采动诱冲动能估算及冲击危险性评价

Estimation of dynamic energy induced by coal mining and evaluation of burst risk

  • 摘要: 能量积聚与释放作为煤矿冲击地压发生的基本力学机制,成为近些年来学术界与工程界关注的热点之一。如何突破传统的应力-应变曲线为基础的形变能诱灾机理现状,探讨动能驱动诱冲机理是科学解答冲击地压的瓶颈。根据回采工作面开采所引起的支承分布压力变化,基于开采扰动原理,推导了因采动导致煤体内产生动能计算方法,得到了不同深度、不同塑性区宽度、不同推进度与所产生动能之间关系,提出了冲击危险性动能评估指标。研究表明,工作面超前支承压力集中区产生的高变形能的释放是煤体破坏的必要条件,而支承压力变化促使变形能释放转化形成的动能是驱动煤体动力破坏失稳的充分条件;通过对开采进尺小于和大于塑性区宽度时支承压力变化所引起动能计算发现,当开采进尺要大于0.8倍的塑性区宽度时将开始产生动能;当开采进尺一定时,若塑性区宽度越大,则产生的动能就越小,因此松动爆破、大直径卸压钻孔等手段增大塑性区宽度有利于动能的降低;若开采进尺越大,则产生动能就越高,因此,降低推采速度减少进尺有利于降低产生的动能,基于获得的开采进尺与动能量级的关系,可以定量给出满足防冲要求的安全开采进尺,这为解答如何确定不同冲击地压煤层容许进尺提供了定量方法;根据单位体积煤体所承受动能与单位体积煤体所能够贮存的弹性能的比值,定义冲击危险性动能评估指标,强调动能驱动机制,此将更有利于判断冲击危险性程度。

     

    Abstract: As the basic mechanical mechanism of coal bump in coalmine, energy accumulation and release has become one of the focuses in the academic and engineering fields in recent years. How to break through the present situation of deformation energy induced disaster mechanism based on traditional stress-strain curve, and research the kinetic energy driving mechanism, is a bottleneck of learning coal bump scientifically. According to the change of abutment pressure caused by mining and the rationale of mining disturbance, authors deduced a calculation method of mining kinetic energy, obtained the relationship between kinetic energy and depth, width of plastic zone, and advancing degree, and put forward a risk assessment index of mining kinetic energy. It was found that the release of high strain energy caused by concentrated abutment pressure is only a necessary condition for coal failure, the release and transformation of strain energy into kinetic energy is a sufficient condition for coal dynamic failure or coal bump. By deducing the kinetic energy calculation formula caused by abutment pressure change when advance of coal face is less than or greater than width of plastic zone. It was found that kinetic energy will be generated when mining advance is larger than 0.8 times the width of plastic zone. When mining advance is as a constant, the greater the width of plastic zone, the less the kinetic energy transferred. Therefore, such means to increase the plastic zone width as loose blasting, large diameter borehole pressure releasing and others, are conducive to the reduction of kinetic energy. The larger the mining advance, the higher the transferred kinetic energy. Therefore, reducing mining advance is conducive to reducing the transferred kinetic energy. The larger the mining advance is, the higher the kinetic energy transferred, thus, the reduction of mining velocity or the reduction of mining advance is beneficial to reduce kinetic energy. It provides a quantitative method for determining allowable advance of coal seam with different coal bump degree. The ratio of the kinetic energy per unit volume of coal to the elastic strain energy was defined as a risk assessment index of kinetic energy impact, which emphasizes driving mechanism of kinetic energy and is more conducive to judge the risk degree of coal bump.

     

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