Novel Excavation and Construction Method of an Underground Highway Tunnel above Operating Metro Tunnels

摘要

Security of metro tunnels is extremely important, but the influence of new underground construction on existing tunnels has become more and more important. To control the existing tunnel deformation induced by an adjacent excavation, a novel construction method for excavations crossing above underlying tunnels, referred to as the divided alternate excavation method ( DAEM), is presented in this paper. In this method, several dividing walls are constructed to divide the overlying excavation into small independent pits. During construction, several small pits are excavated at intervals simultaneously, and the remaining soil in other pits can resist the tunnel heave. After the underground structures of these pits are constructed, soil is backfilled onto their roof to decrease the rebound of the existing tunnels, and the remaining small pits can then be constructed. The proposed construction method is applied in the case of tunnel excavation above running metro tunnels. Field data reveal that the novel method has advantages in controlling deformation of the underlying metro tunnels. (C) 2014 American Society of Civil Engineers.