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<p>Instability failure of bolted fractured rock masses is not typically observed at the beginning stage. Instead, their deformation continuously adjusts over time in response to the continuous application of a constant load, resulting in creep failure. The presence of bolt influences the failure of rock by changing the stress distribution within the rock mass. To reveal the influence of bolts on fractured rock masses, double-fractured sandstone specimens reinforced with 0, 1, and 2 horizontal bolts were fabricated. The mechanical properties, deformation failure modes, AE characteristics, and instability precursor data of unbolted, single-bolted, and double-bolted specimens were compared and analyzed. The results show that: (1) The mechanical properties of bolted fractured rock mass have been significantly improved. The long-term strength of single-bolted and double-bolted specimens was 35.93% and 49.88% higher than that of unbolted specimens, respectively; (2) Compared with the unbolted specimen, the axial strain of the double-bolted specimen decreased by 20.55% and 32.97% at stress levels of 40 and 60&#xa0;MPa, respectively, indicating that the bolt effectively restrained specimen deformation; (3) The AE energy, cumulative ring count, and peak frequency of bolted fractured rock samples decreased at the same stress level, with the AE energy of the double-bolted sample being only 0.6 times that of the unbolted sample; (4) An analysis of the AE ratio of the ring count to the duration and the rise time to amplitude (AF-RA) value, along with the macroscopic failure characteristics, revealed the reinforcement mechanism of the bolt. As the number of bolts increased, the final failure mode transitioned from shear failure to tensile shear failure; (5) Based on the critical slowing down features of AE signals, a sudden and significant increase in both variance and autocorrelation coefficient can serve as an early warning signal for rock failure. It can be used to determine the long-term strength and predict short-term failure of bolted fractured sandstone. This presented study can provides a basis for the analysis of the creep process in bolted fractured rock masses.</p>

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Critical slowing down characteristics of acoustic emission for bolted fractured sandstone failure under stepwise loading

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年11月14日

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  • Huaichang Yu,
  • Guanqiang Wang,
  • Changdong Li,
  • Fei Zhao,
  • Yu Wang,
  • Luqi Wang,
  • Houguo Fang,
  • Shishun Deng

摘要

Instability failure of bolted fractured rock masses is not typically observed at the beginning stage. Instead, their deformation continuously adjusts over time in response to the continuous application of a constant load, resulting in creep failure. The presence of bolt influences the failure of rock by changing the stress distribution within the rock mass. To reveal the influence of bolts on fractured rock masses, double-fractured sandstone specimens reinforced with 0, 1, and 2 horizontal bolts were fabricated. The mechanical properties, deformation failure modes, AE characteristics, and instability precursor data of unbolted, single-bolted, and double-bolted specimens were compared and analyzed. The results show that: (1) The mechanical properties of bolted fractured rock mass have been significantly improved. The long-term strength of single-bolted and double-bolted specimens was 35.93% and 49.88% higher than that of unbolted specimens, respectively; (2) Compared with the unbolted specimen, the axial strain of the double-bolted specimen decreased by 20.55% and 32.97% at stress levels of 40 and 60 MPa, respectively, indicating that the bolt effectively restrained specimen deformation; (3) The AE energy, cumulative ring count, and peak frequency of bolted fractured rock samples decreased at the same stress level, with the AE energy of the double-bolted sample being only 0.6 times that of the unbolted sample; (4) An analysis of the AE ratio of the ring count to the duration and the rise time to amplitude (AF-RA) value, along with the macroscopic failure characteristics, revealed the reinforcement mechanism of the bolt. As the number of bolts increased, the final failure mode transitioned from shear failure to tensile shear failure; (5) Based on the critical slowing down features of AE signals, a sudden and significant increase in both variance and autocorrelation coefficient can serve as an early warning signal for rock failure. It can be used to determine the long-term strength and predict short-term failure of bolted fractured sandstone. This presented study can provides a basis for the analysis of the creep process in bolted fractured rock masses.