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℃.