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Tunnel construction is a subset of underground construction. There are three basic types of tunnel construction in common use: Cut-and-cover tunnel, constructed in a shallow trench and then covered over. Bored tunnel, constructed in situ, without removing the ground above. They are usually of circular or horseshoe cross-section.
WSDOT evaluated five proposals in 2003–2004 and decided that the six-lane cut-and-cover tunnel was the preferred alternative. Rebuilding the viaduct was retained as a backup plan. [38] However, due to the costs and scope of the project, other options were still being discussed in the local media.
Cut-and-cover construction at Saint-Michel on Paris Métro Line 4 (c. 1910) Cut-and-cover is a simple method of construction for shallow tunnels where a trench is excavated and roofed over with an overhead support system strong enough to carry the load of what is to be built above the tunnel. [29] There are two basic forms of cut-and-cover ...
Plan for world heritage site condemned as ‘absolutely monstrous scheme’ and ‘tragedy for globally recognisable icon’ Stonehenge A303 road tunnel approved after years-long battle, prompting ...
In 1995 it was proposed to build a tunnel for the A303 underneath the World Heritage Site. A conference agreed on a 2.5-mile (4 km) bored tunnel; however, the government instead proposed a cut and cover tunnel, with plans being published in 1999.
Deep level underground is construction that is 20 m (66 ft) or more below ground and not using the cut-and-cover method, especially train stations, air raid shelters and bunkers, and some tunnels and mines. Cut-and-cover is a simple method of construction for shallow tunnels where a trench is excavated and roofed over with an overhead support ...
A 1974 state plan again proposed an extension to Park Street, while the 1978 and 1983 Program for Mass Transportation updates called for an extension to Charles/MGH instead. [15] A 1986 MBTA feasibility study for an extension to Charles/MGH evaluated a cut-and-cover tunnel beginning west of Bowdoin Street with no changes to Bowdoin station.
Environmental concerns with the Delta tunnel. The plan arrives with the state in the throes of one of the worst droughts ever recorded. But a proposal to replumb the Delta, in one form or another ...