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Section E4b, Greenbelt Route, New Hampshire Avenue

NATM Consultant
Estimated cost: Commencement:
December 29, 1994
Completion date:
December 29, 1996
Washington, DC
United States
Technical data:

Two 20 ft diameter, 3.050 ft long with a minimum overburden of 45 ft and one elliptical shaft excavated and supported according to the principles of NATM as part of the Section E4b. Horizontal grout umbrellas up to 400 ft in length were installed as pre-support at the portals.

Geology description:

Potomac Group Soils, compact to hard; comprising silty fine to medium sand with some gravel and hard silty clay.

Service areas:
Typical Cross Section
Grouted Pipe Spiling as Pre-Support
Top Heading and Bench with Face Stabilization Wedge
Waterproofing and drainage pipe at invert
Cross section, Top heading and bench
Waterproofing of tunnel wall