With a background of some 50 years of experience in the immersed tunnel industry, most recently having been in charge of inspection during the construction of the Bosporus Rail Tunnel, and having the privilege of working with engineers in Norway on various aspects of their SFT projects for a basis, the author presents some concepts for the design and construction of a long submerged floating tunnel in deep water. These concepts are presented as sketchy ideas only supported by rudimentary calculations and assumptions. It is hoped however, that some of these ideas might at be useful in the future development of viable, long crossings in deep water. Such crossings are the challenges often faced by engineers in a country like Norway with its deep, wide fjords. An SFT design premise that has been written about by the author over the years (most recently at the Fifth Strait Crossing Symposium 2009 held in Trondheim, Norway [1]) is that an SFT should be designed to float and remain stable even if its roadway or track ducts were to be completely flooded. There is no doubt this requirement would be considerably more costly than the SFTs presently being considered. The author feels very strongly however, that an owner, either governmental or private (as in a toll road), would never finance a water crossing that could be completely destroyed in the event of a single flood. If a flood were to occur that would slacken the tethers of an SFT. as presently conceived, the whole tunnel crossing would quickly become unstable and collapse in ruin at the bottom of the waterway. Floods have occurred in many tunnels as a result of carelessness, water mains breaking, or even the failure of a bulkhead. Such floods, ranging from minor to major, would have destroyed an SFT. This paper touches on methods to provide stability against flooding, construction methods and equipment that could be used to cast and install anchor blocks attached to braced "tether towers", a sequence of construction with methods to lower, join and align, modular tunnel elements, how to attach the tether towers and equalize the tensile loadings, and a method to stabilize the completed SFT laterally while providing for elongation or contraction due to temperature changes. The methods described are felt to incorporate doable construction techniques.
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