Collapse of tunnels: soil-structure interaction failures

Professor Robert MairCambridge University

Engineering Department

Tunnelling with shield and rings.

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

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