多层采空区流场动态平衡调压防灾机理研究

When mining the close coal seams with risk of spontaneous combustion, the working face interconnect with upper multi-layer goaf and ground surface. Then stereoscopic cross air leakage network is formed. In order to prevent spontaneous mine fire caused by multi-source air leakage, we study on the disaster prevention mechanism with pressure dynamic balance of the flow field in multi-layer goaf. This program establishes mathematical analysis and numerical calculation model of the flow field in multi-layer goaf based on the analysis on the parameter of multi-layer goaf collapse morphology. It studies the rules of gas migration among the ground surface, the multi-layer goaf and multi-stope when these fields are connected. Under the multi point connected condition of a single working face and the upper multi-layer goaf, we establish a local dynamic balance control model for the flow field in multi-layer goaf, choose the key area to regulate the pressure and theoretically analyse the critical range of the pressure adjustment, which reveal the mechanism of local dynamical balance of the flow field pressure adjustment in multi-layer goaf. Under the multi point connected condition of multi working face and the upper multi-layer goaf, we construct an integral control model for multi point pressure regulation of the flow field in multi-layer goaf and we also theoretically calulate and unified control the wind pressure value of the mining faces, and then we reveal the overall dynamic balance mechanism for multi point pressure regulating of the flow field in multi-layer goaf. Based on the theoretical analysis above, this program studies the wind pressure automatic frequency control algorithm and develops the control program, then designs pressure automatic control system for the flow field in multi-layer goaf. The expected results can lay a theoretical foundation for the comprehensive prevention and control of spontaneous combustion in multi working face and multi-layer goaf.

近距离易自燃煤层群开采，工作面与上部多层采空区、地表相互连通形成复杂的立体交叉漏风网，为防治多源点漏风诱发的自燃灾害，进行多层采空区流场动态平衡调压防灾机理研究。基于多层采空区垮落形态基础参数分析，建立多层采空区流场数学分析与数值计算模型，研究地表—多层采空区—多采场相互连通形态下的气体运移规律；单一工作面采场与上部多层采空区多点连通，建立多层采空区流场局部动态平衡控制模型，选取关键局部区域进行调压，理论分析调压临界范围，揭示多层采空区流场调压局部动态平衡机理；多工作面采场与上部多层采空区相互连通，建立多层采空区流场多点调压整体控制模型，理论计算并统一调控各工作面采场的风压值，揭示多层采空区流场多点调压整体动态平衡机理；以上述机理研究为基础，进行风压自动变频调控算法研究与控制程序开发，设计多层采空区流场调压自动控制系统。预期成果可为全面防治煤层群多工作面、多层采空区自燃灾害奠定理论基础。

我国多数矿区为近距离煤层群开采，顶板垮落导致多层采空区相互连通，多源点漏风诱发遗煤自燃，且自燃隐患区域探测困难，使得易自燃煤层群的自燃火灾防治一直是亟待解决的难题。本项目在分析获取多层采空区垮落形态参数与气体运移规律的基础上，从动态调压通风的全新角度入手，以实现下部采场与上部多层采空区的风压局部动态平衡为目标，开展调压通风防灾机理与自动调控系统研究，既可避免上部多层采空区有毒有害气体涌入工作面，又可防止工作面新鲜风流过量流入上部多层采空区引起遗煤自燃。研究结果表明：多层采空区 60°以上纵向裂隙占比10.08%，是决定多层采空区导气性的关键所在，与近水平裂隙交错分布，形成立体交叉漏风通道，各级风压排序为：采场风压＜多层采空区风压＜地表大气压，漏风经高角度纵向裂隙进入多层采空区，并通过近水平横向裂隙不断扩散运移，使得自燃火区具有隐蔽性强、覆盖面域广等特征；采空区遗煤受浸水、贫氧等复杂条件影响，氧化活性高于原煤，氧化自燃的临界氧气浓度为6%，低于原煤的8%；建立了多层采空区流场局部动态平衡控制模型，以工作面回风端作为风压调控的源点，给出了工作面回风端与上部相邻采空区的风压差值调控范围28～58Pa，达到多层采空区—工作面流场的风压局部动态平衡状态；对于以多层采空区为连通通道的多个工作面同时进行风压调控，构建风压增益系数矩阵来描述各个调控区域的空间连通状态，建立了多层采空区流场多点调压整体控制模型，统一分析并合理调控各区域的风压值，保证相互连通的各个工作面均保持风压局部动态平衡，避免风流“压来压去”的循环状态；构建了多层采空区流场多参数调压控制系统，并进行系统硬件与软件设计，主要由局部通风机、PLC控制变频器、压差传感器、CO传感器、CH4传感器、风速传感器、风门等组成，调压控制策略包括：CO/CH4浓度控制策略、风量控制策略、风压控制策略等。研究成果对于老矿区煤层群开采的自燃火灾防治具有重要的理论指导与实用价值。