1. Tunnelling Across a River Using Immersed Tube Tunnelling Click through the slide show to see key stages in creating a tunnel across a river using Immersed Tube Tunnelling © Mott MacDonald Group Limited 2006 Within each slide, click to progress to the next stage of construction

2. Establish immersed tube tunnel anchor points Submerge immersed tube tunnel Reinstate river bed Construct diaphragm walls Construct cofferdam wallsFill cofferdam walls Drain cofferdam Remove and store quay wall Excavate and ground anchor Install support piles Construct tunnel box structure Reinstate quay wall Prop quay wall Fill behind quay wall Demolish quay wall cofferdam Construct cofferdam walls Fill cofferdam walls Drain cofferdamRemove and store quay wall Excavate and ground anchor Install support piles Construct tunnel box structure Reinstate quay wall Prop quay wall Fill behind quay wall Demolish quay wall cofferdam Dredge across riverInstall stub support piles Fetch immersed tube tunnel Rotate immersed tube tunnel into position Construct closure joint Tunnelling Across a River Using Immersed Tube Tunnelling © Mott MacDonald Group Limited 2006

3. Bedrock Silt Clay Dredge silt Dredge clay Blast and excavate into bedrock Install stub pilesLower immersed tube tunnel Grout beneath immersed tube tunnel Cast protective concrete slab Allow riverbed to reinstate Fill surroundings with sand and interlocking armour Tunnelling Across a River Using Immersed Tube Tunnelling © Mott MacDonald Group Limited 2006