ABSTRACT
The National Expressway No.3 connects both the northern and southern ends of Taiwan. The feasibility study of this expressway commenced in 1983, followed by the planning, design and construction, and was completed for operation in January 2004. The total length of this expressway (Fig. 1), including the main route and branches, is 518 km (TANEEB, 2004). There are 14 tunnels with a total length of 13.6 km in Expressway No.3 of which 12 of them are located in the northern section, thus a tunnel group is formed. Most of these twin-tube three lanes tunnels passing through unfavorable topography and adverse geology; therefore, the tunneling works were always critical during the construction.
