不同加载速率含水煤层渗透性及声发射实验研究

发布时间：2018-04-24 03:31

本文选题：含水率 + 加载速率　；参考：《太原理工大学》2017年硕士论文

【摘要】：众所周知,我国煤矿中危害最大的灾难即煤岩瓦斯动力灾害,其中煤与瓦斯突出事故的危险性及危害性首居其位。可采前,煤体原应力处于平衡状态,但当采动加载时原平衡状态转变为增加垂直应力到超过荷载极限,同时降低水平应力的采动响应过程。发生煤与瓦斯突出时产生变形、破裂过程中会以声波的形式进行传播煤岩体内部微裂隙结构、地应力变化等可以作为预兆信息,本论文利用WYS-800微机控制电液伺服三轴瓦斯渗流实验装置及声发射检测系统,结合水分、瓦斯及不同加载速率综合因素,改进了加载条件及过程,除了研究力学性质、声发射信号序列演化规律,并新添加了渗流性能。具体研究内容如下:(1)不同加载速率下试件的应力应变力学特性很相似,但随着试件加载速率的增大,轴向应力峰值明显降低。同时不同加载速率加载过程试件出现体积扩容现象。(2)在瓦斯压力为1MPa、围压卸载速率为0.01MPa/s加载条件下,煤样渗流速率、渗透率与加载速率呈正相关非线性趋势,但渗流速率、渗透率随着加载速率增大其变化速率减小。指数函数k=a-bc~x可以更好表征加载速率与渗流速率、渗透率关系,其中a、b、c为拟合系数。该关系式中对于高含水率试件拟合度会更高。(3)与高含水率试件相比,含水率煤样的渗透率和渗流速率随着含水率的增大。相同含水率条件下,加载速率的变化幅度越大,渗透率和渗流速率增大的幅度也越大。不同含水率下的含瓦斯煤渗透率呈现一定下降趋势,且含水率与渗透率之间符合二次多项式关系,加载速率越大,拟合效果越好。(4)煤体初始瓦斯渗流过程中声发射信号出现间歇性特征,即出现一个密集段后紧接着一个短暂的间歇段,间歇段内的信号相比于密集度较微,整个渗流过程声发射信号逐渐减弱。但随着含水率的增大,初始瓦斯渗流过程声发射信号呈现逐渐增大趋势。(5)不同含水率条件下试件受载过程中声发射计数率变化与应力变化趋势几乎一致。随着含水率的递增,应力峰值及声发射累积计数呈现减弱趋势。对比不同加载速率下含瓦斯煤受载过程的声发射特征参数表明加载速率越大,试件整个过程声发射事件数越多,且平均幅值越大。在试件破坏前,声发射事件数积聚增多,直至破坏。其中可用幂函数来表征加载速率与声发射累积计数之间的关系。此论文研究的是利用声发射技术捕捉有效声波预兆信息,监测分析的结果对于监测煤体内部损伤机制、演化过程及优化含瓦斯煤动力灾害的预测预防治理措施有实际应用意义。
[Abstract]:It is well known that coal and gas power disaster is the most harmful disaster in coal mine in China, in which coal and gas outburst accidents are the most dangerous and harmful. Before mining, the original stress of coal body is in equilibrium state, but the original equilibrium state changes to increase vertical stress to exceed the limit of load when mining is loaded, and at the same time reduce the dynamic response process of horizontal stress. When coal and gas outburst occur, deformation will occur, and in the process of rupture, the micro-fracture structure of coal and rock mass will be propagated in the form of sound waves, and the variation of in-situ stress can be used as a precursor information. In this paper, WYS-800 microcomputer is used to control the electro-hydraulic servo triaxial gas seepage experimental device and acoustic emission detection system. Combined with the comprehensive factors of moisture, gas and different loading rates, the loading conditions and processes are improved, except for the study of mechanical properties. The evolution rule of acoustic emission signal sequence and the new seepage performance are added. The results are as follows: (1) the stress-strain properties of specimens at different loading rates are very similar, but with the increase of loading rate, the axial stress peak value decreases obviously. At the same time, under the condition of gas pressure of 1MPa and confining pressure of 0.01MPa/s loading, the seepage rate, permeability and loading rate of coal sample are positively correlated with nonlinear trend, but the seepage rate is positive. The permeability decreases with the increase of loading rate. The exponential function k=a-bc~x can better characterize the relationship between loading rate, seepage rate and permeability. In this relation, the fitting degree of high moisture content specimen will be higher than that of high water cut sample, and the permeability and seepage rate of water cut coal sample will increase with the increase of water content. Under the same water cut, the larger the range of loading rate, the larger the increase of permeability and seepage rate. The permeability of gas-bearing coal under different water cut shows a certain decreasing trend, and the relation between water cut and permeability accords with quadratic polynomial relation, and the loading rate is higher. The better the fitting effect is, the more intermittent the acoustic emission signals appear in the initial gas seepage process of coal body, that is, a dense section followed by a short interval section, and the signal in the intermittent section is less than that in the dense section. The acoustic emission signal decreases gradually during the whole seepage process. However, with the increase of water content, the acoustic emission signal of initial gas seepage process gradually increases. 5) under different water content, the change of acoustic emission counting rate is almost consistent with the change trend of stress. With the increase of water content, the peak stress and the cumulative acoustic emission (AE) count tend to weaken. Compared with the acoustic emission characteristic parameters of the loading process of gas-bearing coal under different loading rates, the larger the loading rate, the more the number of acoustic emission events and the larger the average amplitude. Before the specimen was destroyed, the number of acoustic emission events accumulated and increased until the damage. The power function can be used to characterize the relationship between loading rate and cumulative acoustic emission counting. In this paper, acoustic emission technology is used to capture effective acoustic precursor information. The results of monitoring and analysis are of practical significance for monitoring the internal damage mechanism of coal body, the evolution process and optimizing the prevention and control measures for the prediction and control of coal-bearing power disaster.
【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】：TD713

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