冲击载荷下含瓦斯煤岩组合体动力学行为及破坏特征分析

Analysis of dynamic behavior and damage characteristics of gas-bearing coal-rock combinations under impact loading

  • 摘要: 为探究冲击载荷作用下含瓦斯煤岩组合体的动力学行为与破坏特征,利用含瓦斯煤岩冲击损伤−渗流试验系统和工业显微CT扫描系统,设计并开展了三轴动态压缩试验。通过试验重构了煤岩组合体在动态加载前后的三维裂隙结构,对比分析了不同CO2气体压力下煤岩组合体的动态应力−应变曲线、力学参数、能量耗散规律、裂隙扩展规律和冲击破坏特征。结果表明:在冲击载荷作用下,煤岩组合体的应力−应变曲线可分为初始变形阶段、煤控弹性阶段、过渡阶段、岩控弹性阶段、应变硬化阶段和宏观破坏阶段。随着CO2气体压力的增加,煤岩组合体的动态抗压强度逐渐降低,动态峰值应变和应变率呈指数下降趋势。煤岩组合体的第一弹性模量随CO2气体压力增加先增大后减小,第二弹性模量则在一定范围内波动变化。在冲击载荷作用下,煤岩组合体的入射能 > 吸收能 > 反射能 > 透射能。随着CO2气体压力的增加,4种能量均呈现出逐渐减小的趋势,但各能量成分所占比例基本保持不变。CO2气体压力的增加导致其对煤体的劣化作用增强,从而使组合体内部裂隙体积和裂隙表面积增加。随着CO2气体压力增大,煤岩组合体的轴向切片上的剪切裂隙与张拉裂隙面积均有所增加。煤岩组合体的主要破坏形式是压剪破坏,破坏多出现在煤体部分,而岩体部分的破坏形式往往受到煤体影响。

     

    Abstract: To investigate the dynamic behaviors and damage characteristics of gas-containing coal-rock combinations under impact loading, a triaxial dynamic compression experiment was designed and conducted using a gas-containing coal-rock impact damage-seepage experimental system and an industrial micro-CT scanning system. The 3D crack structures of coal-rock combinations before and after dynamic loading were reconstructed through experiments. The dynamic stress-strain curves, mechanical parameters, energy dissipation laws, crack propagation patterns and impact damage characteristics of coal-rock combinations under different CO2 gas pressures were comparatively analyzed. The results indicate that the stress-strain curves of the coal-rock combinations under impact loading can be divided into the initial deformation stage, coal-controlled elastic stage, transition stage, rock-controlled elastic stage, strain hardening stage and macroscopic failure stage. With increasing CO2 gas pressure, the dynamic compressive strength of coal-rock combinations gradually decreases, while the dynamic peak strain and strain rate exhibit an exponential decline. The first elastic modulus of coal-rock combinations initially increases and then decreases with increasing CO2 gas pressure, while the second elastic modulus fluctuates within a certain range. Under impact loading, the incident energy of coal-rock combinations is greater than the absorbed energy, which in turn exceeds the reflected and transmitted energies. With increasing CO2 gas pressure, all four energy components show a decreasing trend, while their relative proportions remain essentially unchanged. The increase in CO2 gas pressure enhances the degradation effect on the coal, leading to an increase in the internal crack volume and crack surface area of coal-rock combinations. With the increase in CO2 gas pressure, the shear and tensile crack areas on the axial slices of coal-rock combinations increases. The primary damage mode of coal-rock combinations is compression-shear damage, which predominantly occurs in the coal component, while the damage mode of the rock component is often influenced by the coal component.

     

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