Under the sea in Norway

The methods for constructing subsea tunnels in Norway are reviewed. All Norwegian subsea tunnels have been excavated by drill-and-blast and have achieved an average advance rate of 40-80 m-week. The total construction cost of a subsea road tunnel amounts to $4,500-10,000/m of tunnel, of which the excavation part (drill, blast and mucking out) constitutes about $1,500/m. The rock supporting works, which are designed for the rock-mass conditions encountered in the tunnel, mainly consist of fiber-reinforced shotcrete and rock bolts. The permanent water leakage amounts to 0.1-0.45 m3/min/km of tunnel.