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Alan Spray Ted Allen. Tunnelling Under the Thames. Docklands Light Railway (DLR) Woolwich Extension. Geological Context. Initially Alluvium, gravels and Bullhead beds Water-bearing Upper Chalk Non-Clastic Carbonate Cretaceous period Medium – wide joints - PowerPoint PPT Presentation
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Alan SprayTed Allen
Docklands Light Railway (DLR) Woolwich Extension
• Initially Alluvium, gravels and Bullhead beds
• Water-bearing Upper Chalk• Non-Clastic Carbonate • Cretaceous period• Medium – wide joints• Large flints – non carbonate• Relative strengths
Flint damageWater-bearing chalk
Maintenance – dry refuges
Drilled until cutter broke
Intensive pumping - luck
Repairs to cutter Dig heading Replacements/reinforcements Welding
Stronger cutters
Better investigation More remedial works
Build a bridge