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Alan Spray Ted Allen Docklands Light Railway (DLR) Woolwich Extension

Tunnelling Under the Thames

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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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Page 1: Tunnelling Under the Thames

Alan SprayTed Allen

Docklands Light Railway (DLR) Woolwich Extension

Page 2: Tunnelling Under the Thames

• Initially Alluvium, gravels and Bullhead beds

• Water-bearing Upper Chalk• Non-Clastic Carbonate • Cretaceous period• Medium – wide joints• Large flints – non carbonate• Relative strengths

Page 3: Tunnelling Under the Thames

Flint damageWater-bearing chalk

Maintenance – dry refuges

Page 4: Tunnelling Under the Thames

Drilled until cutter broke

Intensive pumping - luck

Repairs to cutter Dig heading Replacements/reinforcements Welding

Page 5: Tunnelling Under the Thames

Stronger cutters

Better investigation More remedial works

Build a bridge

Page 6: Tunnelling Under the Thames