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<p>Quantitative characterization of permeability evolution and failure modes in deep rock engineering is essential for predicting seepage risks. This study investigated the mechanical behavior and cross-scale failure mechanisms of limestone using multi-stress path experiments. Acoustic emission (AE) monitoring and digital rock physics (DRP) techniques were used to evaluate the spatiotemporal evolution of cracks and their influence on permeability evolution, and post-failure pore structure characteristics and seepage behavior were revealed. Results demonstrated that unloading confining pressure (UCP) reduced axial bearing capacity by 12.8% compared to constant confining pressure (CCP), leading to stepwise increases in permeability. Under UCP, permeability of matrix-type, filled-crack-type, and crack-type specimens increased by 123.4%, 240.0%, and 42.9% respectively. Shear cracks were predominant under CCP, whereas UCP primarily induced mixed-mode tensile-shear cracks. This distinction caused a transition in macroscopic failure modes, from single shear slip (CCP) to an evolving coordinated crack network (UPC). Further investigations identified dual regulatory effects of crack type on permeability. Compression-dominant shear cracks induced flow channel closure, reducing permeability by 20.6%-87.5%, while mixed-mode tensile-shear cracks enhanced flow network connectivity, increasing permeability by 208.6%-934.1%. The fractal dimensions of 3D reconstructed pore models were 1.49–2.01 for CCP specimens (S1-S3) and 1.97–2.15 for UCP specimens (S4-S6). Correspondingly, average flow velocities in UCP specimens (S4-S6) were 2.1% to 91.6% higher than their CCP counterparts (S1-S3), confirming that UCP-induced heterogeneity improved seepage capacity. Numerical simulations aligned well with AE signatures and observed failure modes, validating the reliability of this cross-scale methodology.</p>

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Integrated micro-macro investigation of permeability evolution and failure modes in limestone: Combining acoustic emission monitoring with digital rock physics characterization

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年4月13日

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  • Haitao Zhao,
  • Yishuai Liu,
  • Yongfu Liu,
  • Jing Li

摘要

Quantitative characterization of permeability evolution and failure modes in deep rock engineering is essential for predicting seepage risks. This study investigated the mechanical behavior and cross-scale failure mechanisms of limestone using multi-stress path experiments. Acoustic emission (AE) monitoring and digital rock physics (DRP) techniques were used to evaluate the spatiotemporal evolution of cracks and their influence on permeability evolution, and post-failure pore structure characteristics and seepage behavior were revealed. Results demonstrated that unloading confining pressure (UCP) reduced axial bearing capacity by 12.8% compared to constant confining pressure (CCP), leading to stepwise increases in permeability. Under UCP, permeability of matrix-type, filled-crack-type, and crack-type specimens increased by 123.4%, 240.0%, and 42.9% respectively. Shear cracks were predominant under CCP, whereas UCP primarily induced mixed-mode tensile-shear cracks. This distinction caused a transition in macroscopic failure modes, from single shear slip (CCP) to an evolving coordinated crack network (UPC). Further investigations identified dual regulatory effects of crack type on permeability. Compression-dominant shear cracks induced flow channel closure, reducing permeability by 20.6%-87.5%, while mixed-mode tensile-shear cracks enhanced flow network connectivity, increasing permeability by 208.6%-934.1%. The fractal dimensions of 3D reconstructed pore models were 1.49–2.01 for CCP specimens (S1-S3) and 1.97–2.15 for UCP specimens (S4-S6). Correspondingly, average flow velocities in UCP specimens (S4-S6) were 2.1% to 91.6% higher than their CCP counterparts (S1-S3), confirming that UCP-induced heterogeneity improved seepage capacity. Numerical simulations aligned well with AE signatures and observed failure modes, validating the reliability of this cross-scale methodology.