高岩温隧道初期支护应力场及安全性研究

为评价高岩温隧道施工过程中初期支护的安全性，研究了高岩温隧道初期支护温度场、应力场的施工期特征和演变规律. 首先通过热-应力耦合三维数值模拟和现场测试，研究了不同原始围岩温度场中，高岩温隧道开挖过程中初期支护温度场的变化规律；其次考虑围岩荷载和温度荷载共同作用，分析了高岩温隧道开挖过程中初期支护应力场的变化规律；最后基于初期支护应力值，评价了高岩温隧道初期支护的安全性. 研究结果表明:受施工通风影响，初期支护温度在隧道开挖后急剧降低，约5 d后基本与洞内气温一致；受施工工序影响，初期支护最大拉应力先增后减，最大压应力持续增加；随着围岩初始温度增大，在不同施工步序中，初期支护的最大拉应力和最大压应力均增大；初期支护安全性由喷射混凝土抗拉强度控制，当围岩初始温度大于60℃时，C25喷射混凝土将发生拉裂破坏. 

Study on Stress Field and Security of Primary Support in High Rock Temperature Tunnel

The characteristics and changing behaviour of the initial support in high rock temperature tunnel were studied to evaluate security during the construction process. First, the temperature field of the initial support was analysed during the construction process of high rock temperature tunnel by using thermal-stress coupling numerical simulations and in-situ testing. Second, the stress field of the initial support, which bore the rock load and temperature load, was analysed over the construction process of high rock temperature tunnel. Finally, based on the stress of primary support, the security of primary support in high rock temperature tunnel was evaluated. The results show that the temperature of primary support sharply decreases after tunnel excavation and is equivalent to the air temperature in the tunnel after about 5 days. During the construction process, the maximum tensile stress of primary support first increases and then decreases. However, the maximum compressive stress always increases. With increased initial rock temperature, the maximum tensile and compressive stress of the primary support also increase. The security of the primary support depends on the tensile strength of shotcrete, and the C25 shotcrete will be damaged if the initial rock temperature exceeds 60℃.