In addressing the frontier issue of high-temperature damage mechanisms in underground engineering fires and their impact on lining concrete and surrounding rock mechanical properties, this study focuses on C35 concrete as the primary subject of investigation, with granite from tunnel sections in the Sichuan-Tibet region serving as a reference. The research analyzes the evolution of damage and mechanical responses of rock-like materials after exposure to high-temperature fire. The findings indicate that under high-temperature conditions, granite and concrete experience increased cross-sectional porosity due to factors such as cementitious material failure, mineral expansion, and decomposition. This porosity exhibits temporal and spatial characteristics, increasing logarithmically with exposure time and decreasing linearly with specimen height from the heated surface. As the high-temperature test time increases, the peak stress of granite and concrete specimens gradually decreases, and the rate of decrease gradually increases.The maximum peak stress reduction rates of the three strain rates were 80.49 %, 82.68 % and 59.42 % for granite specimens, and 47.48 %, 51.68 % and 50.98 % for concrete specimens. The compressive strength shows a negative correlation with exposure time, accompanied by a transition from brittle to ductile failure characteristics. These research conclusions hold significant theoretical importance for understanding the evolution of damage and changes in mechanical properties of surrounding rock and lining concrete after high-temperature fires in underground engineering, providing fundamental data for post-fire safety assessments.

中文翻译：

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高温燃烧对类岩石材料损伤演化和力学性能的影响研究


针对地下工程火灾高温损伤机理的前沿问题及其对衬砌混凝土和围岩力学性能的影响，本研究以 C35 混凝土为主要研究对象，以川藏地区隧道段的花岗岩为参考。该研究分析了岩石状材料在暴露于高温火灾后的损伤和机械响应的演变。研究结果表明，在高温条件下，由于胶凝材料失效、矿物膨胀和分解等因素，花岗岩和混凝土的横截面孔隙率增加。这种孔隙率表现出时间和空间特征，随曝光时间对数增加，并随样品距加热表面的高度线性减少。随着高温试验时间的增加，花岗岩和混凝土试件的峰值应力逐渐减小，下降速度逐渐增大。3种应变率的最大峰值应力折减率对花岗岩试件分别为80.49 %、82.68 %和59.42 %，对混凝土试件的峰值应力折减率分别为47.48 %、51.68 %和50.98 %。抗压强度与暴露时间呈负相关，并伴有从脆性到延性失效特征的转变。这些研究结论对于理解地下工程高温火灾后围岩和衬砌混凝土损伤的演变和力学性能的变化具有重要的理论意义，为火灾后安全评估提供了基础数据。