Bering Strait

Tunnel Design Concepts

Tunnel sections can be prefabricated, floated into position, and lowered into place.

Segment models of prefabricated tunnel sections and pipe shaped segment.

(Click image for a more detailed photo.)

These are models of arch-type segments of two possible types of prefabricated tunnels for the Bering Strait QUADRAIL railway crossing. These are HO, or 1:87 scale, models that are 12 inches in length, or 87 feet actual length. These models would be about 303 feet in full length (about the length of a football field), or five miles in real life.

The segment depicted on the left in the above photo is a dual QUADRAIL track tunnel segment and the one on the right is a single QUADRAIL track tunnel segment. The walls and floor of the segments is approximately 6 feet thick. (Actual thickness to be determined by structural engineering.) The superstructure framing could be fabricated with arch-shaped H-beams and H or I-beam horizontal segments imbedded in the flooring. A type of concrete could be used that presents a barrier to seawater penetration in order to prevent corrosion of the superstructure framing. A steel liner plate could be used for the inner walls of the tunnels. This would serve as the inner forms for pouring the concrete. The outer forms could be made of fiberglass, or some type of plastic, in the form of removable sections that could be reused for the consecutive fabrication of identical tunnel sections.

The tunnel sections would be fabricated in a dry area surrounded by man-made dikes fabricated from excavated rock and crushed stone. The tunnel sections would be temporarily capped on the ends to make them air and watertight. They would be subjected to about 8 atmospheres of pressure when set in their respective permanent locations in trenches in the Bering Strait. The current depth in these locations is about 30 fathoms (180 feet) between the Diomede Islands and the coast of Charles Prince of Whales, Alaska and 27 fathoms (162 feet) between the coast of Russia and the Diomede Islands.

The dual QUADRAIL tunnel sections would experience higher structural loading forces than the single tunnel sections. However, half of the number of individual tunnels would be required for the dual QUADRAIL design and more space would be available for utilities (fiber-optic telecommunication lines, electric power transmission lines, and possible oil and natural gas pipelines), and allow more area for bypass air induced by “piston action”, as trains pass through the tunnel. The dug trenches would have to be deeper for the dual QUADRAIL tunnel sections than for the single tunnel sections. However, the overall trench width would be a bit wider for the single tunnel sections for placement reasons.

One possibility for the fabrication site structure is a long temporary steel structure of sufficient length to allow for the length of the tunnel sections, fabrication equipment and materials, and width that allows space for the width of all tunnel sections to be fabricated plus work area. Another possibility is a large inflatable temporary structure similar in design to temporary aircraft hangers like the ones used in the military. Tunnel section fabrication in the Bering Strait area has the advantage of shorter towing distance and time and less exposure to harsh seas during transport. The major disadvantage is the harsh climate. The temporary fabrication structures would have to be heated in a region that experiences temperatures as low as –50 degrees Fahrenheit.

The QUADRAIL tracks shown in the models are for illustration purposes. The track would not be laid till after the tunnel system was complete, thus reducing overall weight of the sections. The size, shape, wall thickness, average density of the tunnel sections and the volume displacement and local seawater density would determine the buoyancy of the tunnel segments. If the buoyancy is slightly positive, then the tunnel segments could be floated into position, then temporarily flooded and sunk into their respective trenches till sea walls and dikes are fabricated and the water pumped out. If the buoyancy were slightly negative, then pontoon barges with cables and winches would be required to tow the tunnel segments to their respective trenches. If it proves impossible to design prefabricated tunnel segments this long then bored tunnels would have to be considered.

William C. Simpson

February 9, 2009

Location of Tunnel on Nautical Chart