为探索瓦斯压力影响下的含瓦斯煤裂隙动态演化特征及其规律，利用受载煤岩工业CT扫描系统开展了三轴压缩条件下的含瓦斯煤原位工业CT扫描试验，获取了不同变形阶段的含瓦斯煤原始CT图像和应力-应变曲线等测试结果，通过三维重构技术得到了含瓦斯煤的数字化模型，运用图像分析处理软件对数字化模型进行了裂隙结构的精确提取，实现了含瓦斯煤内部裂隙结构空间形态的可视化展布，并结合分形理论对含瓦斯煤内部裂隙结构进行了定性和定量分析。研究结果表明：围压一定时，不同瓦斯压力下受载含瓦斯煤的全应力-应变曲线变化趋势大致相同，均经历了5个变形阶段，即初始压密阶段、线弹性变形阶段、塑性屈服阶段、峰值破坏阶段和残余变形阶段，含瓦斯煤的峰值强度、弹性模量和残余强度均随瓦斯压力的增大而线性减小；全应力-应变过程中，在瓦斯压力作用下，含瓦斯煤二维裂隙的分形维数和裂隙像素比变化趋势基本一致，呈现出先减少（或不变）后加速增大再增速放缓的变化规律；含瓦斯煤三维裂隙的裂隙率、裂隙密度和三维分形维数变化趋势基本一致，均呈现出缓慢下降、缓慢增长和急剧增长的三阶段式演化规律；破坏失稳后，含瓦斯煤裂隙像素比和二维分形维数随瓦斯压力的增加而线性增大，并且含瓦斯煤的裂隙密度、裂隙率和三维分形维数也随之线性增加；瓦斯气体的存在促进了受载含瓦斯煤的裂隙扩展和贯通，二维裂隙和三维裂隙的数量及网络复杂程度随着瓦斯压力的升高均增大；吸附瓦斯的非力学作用和游离瓦斯的气楔膨胀作用共同导致了含瓦斯煤力学性质的整体弱化。

In order to explore the dynamic evolution characteristics and laws of gas-bearing coal fractures under the influence of gas pressure, the in-situ industrial CT scanning test of gas bearing coal under triaxial compression was carried out by using the industrial CT scanning system of loaded coal and rock.The original CT scanning images and stress-strain curves of gas-bearing coal at different deformation stages were obtained, the digital model of gas-bearing coal was obtained using 3D reconstruction technology, and the fracture structure of the digital model was accurately extracted by using an image analysis and processing software.The spatial morphology of internal fractures of gas-bearing coal was visualized successfully, and the internal fracture structure of gas bearing coal was analyzed qualitatively and quantitatively.The results show that when the confining pressure is constant, the variation trend of the full stress-strain curve of gas bearing coal under different gas pressures is roughly the same.They all go through five deformation stages, namely initial compaction stage, linear elastic deformation stage, plastic yield stage, peak failure stage and residual deformation stage, and the elastic modulus and residual strength decrease linearly with the increase of gas pressure.In the whole stress-strain process, under the action of gas pressure, both the fractal dimension and the fracture pixel ratio of two-dimensional fracture of gas-bearing coal similarly first decrease or are constant, then increase rapidly and then slowly.The change trend of fracture rate, fracture density and three-dimensional fractal dimension of three-dimensional fracture of gas-bearing coal is basically same, showing a three-stage evolution law of slow decline, slow rise and rapid increase.After failure, the pixel ratio and two-dimensional fractal dimension of gas-bearing coal increase linearly with the increase of gas pressure, as well as the fracture density, fracture rate and three-dimensional fractal dimension.The existence of gas promotes the fracture expansion and coalescence, and the number and complexity of two-dimensional and three-dimensional fractures increase with the increase of gas pressure.The non-mechanical action of adsorbed gas and gas wedge expansion of free gas lead to the overall degradation of mechanical properties of gas-bearing coal.

1 试验设备与步骤

   1.1 煤样制备

   1.2 试验设备与系统

   1.3 试验方案与步骤

2 含瓦斯煤力学性质分析

3 不同瓦斯压力下的二维裂隙演化特征分析与表征

   3.1 不同瓦斯压力下二维裂隙演化特征分析

   3.2 不同瓦斯压力下二维裂隙扩展响应量化分析

4 不同瓦斯压力下的三维裂隙演化特征分析与表征

   4.1 不同瓦斯压力下三维裂隙演化特征分析

   4.2 不同瓦斯压力下三维裂隙扩展响应量化分析

   4.3 瓦斯压力对煤体弱化机理分析

5 结论