• A3 - dual carriageway link between London and Portsmouth

• 6.5km new road, 1.77km in bored tunnel• £371 million• Construction started January 2007• Project finish date 2012

Where?

Construction Overview• Twin Bore 2 lane Tunnel

• Tunnel Length – 1.2 miles

• Depth – Varies between 20 – 60m

• 7.3m wide 2 lane carriageway

• Estimated Earth Excavation – 300,000 cubic metres

• Longest non-estuarial crossing in England

Solution Adopted• Slope Stability

• Soil Nails

• Geogrid Reinforcement

• Minimising Visual Impact

• Soil Pouches

• Place Soil and Vegetation

• Hydroseed Spray

Solution Adopted continued…..

• Structural Reinforcement for Tunnel Face

• Rock Nails/Bolts

• Short

• Concrete Grout

• Ground Anchors

• Long

• High Tensile Steel

Solution Adopted continued…..

Sprayed Concrete Lining (SCL)

• Roof Supporting Spiles

• Primary sprayed concrete shell

• Waterproofing Membrane

• Reinforcement Steel

• Cast Concrete lining• Shotcrete• 200mm thick

Alternative Methods• New Austrian Tunneling Method (NATM)

• Tunnel Boring Machines (TBM) • New Tunnel PLS (Pre-Lining Support)

What Will It Look Like?

Thankyou for Listening

• Any Questions?