Tunnelling Under the Thames

1
Tunnelling Under the Thames

• Alan Spray
• Ted Allen

Docklands Light Railway (DLR) Woolwich Extension
2
Geological Context

• Initially Alluvium, gravels and Bullhead beds
• Water-bearing Upper Chalk
• Non-Clastic Carbonate
• Cretaceous period
• Medium wide joints
• Large flints non carbonate
• Relative strengths

3
The Problem

• Flint damage
• Water-bearing chalk
• Maintenance dry refuges

4
Solution Adopted

• Drilled until cutter broke
• Intensive pumping - luck
• Repairs to cutter
• Dig heading
• Replacements/reinforcements
• Welding

5
Alternatives

• Stronger cutters
• Better investigation
• More remedial works
• Build a bridge

6
Thanks for Listening