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<p>The heterogeneity and anisotropy of black shale cause significant variations in its mechanical behavior under different environmental conditions, which complicates the accurate prediction of stability and failure modes in mining, tunnel construction, and other underground engineering projects. Thus, triaxial compression and microindentation tests, combined with discrete element method (DEM) simulations using particle flow code (PFC) analysis, were conducted on Shawozi Group black shale samples. The aim is to analyze the meso-mechanical properties of black shale and examine the relationship between its failure mechanisms and mechanical properties at both macro- and microscales. The findings reveal that, during triaxial compression tests conducted under various confining pressures, the compressive strength of black shale increases with increasing confining pressure. The microindentation tests successfully quantified the indentation modulus, elastic modulus, and hardness of black shale, revealing a significant positive correlation between hardness and the elastic modulus. In light of the test results, a loading rate of 15&#xa0;N/min and a maximum load of 20&#xa0;N were determined to be the optimal parameters. Additionally, the parallel bonded model by DEM simulations performed using PFC effectively simulates the distribution of force chains, crack failure and displacement contour diagrams of black shale during both triaxial compression and microindentation tests. Under a 10&#xa0;N loading condition, the cementation bonds of the rock sample were not destroyed, resulting in significant residual stress, which led to a large difference between the loading and unloading displacement contours. In contrast, under 15&#xa0;N and 20&#xa0;N loading, shear sliding and bond breakage occurred between the particles, causing the rock sample to fail to return to its original state, leading to a smaller difference between the loading and unloading displacement contours. By comparing the outcomes of macro- and meso-mechanical property tests, this study further substantiates the strong correlation between microindentation tests and conventional mechanical assessments, thereby providing a scientific foundation for a more profound understanding of the mechanical properties of black shale and the underlying mechanisms of disaster occurrence.</p>

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Multiscale Numerical and Experimental Evaluation of Microindentation Tests for Characterizing the Strength and Failure Mechanisms of Black Shale

  • 期刊论文

  • 发表日期：

    2025年10月22日

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  • Xiaoning Li,
  • Enjian Wu,
  • Wu Bo,
  • Gen Zhang,
  • Gopi Krishna Basyal,
  • Sixiang Ling,
  • Tangyao Wang,
  • Chunwei Sun

摘要

The heterogeneity and anisotropy of black shale cause significant variations in its mechanical behavior under different environmental conditions, which complicates the accurate prediction of stability and failure modes in mining, tunnel construction, and other underground engineering projects. Thus, triaxial compression and microindentation tests, combined with discrete element method (DEM) simulations using particle flow code (PFC) analysis, were conducted on Shawozi Group black shale samples. The aim is to analyze the meso-mechanical properties of black shale and examine the relationship between its failure mechanisms and mechanical properties at both macro- and microscales. The findings reveal that, during triaxial compression tests conducted under various confining pressures, the compressive strength of black shale increases with increasing confining pressure. The microindentation tests successfully quantified the indentation modulus, elastic modulus, and hardness of black shale, revealing a significant positive correlation between hardness and the elastic modulus. In light of the test results, a loading rate of 15 N/min and a maximum load of 20 N were determined to be the optimal parameters. Additionally, the parallel bonded model by DEM simulations performed using PFC effectively simulates the distribution of force chains, crack failure and displacement contour diagrams of black shale during both triaxial compression and microindentation tests. Under a 10 N loading condition, the cementation bonds of the rock sample were not destroyed, resulting in significant residual stress, which led to a large difference between the loading and unloading displacement contours. In contrast, under 15 N and 20 N loading, shear sliding and bond breakage occurred between the particles, causing the rock sample to fail to return to its original state, leading to a smaller difference between the loading and unloading displacement contours. By comparing the outcomes of macro- and meso-mechanical property tests, this study further substantiates the strong correlation between microindentation tests and conventional mechanical assessments, thereby providing a scientific foundation for a more profound understanding of the mechanical properties of black shale and the underlying mechanisms of disaster occurrence.