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From within the Tunnel

Crossrail Farringdon Station - Geotechnical Assessment

Service Performed
Temporary works design included design of tunnels prior to ring closure and 28 day strength as well as depressurisation design.
Commencement - Services
May 01, 2013
Completion - Services
October 01, 2015
Location
Cnr Charterhouse St & Farringdon Rd
London
EC1M3HN
United Kingdom
Geology description

Excavation encountered almost all the London basin units but mainly Lambeth Group, comprising stiff to very stiff overconsolidated clays to water bearing sand units.

Geology types
Description

The station is located in central London between Tottenham Court Road and Liverpool Street Crossrail (CRL) Stations. Constructed in the geologically most complex area in the whole of CRL, an optimised geotechnical and SCL tunnel design was implemented, which resulted in significant time and cost benefits for the project. Using a dynamic 3D geological model in conjunction with SCL tunnelling represented a key element of the geotechnical risk management framework.

Activity
Service areas
Construction methods
Special Construction techniques
Tunneling under
Groundwater control
From within the Tunnel
Max Overburden
25 m
Max Excavation Area (m2)
95
Tunnel length
1000 m
Qualitative geotechnical risk mapping
Exerpt of the 3D finite element model
Project number
222D5
Min Overburden
5 m
Final cost
£300 million GBP

Devil's Slide Tunnels

Service Performed
Construction inspection and scheduling for initial and final liner and waterproofing; analysing monitoring data and project's progress; daily site inspection and ground conditions reports.
Commencement - Services
November 01, 2007
Completion - Services
March 01, 2011
Location
585 Linda Mar Boulevard
Pacifica, CA 94044
United States
Geology description

The geological setting comprised quartz diorite, marine sandstone, conglomerate and clay-siltstone. Four main fault zones were encountered.

Geology types
Description

Devil's Slide is located south of the City of Pacifica in California along the coastal road of Highway 1. Landslides and grade subsidence in the Devil's Slide area along Route 1 have led to the road being closed for extended periods causing significant economic loss to the surrounding communities. The solution: Construct a tunnel through the mountain to bypass the dangers and reoccurring problems. Construction of 1250m twin tunnels, 9m wide, 6.8m high using Sequential Excavation Method (SEM). Additionally, drill and blast and roadheader excavation through weathered rock utilised.

Activity
Final cost
$273,000,000
Construction methods
Special Construction techniques
Groundwater control
From within the Tunnel
Max Overburden
~250m
Tunnel length
1250m
Drill jumbo drilling blast holes in top heading advance face
Finished southbound tunnel with textured cast-in-situ concrete
Tunnel Portals
Aerial view of completed portals
Project number
272E
Min Overburden
<5m at portals
Final cost
$273 million USD

Beacon Hill Station

Service Performed
NATM / SEM station design and construction supervision.
Estimated cost
$250,000,000
Commencement - Services
February 26, 2000
Completion - Services
December 28, 2007
Location
401 S. Jackson Street
Seattle, WA 98104
United States
Technical data

NATM Light Rail Station located 150 ft (46 m) beneath surface. Station complex includes central elevator/access shaft, concourse, opposing platform tunnels and cross passages. Platform Tunnel Section: 36 ft w x 31 ft h; Platform Tunnel Area: 925 sqft (86 m²); total Station Excavation Area: 63,000 sqft (5853 m²).

Geology description

Over-consolidated glacial clay and till with fracutured zones. Intermittent sand and silt layers with perched groundwater.

Geology types
Description

The Beacon Hill Tunnels and Station are part of the 22.5km initial segment of the Sound Transit Central Link Light Rail Line that will establish a high capacity commuter connection from downtown Seattle to Tacoma. The 1300m running tunnel under Beacon Hill will be mined by Earth Pressure Balance Machine (EPB), while the deep mined Station will be constructed using slurry walls and the New Austrian Tunneling Method (NATM), referred to as Sequential Excavation Method (SEM) for this project.

Activity
Bid cost
$280,000,000
Final cost
$280,000,000
Construction methods
Tunneling under
Groundwater control
From within the Tunnel, Groundwater Lowering, Vacuum Lances
Max Overburden
Min:120 Max:140
Beacon Hill Station layout
Tunnel excavation under way
3D rendering of Beacon Hill Station complex
Platform tunnel cross section
Schwind Thomas
Installation of Vacuum Dewatering
Rendering of Beacon Hill Station
Project number
325
Final cost
$280 million USD