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<p>The dynamic loads and vibrations generated during the construction of adjacent tunnels are not clearly understood, posing potential risks to the safe operation of existing facilities. The physical and mechanical properties and fracture toughness characteristics of the native granite and tuff were investigated to provide a quantitative basis for optimizing blasting excavation parameters and ensuring the stability of existing facilities. Taking a typical in-situ rock sample located within a tunnel that passes through existing water supply pipelines as the research object, a test method combining indoor dynamic and static mechanical tests as well as fracture toughness tests was proposed to reveal the physical and mechanical properties and fracture toughness characteristics of the native granite and tuff beneath the pipeline in the tunnel, in order to further ensure the safe operation and maintenance of the existing facilities. The results show that: (1) Under static loading, granite exhibits higher compressive strength and tensile strength compared to tuff. (2) Dynamic tests using SHPB reveal that the peak stress and fragmentation degree of both rocks increase with impact gas pressure, with granite consistently showing superior dynamic strength and impact resistance. (3) Fracture toughness tests on CCNSCB specimens indicate that both granite and tuff exhibit increased fracture toughness with loading rate and energy, with average values for granite considerably exceeding those of tuff, indicating weaker crack propagation resistance in tuff. (4) DIC and high-speed imaging analyses demonstrate that tuff exhibits greater crack extension length, speed, and opening width than granite under identical impact conditions. (5) Microscopic observations confirm that failure occurs along structural weak surfaces in both rocks, with tuff displaying more pronounced crack branching and interfacial debonding. These findings translate directly into quantitative engineering guidance: for tuff, a maximum allowable PPV of 15–20&#xa0;cm/s is recommended to prevent crack initiation, requiring a 30–40% reduction in charge weight per delay compared to granite sections. This integrated methodology (linking mineralogy, fracture toughness, and crack propagation dynamics) offers quantitative threshold basis of PPV limits and charge weight reductions for blasting safety assessment near pipelines.</p>

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Dynamic Fracture and Mechanical Behaviour of Rock in Tunnels Adjacent to Existing Pipelines

  • 期刊论文

  • 发表日期：

    2026年5月25日

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  • Suqian Ni,
  • Beiqi Zhang,
  • Zhaoyang Song,
  • Zhiqiang Liu,
  • Feng Gao,
  • Ying Xu,
  • Xiukang Shen

摘要

The dynamic loads and vibrations generated during the construction of adjacent tunnels are not clearly understood, posing potential risks to the safe operation of existing facilities. The physical and mechanical properties and fracture toughness characteristics of the native granite and tuff were investigated to provide a quantitative basis for optimizing blasting excavation parameters and ensuring the stability of existing facilities. Taking a typical in-situ rock sample located within a tunnel that passes through existing water supply pipelines as the research object, a test method combining indoor dynamic and static mechanical tests as well as fracture toughness tests was proposed to reveal the physical and mechanical properties and fracture toughness characteristics of the native granite and tuff beneath the pipeline in the tunnel, in order to further ensure the safe operation and maintenance of the existing facilities. The results show that: (1) Under static loading, granite exhibits higher compressive strength and tensile strength compared to tuff. (2) Dynamic tests using SHPB reveal that the peak stress and fragmentation degree of both rocks increase with impact gas pressure, with granite consistently showing superior dynamic strength and impact resistance. (3) Fracture toughness tests on CCNSCB specimens indicate that both granite and tuff exhibit increased fracture toughness with loading rate and energy, with average values for granite considerably exceeding those of tuff, indicating weaker crack propagation resistance in tuff. (4) DIC and high-speed imaging analyses demonstrate that tuff exhibits greater crack extension length, speed, and opening width than granite under identical impact conditions. (5) Microscopic observations confirm that failure occurs along structural weak surfaces in both rocks, with tuff displaying more pronounced crack branching and interfacial debonding. These findings translate directly into quantitative engineering guidance: for tuff, a maximum allowable PPV of 15–20 cm/s is recommended to prevent crack initiation, requiring a 30–40% reduction in charge weight per delay compared to granite sections. This integrated methodology (linking mineralogy, fracture toughness, and crack propagation dynamics) offers quantitative threshold basis of PPV limits and charge weight reductions for blasting safety assessment near pipelines.