<p>Deep mining operations, especially during roadway excavation, are subjected to complex stress paths where static deviatoric loads coexist with transient stress waves generated by mine-induced earthquakes, blasting, and fault slips. Understanding how such coupled loading drives cumulative damage in coal and controls residual stability is critical for roadway stability. In this study, a purpose-built true-triaxial split-Hopkinson pressure bar apparatus imposed stress waves on coal specimens held under representative static deviatoric stresses. The pre-damaged specimens were subsequently reloaded in uniaxial compression, with surface deformation tracked by digital image correlation and crack activity monitored by acoustic emission. The results indicated that stress waves follow an exponential attenuation law dependent on deviatoric stress. Specifically, as deviatoric stress increases, the attenuation coefficients for incident, reflected, and transmitted waves rise by 85.94%, 15.79%, and 6.92%, respectively, accompanied by a ~ 7.5% reduction in attenuation duration. During reloading, higher deviatoric stress produces more strain-localization bands, while reducing the standard deviation and coefficient of variation by up to 36.50%, decreasing the GINI coefficient toward zero, and increasing entropy by 79.12%, suggesting a shift from axial to more complex orientations with higher proportions of shear cracks. Post-failure, the fragment-size distributions display finer fragmentation, with median size <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$({D}_{50})$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">(</mo> <msub> <mi>D</mi> <mn>50</mn> </msub> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> and geometric mean size <InlineEquation ID="IEq2"> <EquationSource Format="TEX">$({D}_{g})$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">(</mo> <msub> <mi>D</mi> <mi>g</mi> </msub> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> reduced by 15.48% and 15.39%, respectively, and fractal dimension increased by 5.18%, indicating more severe structural damage. These results elucidate the mechanisms of damage accumulation and instability under coupled static–dynamic loading and provide quantitative guidance for hazard assessment and support design in deep coal mining.</p>

Damage Evolution and Failure Characteristics of Coal Under Reloading After Coupled Action of Static Deviatoric Stress and Stress Waves

期刊论文
发表日期：

2026年3月27日

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Xiayan Zhang,
Enyuan Wang,
Rongxi Shen,
Zhoujie Gu,
Zhenhua Hu,
Huihan Yang,
Yijiang Zong

摘要

Deep mining operations, especially during roadway excavation, are subjected to complex stress paths where static deviatoric loads coexist with transient stress waves generated by mine-induced earthquakes, blasting, and fault slips. Understanding how such coupled loading drives cumulative damage in coal and controls residual stability is critical for roadway stability. In this study, a purpose-built true-triaxial split-Hopkinson pressure bar apparatus imposed stress waves on coal specimens held under representative static deviatoric stresses. The pre-damaged specimens were subsequently reloaded in uniaxial compression, with surface deformation tracked by digital image correlation and crack activity monitored by acoustic emission. The results indicated that stress waves follow an exponential attenuation law dependent on deviatoric stress. Specifically, as deviatoric stress increases, the attenuation coefficients for incident, reflected, and transmitted waves rise by 85.94%, 15.79%, and 6.92%, respectively, accompanied by a ~ 7.5% reduction in attenuation duration. During reloading, higher deviatoric stress produces more strain-localization bands, while reducing the standard deviation and coefficient of variation by up to 36.50%, decreasing the GINI coefficient toward zero, and increasing entropy by 79.12%, suggesting a shift from axial to more complex orientations with higher proportions of shear cracks. Post-failure, the fragment-size distributions display finer fragmentation, with median size $({D}_{50})$ $(D_{50})$ and geometric mean size $({D}_{g})$ $(D_{g})$ reduced by 15.48% and 15.39%, respectively, and fractal dimension increased by 5.18%, indicating more severe structural damage. These results elucidate the mechanisms of damage accumulation and instability under coupled static–dynamic loading and provide quantitative guidance for hazard assessment and support design in deep coal mining.