极近距离煤层采空区叠加区瓦斯与煤自燃复合致灾机理研究

The coupling mechanism of co-existence hazards for coal spontaneous combustion and gas in goaf is one of the key scientific problems to control gas and coal fire. When the ultra-close multi-seam forms an overlapping area, there is a lack of further study on this problem. In order to solve this problem, the project intends to build the middle strata instability mechanics model in ultra-close multi-seam by physical similarity simulation experiment, reveal the formation mechanism of overlapping area of goaf. In the process of repeated mining, the fissures in the digital image are extracted-analyzed-reconstructed, the repeat mining fissure elliptic paraboloid zone equation is established, and the gas desorption-diffusion-seepage law of overlapping area of goaf is obtained. The coal spontaneous combustion parameters based on complex coupling factors (gas content, secondary oxidation and ventilation conditions) were obtained by using the programmed temperature experiment and the large coal spontaneous combustion experimental platform. Based on the theories of porous media hydrodynamics, combustion fluid mechanics and Langmuir gas adsorption, a mathematical model of repeated mining fissure scale spatial gas migration based on gas desorption desorption effect and coal oxidation theory is proposed. It can reveal the coupling hazard mechanism of gas and coal fire for overlapping area of goaf in ultra-close multi-seam. The CFD numerical simulation and industrial field test were used to research the gas migration and spontaneous combustion of the overlapping area of goaf. It can provide some theoretical and technical support for effective prevention and control of gas and spontaneous combustion complex disaster in overlapping area of goaf.

采空区瓦斯与煤自燃复合致灾机理是矿井瓦斯与煤火防治的关键科学问题之一，但在极近距离煤层采空区形成叠加区的条件下对其研究较少。针对该问题，项目拟通过物理相似模拟实验，构建极近距离煤层中间岩层的破断失稳力学模型，揭示采空区叠加区形成机制；对重复采动数字图像进行裂隙提取-分析-重构，建立重复采动裂隙椭抛带方程，得到采空区叠加区瓦斯解吸-扩散-渗流规律；通过煤自燃试验，获得复杂多因素（瓦斯含量、二次氧化和通风条件）的煤自燃特征参数；利用多孔介质流体动力学、燃烧流体力学和Langmuir气体吸附等理论，提出基于瓦斯吸附解吸效应和煤体氧化理论的重复采动裂隙尺度空间气体运移数学模型，以揭示极近距离煤层采空区叠加区瓦斯与煤自燃复合致灾机理；运用CFD数值模拟和现场试验，研究采空区叠加区瓦斯运移及自燃氧化升温规律，这可以为有效防控采空区叠加区瓦斯与自燃复合灾害提供一定的理论和技术支持。

本项目基于极近距离易自燃煤层群开采实际条件，通过理论分析、实验室测试、相似材料模拟、数值模拟、现场工业性试验等方法，研究极近距离易自燃煤层群采动覆岩裂隙演化规律，复合采空区遗煤自燃特性及自然发火规律，分析了近距离煤层复合采空区瓦斯与煤自燃耦合致灾区域，提出极近距离煤层复合采空区瓦斯与煤自燃耦合致灾机理，优化、开发适于极近距离易自燃煤层群的瓦斯抽采与防灭火协同防控技术体系。主要研究内容及成果如下：..选择典型的瓦斯与煤自燃灾害共存矿井，利用程序升温实验装置，研究了不同粒度煤样的自燃特性参数，得到经历二次氧化煤样的自燃规律。基于自主研发的瓦斯吸附与自燃性程序升温一体化装置，研究了瓦斯含量对煤自燃特性的影响规律。利用大型煤自燃发火实验台，掌握了煤自燃发生、发展的过程，明确了煤自然发火的规律。.通过物理相似模拟试验及UDEC数值模拟，分析了极近距离煤层群开采后上覆岩层垮落特性、底板应力分布及覆岩裂隙演化规律。极近距离煤层群在重复采动条件下，形成了不同于单层煤开采的覆岩裂隙演化规律及支承压力分布特征，在整个下行开采过程中，覆岩裂隙经历了产生、扩张、压实、再扩张、再压实等5个动态变化阶段。在实验分析的基础上，建立了极近距离煤层重复采动裂隙椭抛带的空间分布数学模型。.构建了裂隙尺度空间瓦斯与煤自燃耦合致灾机理，提出裂隙场、温度场及渗流场3场交汇时致灾充要条件。引入分形理论对采动裂隙网络进行素描，得到上下两层煤不同推进距离的分形维数，进而得到采空区孔隙-裂隙分形特征，构建了采空区裂隙场气体运移方程；基于分子动理论，构建煤体内部气体扩散方程。.建立CFD模型，从通风、抽采、注氮3个方面分别进行了模拟，分析了三者对采场自燃“三带”和瓦斯分布的影响，并结合理论分析，从而确定了防治复合采空区瓦斯与煤自燃共生灾害的防治方法。并现场试验了巷道超前钻孔导流抽采和复合采空区注氮防灭火技术，验证了协同防控技术效果，建立了适合极近距离煤层复合采空区瓦斯与煤自燃共生灾害协同防控技术体系。