Abstract

Permeability is a fundamental index that is closely related to rock damage in geotechnical engineering. In this study, dynamic triaxial compression tests were performed using a modified split Hopkinson pressure bar (SHPB) for a range of incident energies, confining pressures, and number of impacts to study the mechanical behavior and permeability evolution of sandstone after dynamic loading under realistic in-situ stress. The damage factor of rock before and after the impact was measured and calculated using a rock wave velocity measurement device, and the rock permeability was tested following the pulse-decay method with a MTS-815 testing system. The results show that the peak stress, strain, plasticity, damage, and permeability of sandstone all increase with increasing incident energy. Only the peak stress increases with increasing confining pressure, whereas the other physico-mechanical parameters decrease. The opposite result is obtained in response to an increased number of impacts. The dynamic stress–strain curves are categorized into classes I and II based on the post-peak behavior and fracture pattern. The quantitative relationships between energy, damage, and permeability are discussed. The absorbed energy per unit volume follows a negative exponential relationship with the damage factor and a positive linear relationship with the permeability enhancement index. The damage factor follows a positive exponential relationship with the permeability enhancement index. The permeability enhancement is mainly due to increased connectivity of the pores and channels in the rock caused by crack propagation and coalescence, and the rock damage and fracture are controlled by the absorbed energy.

Article Highlights

• The mechanical behavior and permeability evolution of sandstone are determined from triaxial SHPB and triaxial permeability tests.

• The effects of incident energy, confining pressure, and impact number on the dynamic physico-mechanical properties are analyzed.

• The functional relationships between rock damage, permeability, and energy are obtained.

中文翻译：

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动态加载后围压砂岩力学行为及渗透率演化

摘要

渗透率是岩土工程中与岩石破坏密切相关的基本指标。在这项研究中，使用改进的分裂式霍普金森压力棒 (SHPB) 进行动态三轴压缩试验，以研究在真实环境下动态加载后砂岩的力学行为和渗透率演变，以研究一系列入射能量、围压和冲击次数。 - 原位应力。采用岩石波速测量装置测量和计算冲击前后岩石的损伤系数，并采用MTS-815测试系统采用脉冲衰减法测试岩石渗透率。结果表明，砂岩的峰值应力、应变、塑性、损伤和渗透率都随着入射能量的增加而增加。只有峰值应力随着围压的增加而增加，而其他物理力学参数则减少。响应增加的冲击次数获得相反的结果。动态应力-应变曲线根据峰值后行为和断裂模式分为 I ​​类和 II 类。讨论了能量、损伤和渗透率之间的定量关系。单位体积吸收能量与损伤因子呈负指数关系，与渗透率增强指数呈正线性关系。损伤因子与渗透率增强指数呈正指数关系。渗透率增强主要是由于裂缝扩展和聚结导致岩石中孔隙和通道的连通性增加，

文章亮点

• 砂岩的力学行为和渗透率演化由三轴 SHPB 和三轴渗透率测试确定。

• 分析了入射能量、围压和冲击次数对动态物理力学性能的影响。

• 获得了岩石损伤、渗透率和能量之间的函数关系。