Li Minmin, Liang Weimin, Yue Gaowei, Yue Jiwei, Zheng Xinjun
School of Civil Engineering, Henan Polytechnic University, Jiaozuo 454000, China.
School of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo 454000, China.
ACS Omega. 2020 Apr 21;5(17):9957-9968. doi: 10.1021/acsomega.0c00269. eCollection 2020 May 5.
A mount of bedding and cleat in a coal body causes that the mechanical property and gas permeability are anisotropic in a coal seam, partly. To reveal the permeability change law of the impacted coal, a self-developed vertical split Hopkinson pressure bar (SHPB) device is used to carry out the dynamic impact mechanical property tests of coal samples in three different coring directions under five impact loads and then the permeability of the impacted coal samples is measured by a permeability measuring instrument under different gas pressures. Finally, a calculation model for the anisotropic coal permeability is established to analyze the permeability distribution law in any direction with different angles to the bedding plane. The results show that with an increase in impact height the dynamic peak stress of coal samples increases gradually, which shows a linear growth relationship. The permeability of the impacted coal samples is much larger than that of raw coal samples, and the bigger the impact load, the larger the permeability. Moreover, under the same impact load and gas pressure, the permeability is the largest in parallel to the bedding direction, followed by that in oblique 45° to the bedding direction, and the smallest in perpendicular to the bedding direction. The permeability calculated by the anisotropic model in oblique 45° to the bedding direction is in good agreement with the measured results, and the errors are no more than 10%, which will provide a theoretical basis for the permeability distribution law of the coal seam after deep-hole blasting.
煤体中的层理和割理使得煤层的力学性质和透气性在一定程度上呈现各向异性。为揭示受冲击煤体的渗透率变化规律，采用自行研制的立式分离式霍普金森压杆（SHPB）装置，对煤样在三个不同取芯方向、五种冲击载荷作用下进行动态冲击力学性能试验，然后用渗透率测量仪在不同气体压力下测量受冲击煤样的渗透率。最后，建立了各向异性煤渗透率计算模型，分析了与层面成不同角度的任意方向上的渗透率分布规律。结果表明，随着冲击高度的增加，煤样的动态峰值应力逐渐增大，呈线性增长关系。受冲击煤样的渗透率远大于原煤样，冲击载荷越大，渗透率越大。而且，在相同冲击载荷和气体压力下，平行于层面方向的渗透率最大，与层面成45°斜交方向次之，垂直于层面方向最小。与层面成45°斜交方向的各向异性模型计算渗透率与测量结果吻合较好，误差不超过10%，为深孔爆破后煤层渗透率分布规律提供了理论依据。
