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<p>This study investigates the mechanical behavior of undamaged sandstone specimens (USSs) and highly damaged sandstone specimens (HDSSs) through a series of multilevel cyclic loading (MLCL) tests conducted at different loading frequencies. The mechanical response, energy evolution, resistivity variation, and damage progression of the rock during loading were systematically examined. The results demonstrate that initial damage significantly reduces the strength and stiffness of the rock, whereas increasing the loading frequency tends to enhance its mechanical performance. In terms of energy evolution, both loading frequency and initial damage reduce the rate of elastic energy storage in rock during cyclic loading. Meanwhile, the presence of initial damage promotes energy dissipation, whereas an increase in loading frequency suppresses the level of energy dissipation. Resistivity exhibits a nonlinear evolution with the number of cycles, initially increasing and then decreasing, indicating a shift in the dominant mechanism from hardening to damage. Furthermore, a novel damage variable that simultaneously accounts for initial and residual damage is proposed, based on which an exponential damage accumulation model is established. In addition, the study clarifies the interaction mechanism between loading frequency and initial damage during the MLCL process. These findings provide valuable insights for hazard prevention and control in deep resource extraction.</p>

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Mechanical Response and Degradation Mechanism of Highly Damaged Sandstone Under Different Loading Frequencies

  • 期刊论文

  • 发表日期：

    2026年4月4日

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  • Yongan Ma,
  • Chong Yu,
  • Haibo Li,
  • Zun Cheng,
  • Yaqun Liu,
  • Haibin Wang

摘要

This study investigates the mechanical behavior of undamaged sandstone specimens (USSs) and highly damaged sandstone specimens (HDSSs) through a series of multilevel cyclic loading (MLCL) tests conducted at different loading frequencies. The mechanical response, energy evolution, resistivity variation, and damage progression of the rock during loading were systematically examined. The results demonstrate that initial damage significantly reduces the strength and stiffness of the rock, whereas increasing the loading frequency tends to enhance its mechanical performance. In terms of energy evolution, both loading frequency and initial damage reduce the rate of elastic energy storage in rock during cyclic loading. Meanwhile, the presence of initial damage promotes energy dissipation, whereas an increase in loading frequency suppresses the level of energy dissipation. Resistivity exhibits a nonlinear evolution with the number of cycles, initially increasing and then decreasing, indicating a shift in the dominant mechanism from hardening to damage. Furthermore, a novel damage variable that simultaneously accounts for initial and residual damage is proposed, based on which an exponential damage accumulation model is established. In addition, the study clarifies the interaction mechanism between loading frequency and initial damage during the MLCL process. These findings provide valuable insights for hazard prevention and control in deep resource extraction.