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?