温度应力作用下大断面隧道衬砌结构力学特性及裂损机理研究

The structure stress of large cross-section tunnel lining is complex. The lining structure is easy to crack under the repeated effect of periodic temperature stress, which exacerbates the integral damage of lining, affects the durability of tunnel structure, and even threatens the operation safety of tunnel. This application intends to set three lane highway tunnel in cold area as the background to explore the mechanical property of large cross-section tunnel lining structure under the repeated effect of temperature stress, to reveal the damage mechanism of lining structure, to propose the methods and reasonable support parameters to prevent and reduce the cracking damage of large cross-section tunnel lining caused by temperature stress. The research combines theory with experiment. The long-term stress state monitoring for lining structure is carried out through the Fiber Bragg grating testing technology. The stress and fracture mechanical behavior of tunnel lining structure are tested in the model test through strain gauge electric logging and photoelastic coating methods, in order to explore the mechanical property and mechanical behavior of cracking damage of large cross-section tunnel lining structure under the repeated effect of temperature stress. Combined the fracture mechanics with concrete Double-K fracture criterion, the crack propagation criterion of large cross-section tunnel lining is constructed under the effect of periodic temperature stress; the mechanical constitutive model of periodic temperature stress and lining cracking damage parameters of large cross-section tunnel is proposed; the cracking damage mechanism of large cross-section tunnel lining is revealed under the effect of temperature stress. The results can lay theoretical basis for the study of the durability of large cross-section tunnel lining structure.

大断面隧道衬砌结构受力复杂，周期性温度应力反复作用下极易产生开裂，加剧衬砌整体破坏，影响隧道结构耐久性，甚至威胁隧道运营安全。本项申请拟以寒冷地区公路三车道隧道为背景，探索温度应力反复作用下大断面隧道衬砌结构力学特性，揭示其衬砌裂损机理，提出防止和减小温度应力引起大断面隧道衬砌裂损的方法和衬砌合理支护参数。研究方法拟以理论与试验并重，采用光纤光栅测试技术，对衬砌结构力学状态进行长期监测，采用应变片电测和光弹贴片技术对模型试验衬砌构件受力和裂缝力学行为进行测试，探索温度应力反复作用下大断面隧道衬砌结构力学特性和裂损力学行为；结合断裂力学和混凝土双K断裂准则，建立温度应力反复作用下大断面隧道衬砌裂缝扩展准则，提出大断面隧道周期性温度应力与衬砌裂损参数力学本构模型，揭示温度应力作用下大断面隧道衬砌裂损机理。成果可为大断面隧道衬砌结构耐久性研究奠定理论基础。

大断面隧道衬砌结构受力复杂，周期性温度应力反复作用下极易产生开裂，加剧衬砌整体破坏，影响隧道结构耐久性，甚至威胁隧道运营安全。本项目以寒冷地区三车道和四车道公路隧道为依托，采用理论分析、现场测试、模型试验和数值模拟等方法，对温度应力作用下大断面隧道衬砌结构力学特性及裂损机理进行相关研究，取得以下研究结果：. （1）自主研发了隧道地质力学模型试验设备和隧道衬砌风冷装置，实现了温度循环和荷载同步自平衡双加载，开展了不同配筋率、不同扁平率下衬砌破坏试验和温度循环作用下带裂缝衬砌加荷试验。. （2）根据材料热应力产生的基本原理，提出了采用颗粒膨胀收缩模拟材料热胀冷缩物理过程的计算原理，建立了PFC隧道颗粒流离散元计算模型，实现了利用颗粒流离散元进行温度应力作用下衬砌开裂的数值模拟计算。. （3）采用结构力学方法，建立了隧道二次衬砌钢筋混凝土偏心受压计算模型和隧道二次衬砌混凝土结构荷载计算模型，通过现场实测的混凝土应力和钢筋应力计算结构轴力、弯矩和安全系数，分析评价水化热阶段、夏季和冬季二次衬砌的受力情况和安全性，以及反算二次衬砌承受的荷载值，评价温度对二次衬砌结构安全性的影响。. （4）揭示了施工阶段和温度应力作用下扁平大断面隧道变形规律和结构承载特性，探明了扁平大断面隧道衬砌结构开裂力学行为和裂缝扩展机制，分析了温度循环作用下带裂缝衬砌结构力学特性和裂缝扩展演化过程，揭示了温度应力作用下扁平大断面隧道衬砌裂损机理，建立了荷载和裂缝宽度力学本构模型。. （5）分析了扁平率、配筋率对隧道衬砌极限承载力的影响，建立了隧道二次衬砌横向和纵向温度应力计算模型，推荐了不同地区二次衬砌模板台车长度建议值，给出了单洞四车道大断面公路隧道合理的断面扁平率和支护结构设计参数，确保了依托工程的结构安全与稳定。