煤体的三维微观重构及其与瓦斯耦合的动力学基础研究

With industrial Micro-focus CT scanning system, this study will develop the three-dimensional modeling treatment technology of the sectional image of coal to realize the three-dimensional characterization of the pore structure. All this can offer basic data for the study of gas adsorption / desorption process in microcosmic size. This usage also reveals the coupling process of coal and gas as well as their stress / strain, gas adsorption / desorption, shearing and seepage of gas from the microscopic scales. In order to study on the seepage characteristics of gas, the new NC coal joint test-bed of shearing seepage and coupling will been used when it is sheared in the coal. In the case that the temperature and the humidity is constant and the radial strain gets strict constraints, the project intends to measure the permeability under different pore pressure and different pressure difference, meanwhile, we will create the mathematical model of permeability and gas pressure. Through verifying the reliability of the mathematical model based on the experimental data, we can obtain the evolution process of the coal permeability under the conditions of the fact that gas pressure changes, and create a coupling dynamics model of gas migration and coal deformation and then we couple it with three-dimensional reconstruction model, through which we can obtain the coal stress / strain, gas adsorption / desorption and migration principle with the variable pressure state, and establish the micro-network simulation model of gas migration in coal with the constraint condition of macro parameters such as porosity, permeability and so on. The results will provide experimental basis for the study of control technology as well as the mechanism of coal and gas outburst.

为了从微观上揭示采动条件下煤体内瓦斯的运移规律，以煤体微观结构特性和瓦斯为研究对象，首先使用微焦点CT系统，采用细化算法和定义局部圆柱形搜索区域的方法对煤体的断层图像三维建模处理技术进行开发，实现对煤孔隙特征的三维可视化；然后进行煤体中瓦斯的剪切渗流实验研究，分析在剪切作用下煤中瓦斯的渗流特性；采用气体渗透稳态法，在恒温、恒湿和径向应变受到严格约束的情况下，测定不同孔隙压力和不同压差条件下的渗透率，得出煤体在应力变化状态下瓦斯的解吸/吸附和运移模型；并将其与煤体三维重构网络模型进行耦合。项目预期将揭示微观状态下瓦斯在煤体中的运移特性，实现煤体三维孔隙结构的微观重构，建立基于三维微观结构的煤与瓦斯动力学模型。项目的研究成果对于煤与瓦斯突出机理的深入研究具有重要意义，可以为煤与瓦斯突出的防治提供科学依据。

为了获取能够表征煤体孔裂隙结构的真实物理模型，进而通过数值模拟探讨其内部瓦斯渗流规律。首先借助于µCT225KvFCB高精度CT系统得到了大柳塔煤矿长焰煤CT数据。采用补充后的DTM法对煤样CT数据进行阈值分割。使用基于Matlab语言的三维重建程序结合逆向工程技术，提出了一种将煤体CT三维数据转换为CAD数字模型的方法。其次利用自主研发的真三轴气固耦合煤体渗流试验系统，探究煤岩在变轴压加载下的变形破坏和瓦斯渗流演化规律。以原煤煤粉压制的煤体试件为研究对象，采用含瓦斯煤热流固耦合三轴伺服渗流试验系统，进行了五种不同轴压加载路径下的煤体三轴压缩及瓦斯渗流试验。同时基于煤样单轴压缩和抗拉物理实验的实测宏观参数，推算出模拟含瓦斯煤变形破坏所需的细观参数，利用平行黏结模型和推导得出的细观参数对煤体进行了不同围压和瓦斯压力条件下常规三轴试验的颗粒流模拟，并将模拟结果与物理实验结果进行对比及误差分析，对煤体宏观力学参数的变化规律进行了总结。再则利用煤体三维重构模型进行了煤体瓦斯渗流的有限元数值模拟试验,探究了瓦斯在裂隙煤体中的流动规律，分析了裂隙的空间几何形状及位置对瓦斯渗流的影响，以及有效孔隙率对渗透率和渗透速度的影响。最后通过三维突出模型的构建和不规则突出孔洞体积的求解得出了突出煤体释放的弹性势能，结合突出过程中瓦斯内能和突出后能量的分析，得到煤与瓦斯突出发生的能量条件模型与突出强度预测模型。在统计十次瓦斯突出事故的基础上，对能量条件模型与强度预测模型进行验证。在突出能量条件模型基础上，采用Morris筛选法对突出影响因素的灵敏度进行了分析。项目的研究成果对于煤与瓦斯突出机理的深入研究具有重要意义，可以为煤与瓦斯突出防治与瓦斯抽采提供科学依据。