承压破碎煤体多场耦合渗透性演变及氧化动力行为研究

This project is starting from the depositional environment of the broken coal in gob, focusing on the effects of the stress field, moisture, seepage field to the dynamic process of coal oxidation, and regarding the residual coal as the compacted broken coal, then by constructing the relevant experimental platform, the axial stress load,coal samples with different water contained, similar seepage environment, to study the permeability evolution and oxidation dynamic behavior with multi-field coupling of the compacted broken coal. Through the project implementation, a multi-field coupling method and test platform of the compacted broken coal spontaneous combustion could be put forward and built. The porosity and permeability evolution model of the compacted broken coal during the process of multi-field coupling oxidation could be established. The multi-field coupling oxidation behavior characteristics and differences could be revealed. And, the gas-liquid-solid three phase coupling model of coal spontaneous combustion could be established. This topic can solve the current problem of coal oxidation experiment cannot load stress, and obtain the oxidation characteristics and internal mechanism during the process of multi-field coupling. Supplementing and perfecting the problem of the porosity and permeability setting in the process of multi-field coupling coal spontaneous combustion, and realizing the gas-liquid-solid three phase coupling of coal spontaneous combustion. Above, which have important theoretical and practical significance to the compacted broken coal spontaneous combustion in gob.

本项目从采空区遗煤堆积环境出发，着眼于应力场、水分、渗流场下的煤自燃氧化动态进程，将采空区应力场下的遗煤抽象为承压破碎煤体，通过搭建相关实验平台、轴向应力加载、不同外加水分煤样、相似渗流环境，开展多场耦合条件下承压破碎煤体的渗透性演变及氧化动力行为研究。通过项目实施，提出及建立一种承压破碎煤体自燃多场耦合研究的实验方法与测试平台；建立承压破碎煤体多场耦合氧化过程中的空隙率、渗透率演变模型；揭示承压破碎煤体多场耦合氧化行为特征及差异性致因；建立承压破碎煤体气-液-固三相自燃耦合模型。本课题可解决目前在煤自燃实验研究中不能加载应力的问题，获得应力加载下破碎煤体多场耦合下的氧化特征及内在机制；完善煤自燃多场耦合过程中空隙率、渗透率设置，实现煤自燃气-液-固三相耦合。这对研究采空区承压破碎煤体自燃具有重要的理论及现实意义。

随着煤矿开采深度的增加将导致地应力增大，地温升高，煤岩破碎程度增大，致使煤自燃灾害越发严峻。采空区破碎遗煤受覆岩应力逐渐恢复的影响，致使采空区处于不同的压实状态，进而导致空隙率、渗透率不同，这对煤自燃氧化进程具有重要影响。.本项目着眼于应力场、水分、渗流场下的煤自燃氧化动态进程，将采空区遗煤的堆积状态抽象为承压破碎煤体，建立了承压破碎煤体多场耦合低温氧化实验平台，开展了应力-温度-渗流耦合条件下承压破碎煤体的渗透性演变及氧化动力行为研究。通过该项目研究：1）掌握了应力、水分、温度等因素影响下破碎煤体的应变量、碎胀系数、空隙率以及渗透率的变化特征，明确了应力-温度-水分多场耦合条件下破碎煤体的渗透参数演变特征；2）依据多孔介质变形理论及耦合渗流实验，建立了承压破碎煤体的渗透参数演变模型；3）随着轴向应力的增大，破碎煤体二次破碎后的分形维数D逐渐增大，建立了Weibull破碎费模型描述了采空区破碎煤体的二次破碎特性；4）通过开展承压破碎煤体多场耦合氧化实验，得到了不同耦合条件下的耗氧速率、CO、CO2、CnHm的气体产生速率及放热特征，对比分析承压破碎煤体在不同耦合条件下的氧化行为差异性，识别造成承压破碎煤体多场耦合氧化行为差异性的内在致因；5）基于理论分析、实验数据，建立了承压破碎煤体气-液-固三相煤自燃耦合理论模型；6）研究发现在一定加载强度内随着应力加大耗氧速度增加、放热强度增加及标志性气体发生温度点提前，应力加载在一定程度上加速了煤的低温氧化进程。.通过上述研究，建立了承压破碎煤体多场耦合作用下渗透参数演变模型、识别了承压破碎煤体氧化动力行为特征、分析了应力加载对煤自燃氧化进程的影响及作用、建立了承压破碎煤体气-液-固三相煤自燃耦合理论模型。该研究对认知采空区应力环境对煤自燃氧化过程具有一定的理论与现实意义，所开发的承压破碎煤体低温氧化平台为煤自燃发火过程研究提供了一种新手段。