多相热流叠加下受载煤体氧化热动力特性研究

Deep coal seam exists in high temperature and hot material environment made of high temperature surrounding rock, high temperature water-gas heat flux and magmatic hydrothermal fluids for a long time, so that it is easy to cause the disasters of spontaneous combustion of coal, thermal disaster and gas burning explosion basis of the heat after mining. At present, a systematical study about heat flow on its mechanical properties of coal and heat transfer and oxidation mechanism has not been carried out. The project is to develop research on fracture evolution of coal mass and permeability characteristics of heat flux under the different condition of surrounding rock temperature, different thermal flow properties and different loaded. Fracture evolution of the specimen under loading, heat effect in the deformation and laws of local temperature rise were studied by using optical fiber temperature measuring system and acoustic emission equipment. The quantitative relationship of thermal fluid seepage and heat transfer and derivative of oxidizing gas was analyzed to obtain distribution and variation of temperature loaded coal in the process of cracks and build model of coal fraction flow and heat transfer based on the parameters such as width of fracture, temperature difference, current velocity and density of heat resource etc. The evolvement mechanism of thermal characteristics and its main controlling factors of coal fraction under the superposition of multiphase thermal were studied by numerical simulation. As a result, the formation of high temperature flow and characteristic of coal spontaneous combustion oxidation of loaded coal under coupling effect of fracture field, seepage field and temperature field were gained, and reveal the mechanism of disaster evolution and the thermodynamic characteristics of coal oxidation of loaded coal under the superposition of multiphase thermal flow.

深部煤层长期赋存于高温围岩、水气热流和岩浆热液的高温热物质环境中，使采动后易引发以热为基础的煤自燃、热灾害、瓦斯燃烧等灾害，其彼此相互演变且错综复杂。基于目前有关热流对受载煤体氧化特性及热演变机制尚未开展系统的研究。本项目开展不同围岩温度、不同热流物性和不同载荷条件下煤体裂隙演化与热流渗透特性研究，采用光纤测温系统和声发射仪研究受载试样裂隙演化、形变热效应及局部温升规律。分析热流渗流传热与氧化气体衍生的定量关系，获得受载煤体裂隙演化过程中温度的分布与变化规律，建立基于隙宽、温差、流速和热源密度等参数下煤体裂隙渗流-传热模型。通过数值模拟研究多相热流叠加下受载煤体氧化热特性演变机制及其主控因素，获得裂隙场、渗流场和温度场耦合作用下受载煤体高温形成条件与煤氧化自燃特性，揭示多相热流作用下受载煤体氧化热动力特性及触发灾害相互演变机制。

随着浅部煤炭资源的逐渐减少甚至枯竭，国内外矿山都相继进入深部开采状态，针对随埋深增加热流越明显的现象，又基于高温热流的存在会对煤的氧化危险程度和早期灾害判识造成极大的影响等问题。本项目开展一系列高温热流作用条件下，受载煤体热演变及氧化热动力特性、渗流传热及氧化气体衍生规律、裂隙演化与热流携热渗流特性及裂隙渗流-传热模型与裂隙蓄热温升效应的研究，分析了热流对煤体力学性能和热物理性能的影响。获得了热流渗透下受载煤体裂隙演化规律和热流传热特性及氧化自燃规律，揭示受载煤体氧化高温热源的形成与传播引起煤体的蓄热氧化温升效应。指出煤层赋存初始载荷的大小与煤体的氧化能力非线性正向相关，而是氧化能力随初始载荷变化曲线呈现出“驼峰”状，且初始载荷为25MPa时煤样氧化能力最强；指出反复加卸荷煤体氧化过程中CO产生速率、O2消耗速率均较原始煤样要高，且随着加卸荷次数的增加上述指标气体参数值逐渐增大；证明围岩地温及气流温度对煤氧化特性产生显著影响，围岩地温及气流温度越高，煤氧化自燃性越强；发现风量为150mL/min时，煤体更容易蓄热升温，自燃危险性更高；建立煤体氧化难易程度与煤层赋存应力环境和煤体强度之间的关系式，即：σO=kσst，当k=1.136时，煤层赋存的应力环境采动后最易于氧化；当k<1.136时，k值越小，煤层赋存的应力环境采动后越难于氧化，当k>1.136时，k值越大，表明煤层赋存的应力环境采动后越难于氧化；获得煤体内部的障碍物能够有效的抑制热流在煤裂隙的传热的规律；揭示了高温热流诱发煤氧化自燃特性及灾害相互演变微观机制。在此基础上，深入研究了热流作用下受载煤体氧化热动力特性，为矿井开采过程中热灾害、煤自燃和瓦斯燃烧爆炸等灾害之间的演变规律提供技术支撑和理论依据。