循环冲击层理煤岩动力学行为及破坏规律研究

为研究复杂地况下含特征层理煤岩的动态力学行为，采用■50 mm分离式霍普金森压杆实验系统，对含层理(0°、30°、45°、60°、90°)煤岩进行动态三轴循环冲击实验研究，并结合3D轮廓扫描仪量化其断裂界面，分析层理效应和围压效应对煤岩动态力学特性及其损伤破坏规律的影响。研究表明：围压的施加使煤岩应力-应变曲线出现弹性后效现象；较无围压状态，抗压强度提高3.9～4.2倍，失效应变增大2.59～3.05倍。随着层理角度的增大，煤岩的动态抗压强度、弹性模量和能量透射率均呈现先降低后升高的U形分布，在层理角为45°时均达到最小值；能量吸收率和断面粗糙度呈现先增大后减小的∩形分布，损伤变量呈现N形分布，在层理角为45°时达到最大值。煤岩的损伤破坏特征随层理角度的变化可概括为张拉破坏（0°）-剪切破坏（30°、45°和60°）-劈裂破坏（90°）的演变过程，所得特征规律可为实际复杂环境下煤层气资源安全高效开采提供理论支持。

On dynamic behaviors and failure of bedding coal rock subjected to cyclic impact

Dynamic triaxial cyclic impact experiments on the coal rock samples with the bedding angles of 0°, 30°, 45°, 60°, and 90°, respectively, were conducted using a 50-mm split Hopkinson pressure bar (SHPB) system to study the dynamic mechanical behaviors of the coal rock with characteristic bedding under complex ground conditions. A 3D profile scanner was utilized to quantify the fracture interface roughness and to investigate the bedding effect on the dynamic fracture process of the coal rock. The bedding angle effect and confining pressure effect on the dynamic properties of the coal rock were explored by combining dynamic parameters such as compressive strength, elastic modulus, energy distribution evolution with the fracture surface roughness variation. The research shows that when confining pressure is applied, the stress-strain curve of the coal rock has an elastic aftereffect. The dynamic compressive strength and failure strain of the bedding coal rock with confining pressure are respectively 3.9?4.2 and 2.59?3.05 times higher than those without confining pressure. As the bedding angle increases, the dynamic compressive strength, elastic modulus, and energy transmitted ratio of the coal rock display the U-shaped distribution, which decreases first and then increases, reaching the minimum at the bedding angle of 45°. Meanwhile, the energy absorbed ratio and fracture surface roughness show the ∩-shaped distribution, first increasing and then decreasing, and the damage variable shows the N-shaped distribution, reaching the maximum at the bedding angle of 45°. The failure of the coal rock with 45° bedding is the most serious, which is more prone to intergranular and spalling fractures. However, the 90° bedding coal rock is more likely to absorb energy and to form transgranular fractures, resulting in a large number of mesoscopic fractures. Variation of the damage characteristics of the coal rocks with bedding angle can be summarized as a tensile damage (0°)-shear damage (30°, 45°, 60°)-splitting damage (90°) evolution process. The relevant characteristic results obtained from the experiments can provide a theoretical support for the safe and efficient exploitation of coalbed methane resources in the complex environment under practical working conditions.