不同含水率煤瓦斯渗流特性及声发射特征试验研究

发布时间：2018-05-04 20:43

本文选题：含水率 + 瓦斯压力　；参考：《太原理工大学》2017年硕士论文

【摘要】：现阶段开采的煤矿中,有一半以上是属于高瓦斯矿井甚至是突出矿井,瓦斯事故是煤矿安全事故中强度最大,伤亡最严重的。煤矿发生瓦斯事故造成的后果对于家庭、煤矿企业及国家都是难以承受的,因而煤矿开采过程中的首要任务就是进行瓦斯事故的防治,瓦斯事故的防治不仅关系到煤矿的安全生产,还会影响我国的可持续发展的进程。高效和大规模的进行瓦斯抽采和煤层气开发是防治瓦斯事故和瓦斯利用的基本手段,而瓦斯抽采的难易程度取决于瓦斯在煤层中的赋存情况和渗流特性。本文在前人研究的基础上,以取自西山煤电官地矿3#煤层的煤样为实验基础,利用电液伺服三轴渗流实验装置及声发射检测仪对含瓦斯煤在不同含水率及瓦斯压力条件下的渗流特性及在实验过程中的声发射的特征进行了研究,对煤矿开采中瓦斯事故的防治和运用水力压裂提高瓦斯的抽采效果具有一定的指导意义。具体的研究结果如下:(1)瓦斯压力和煤的渗透率存在着明显的非线性关系,与二次多项式具有很高的拟合度。在含水率一定的条件下,随着瓦斯压力的增加,煤的渗透率发生了变化,且煤样的渗透率在瓦斯增大的过程中先减小后增大,整个实验过程形成明显的“V”型抛物线趋势,有明显的Klinkenberg效应。轴压为4MPa,围压为3MPa时,临界瓦斯压力为1.0MPa。(2)在瓦斯压力恒定时,渗透率、渗流速度都随着煤的含水率的增加而减小,并且减小的速度逐渐变缓,都能与二次多项式具有很好的拟合效果。当瓦斯压力为0.5MPa时,煤的含水率从0.19%变化到2.12%的过程中,渗透率降低幅度达到了92.9%。(3)不同瓦斯压力或者不同含水率条件下,煤受到轴向应力变形直至破坏的过程中,表现出来的轴向应力—应变的关系相似。含水率一定时,随着瓦斯压力的增大,轴向应力提前进入峰值,过了峰值之后,轴向应力的下降速度变缓,即瓦斯压力越小,煤的脆性越强,瓦斯压力越大,煤的脆性降低,塑性增强。瓦斯压力恒定时,含水率高的煤比含水率低的煤,轴向力到达峰值之后的下降速度平缓,破坏类型趋向于塑性破坏。(4)不同瓦斯压力或者含水率条件下,声发射事件率比轴向应力提前到达最大值。瓦斯对煤有软化作用,瓦斯压力逐渐增大的过程中,煤的破坏类型从突然破裂渐变成稳定破坏。含水率越高,声发射事件率就越小,煤的轴向应变的跨度比较小,声发射事件率延续的时间比含水率小的煤短。
[Abstract]:More than half of the coal mines mined at the present stage belong to high gas mines or even outburst mines. Gas accidents are the most intense and the most serious casualties in coal mine safety accidents. The consequences of gas accidents in coal mines are unbearable for families, coal mining enterprises and countries. Therefore, the first task in the process of coal mining is to prevent and cure gas accidents. The prevention and treatment of gas accident not only relates to the safety of coal mine production, but also affects the process of sustainable development of our country. High efficiency and large-scale gas extraction and coalbed methane development are the basic means to prevent and cure gas accidents and gas utilization, and the difficulty of gas extraction depends on the occurrence and seepage characteristics of gas in coal seam. On the basis of previous studies, the coal samples taken from the coal seam of Xishan Coal Mine are taken as the experimental basis. The percolation characteristics of gas-bearing coal under different water content and gas pressure and the characteristics of acoustic emission in the process of experiment were studied by using electro-hydraulic servo triaxial seepage experimental device and acoustic emission detector. It has certain guiding significance for prevention and control of gas accident in coal mine mining and application of hydraulic fracturing to improve gas drainage effect. The specific results are as follows: (1) Gas pressure and coal permeability have obvious nonlinear relations, and have a high fitting with quadratic polynomial. Under the condition of constant water cut, the permeability of coal changes with the increase of gas pressure, and the permeability of coal sample decreases first and then increases in the process of gas increase, and the whole experiment process forms an obvious "V" type parabola trend. There is obvious Klinkenberg effect. When the axial pressure is 4MPa, the confining pressure is 3MPa, the critical gas pressure is 1.0MPa.m2) when the gas pressure is constant, the permeability and percolation velocity decrease with the increase of water content of coal, and the decreasing speed becomes slower. It has good fitting effect with quadratic polynomial. When the gas pressure is 0.5MPa, the moisture content of coal changes from 0.19% to 2.12%, and the permeability decreases by 92.9%. 3) under different gas pressure or different moisture content, the coal is subjected to axial stress deformation until failure. The relationship between axial stress and strain is similar. When the moisture content is constant, the axial stress reaches the peak value in advance with the increase of gas pressure. After the peak value, the decreasing speed of axial stress becomes slower, that is, the smaller the gas pressure, the stronger the brittleness of coal, the greater the gas pressure, and the lower the brittleness of coal. Plastic strengthening. When the gas pressure is constant, the decrease rate of axial force after the peak value of axial force reaches the peak, and the failure type tends to be plastic failure. 4) under different gas pressure or water content, the coal with high moisture content is lower than that of coal with high water content. The AE event rate reaches the maximum ahead of the axial stress. Gas softens the coal, and when the gas pressure increases gradually, the failure type of coal changes from sudden rupture to steady failure. The higher the water content is, the smaller the AE event rate is, and the span of axial strain of coal is smaller, and the duration of AE event rate is shorter than that of coal with low moisture content.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD712

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