ABSTRACT
A hypothetical tunnelling condition in which the tunnel is excavated under a four lane roadway bridge is considered as shown in Figure 1. For simplicity, it was assumed that the direction of tunnel driving is perpendicular to the axis of the bridge. A typical tunnel cross section in urban tunnelling was considered in this investigation. The tunnel has a maximum height and width (D) of 8.0 m and 11.0 m, respectively, giving the net excavation area of approximately 87 m2.
