Study on the supporting time of the secondary lining of the highway tunnel with weak surrounding rock

Based on the Dongxiu tunnel project of Liyu highway under construction in Guangxi province of China, this paper attempts to study the supporting time of the secondary lining of the highway tunnel with weak surrounding rocks. Firstly, the measurement data of typical section of the tunnel is fitted and used to reveal the evolution law of the settlement of the tunnel vault and peripheral convergence of the sidewall. Then the three-dimensional simulation is carried out to verify the rationality of the evolution law. After that, the supporting time of the secondary lining is determined relying on the results of field monitoring and numerical simulation. The results show that, both the settlement of the tunnel vault and the peripheral convergence for the Dongxiu tunnel can be characterized by exponential function, and it is reasonable to construct the secondary lining at 24th-25th day after excavation. The results can not only guide the subsequent construction on site but also provide reference for the determination of supporting time of the secondary lining of similar tunnel projects.