1. Collapse of tunnels: soil-structure interaction failures
Professor Robert Mair
Cambridge University Engineering Department

2. Tunnelling with shield and rings.

3. New Austrian tunnelling method
New Austrian tunnelling method. Sprayed concrete lining onto unsupported walls.

6. Conclusions Tunnel collapses usually catastrophic
Soil-structure interaction important in tunnel lining design – time-dependent soil pressures depend on stiffness of lining
Shape is critical: ‘horseshoe’ tunnel lining vulnerable to structural failure – Toulon
Sprayed concrete vulnerable to construction defects in lining – eventual instability – Heathrow