渗流-温度耦合作用下深部氧化煤体自燃行为多尺度演化特征研究

Along with the gradual increase of mining depth in coal mines, the permeability, environmental temperature and air flow temperature of coal seam in deep coal mining are progressively increased, compared with shallow coal mining seam, the deep coal mining seam is easier to breed coal spontaneous combustion disasters, especially oxidized deep re-mining seams, which restrict the safe and efficient mining of deep coal. To master the spontaneous combustion mechanism of oxidized coal in complex deep mining environment is the theoretical basis for the effective prevention and control of coal spontaneous combustion fire in deep coal mining seam. This project intends to study thoroughly the multi-scale evolution characteristics of spontaneous combustion behavior and the disaster causing mechanism of deep oxidized coal under the seepage and temperature coupling. On the basis of obtaining the physical and chemical structure features of coal samples, the multi-scale experimental methods combining macro-scale, meso-scale and micro-scale was employed; the evolution laws of spontaneous combustion behavior and the variation characteristics of major functional groups and free radicals of deep oxidized coal under seepage and temperature coupling will be investigated; the dynamic evolution laws of meso-characteristics such as permeability characteristics and pore-fissure structure of unloaded coal body will be clarified; and a quantitative characterization model of the quantitative structure-activity relationship between macroscopical spontaneous combustion behavior and microstructural characteristics of deep coal body will be established. This project is aimed at revealing the mechanism of spontaneous combustion of deep oxidized coal under the seepage and temperature coupling. In addition, the inducing mechanism of the spontaneous combustion behaviors evolution of the deep coal with different oxidation degrees will also be ascertained. The research results provide a scientific basis for predicting, preventing and the spontaneous combustion degree forecasting of coal spontaneous combustion and re-combustion of coal in complex environment of deep mining coal seam.

随着煤矿开采深度逐渐加大，致使深部开采煤层渗透性、环境温度和气流温度逐步增高，与浅部开采煤层相比，更易孕育煤自燃灾害，特别是已发生氧化的深部复采煤层，制约了深部煤炭的安全高效开采；掌握深部氧化煤体自燃机制是有效防治深部煤层自燃火灾的理论基础。本项目拟对渗流-温度耦合作用下深部氧化煤体自燃行为的多尺度演化特征及致灾机制进行研究。在获得煤样物理化学结构特征的基础上，采用宏观、细观与微观相结合的多尺度试验方法，探清渗流-温度耦合作用下深部氧化煤体自燃行为的演化规律及其主要官能团和自由基的变化特征；明晰卸荷煤体渗透特性、孔裂隙结构等细观特征的动态演变规律；并通过建立宏观自燃行为与微观结构特征之间定量构效关系的量化表征模型；揭示渗流-温度耦合作用下深部氧化煤体自燃机理；阐明深部不同氧化程度煤体自燃行为产生演变的诱发机制；为深部开采煤层复杂环境下的煤自燃与复燃火灾预测、预防和自燃程度预报提供科学依据。

我国有56% 的煤矿存在自然发火危险，矿井煤自燃火灾占煤矿火灾总数的90%以上，矿井煤自燃火灾已成为制约我国高产高效煤矿安全绿色开采与发展的主要因素之一；与此同时，随着浅部煤炭资源逐渐减少，深部开采已成为趋势；深部煤岩工程响应具有“三高一强扰动”的特点，使得煤岩孔裂隙结构演变愈加复杂，导致深部开采煤层更易孕育煤自燃灾害，尤其是已发生氧化的深部复采煤层，为煤炭安全绿色开采带来了新的挑战；掌握深部煤体自燃行为的演化特征和致灾机制显得极为重要。本项目考虑深部煤层强渗透性和高环境温度的耦合灾害效应，自主搭建实验平台测定了煤自燃行为演化规律及微观结构特征，结合量子化学计算方法和链锁自燃理论等相关理论，从活化能演化和活性基团-自由基联合反应角度构建了煤氧逐级自活化协同链式反应自燃模型；采用宏观、细观与微观相结合的多尺度试验方法，得到了卸载煤体渗透率随卸载应力、温度的动态变化规律；分析了煤体氧化自燃过程宏观自燃行为与微观结构特征之间的内在关联，探清了热力耦合作用下煤体渗透特性对深部煤体自然发火行为的强化效应；揭示了渗流-温度耦合下深部煤体多尺度氧化自燃机理；掌握了在渗流-温度耦合作用下，随着预氧化程度的增加，深部氧化煤体复燃过程微观结构特征的动态演变规律；阐明了深部不同预氧化程度煤体复燃行为产生演变的多尺度诱发机制。研究成果完善了深部开采煤体氧化自燃理论，为深部开采煤层复杂环境下煤自燃与复燃火灾的高效防控技术研发和提升奠定了科学依据。