煤田火区煤岩体热物性参数及热破坏特性研究

发布时间：2018-07-05 19:30

本文选题：热物理性质 + 热破坏　；参考：《西安科技大学》2016年硕士论文

【摘要】：煤田火区的燃烧造成我国环境的污染、地质塌陷、资源浪费和生态系统破坏。煤岩体的热物理性参数和热破坏特性决定着煤田火的时空发展演化。为了研究乌达煤田火区的煤岩体热物理性参数和热破坏特性,论文运用实验、理论分析和数值模拟相结合的方法对火区的花岗岩、砂岩和煤样分别进行研究,并且分析了其特征和机理。运用激光闪光LFA457装置,分析了煤和岩样的热物理特性。同温度,煤样的热扩散系数和导热系数随着挥发分含量的升高而逐渐降低,然而比热容呈现出逐渐升高的趋势,其由物质本身决定的热物理性质的变化主要受到温度影响和发生的物理化学复杂反应影响;并且结合热重实验分析煤样热物理性质变化的原因和特征温度;花岗岩和砂岩的热扩散系数和导热系数在相同的温度下比煤的高,主要是因为煤样中进行更复杂的化学反应和煤岩样所含矿物质成分差异造成的;花岗岩和砂岩的热扩散系数和导热系数随着温度升高而降低,而且比热容随温度呈现出增大的趋势;当温度升高到一定程度时,岩石的导热系数和热扩散系数基本稳定不变。导热系数随温度的变化情况,对于砂岩而言,主要是由于其自身基本都是晶体结构导致的,然而煤样主要是由于挥发分的含量和矿物质相变的影响,而花岗岩主要受到变质矿物质的影响。通过对不同温度下煤样和泥岩的CT扫描,运用Drishti软件对CT扫描图形进行了三维重建,并且结合MATLAB对样品的裂隙和孔隙率进行了计算。25 300°C阶段,煤样的裂隙和孔隙主要是由于热破坏和内部的气体以及水分蒸发导致的;300 500°C阶段,裂隙的发展主要是由于内部矿物质成分的分解和化学动力学作用引起的,即热解导致内部大量的烯烃类物质释放。岩样在低于300°C时,其内部孔隙增加,主要是因为岩样内的水分以水蒸气的形式蒸发和部分物质挥发引起的;在300 500°C试样内部形成的孔隙和破坏损伤主要是样品中矿物质的相变和热膨胀不均以及矿物质的变质造成的。运用RFPA数值模拟软件,模拟了岩样在温度和压力耦合作用下的热破坏,分析研究了其热破坏的模式和其发生热破坏的特征。模拟破坏的模式与CT实验煤岩裂隙发展特征基本相同,孔隙、裂隙随着温度的升高,其发展演化逐渐加快,而且其发展特性主要是沿着原有裂隙的通道继续延长和加宽,同时也有部分新生裂隙产生。
[Abstract]:The combustion of coalfield fire area causes environmental pollution, geological collapse, resource waste and ecosystem destruction in China. The thermal physical parameters and thermal failure characteristics of coal and rock mass determine the development and evolution of coal fire in time and space. In order to study the thermal physical parameters and thermal failure characteristics of coal and rock mass in the Wuda coal field, this paper studies the granite, sandstone and coal samples in the fire area by means of experiments, theoretical analysis and numerical simulation. Its characteristics and mechanism are analyzed. The thermal physical properties of coal and rock samples are analyzed by using laser flash LFA457 device. At the same temperature, the thermal diffusivity and thermal conductivity of coal samples decrease with the increase of volatile matter content, but the specific heat capacity increases gradually. The changes of the thermo-physical properties determined by the matter itself are mainly affected by the temperature and the complex physicochemical reactions, and the causes and characteristic temperatures of the changes of the thermo-physical properties of coal samples are analyzed by thermogravimetric experiments. The thermal diffusivity and thermal conductivity of granite and sandstone are higher than that of coal at the same temperature, mainly due to the more complex chemical reaction in coal samples and the difference of mineral composition in coal and rock samples. The thermal diffusivity and thermal conductivity of granite and sandstone decrease with the increase of temperature, and the specific heat capacity increases with temperature, and the thermal conductivity and thermal diffusivity of rock remain stable when the temperature increases to a certain extent. The variation of thermal conductivity with temperature is mainly due to the crystal structure of sandstone itself, but the coal sample is mainly due to the content of volatile matter and the effect of mineral phase transition. Granite is mainly influenced by metamorphic minerals. Through CT scanning of coal samples and mudstones at different temperatures, 3D reconstruction of CT scanning patterns was carried out by using Drishti software, and the fracture and porosity of samples were calculated with MATLAB. The fractures and pores of coal samples are mainly caused by thermal failure and internal gas and water evaporation in the 500 掳C stage. The development of the fractures is mainly caused by the decomposition of the internal mineral components and the chemical kinetics. Pyrolysis results in the release of a large amount of olefins. When the rock sample is below 300 掳C, the internal porosity increases mainly because the moisture in the rock sample evaporates in the form of water vapor and some matter volatilizes. The porosity and damage formed in the sample of 300 ~ 500 掳C are mainly caused by the phase transition and uneven thermal expansion of the minerals in the sample and the metamorphism of the minerals. The numerical simulation software RFPA is used to simulate the thermal failure of rock samples under the coupled action of temperature and pressure. The mode of thermal failure and the characteristics of thermal failure of rock samples are analyzed and studied. The model of simulated failure is basically the same as that of CT experimental coal and rock fractures. With the increase of temperature, the development and evolution of fractures are gradually accelerated, and the development characteristics of these fractures are mainly extended and widened along the original fissure channels. At the same time, there are some new fissures.
【学位授予单位】：西安科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TD752

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