Optimal analysis of mid-board of shallow double-arch tunnels under unsymmetrical pressure

The FEM was used to calculate and analyze the bearing character of shallow double-arch tunnel with different mid-boards under unsymmetrical pressure.The unsymmetrically pressed shallow double-arch tunnels which adopted multiple bent mid-board would be helpful to improve the bearing character of the mid-board and to decrease the concentration of stress and the displacement of the up mid-board.Ultimately the adoption of the multiple bent mid-board could lower the possibility of cracking of mid-board.Therefore a theoretical basis to design unsymmetrically pressed shallow double-arch tunnels was provided.