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<p>The damage mechanism of rock masses under coupled fire-induced high temperatures and acidic groundwater presents a critical challenge that hinders the long-term stability of tunnels. These coupled conditions characterize prevalent hazard scenarios in tunnels, where high temperatures resulting from tunnel fires often coexist with acidic groundwater generated by sulfide oxidation or industrial contamination. Collectively, these conditions pose significant threats to the integrity of rock masses. This study systematically investigated the deterioration patterns of diorite, a representative rock mass in tunnels, subjected to simulated thermal (25&#xa0;°C, 400&#xa0;°C, 800&#xa0;°C) and chemical (immersion in a pH = 2 sulphuric acid solution for 120&#xa0;days) treatments. It elucidated the damage evolution mechanisms of diorite under thermally-chemically sequential effects through a combination approach of X-ray computed tomography (CT), scanning electron microscopy (SEM), X-ray diffraction (XRD), and static/dynamic mechanical testing. The results demonstrated that thermal-acid treatment significantly accelerated the diorite degradation, particularly within the temperature range of 400–800&#xa0;°C. After thermal treatment at 800&#xa0;°C, the porosity of the diorite increased by 19.75 times compared to the original specimen, while the P-wave velocity decreased by 82.71%. Subsequent acid corrosion further elevated the porosity to 27.25 times the original value, resulting in only 10.66% of the initial P-wave velocity being retained. Mechanical tests revealed synchronous reductions in strength, elastic modulus, and fracture toughness, accompanied by a transition from brittle to ductile deformation behavior. Failure modes exhibited fragmentation characteristics with significantly increased complexity of crack networks. Micro-mechanism analyses showed that high temperatures induced mineral phase transitions and thermally-generated microcracks, while acidic solutions accelerated crack propagation via H⁺ dissolution effects, leading to a synergistic "thermal damage-chemical corrosion" deterioration mechanism. Three-dimensional (3D) CT reconstruction demonstrated a 29-fold increase in pore volume following the treatment at 800&#xa0;°C and acid corrosion.</p>

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Experimental Study on Multiscale Damage Mechanism of Diorite Under the Effects of High Temperature and Acidic Environment

  • 期刊论文

  • 发表日期：

    2025年11月20日

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  • Henggen Zhang,
  • Tao Liu,
  • Weihua Wang,
  • Yuxue Cui,
  • Dingfei Zhang

摘要

The damage mechanism of rock masses under coupled fire-induced high temperatures and acidic groundwater presents a critical challenge that hinders the long-term stability of tunnels. These coupled conditions characterize prevalent hazard scenarios in tunnels, where high temperatures resulting from tunnel fires often coexist with acidic groundwater generated by sulfide oxidation or industrial contamination. Collectively, these conditions pose significant threats to the integrity of rock masses. This study systematically investigated the deterioration patterns of diorite, a representative rock mass in tunnels, subjected to simulated thermal (25 °C, 400 °C, 800 °C) and chemical (immersion in a pH = 2 sulphuric acid solution for 120 days) treatments. It elucidated the damage evolution mechanisms of diorite under thermally-chemically sequential effects through a combination approach of X-ray computed tomography (CT), scanning electron microscopy (SEM), X-ray diffraction (XRD), and static/dynamic mechanical testing. The results demonstrated that thermal-acid treatment significantly accelerated the diorite degradation, particularly within the temperature range of 400–800 °C. After thermal treatment at 800 °C, the porosity of the diorite increased by 19.75 times compared to the original specimen, while the P-wave velocity decreased by 82.71%. Subsequent acid corrosion further elevated the porosity to 27.25 times the original value, resulting in only 10.66% of the initial P-wave velocity being retained. Mechanical tests revealed synchronous reductions in strength, elastic modulus, and fracture toughness, accompanied by a transition from brittle to ductile deformation behavior. Failure modes exhibited fragmentation characteristics with significantly increased complexity of crack networks. Micro-mechanism analyses showed that high temperatures induced mineral phase transitions and thermally-generated microcracks, while acidic solutions accelerated crack propagation via H⁺ dissolution effects, leading to a synergistic "thermal damage-chemical corrosion" deterioration mechanism. Three-dimensional (3D) CT reconstruction demonstrated a 29-fold increase in pore volume following the treatment at 800 °C and acid corrosion.