【作者】 张天军；

【导师】 李树刚；

【作者基本信息】 西安科技大学 ， 安全技术及工程， 2009， 博士

【摘要】 含瓦斯煤岩体的采掘失稳会引发岩爆、煤爆、冲击地压、煤与瓦斯突出等多种动力灾害,特别是在富含瓦斯煤岩体中,这些灾害发生更加频繁。研究富含瓦斯煤岩体的失稳机理,对于减少灾害事故,改善煤矿生产的安全状况,具有重要工程意义。富含瓦斯煤岩体采掘失稳是一动态演化过程,对煤岩体变形、破坏和失稳机理需要用非线性力学理论进行研究。本文综合应用实验室试验、理论分析、数值模拟等方法研究了富含瓦斯煤岩体采掘失稳的非线性力学机理。论文共分6章,其主要研究内容及学术贡献如下:(1)对陕西下峪口煤矿和崔家沟煤矿煤样进行了电镜扫描试验、单轴压缩试验、三轴压缩试验。试验结果显示,富含瓦斯煤的破坏特征符合Coulomb-Mohr强度准则,非突出矿煤样相对突出矿煤样具有较大的抗压强度和弹性模量,具有较小的泊松比。(2)利用瞬态渗透法对富含瓦斯煤样进行了渗透性试验,结果表明,全应力应变过程渗透率的变化与试样内部裂隙的发展变化过程密切相关。非突出矿煤样易于形成贯通裂隙,突出矿煤样较松软,不易形成贯通裂隙,因此其峰后渗透率远小于非突出矿煤样。针对富含瓦斯煤样渗流的非Darcy流特性,计算了渗流失稳时的临界压力梯度。结果显示,非突出矿井煤样的渗流失稳多发生在峰后;突出矿井煤样在峰值强度前后均易发生渗流失稳并且其临界压力梯度较大,因此渗流失稳的过程更加短暂和迅速。这一结果与矿井实际发生渗流失稳的情况相符合。(3)在WY-98B瓦斯吸附常数测定仪基础上,研制了瓦斯解吸激振及测试系统,研究了温度、粒径及激振力等因素对煤吸附解吸瓦斯性能的影响。基于吸附等温线拟合了温度在[293K,323K]范围时Langmiur吸附常数与温度的关系式;得到了粒径与瓦斯吸附量之间的关系,发现煤的粒径小于0.045mm时,粒径的减小不会使吸附量明显的增大;获得了煤样在低频振动作用下的解吸特性曲线,研究认为,振动作用改变了煤体的吸附微孔,使瓦斯与煤体产生相对运动而脱附,同时振动过程为解吸提供了热能。因此,低频激振能够加快煤体中的瓦斯解吸速度并增大解吸量。(4)采用多尺度耦合理论,建立了煤岩体的微单元三维强度分布模型及其受力的邻近单元加权分担模型,针对富含瓦斯煤的强度分布性能,应用有效应力原理,建立了含有损伤分数、名义应力、温度、瓦斯压力等多个控制参量的富含瓦斯煤体宏观破坏概率函数和多尺度敏感性函数;研究发现,损伤分数和压力越大、温度越低,煤的宏观破坏概率越大,破坏的多尺度敏感性越高。(5)根据工程观测和试验结果,建立了层状煤岩体及层裂煤岩体的薄板力学模型。采用尖点突变理论导出了煤岩采掘失稳的判据;采用燕尾突变理论研究了采掘过程中爆破、钻探及瓦斯动压力等动载因素对层状煤岩稳定性的影响,分析了不同势函数下岩板的失稳特征。研究表明,富含瓦斯煤岩体的采掘失稳除了与其物理、力学性质和几何尺寸有关外,还与岩板面内载荷、法向载荷和法向动载的大小及变化路径有关。(6)采用突变级数法对富含瓦斯煤岩体发生煤与瓦斯突出的危险性进行了预测,计算表明,突变级数法用于煤与瓦斯突出的危险性预测能取得较高的准确率。更多还原

【Abstract】 Mining instability of coal rocks containing gas may result in various disasters, such as rock bust, coal outburst, and gas outburst. In the case of gas-rich coal rocks, these disasters occur even more frequently. Therefore, it is very important in engineering practice to study the instability mechanism of gas-rich coal rocks, so that disaster accidents may be reduced and coal mine production safety can be improved. The mining instability of gas-rich coal rocks is a dynamic evolution process. To study the mechanism of deformation, collapse, and instability of coal rocks, non-linear mechanical theory is used. In the dissertation research, laboratory tests, theoretical analysis, and numerical simulation methods are comprehensively used to study the non-linear mechanical mechanism of mining instability of gas-rich coal rocks. The dissertation is divided into 6 chapters, and the major research contents and academic contributions are as follows:(1) Coal samples from two gas-rich coal mines in Shanxi, the Xiayukou Mine and the Cuijiagou Mine, are used to do the EMS tests, uniaxial compression tests, and triaxial compression tests. The test results show that the collapse feature of gas-rich coal rocks accords with Coulomb-Mohr strength criterion and the coal samples from non-outburst coal mines, in comparison with those from outburst mines, have larger compressive strength, larger modulus of elasticity, and smaller Poisson ratio.(2) The transient permeability method is used to do permeability tests for gas-rich coal samples. The test results show that the change of permeability during complete stress-strain process is closely related with the development and change of internal cracks of coal samples. Coal samples from non-outburst coal mines form transfixion cracks easily. While coal samples from outburst mines are relatively loose and soft and they do not form transfixion cracks easily, so their after-peak permeability is far less than those of non-outburst mines. Based on the permeability characteristics of non-Darcy flow of coal samples from gas-rich mines, critical pressure gradient at seepage instability is computed. The result shows that seepage instability of coal samples of non-outburst mines usually occurs after the peak strength; while the seepage instability of coal samples of outburst coal mines occurs both before and after the peak strength, and its critical pressure gradient is relatively large, therefore, the seepage instability process is short and quick. This result accords with actual conditions of seepage instability of coal mines.(3) On the basis of the WY-98B Gas Adsorption Constant Determinator, a gas- desorption exciting and testing system is developed. The impact of temperature, particle size, and exciting force on gas-adsorption and desorption properties of coals is studied. The relation between Langmuir adsorption constant and temperature is fitted from the adsorption isotherm within the adsorption temperature range of 293K and 323K. The relationship between particle size and gas adsorption is obtained, and it is found that when the coal particle size is smaller than 0.045mm, the decreasing of particle size will not increase adsorption significantly. The curve of desorption characteristic of coal samples under the action of low-frequency exciting fore is found. The study shows that exciting vibration has changed the adsorptive micro-pores of coal rocks, caused gas and coal rock to move relatively, so that gas has been removed out of coal rocks. Meanwhile, vibrating process provides desorption with heat energy. Thus, low-frequency exciting force can speed up gas desorption in coal rocks and increase desorption quantity.(4) The multi-scale coupling theory is used to build three-dimensional strength distribution model of tiny element of coal rocks and the weighted adjacent element force-sharing model. Based on the strength distribution properties of gas-rich coal rocks and by using the effective strength principle, the macroscopic failure probability function and the multi-scale sensitivity function of gas-rich coal rocks are established. These functions have damage fraction, nominal stress, temperature, and gas pressure as their control parameters. The study shows that when the damage fraction and the pressure are greater and the temperature is lower, the macroscopic failure probability of the coal rocks is larger and the multi-scale sensitivity of the failure is higher.(5) Based on engineering observation and test results, mechanics models of thin plate are established for layered coal rocks and spalled coal rocks. Cusp catastrophe theory is used to derive the determining criterion of mining instability of coal rocks. And swallowtail catastrophe theory is used to study the impact of dynamic factors, such as explosion, drilling, and dynamic gas pressure on the stability of layered rocks, and to analyze the instability characteristics of rock plate under different potential functions. The study shows that the mining instability of gas-rich coal rocks depends not only on the physic and mechanical properties and the rock size, but also on the in-plane loads, normal loads, and the magnitude and changing path of dynamic normal loads.(6) Catastrophe progression method is used to predict the risk of coal and gas outburst of gas-rich coal rocks. The calculation shows that the prediction yields relatively high accuracy.更多还原