Gibraltar Strait Crossing - An Alternative: a Submerged Bridge-Tunnel

Abstract

This paper discusses a proposed submerged bridge-tunnel for a road- rail crossing of the Straits of Gibraltar, using the shortest (14km long) of the three possible routes. It is an alternative design to three other proposed crossing structures. Its advantages of design, construction time, cost, etc., are due mainly to: (1) eliminating gravity loads by hydrostatic buoyancy forces; (2) absence of wind and temperature influences; (3) partial or complete absence of many preliminary expensive and time-consuming studies and investigations. The proposed structural system would carry the tunnel tubes on bridges at 30m below sea level, for: (1) free navigation over it; (2) possible underwater external observation from above; (3) protection against waves and storms. A possible tunnel cross section would be the same along its whole length. There would be three basic tubes, two for one-way road traffic, and a third between them for rail traffic; to improve vertical load-bearing capacity, a fourth supporting tube under them is envisaged. The estimation of the design depends mainly on the correct determination of quality and quantity criteria, that are proposed in the paper, and on some structural feasibility problems addressed in another paper by the author. His preliminary feasibility study suggests that principal solutions are available for all major problems.