煤田火区粉砂岩热力学参数测试及受热失稳特性分析
发布时间：2019-06-02 10:18
【摘要】：我国新疆、山西等地现存大面积煤田火区,煤火不仅烧毁大量煤炭资源,而且严重破坏西部脆弱生态环境。煤火演化过程中,火区上部覆岩产生燃烧裂隙,形成新的火区供风通道被认为是火区得以进一步持续发展主要因素之一。燃烧裂隙的产生是火区煤炭烧损火区原有煤岩受力结构发生改变和热力耦合作用下覆岩热力学参数变化共同作用的结果。认识火区覆岩变温条件下峰值应力、弹性模量等热力学参数的变化规律,分析其随温度变化的受热失稳特性,对于揭示煤田火区的演化机制具有十分重要的意义。煤田火区覆岩多以砂岩、粉砂岩、泥岩为主,目前针对砂岩和泥岩的研究较多,而粉砂岩的研究极少。因此,论文以火区粉砂岩为研究对象,开展升/降温条件下的热力学参数实验并对热力学参数与受热失稳特性进行分析研究,推动对火区燃烧裂隙产生规律的认识,并且对火区的治理与数值模拟提供一定指导。本文围绕煤田火区粉砂岩开展原位、单轴、X衍射等实验,主要研究内容和成果如下:采用高温高压岩体三轴试验机对粉砂岩低围压(2MPa),常温~600℃范围内的透气性变化开展了原位实验,发现在常温~600℃范围内,粉砂岩渗透率随温度的升高呈“V”字形演化趋势,在升温过程中粉砂岩的渗透率在300℃左右表现出清晰的温度门槛值特性,300℃之前渗透率呈减小趋势,300℃之后渗透率开始增大;结合声发射特征实验与热物性实验分析可知,渗透率变化是由热膨胀系数、导热系数等参数变化引起热破裂阶段变化所致。采用MTS810实验系统开展了粉砂岩的高温单轴力学实验,测试最高温度为800℃,实验发现出实时升温条件下粉砂岩的峰值应力随温度的升高整体上呈先减小后增大再减小的趋势、弹性模量随温度升高整体呈先增大后减小的趋势;随着温度的升高,100℃的降温损伤对粉砂岩抗变形能力的影响呈波动式下降、对峰值应力的影响在高温段(400℃~600℃)影响较大;粉砂岩力学参数的变化是由物相变化、热破裂、矿物组分等原因造成,并且结合X衍射分析可知,脆性破坏除与弹性模量相关,还可能受方解石、石英等矿物组分含量的影响。结合力学参数、脆性系数、破坏形态探究出升温条件下,粉砂岩在常温~200℃温度段抗压能力呈线性下降,导致覆岩抗压能力低于平衡应力,裂隙进一步发育扩大;200℃~700℃温度段,粉砂岩逐渐转为脆性破坏,虽然随着温度的增加粉砂岩抗压能力增加,但是温度的升高火区煤的烧损量越来越大,覆岩受力平衡结构发生改变,一旦超过峰值应力就会发生脆性破坏,产生大量燃烧裂隙,并在700℃达到最大;当超过700℃,抗变形能力与抗压能力急剧下降,粉砂岩逐渐失去抗压能力并开始软化,致使岩石再次呈延性破坏。
[Abstract]:A large area of coal field fire exists in Xinjiang, Shanxi and other places in China. Coal fire not only burns down a large number of coal resources, but also seriously destroys the fragile ecological environment in the west. In the process of coal fire evolution, the overburden rock in the upper part of the fire area produces combustion cracks, and the formation of a new air supply channel in the fire area is considered to be one of the main factors for the further sustainable development of the fire area. The formation of combustion cracks is the result of the change of the original coal and rock stress structure and the change of thermal mechanical parameters of overlying rock under the action of thermodynamic coupling. It is of great significance to understand the variation of thermodynamic parameters such as peak stress and elastic modulus under the condition of variable temperature of overlying rock in fire area, and to analyze the thermal instability characteristics of overlying rock with temperature, which is of great significance to reveal the evolution mechanism of coal field fire area. Most of the overburden rocks in coalfield fire area are sandstone, siltstone and mudstone. At present, there are many studies on sandstone and mudstone, but the research on siltstone is very few. Therefore, taking siltstone in fire area as the research object, the experiment of thermodynamic parameters under the condition of rising / cooling is carried out, and the thermodynamic parameters and thermal instability characteristics are analyzed and studied in order to promote the understanding of the law of combustion cracks in fire area. It also provides some guidance for the treatment and numerical simulation of fire area. In this paper, in situ, uniaxial and X-ray diffraction experiments are carried out on siltstone in fire area of coalfield. The main research contents and results are as follows: low confining pressure (2MPa) of siltstone is studied by triaxial testing machine of high temperature and high pressure rock mass. In situ experiments were carried out on the variation of air permeability in the range of room temperature ~ 600 鈩，
本文编号：2491018
[Abstract]:A large area of coal field fire exists in Xinjiang, Shanxi and other places in China. Coal fire not only burns down a large number of coal resources, but also seriously destroys the fragile ecological environment in the west. In the process of coal fire evolution, the overburden rock in the upper part of the fire area produces combustion cracks, and the formation of a new air supply channel in the fire area is considered to be one of the main factors for the further sustainable development of the fire area. The formation of combustion cracks is the result of the change of the original coal and rock stress structure and the change of thermal mechanical parameters of overlying rock under the action of thermodynamic coupling. It is of great significance to understand the variation of thermodynamic parameters such as peak stress and elastic modulus under the condition of variable temperature of overlying rock in fire area, and to analyze the thermal instability characteristics of overlying rock with temperature, which is of great significance to reveal the evolution mechanism of coal field fire area. Most of the overburden rocks in coalfield fire area are sandstone, siltstone and mudstone. At present, there are many studies on sandstone and mudstone, but the research on siltstone is very few. Therefore, taking siltstone in fire area as the research object, the experiment of thermodynamic parameters under the condition of rising / cooling is carried out, and the thermodynamic parameters and thermal instability characteristics are analyzed and studied in order to promote the understanding of the law of combustion cracks in fire area. It also provides some guidance for the treatment and numerical simulation of fire area. In this paper, in situ, uniaxial and X-ray diffraction experiments are carried out on siltstone in fire area of coalfield. The main research contents and results are as follows: low confining pressure (2MPa) of siltstone is studied by triaxial testing machine of high temperature and high pressure rock mass. In situ experiments were carried out on the variation of air permeability in the range of room temperature ~ 600 鈩，
本文编号：2491018
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