超临界CO_(2)作用下不同煤厚煤岩体破裂过程声发射特性研究

Acoustic Emission Characteristics Study of Coa-Rock Mass Fracture with Different Coal Thickness Under Supercritical CO_(2) Interaction

将CO_(2)注入到深部地层的不可采煤层中,是CO_(2)长期封存的有效手段。但高温高压下达到超临界状态的CO_(2)会大幅劣化煤体力学性能。为研究超临界CO_(2)作用前后煤厚对RCR(岩-煤-岩)组合体单轴压缩破裂过程声发射特性的影响,对煤岩组合体进行单轴压缩试验并进行声发射监测。研究结果表明:随煤厚的增加,组合体抗压强度、弹性模量、声发射峰值计数、能量及累积能量呈下降趋势,声发射累计计数呈上升趋势,能量积聚时间变久,破坏时发生的应变和所需时间不同程度增大;超临界CO_(2)浸泡后,不同煤厚组合体抗压强度、弹性模量、声发射峰值计数、累计计数、能量及累积能量降幅明显,破坏时发生的应变和所需时间不同程度减小;超临界CO_(2)作用后的组合体更易失稳,能量积聚时间变短。随着煤厚增加失稳趋势变大,但能量释放逐渐缓和。研究成果可为CO_(2)地质封存稳定性提供参考。

Injecting CO_(2)into deep unminable coal seam is an effective means for long-term storage of CO_(2).However, CO_(2)in supercritical state under high temperature and high pressure will greatly degrade the mechanical properties of coal. In order to study the influence of coal thickness on AE(acoustic emission) characteristics of RCR(rock-coal-rock) composite under uniaxial compression before and after supercritical CO_(2)treatment, the uniaxial compression test and AE monitoring of composite were carried out. The results are concluded as follows. With the increase of coal thickness, the compressive strength, elastic modulus, AE peak count, energy and cumulative energy of the composite decrease, while the cumulative AE count increases, energy accumulation time becomes longer, and the strain and time required for failure increase to varying degrees. After supercritical CO_(2)immersion, the compressive strength, elastic modulus, AE peak count, cumulative count, energy and cumulative energy of the composite with different coal thickness decrease significantly, and the strain and time required for failure decrease to varying degrees. The composite after supercritical CO_(2)is more likely to lose stability, and the energy accumulation time becomes shorter. With the increase of coal thickness, the instability trend becomes larger, but the energy release gradually slows down. The research results can provide a reference for the stability of CO_(2)geological storage.