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<p>Although southern China typically experiences a warm climate, the slope rock masses in high-altitude open-pit mines situated in mountainous regions (e.g., the Zijinshan Gold-Copper Mine) are subjected to significant mechanical degradation due to Dry–Wet-Freeze–Thaw (DWFT) cycles. These specific microclimates are characterized by frequent temperature fluctuations crossing 0&#xa0;°C in winter combined with abundant seasonal rainfall. This study investigates the mechanical properties and failure processes of fractured rocks using PFC3D discrete element numerical simulations. Rock models with single fractures, parallel double fractures, and cross double fractures were constructed, and DWFT cycles of 0, 1, 5, 10, and 30 were simulated. The effects of DWFT cycles and confining pressures (0 MPa, 1 MPa, 2 MPa, 3 MPa, and 5 MPa) on the mechanical behavior of rock samples with different fracture geometries were analyzed through simulated uniaxial and triaxial compression tests. The proposed numerical model was validated against experimental results. The results indicate that freeze–thaw cycling is the dominant factor in rock strength degradation, accounting for over 55% of the observed reduction. This dominance arises from frost-heave stresses generated by repeated water–ice phase transitions in pores and fractures, which progressively break particle bonds and accumulate nonlinearly with the number of cycles. After 30 cycles, the strength loss of single-fractured rock reached a significant 79.3%, accompanied by a progressive crack propagation pattern from the periphery toward the center. Fracture geometry has a notable impact on strength performance: rocks with a single fracture exhibit the highest strength, followed by those with cross double fractures, while those with parallel double fractures show the lowest strength. A multiple regression model was developed to predict peak strength and elastic modulus. Furthermore, a nonlinear relationship between mechanical parameters, DWFT cycles, and confining pressure was identified. These results provide a theoretical basis for evaluating rock mass stability and guiding disaster prevention and mitigation strategies in environments affected by DWFT conditions.</p>

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Mechanical Degradation and Failure of Fractured Rock Masses Under Dry–Wet-Freeze–Thaw Cycles

  • 期刊论文

  • 发表日期：

    2026年1月6日

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  • Jin Shen,
  • Jianpeng Liu,
  • Xiaoshuang Li,
  • Yunmin Wang

摘要

Although southern China typically experiences a warm climate, the slope rock masses in high-altitude open-pit mines situated in mountainous regions (e.g., the Zijinshan Gold-Copper Mine) are subjected to significant mechanical degradation due to Dry–Wet-Freeze–Thaw (DWFT) cycles. These specific microclimates are characterized by frequent temperature fluctuations crossing 0 °C in winter combined with abundant seasonal rainfall. This study investigates the mechanical properties and failure processes of fractured rocks using PFC3D discrete element numerical simulations. Rock models with single fractures, parallel double fractures, and cross double fractures were constructed, and DWFT cycles of 0, 1, 5, 10, and 30 were simulated. The effects of DWFT cycles and confining pressures (0 MPa, 1 MPa, 2 MPa, 3 MPa, and 5 MPa) on the mechanical behavior of rock samples with different fracture geometries were analyzed through simulated uniaxial and triaxial compression tests. The proposed numerical model was validated against experimental results. The results indicate that freeze–thaw cycling is the dominant factor in rock strength degradation, accounting for over 55% of the observed reduction. This dominance arises from frost-heave stresses generated by repeated water–ice phase transitions in pores and fractures, which progressively break particle bonds and accumulate nonlinearly with the number of cycles. After 30 cycles, the strength loss of single-fractured rock reached a significant 79.3%, accompanied by a progressive crack propagation pattern from the periphery toward the center. Fracture geometry has a notable impact on strength performance: rocks with a single fracture exhibit the highest strength, followed by those with cross double fractures, while those with parallel double fractures show the lowest strength. A multiple regression model was developed to predict peak strength and elastic modulus. Furthermore, a nonlinear relationship between mechanical parameters, DWFT cycles, and confining pressure was identified. These results provide a theoretical basis for evaluating rock mass stability and guiding disaster prevention and mitigation strategies in environments affected by DWFT conditions.