Study on key technology of tunnel fabricated arch and its mechanical mechanism in the mechanized construction

There are many challenges in the construction of tunnels with large section, such as weak surrounding rock control, low efficiency of the artificial construction and poor safety. To solve these problems, a new mechanized construction technology of the fabricated arch is put forward. This technology includes fabricated confined concrete (CC) arches, intelligent arch installation equipment and corresponding matching devices. With Longding Tunnel in China as the engineering background, laboratory and numerical comparative experiments are conducted on CC arches. The results show that the strength of the CC arch is 2.05 times that of the traditional arch. At the same time, a numerical calculation is carried out on the mechanical mechanism of the fabricated CC arch during the mechanized construction. The results show that the stress on each cross-section of the arch decreases as the arch inclination angle increases and the largest stress is 101.2 MPa on the vault in the arch lifting. In order to avoid the arch damages during the installation, a reinforcement method is proposed to lift the key parts of the vault with splints. Based on the above research results, the mechanized construction of the fabricated arch is carried out at the site of Longding Tunnel. The construction efficiency is significantly improved and the deformation of the surrounding rock is effectively controlled.