Keeping Tabs on Two Tunnels (available in Geoenvironmental Special Issue only)

by Alexander I. Feldman, (M.ASCE), Assoc.; Shannon & Wilson, Inc., 400 N. 34th St., Suite 100, P.O. Box 300303, Seattle, WA 98103,
Gerard J. Buechel, (M.ASCE), Vice Pres.; Shannon & Wilson, Inc., 400 N. 34th St., Suite 100, P.O. Box 300303, Seattle, WA,
Michael A. Kucker, Assoc.; Shannon & Wilson, Inc., 400 N. 34th St., Suite 100, P.O. Box 300303, Seattle, WA,
Hollie Ellis, Vice Pres.; Shannon & Wilson, Inc., 400 N. 34th St., Suite 100, P.O. Box 300303, Seattle, WA,


Serial Information: Civil Engineering—ASCE, 1998, Vol. 68, Issue 6, Pg. 2A-6A


Document Type: Feature article

Errata: (See full record)

Abstract: Engineers devised a unique liquid level monitoring system to check vertical movements in 90-year old twin subway tunnels. Construction for the Boston Central Artery/Tunnel project requires that an immersed tube vehicle tunnel be constructed 1.5 m above the existing tunnels. More than 10,000 commuters travel through the subway tunnels daily and the trains must keep running during the five years of construction in the area. The liquid level system is described in detail. It is based on the principle of hydraulic communication between chambers interconnected in sequence by a fluid-filled tube. Changes in the liquid levels are detected by force transducers that measure the weight of liquid in a chamber or the buoyant force of a partially submerged mass. After a pilot test, about 1,000 gages were installed at the site. The system includes the liquid level system, the liquid level gage, and a liquid density gage. Monitoring is done remotely and the system will be checked every two to three hours during the most critical periods of construction. The system can be used for tunnels, dams, bridges or other structures subject to vertical movements.

Subject Headings: Liquids | Monitoring | Subways | Tunnels | Underground construction

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