朱健,胡国忠,许家林,等. 煤层层理对微波破煤增透效果的影响[J]. 煤炭学报,2024,49(5):2324−2337. doi: 10.13225/j.cnki.jccs.2023.0526
引用本文: 朱健,胡国忠,许家林,等. 煤层层理对微波破煤增透效果的影响[J]. 煤炭学报,2024,49(5):2324−2337. doi: 10.13225/j.cnki.jccs.2023.0526
ZHU Jian,HU Guozhong,XU Jialin,et al. Influence of coal seam bedding on the effect of fracturing coal and enhancing permeability by microwave[J]. Journal of China Coal Society,2024,49(5):2324−2337. doi: 10.13225/j.cnki.jccs.2023.0526
Citation: ZHU Jian,HU Guozhong,XU Jialin,et al. Influence of coal seam bedding on the effect of fracturing coal and enhancing permeability by microwave[J]. Journal of China Coal Society,2024,49(5):2324−2337. doi: 10.13225/j.cnki.jccs.2023.0526

煤层层理对微波破煤增透效果的影响

Influence of coal seam bedding on the effect of fracturing coal and enhancing permeability by microwave

  • 摘要: 层理作为一种典型的结构弱面普遍存在于煤层之中,煤层层理与煤基质之间的相对力学性能是决定层理发育煤层微波增透效果的关键。为此,采用自主研制的微波辐射试验装置,对层理面与加载方向之间夹角为0°、30°、45°、60°和90°的煤样开展了微波破煤试验,探究了不同层理方向煤样微观孔隙结构与细观裂隙的演化特征,揭示了微波辐射下层理对煤体孔裂隙结构的数量、尺度与连通性的影响规律;对比分析了微波辐射前、后不同层理方向煤体的气体渗透特性,阐明了煤体在煤层层理与微波破煤叠加影响下的渗透率变化规律,揭示了煤层层理对微波破煤增透的影响机制。结果表明:① 煤层层理对微波破煤增透效果的影响显著,层理面与加载方向之间夹角越大,微波辐射下煤体的束缚孔减少幅度与连通性裂隙增长幅度也更大;与原煤样相比,微波辐射后不同层理方向煤样渗透率之间的数量级差异有效减小,渗透率各向异性弱化明显。② 微波辐射下煤体中细观裂隙发育具有显著的层理效应,具体演化过程为:沿层理面原生裂隙扩展→新的沿层理面裂隙萌生→与层理面相交的裂隙扩展。③ 煤基质与层理面的介电损耗和传热性质差异,使得微波对煤体的热应力分布受制于层理面。当层理面与加载方向垂直或平行时,煤体以张拉破坏为主;当层理面与加载方向斜交时,煤体以剪切滑移破坏为主。

     

    Abstract: As a typical structural weak surface, bedding is ubiquitous in coal seams. The relative mechanical properties between coal seam bedding and coal matrix are the key to determining the effect of enhancing permeability by microwave in coal seams with bedding development. To this end, a self-developed microwave irradiation (MI) test device was used to carry out microwave fracturing coal experiments on coal samples with an angle of 0°, 30°, 45°, 60° and 90° between the bedding plane and the loading direction. The evolution characteristics of microscopic pore structure and microscopic cracks of coal samples with different bedding directions were explored, and the influence of bedding structure on the number, scale, and connectivity of coal pores and fractures under MI was revealed. The gas permeability characteristics of coal in different bedding directions before and after MI were compared and analyzed. The variation law of coal permeability under the influence of coal seam bedding and fracturing coal by microwave was clarified, and the influence mechanism of coal seam bedding on fracturing coal and enhancing permeability by microwave was revealed. The results show that the coal seam bedding has a significant effect on the effect of fracturing coal and enhancing permeability by microwave. The larger the angle between the bedding plane and the loading direction, the greater the reduction of the bound pores and the growth of the connected fractures of the coal under MI. Compared with the original coal samples, the order of magnitude difference between the permeability of coal samples in different bedding directions after MI is effectively reduced, and the permeability anisotropy is obviously weakened. The development of meso-cracks in coal under MI has a significant bedding effect. The specific evolution process is first to expand the original cracks along the bedding plane, followed by the initiation of new cracks along the bedding plane, and finally to expand the cracks intersecting with the bedding plane. The difference of dielectric loss and heat transfer properties between coal matrix and bedding plane makes the thermal stress distribution of coal subject to the bedding plane. When the bedding plane is perpendicular or parallel to the loading direction, the coal body is dominated by tensile failure. When the bedding plane is oblique to the loading direction, the coal body is dominated by shear slip failure.

     

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