1. Lausanne Metro Tunnel Collapse 2005 James McMulkin, Claire Rose, Ashley Rogers

2. Lausanne

4. Lausanne Metro

5. Foreland Basin / Molasse Deposit

6. Foreland Basin/Molasse Deposit

7. Moraine

8. Umbrella Vault NATM

9. 22 nd 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 50m 3 entered the tunnel Large crater below Rue Saint Laurent

10. What Water?

11. Engineering Solutions for Specific Problem: Identifying Problem Initial problem with acquiring reliable & thorough ground investigation data Critical assumptions were made between boreholes 50m apart along the run of the tunnel path Possible techniques to obtain geological data: Seismic Refraction (Observation of vibration reflection/refraction Ground Resistivity Measurement Ground Penetrating Radar

12. Improving soil strength should have been essential to allow for safe tunnelling Engineering Solutions for Specific Problem: Solving the Problem Soil compaction (surcharging) Vertical drain wells Improve soil stability by installing piles Remove water void Excavate/pump/fill Drill/pump/fill

13. 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