The Los Angeles metro rail project forms the first part of a larger rapid transit system for the southern California rapid transit district and comprises a 4.4 mile line with 5 stations. Two of the challenges to be met in this project are the effects of earthquakes and construction in gassy ground. The design of structures in response to two levels of earthquake are considered -'operating design earthquake' and 'maximum design earthquake'. A series of computer analyses were carried out consisting of two or three dimensional finite element runs using data from the 1971 San Fernando earthquake. Details are given of comprehensive geotechnical reports and gas sampling carried out for the project. Officially classified as 'gassy', details are given of the concentrations of gases found and pressures recorded. A ventilation system capable of supplying 100000 cfm is seen as the main solution to excavating in such ground. Entry of gas into the tunnels may be through joints, through the lining itself or through any cracks caused. Measures to be taken to counteract this problem include wrapping in polyethylene, provision of sensors for continuous monitoring and provision of emergency ventilation. (TRRL)

  • Availability:
  • Corporate Authors:

    Mining Journal Limited

    60 Worship Street
    London EC2A 2HD,   England 
  • Authors:
    • MONSEES, J E
  • Publication Date: 1988-3

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Filing Info

  • Accession Number: 00491634
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD, TRIS
  • Created Date: Mar 31 1990 12:00AM