地应力−释能端结构耦合作用下爆破裂缝分布特征及其工程应用

    The distribution characteristics of blasting fractures and their engineering applications under the coupling effect of in-situ stress and energy-releasing end structure

    • 摘要: 预裂爆破作为提升煤层渗透性的有效技术手段,在煤矿瓦斯抽采等领域具有重要应用价值。为精准探究地应力与释能端结构耦合作用下爆破裂缝的分布特征,优化预裂爆破煤层增透技术的施工参数,采用相似材料制作型煤替代原煤开展真三轴条件下的爆破试验,并借助 CT 扫描技术对型煤试件内部的爆破裂缝进行无损检测与精准成像。结果表明:型煤内部爆破裂缝的分布特征与释能端结构紧密相关,释能端上泄能孔的分布形式及数量显著影响爆破裂缝的空间分布形态;单孔结构释能端有利于形成定向长裂缝,多孔结构释能端则有利于复杂裂隙网的构成;地应力对爆破裂缝的形成与扩展具有调控作用,最大水平主应力σ1与最小水平主应力σ3的差值越大,爆破裂缝的扩展能力越强;垂直主应力σ2对爆破裂缝长度的影响能力小于σ1和σ3;在地应力与释能端结构的耦合作用下,前者通过改变煤岩体力学响应特性,影响裂纹扩展方向,后者则通过精准调控爆破能量释放,作用于爆破裂缝分布与形态演化。对刘家梁煤矿5136采煤工作面煤层实施预裂爆破煤层增透措施后,抽采孔的瓦斯抽采效率至少提升2倍,充分证明预裂爆破煤层增透技术的有效性。

       

      Abstract: As an effective technical means to improve the permeability of coal seam, pre-splitting blasting has important application value in the field of coal mine gas drainage. In order to accurately explore the distribution characteristics of blasting cracks under the coupling effect of in-situ stress and energy release end structure, and optimize the construction parameters of pre-splitting blasting coal seam permeability improvement technology, similar materials were used to make briquette instead of raw coal to carry out blasting experiments under true triaxial conditions, and CT scanning technology was used to carry out non-destructive testing and accurate imaging of blasting cracks inside briquette specimens. The experimental results show that the distribution characteristics of blasting cracks in briquette are closely related to the structure of energy release end, and the distribution form and number of energy release holes at the energy release end significantly affect the spatial distribution of blasting cracks. The energy release end of the single-hole structure is conducive to the formation of directional long cracks, and the energy release end of the porous structure is conducive to form a complex fracture network. In-situ stress has a regulating effect on the formation and expansion of blasting cracks. The greater the difference between the maximum horizontal principal stress σ1 and the minimum horizontal principal stress σ3, the stronger the expansion capacity of blasting cracks. The influence of vertical principal stress σ2 on blasting crack length is less than that of σ1 and σ3. Under the coupling effect of in-situ stress and energy release end structure, the former affects the crack propagation direction by changing the mechanical response characteristics of coal and rock mass; the latter acts on the distribution and morphological evolution of blasting cracks by accurately regulating the release of blasting energy. In addition, after the implementation of pre-splitting blasting coal seam permeability improvement measures in the coal seam of 5136 working face of Liujialiang Coal Mine, the gas drainage efficiency of the drainage hole is increased by at least 2 times, which fully proves the effectiveness of the pre-splitting blasting coal seam anti-reflection technology.

       

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