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<p>In underground rock engineering, the surrounding rock often experiences a mixed compression–shear state. To investigate the mechanical properties and failure modes of in-situ rocks under varying compression–shear ratios, this study employed an acoustic emission (AE) monitoring system and digital image correlation (DIC) technology to analyze cylindrical rock (CY) and cubic rock (CU). A series of variable-angle shear tests (VASTs) were conducted by adjusting the mold angle. The experimental results demonstrate that the peak load (<i>P</i><sub>s</sub>) for both types of rocks exhibited a negative correlation with the shear angle (<i>α</i>); specifically, CU exhibit 60%-90% higher <i>P</i>s compared to CY at same <i>α</i>. The cohesive strength (<i>c</i>) calculated from VASTs-CY was lower than that from VASTs-CU, while the internal friction angle (<i>ϕ</i>) was higher, but when <i>α</i> ≥ 60°, the <i>c</i> and <i>ϕ</i> of CY and CU were nearly equal, which was accurate for engineering design. Meanwhile, the expression of the dividing line of the tension–shear crack was proposed by a novel approach that integrates AE parameters, clustering concepts, and genetic algorithms. Based on changes in AE hit rate, both types of rocks exhibited high similarity in their failure processes, displaying significant segmented variations. CY exhibited more active AE activity than CU. As the pressure–shear ratio decreased, local rock damage occurred more easily with greater degrees of damage and less smooth fracture surfaces.</p>

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Specimen Shape Effects on Shear Strength Parameters and Failure Properties of Rocks in Compression–Shear Tests

  • 期刊论文

  • 发表日期：

    2025年2月3日

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  • Minghui Liu,
  • Ruiyang Bi,
  • Jian Zhou,
  • Kun Du

摘要

In underground rock engineering, the surrounding rock often experiences a mixed compression–shear state. To investigate the mechanical properties and failure modes of in-situ rocks under varying compression–shear ratios, this study employed an acoustic emission (AE) monitoring system and digital image correlation (DIC) technology to analyze cylindrical rock (CY) and cubic rock (CU). A series of variable-angle shear tests (VASTs) were conducted by adjusting the mold angle. The experimental results demonstrate that the peak load (Ps) for both types of rocks exhibited a negative correlation with the shear angle (α); specifically, CU exhibit 60%-90% higher Ps compared to CY at same α. The cohesive strength (c) calculated from VASTs-CY was lower than that from VASTs-CU, while the internal friction angle (ϕ) was higher, but when α ≥ 60°, the c and ϕ of CY and CU were nearly equal, which was accurate for engineering design. Meanwhile, the expression of the dividing line of the tension–shear crack was proposed by a novel approach that integrates AE parameters, clustering concepts, and genetic algorithms. Based on changes in AE hit rate, both types of rocks exhibited high similarity in their failure processes, displaying significant segmented variations. CY exhibited more active AE activity than CU. As the pressure–shear ratio decreased, local rock damage occurred more easily with greater degrees of damage and less smooth fracture surfaces.