Abstract

When a tunnel is excavated below groundwater table, the groundwater flow occurs towards the tunnel resulting in the seepage pressure. In this paper, the effect of groundwater flows on the behavior of shotcrete lining installed between ground-liner interfaces was studied considering permeability ratio between the ground and the shotcrete into account. Three-dimensional coupled finite element analysis was performed for this assessment. Seepage forces will seriously affect the shotcrete behavior since arching phenomena do not occur in seepage forces. A parametric study was conducted on the various tunnelling situations including interfacial properties between ground and shotcrete lining, the shape of tunnel cross-section and the thickness of liner, etc. Moreover, the convergence- confinement method (CCM) of a NATM tunnel considering seepage forces was proposed. The result showed that the more watertight is the shotcrete, the smaller is the convergence and the larger is the internal pressure. Therefore, the watertight fiber-reinforced shotcrete is found to be even more advantageous when used in underwater tunnel.