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Will Freelander, Perth City Link – Section Manager, John Holland delivered this presentation at the 2013 Australian Tunnelling conference. The two day conference is supported by the Australasian Tunnelling Society and brings together tunnelling leaders, engineers and industry experts to share best practice in tunnelling design, construction, safety and maintenance. The 2012 program focussed on updates from Australasia’s current and future projects, plus case studies from leading International projects - sharing best practice and lessons learnt from the forefront of the latest tunnelling projects. For more information about the event, please visit the conference website: http://www.informa.com.au/tunnellingconference
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12th Australian Tunnelling Conference
21 – 22 November 2013
The partners
• Perth City Link Rail Alliance project supported by Local, State and
Federal governments:
• $360 million project
• PTA will deliver the project’s first stages:
• Stage 1 (2011- 2014): sink 600 metre section of the Fremantle Line; build
a pedestrian underpass to connect Perth and Perth Underground stations;
and major upgrades to Perth Station
• Stage 2 (2014 - 2016): sink the Wellington Street Bus Station
underground
• MRA will manage the area’s planning and subdivision works, create the
new public spaces and facilitate private sector investment for the overall
Perth City Link project
Rail project overview
• Sinking the Fremantle Line (William Street to Lake/King Street)
• New covered section of the Fremantle Line almost 600metres long
• Total work site exceeds 1.2km in length
• Improving connections between Perth Station and Perth Underground via a new pedestrian underpass
• By 2031, 22,600 people a day will use the new underpass
• Major upgrades to Perth Station, to meet Perth’s future public transport needs and special events.
• A new platform and track is being constructed, involving the extension of Barrack St Bridge
January 2012
July 2011
October 2013
The vision - beyond 2016
The facts
• 83,000 cubic metres of earth moved
• 53,000 cubic metres of concrete poured
• 3,400 metres of track laid
• 200km of cable installed (signals / communications and
power)
BARRACK STREET
HORSESHOE BRIDGE
TUNNEL & DECLINES
PEDESTRIAN
UNDERPASS
CHILD CARE CENTRE
PERTH STATION
Key site areas
Engineering and design challenges
Building a tunnel over two existing tunnels
Eastern Dive
Main Tunnel
Western Dive
Pedestrian Underpass
PUG LINK
Fremantle tunnel
Fremantle and Joondalup Line tunnels
Fremantle
Line tunnel
Joondalup Line
bored tunnels
Staged construction to maintain operating train
station
Operating in a live rail environment
Heritage-listed structures and nearby buildings
Relocating Horseshoe Bridge Pier
Piling in Childcare Centre playground
Dewatering tanks
Instrumentation and monitoring
Located on old Lake Kingsford
Site location - logistics
Proactive approach to community relations
WESTERN DECLINE
MAIN TUNNEL
EASTERN DECLINE
Perth-Fremantle tunnel
Main tunnel
D-wall excavation
Pre-cast roof planks
Topping slab
Insitu base slab
Western decline
Eastern decline
Tunnel excavation
Fremantle Line tunnel – rail track
Construct Diaphragm
Walls
Initial Bulk Excavation Construct Roof Slab
Partial Excavation
Complete Bulk Excavation
/ Dewatering
Construct Base Slab
Lateral Earth Pressures
RL 8.9 (Nom.)
Construction sequence
3D plaxis modeling
Joondalup and Fremantle Line tunnel interface
MAIN TUNNEL
Key design considerations
Proximity to existing tunnels
• current state of tunnel
• cracking of segment linings
• leaks at segment joints and bolt pockets
• Effects of construction on existing defects
Key design considerations
Groundwater control
• Tunnel heave
• Release of overburden pressure
• Buoyancy due to high groundwater level
Key design considerations
Stabilisation of diaphragm wall
toe
Primary support
Diaphragm wall panels
Prestressed Hanger
Beam
CSM – grouted base
Key design considerations
Soil movement minimisation
• Minimisation of soil pressure relief
• Increased diaphragm wall
stiffness
• Grout-mix base restraint to
diaphragm walls
• Staging of base slab excavation /
construction
Advantages of adopted solution
Simplicity of construction
Staged construction
• Facilitates progressive monitoring
• Allows ongoing benchmarking of theoretical results
• Allowed continuous assessment of impact
• Provided avenue for continuous input from design
Tunnel – western decline
Key design issues
Future above-ground developments
• Magnitude of applied loads
• Restrictions on allowable tunnel movements
5.1 MN 12.6 MN 15.2 MN 12.6 MN
Continuous 600
Diaphragm Wall 1200 / 1050 Dia.
Piles
Existing Sheet piling
40 / 30kPa 40 / 30kPa 40 / 30kPa
Staged construction
• Screening to existing decline structure
Construction sequence – stage 1
600 Continuous
Diaphragm Wall
1200 / 1050
Dia. Piles
Piles
Construction sequence – stage 2
Construct Base
Slab
Excavate to a
maximum of 4.2m
Full depth
excavation within
Dive Structure
Construct Buttress
& Infill Walls
Construction sequence – stage 3
Construct Roof Slab
Construction sequence – stage 4
Complete Bulk
Excavation
Pour Bus Ramp
Base Slab
Construction sequence – stage 5
Commission Tunnel &
Dive Structures
Construction sequence – stage 6
Install Piles
adjacent existing
Decline Structure
Construction sequence – stage 7 Construct Roof
Slab over Perth-
Butler Decline
Pedestrian underpass
Pedestrian underpass layout
Pedestrian underpass
Key design considerations
• Distance to operating train
station
• Maintain pedestrian movements
Key design considerations
Top down construction
• Minimise required number of
shutdowns
• Delayed commencement of
stage 1 tunnel works
• Temporary strutting of contiguous
piled walls
Underpass structure
Underpass structure
Underpass structure
Perth Station underpinning
Micro-piling underneath Perth Station
Underpinning beams
Perth Station underpinning
Questions?
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