Abstract
This study proposes a tunnel roof support structure formed by interconnected steel pipes for use in the planned enlarged tunnel sections of the Tokyo Outer Ring Road and evaluates the feasibility of such a tunnel support structure. The design of the structure expects the soil between adjacent steel pipes to bear axial force. The load-bearing capacity of the connected pipe roof structure is affected by the outward confinement provided by the tunnel and ground improvement. In this study, a full-scale compressive loading test was conducted to investigate the effects of bolt confinement and ground improvement on the load-bearing capacity of the connected pipe roof structure against axial force.
