Sao Paulo collapse: NATM used despite failure history

The decision to use the New Austrian Tunnelling Method (NATM) on the section of the Sao Paulo Metro in Brazil, which collapsed on the 15 January 2007, has been questioned. The collapse at the site of Pinheiros station killed seven people and was the fourth NATM failure on Sao Paulo Metro projects in 25 years. NATM is being used to excavate the 18.5m diameter station tunnel as part of the Metro's Line 4 or Yellow Line. The tunnel is being constructed in gneiss overlain by tertiary sediments consisting of stiff clays and compact sand. A bored tunnel was not considered due to a lack of equipment. John Anderson, leader of the Health and Safety Executive's investigation into the Heathrow Express NATM collapse, questioned the use of NATM for the construction of a large tunnel in potentially poor ground. Prior to the accident, the rate of vertical downward displacements in the tunnel had increased and the decision had been made to install additional support consisting of rock bolts, but the collapse occurred before these had been installed. The contractor blamed heavy rain for the collapse. The Pinheiros River is also close to the tunnel. Tunnelling expert Sir Alan Muir-Wood warned that the presence of water in ground that is otherwise stable can cause problems.


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  • Accession Number: 01061032
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • Files: ITRD
  • Created Date: Sep 10 2007 2:05PM