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煤体倾角突变对煤与瓦斯突出及冲击演化特征影响

The influence of abrupt changes of coal dip angle on coal and gas outburst and impact evolution characteristics

  • 摘要: 为进一步探究深部复杂地质构造煤体倾角突变对煤与瓦斯突出及冲击演化特征影响, 考虑突出实际情况, 设置倾角突变界面, 界面上侧为原煤, 下侧为型煤, 分别用于模拟原生煤体与构造煤体, 通过三维应力加载模拟现场真实工况, 结合冲击力测试仪、声发射检测仪、数据采集仪等监测设备, 开展不同倾角(煤体倾角突变初始角度θI、突变角度θM)突变条件下突出模拟试验, 分析煤体倾角突变对突出强度及冲击参数(冲击力峰值、负压段最大值、急剧变化段时长)的影响。研究结果表明: ①在10°<θI≤20°、10°≤θM≤20°的范围内存在一个煤体倾角突变临界值θT, 当θIθM均大于等于θT时, 易发生低指标突出; 当θI一定时, 临界瓦斯压力与θM成负相关关系, 单位突出强度与θM成正相关关系。②冲击力在模拟巷道内的演化过程可划分为3个阶段: 急剧变化阶段、波动变化阶段及平稳变化阶段。正压阶段高频脉冲A与负压阶段高频脉冲B的数量与密集度均与θM密切相关, 随θM的增大, 冲击力急剧变化阶段波动越发复杂, 高频脉冲A、B在该段内逐渐呈现出高度集中的态势。③冲击力峰值和负压段最大值与瓦斯集中系数成负线性关系, 急剧变化阶段时长与瓦斯集中系数成正线性关系。冲击气流峰值速度和累计AE能量变化趋势基本一致, 均与瓦斯集中系数Iθ成负线性关系, 两者皆在θM大于等于θT时呈现较为显著的变化特征。

     

    Abstract: To investigate the influence of abrupt changes in coal dip angles within deep and complex geological structures on the evolution characteristics of coal and gas outburst and impact evolution characteristics, an interface with an abrupt change in dip angle is established by taking into account the practical situation of coal and gas outbursts. The upper side of the interface consists of virgin coal, while the lower side consists of briquetted coal, which are utilized to simulate the virgin and the tectonic coal, respectively. With monitoring units, such as impact force testers, acoustic emission detectors, and data acquisition systems, coal and gas outburst simulation experiments under three-dimensional stress conditions are conducted considering different conditions of abrupt dip angle (the initial angle of coal dip angle mutation θI, the mutation angle θM) changes. The influence of coal dip angle mutation on outburst intensity and impact parameters (peak impact force, maximum negative pressure, and duration of sharp change) are analyzed. The research results show that within the range of 10°<θI≤20° and 10°≤θM≤20°, a critical value of coal dip angle mutation θT exists. When both θI and θM are greater than or equal to θT, low-index outbursts are prone to occur. Given a constant θI, the critical gas pressure exhibits a negative correlation with θM, while the outburst intensity per unit shows a positive correlation with θM. The evolution process of impact force in the simulated roadway can be divided into rapid change stage, fluctuation change stage and stable change stage. The number and density of high-frequency pulse A in the positive pressure stage and high-frequency pulse B in the negative pressure stage are closely related to θM. With the increase of θM, the fluctuation of the impact force in rapid change stage becomes more complex, and the high-frequency pulses A and B gradually show a highly concentrated trend in this stage. The peak impact force and the maximum value of negative pressure stage have a negative linear relationship with the gas concentration factor Iθ, while the duration of the rapid change stage has a positive linear relationship with the gas concentration factor. The peak velocity of impact airflow and the cumulative AE energy show basically the same trend. Both of them have a negative linear relationship with the gas concentration factor, and exhibit more significant changes when θM is greater than or equal to θT.

     

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