Lausanne Metro Tunnel Collapse 2005

James McMulkin, Claire Rose, Ashley Rogers

Lausanne

Lausanne

Lausanne Metro

Foreland

Basin

/

Molasse

Deposit

Foreland Basin/Molasse Deposit

Moraine

Umbrella Vault NATM

22nd February 2005

Earlier in the day• In rush of water

from the moraine layer led to work stopping

• Investigations were being carried out by the contractor for Lot 1200 to determine the cause

18:00 MET• Tunnel collapse

occurred• 50m3 entered the

tunnel• Large crater below

Rue Saint Laurent

What Water?

Engineering Solutions for Specific Problem:Identifying Problem

• Improving soil strength should have been essential to allow for safe tunnelling

Engineering Solutions for Specific Problem:Solving the Problem

Actual Solution After Collapse

• Collapsed void first reinforced by 11 drilled piles (CFA likely) and grouting

• 800m³ of crushed glass sand used as infill due to good compactability

• Slope design changed due to need to go deeper