物性参数；进而，采用集瓦斯水合固化-三轴压缩-声发射同步监测一体化试验装置，开展水合物物性参数、不同应力路径（单轴压缩、三轴压缩、三轴卸围压以及三轴循环载荷）对含瓦斯水合物突出煤体声发射特征影响试验研究；最后，基于含瓦斯水合物突出煤体声发射计数、能量、振幅、声发射Kaiser效应以及声发射定位等目标参数的变化，揭示其声发射特征及时空演化机制。通过比照水合固化前后突出煤体声发射特征在强度、时间和空间上的差异，探讨瓦斯水合固化技术对突出煤体受载变形破坏过程声发射特征影响规律，建立水合固化技术声发射判断准则，实现利用声发射特征评价水合固化防突作用效果的目标。该课题的研究在推动煤与瓦斯突出防治技术发展方面具有科学意义和工程价值。

为明确含瓦斯水合物突出煤体变形破坏过程声发射特性变化规律，采用气体过量法，基于水分完全反应的假设，通过控制型煤初始含水量来控制水合物饱和度，开展不同饱和度条件下含瓦斯水合物煤体声发射试验，获取含瓦斯水合物煤体变形破坏过程声发射特征参数，分析饱和度对突出煤体声发射特性影响规律。模拟煤矿实际瓦斯气体组分，开展不同晶体类型含瓦斯水合物煤体声发射试验，阐明三轴压缩过程不同晶体类型含水合物煤体声发射特性变化规律。. 研究结果表明：含瓦斯水合物煤样累计声发射振铃计数随饱和度增大而降低。相比于较低饱和度煤样，较高饱和度煤样塑性、弹性和破坏失稳阶段声发射活动较不明显。塑性阶段，较高饱和度煤样累计声发射振铃计数增加较少。晶体类型对煤体声发射特性具有明显影响，相同受载条件下，含II型水合物煤体声发射振铃计数明显小于含I型水合物煤体的。煤样声发射特性随煤样应力响应的变化而变化。弹性阶段，煤样的声发射事件数均较小。随应力、应变的进一步增大，煤样进入屈服、破坏阶段，声发射振铃计数明显增大。加载过程含瓦斯水合物煤体声发射振铃计数变化主要可分为4个阶段，第1阶段，煤样处于弹性阶段，在应力作用下煤样未发生裂纹扩展，声发射计数极低，声发射信号来自于煤样颗粒滑移和微裂纹的闭合；第2阶段，声发射计数出现了几次突然上升，说明微裂隙在逐渐贯通；第3阶段，声发射计数较大且持续时间较长，主要由于煤样抵抗外载持续了一段时间，此时宏观裂纹不断贯通，声发射信号的数量较多；第4阶段声发射计数回归平稳，局部区域微裂纹仍然不断扩展，煤样表现出明显的应变硬化特性。.