TUNNEL UNDER WATER.

New Zealand Herald, Volume LXVI, Issue 20420, 23 November 1929, Page 3 (Supplement)

TUNNEL UNDER WATER.

NEW ENGINEERING FEAT.

BUILT ON LAND AND SUNK. Arc welding, by ■which the scams in great steel tubes may be made "watertight, has made it possible to construct a vehicular tunnel on dry land, float it to position, and sink it in place in the De-

troit River. This method, employed on the new tube between Detroit and "Windsor, Canada, has been found so successful that the tunnel is being built in sections six miles down the river from the tunnel site, by the Canadian Bridge Company, and these sections arc launched like a ship and floated into place. Each 250 ft. section of the tunnel, with an inside diameter of 31ft, and an outside diameter of 35ft., is constructed on regular launch-

ing ways. The sections are built up of 24ft. strips of steel plate electrically welded. After all the joints are tested for possible leaks, bulkheads are placed at either end, and the huge 450-ton tube is launched. Next some 4200 cubic yards of concrete are poured in to form the lining and outside covering Now "weighing approximately 8000 tons, the shell is towed up the river to the tunnel site and sunk into the aitch in the river bed that had been dredged out for it. It, is expected that most of the sections will be in place before cold weather comes. , . ~ The approaches are bored by the largest shield ever used in North Ameiica. It is 35ft, in diameter and 15ft. long. The tunnel from the corner of Randolph and \twater Streets in Detroit to the river cd"C, 466 ft. in length, was completed early this year and the shield -was transferred to the Windsor side where it is now working on the 986-foot approach to the river from that side. The completed tunnel will be almost three-quarters of a mile long, approximately half a-mile of which will be under the river. The roadway will be 22ft. wide and will allow a clearance of more than 14ft. overhead. The width of the roadway will permit the operation of two lanes of traffic continuously with ample space left for a third lane in case of an emergency.