近距离煤层上覆采空区煤自燃动态演化机制及探测技术基础研究

Based on the characters of high-temperature fire source with strong concealment and many leaking passages in overlying goaf while the close distance seam are mined, this project takes the dynamic evolution mechanism of coal spontaneous combustion in overlying goaf as its leading clue. The main propose is to enhance the accuracy of prediction in overlying goaf fire. By using the method of theoretical analysis, numerical calculation and experiment, the laws of leaking air in overlying goaf and workface will be researched. Using the theory of heat transfer, fluid mechanics and porous media, the heat transfer model and gas fluid model of coal spontaneous combustion in goaf will be set up, and the coupling mechanism among seepage field, oxygen concentration and temperature field of loose coal in overlying goaf will be revealed. Secondary oxidation mechanism of coal in overlying goaf while mining the close distance seam will be researched. Using the experimental device developed by research team, the characteristics temperature of coal spontaneous combustion and the corresponding indictors gases which can be identified and quantized easily, will be determined. The determinant criteria for coal spontaneous combustion danger zone in overlying goaf will be constructed. Through analyzing the laws of electrical characteristics of coal and rock caused by environmental factors, the distribution of electrical parameters of rock and coal in overlying goaf will be researched. The research work will elicit a theoretical support to disaster relief decision-making for coal mine fire, and will be helpful to reducing and avoiding the incurrence rate of secondary disaster, and have an important theoretical and practical prospect.

基于近距离煤层开采时上覆采空区漏风通道多以及高温火源点隐蔽性强的特点，本项目以上覆采空区煤自燃动态演化机制为研究主线，立足于提高煤矿上覆采空区火灾预测预报准确性的根本目的，采用理论分析、数值计算、实验的研究方法，研究煤层开采条件下上覆采空区及工作面的漏风规律，利用传热学、渗流力学以及多孔介质等理论，建立采空区煤自然发火热量传递模型和气体渗流模型，揭示上覆采空区松散煤体渗流场、氧气浓度场和温度场耦合机理；研究近距离煤层开采对上覆采空区遗煤二次氧化作用机理，利用自行研制的实验装置，确定煤自燃特征温度和相应的自燃程度量化识别敏感指标气体，构建上覆采空区煤自燃发火危险区域判定准则；分析环境因素对煤岩电性特征的影响规律，研究上覆采空区煤岩电性参数分布特征规律。拟研究成果将为煤矿火灾救灾决策提供理论支撑，有助于减少或避免继发性灾害的发生，具有重要的理论和实践应用前景。

基于近距离煤层开采时上覆采空区漏风通道多以及高温火源点隐蔽性强的特点，本项目以上覆采空区煤自燃动态演化机制为研究主线，采用理论分析、数值计算、实验测试的方法进行项目研究，利用流体力学、热力学以及多孔介质等相关理论，推导出了煤自燃的热量传递方程，构建了近距离煤层上覆采空区多场耦合模型，揭示了其耦合机制。不同空气流量条件下的煤二次氧化实验表明：随温度的升高，不同空气流量条件下煤的耗氧速率、CO、CO2、CH4产生率及放热强度等参数均呈指数规律变化；在同一空气流量下，煤样的一次氧化耗氧速率、放热强度在反应初期小于煤样的二次氧化耗氧速率，但在反应的后期，一次氧化的耗氧速率、放热强度又会大于二次氧化的耗氧速率。通过理论分析与数值计算，得出了不同风速对近距离煤层采空区遗煤自燃的影响规律，得到了采空区氧化带面积的变化规律，推导出了不同风速下采空区煤自燃氧化带面积的计算模型。针对煤矿井下自燃标志气体不健全情况的存在，创建了标志气体不健全煤炭自燃预报模型的构建方法。开发了火灾标志性指标气体综合校正技术，并提出应用一氧化碳指数法来消除风量对气体浓度的影响。设计并搭建了煤电性特征及变化规律的实验测试系统平台，测试结果表明，随浸水煤样温度的升高，其电阻率呈下降趋势，且干燥煤电阻率降低幅度为瘦煤>焦煤>气煤>褐煤，型煤电阻率降低幅度为焦煤>瘦煤>气煤>褐煤；浸水褐煤、浸水焦煤和浸水气煤的介电常数呈下降趋势，而浸水瘦煤的介电常数呈上升趋势，干燥煤介电常数降低幅度为焦煤>褐煤、气煤，瘦煤介电常数先降低后增加，型煤介电常数降低幅度为瘦煤>焦煤>气煤、褐煤；随浸水时间的增加，煤介电常数呈上升趋势，煤电阻率整体呈下降趋势。研究成果为煤矿火灾救灾决策提供了理论支撑和技术保障，具有一定的理论和实践应用前景。