Perth City Link Project

Project Type: Alliance

Owner: Public Transport Authority of Western Australia

Construction Cost: AUD 360 Million

Contractor: John Holland

Contractor: GHD / Geoconsult Asia Singapore

Design Period: 2010 – 2012

Construction Period: 2010 – 2013

 

The Project

The Perth City Link Rail project includes the sinking of the Fremantle Line rail track between William Street and Lake/ King Streets by providing a 600m long cut & cover section to reconnect the CBD with the Northbridge entertainment precinct and create new land for redevelopment.

Additionally associated works such as listed below were constructed as part of the overall project:

• Creating a new tunnel under the northern end of the Barrack Street Bridge to service the new Platform 9
• Extending the existing Joondalup line tunnel roof from Lake to Milligan Streets to be in line with the new Fremantle Line tunnel
• Creating a new 120m long pedestrian underpass to improve connections between Perth Underground Station to all the platforms at Perth Station

The design and construction of the tunnel works was largely controlled by the high groundwater table and soft ground conditions, close proximity to the existing New Metro Rail (NMR) bored tunnels, and allowance for future medium rise buildings to be constructed above the tunnel.

Key Aspects

• Cut & Cover tunnel of approx. 1.2km length
• Geology comprised of Fill, Spearwood Sand, Lake System Alluvium, Guildford and Kings Park formation
• Excavation by excavators
• Diaphragm and secant bored pile retaining walls
• Ground treatment works such as soil mixing, jet grouting and permeation grouting to ensure temporary stability of existing (NMRC rail line) and newly constructed works
• Load bearing bored piles with a diameter of 1,050 and 1,200mm with a depth of up to 37m
• Temporary dewatering and water recharging to limit effects on groundwater drawdown and limit associated settlements

Scope of Works

NOMA Consulting was engaged by Geoconsult to lead the detailed design and provide design support for the following aspects:

• Detailed design of temporary retaining wall systems
• Detailed design of steel strutting and waling
• Detailed design of ground treatment consisting of deep soil mixing, permeation and jet grouting at crossing of existing bored tunnels
• Ground settlement analysis and impact assessment
• Instrumentation and monitoring
• Supporting permanent works designers in regards to loads and expected deformations for all permanent retaining works elements