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Survey of New Tunneling Projects, Their Costs,

Application, and Effect on Rail System Performance

Brian J Larkin, P.E.

Larkin & Associates ‐ San Francisco, CA

Background

• Exclusive Right of Way Operation• At Grade• Grade Separated

• Elevated• Underground / Below Grade


At Grade XROW


Elevated


Subway


Some Tunneling Techniques

• Cut & Cover• Sequential Excavation Method (SEM)• Tunnel Boring Machines


Cut & Cover Tunneling


Sequential Excavation Method


Sequential Excavation Method


• Advantages• Fewer Spoils to Dispose of• Good in Sandy Soils

• Disadvantages• Slow• May Require Extensive Soil Treatment

Tunnel Boring Machines

• Open Faced• Slurry Shield• Earth Pressure Balance (EPB)


Open Faced Machines

• Only Support Themselves • Good for Use in Hard Rock• Danger of Collapse in Soft Ground


Slurry Pressure Balanced


• Slurry Pumped from the Surface• Mixes with Cuttings to Maintain Pressure• Used in Soft Ground with High Water Pressure

and Large Amounts of Ground Water.

Earth Pressure Balanced


• Shielded Cutting Face• Screw Conveyor Removes Spoils• Machine Installs Liner Segments• Advances by Pushing off Liner• Can Advance 50 feet /day

Earth Pressure Balanced


BART Warm Springs Extension

• One mile of cut & cover tunneling• Contract cost - $137 million• $82 million for tunneling • $55 for excavation support to protect aquifer• Birds nests


NYCTA 7th Avenue Subway (SAS)• 8.5 mile extension of No 7 line in Manhattan• Includes freezing ground ahead of TBM• Varying geology includes hills and valleys,

schist, sand and silt• $350 million tunneling Contract• Two tunnels – 15,000 linear feet


NYCTA 7th Avenue Subway (SAS)


East Side Access (ESA)

• Connects LIRR trains to Grand Central Station• Two – 22.5 foot diameter tunnels• Slurry shield machines• 10,500 feet of tunnel - $718 million in

Manhattan


No. 7 Line Extension

• Extends existing line 1.7 miles from Times Square area to Penn Station

• $1.14 billion tunneling contract – two TBMs combined for 9,300 feet of tunneling


SF MTA Central Subway

• Low bid for tunneling contract - $233,584,015• Two 1.7 mile bores• EPB machines


LAMTC Gold Line Eastside Extension

• Includes twin tunnels – two underground stations

• Each tunnel is 7,000 ft.• EPB machines 21ft – 5 in cutting diameter• Cost of tunnels - $268 million


Guadarrama Tunnel

• Tunnel on Madrid – Valladolid HSR line• Each tunnel is 17.65 miles• TBM diameter – 9.5 m (31 ft – 2 in)• Cost of tunnels - $17 billion • Production rate – 50’/day


Guadarrama Tunnel


San Francisco Market Street Subway

• Subway service started in 1979• Total Market Street Ridership –98,000• Post 1979 Ridership – 136,000• Capital Cost - $380 million• Travel Time for 4.5 miles

• Surface – 25 minutes• Subway – 10 minutes


Geary Corridor – San Francisco


Geary BRT


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