Forepoling Design in Weak Medium based on the Convergence-Confinement Method

Umbrella arches are tunnel heading reinforcements used for supporting the unlined portion of the tunnel heading when excavating a tunnel in soft ground or loose soil conditions by open face excavation methods. They are installed at the tunnel face at the top perimeter of the tunnel section. In this paper, the contribution of Convergence–Confinement method for tunneling design, forepoling technique, and Ring-Cut method considered for Gilavand tunnel. Three analysis are considered: top and bench excavation, ring-cut excavation, and top and bench excavation with presence of forepoling condition. The results show that the pre-consolidation is need for top and bench excavation method, however, the settlement is happened by installing supporting systems adjacent tunnel face. The settlement also is occurred in Ring-cut method, however the tunnel is stable. The both stability and settlement is provided, so that supporting system is installed in the close distance of tunnel face

Keywords:

Forepoling Method , Weak Medium , GRC , Settlement