Underground replacement of a 100 year old tunnel using the sequential demolition method

Abstract

The Réseau Express Métropolitain (REM) by la Caisse de dépôt et placement du Québec (CDPQ) is a major transit project in Montréal, Canada. The automated LRT system will include 26 stations connected by 67 km of track. A section of the REM goes through the 5 km long existing Mount Royal Tunnel which was completed in 1917. The southernmost 540 m of the tunnel was constructed using a clever double arch consisting of plain concrete precast segments. A 92 m length of which was not in an acceptable condition after 100 years of deterioration and required replacement. This paper describes the implementation of an innovative sequential demolition and replacement method that was performed completely underground and coined “The Sequential Demolition Method”. The design was developed by Hatch with the Joint Venture CIMA + HATCH (CCH) retained by REM to oversee implementation by the NouvLR on a cost reimbursable approach.