The virginia department of highways and transportation determined that by 1995 traffic crossing the hampton roads harbor area would be too great to be handled effectively by the james river bridge andthe hampton roads bridge-tunnel. A third crossing, interstate 664, was planned to assume a major portion of the projected traffic load.the two portal islands, each reached by an approach bridge, providetunnel access north and south of the newport news navigation channel. Construction of the islands involved removal of the top layer of muck soil from the bay floor, backfilling with sand, and placing hydraulic sand fill within a stone dike system. four-lane i-664 crossesthe islands first at grade and then within an open approach structure until it reaches the multistory ventilation building. it then passes through a lower level of the building and enters a sunken tube tunnel that takes it under the navigation channel. The circular-steel-shell, concrete-fill construction concept was used for the double-bore tunnel 4, 454 ft long face-to-face of the ventilation buildings. The structure is the fourth sunken tube highway tunnel in the unitedstates with twin bores. Each bore contains a 26-ft-wide roadway fortwo lanes of traffic. The tunnel is placed in an excavated trench and then backfilled. The tunnel-island project is to be completed in 1990. this paper appeared in transportation research record no. 1150, tunneling. for covering abstract see irrd no 818446.
Abstract