L.A. TUNNELERS OVERCOME GASSY SOIL

Problems that constructors have had to overcome in their design and construction of the Southern California Rapid Transit District's (RTD) $3.75-billion, Metro Red Line in Los Angeles are described. Line segments are being constructed by tunnel boring machines and crossovers are excavated by cut-and-cover techniques. The area sits atop oil and abondoned natural gas wells; the quantification and management of the uncharted presence of hydrocarbons is described. Besides the extensive monitoring, contractors are required to use explosion-proof equipment in mining operations and to install ventilation systems that will provide an air velocity of 100,000 cu ft per minute during construction. A central gas monitoring system developed expressly for the Red Line will be installed to measure methane gas and hydrogen sulfide. A 100-mil thick, high density polyethylene (HDPE) membrane is being used to encapsulate the tunnels and stations. Construction has been slowed by large boulders. The design also accounted for a moderate-scale earthquake expected within 100 years; the structure was made ductile by adding 5 to 10% more reinforcing steel to tunnel joints to absorb the imposed deformation. Other seismic design criteria are also noted. The construction involved the moving of a great number of utilities, remedying leakages, and cleaning asbestos used to insulate utilities. A unique vertical conveyor was used to move muck to a truck-laoding bin 46 ft above street level. The protection of downtown buildings from settlement after tunnel excavation is described. A carefully orchestrated traffic control plan that maintained traffic flow above ground is noted.

• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/issn/08919526
• Corporate Authors:

  McGraw-Hill, Incorporated

  330 West 42nd Street
  New York, NY  United States  10036
• Publication Date: 1989-6-8

Media Info

• Pagination: p. 38-43
• Serial:
  • Engineering News-Record
  • Volume: 222
  • Issue Number: 23
  • Publisher: McGraw-Hill, Incorporated
  • ISSN: 0891-9526

Subject/Index Terms

• TRT Terms: Construction; Conveyors; Earthquake resistant design; Earthquake resistant structures; Excavation and tunneling; Hydrogen sulfide; Methane; Monitoring; Mucking; Natural gas; Oils; Public utilities; Settlement (Structures); Subways; Ventilation systems; Work zone traffic control
• Uncontrolled Terms: Utilities
• Old TRIS Terms: Polythene membrane; Subway construction
• Subject Areas: Bridges and other structures; Construction; Design; Highways; Public Transportation; I25: Design of Tunnels;

Filing Info

• Accession Number: 00485150
• Record Type: Publication
• Files: TRIS
• Created Date: Jun 30 1989 12:00AM