Many people may consider the trend towards tunnelling to be a natural progression for Australia’s famous city Sydney, with its wonderful sandstone bedrock, but another major driving factor has been the Underground Space Project carried out by the Warren Centre and the University of Sydney in 1995 to 1996.
As a result of this Sydney City Council now has a long term plan for underground development. Up to that time underground construction progressed piecemeal on numerous metro systems and stations with associated shopping malls, service tunnels for telecommunications, water and sewerage, and of course the submerged tube Cross Harbour Tunnel. Less known perhaps are the larger excavations for the Opera House Car Park and The North Head Pumping Station.
The start of the Underground Space Project coincided with construction of the first underground storage for LPG in Australia at Sydney’s Port Botany. Some 60,000t of propane is stored in four caverns, 14m wide, 11m high and 230m long, built 150m below surface in the aforementioned Hawkesbury Sandstone. A water curtain gallery excavated 15m above the cavern ensures the groundwater profile is maintained at all times.
Since 1995 many schemes in Sydney have followed, some of which had been put forward many years before. These include the Eastern Distributor Tunnel completed in 1999 and the recently completed M5 Extension, the Cross City Tunnel currently out to tender, and the M2 – Gore Hill Tunnel which is currently in Environmental Impact Study (EIS) and when constructed will complete the Sydney freeway bypass system.
The Eastern Distributor was a US$466M BOOT scheme awarded to Airport Motorway with Leighton Contractors performing detailed design and construction work. The project included 1.7km of double decker tunnel forming part of a 6km motorway connecting the Cahill Expressway at Woolloomooloo to Southern Cross Drive at Zetland. Excavated in the upper levels of the Hawkesbury Sandstone and crossing the Great Sydney Dyke, the project includes spans up to 22m excavated by roadheaders by both Concrete Construction and McConnell Dowell as sub-contractors. The Eastern Distributor also included a land bridge at the Domain. A similar scheme is now considered at the Observatory for the approaches to the Harbour Bridge.
The US$436M Federal funded M5 Extension linking Beverly Hills with General Holmes Drive at Sydney Airport included 4km of twin two-lane tunnels in hardrock and a 700m ventilation tunnel, plus a cut and cover tunnel built in a coffer dam to cross the Cooks River. The contractor, a JV of Baulderstone Hornibrook and parent company Bilfinger + Berger excavated the tunnels through sandstone using five roadheaders.
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By GlobalDataThe much awaited Cross City Tunnel consists of 1.25km of tollroad beneath Sydney CBD to bypass 18 sets of traffic lights and free up the north-south bus routes. The proposal will be a double decker tunnel like the Eastern Distributor. The US$200M design build contract is currently in the tender stage with three contractor JVs, Cross City Consortium; E-Tube; and the Sydney City Tunnel Consortium on the shortlist. Construction is set to start later this year.
The M2 – Gore Hill tunnel will provide a 3.4km freeway via twin two-lane tunnels beneath Lane Cove, forming the missing link between the M2 at East Ryde and Gore Hill Freeway at Artarmon. The tunnel will be driven through Hawkesbury Sandstone and Ashfield Shale.
Another major tunnelling scheme recently completed in Sydney is the Northside Storage Tunnel, providing storage facilities for wastewater to clean up the harbour during heavy rainfall. This project consisted of 22km of bored tunnels between 3.8m to 6.6m diameter and also included access declines, ventilation shafts and underground caverns. The scheme was thought to be the first tunnelling project to be constructed in Australia as an alliance that included contractors Transfield, Montgomery Watson Australia and Connell Wagner.
The West Ryde Stormwater Tunnel was completed in 1999 and included 1.8km of 3.5m diameter tunnel excavated by roadheader and a 300m section of cut and cover construction and 180m of micro tunnel. However the proposed Vaucluse sewer to run 3.5km from Vaucluse to Bondi in hard rock at 2.4m to 3.5m diameter has been delayed due to lack of funding.
The New Southern Railway valued at over US$342M was completed by JV Transfield/Bouygues in 2000 and provides a direct link from Sydney’s Kingsford Smith Airport to the CBD for the Olympics. This was a BOOT scheme of 10km of 10.5m diameter tunnel, including 5.8km of soft ground excavation beneath Sydney Airport by TBM and the rest in hard rock by roadheader. The project also included four new stations with major cut and cover boxes at the international and domestic stations.
A 5.3km extension to the existing rail network to the Olympic site at Homebush included an innovative tunnelling scheme with 300m of driven tunnel and 560m of cut and cover precast concrete arch tunnels, and a new 200m long station. The $98M project was completed in 1998.
A rail loop for trains into the CBD from the west has been considered for nearly 100 years and although reduced from the format proposed in the EIS a few years ago, the Parramatta Rail Link is now out to tender. The revised scheme only provides for the section between Chatswood and Epping but still includes some 16km of tunnels beneath National Parklands and a cost of some US$800M. Four consortia, Leighton Contractors; Baulderstone Hornibrook/Bilfinger + Berger; Thiess/Hochtief; and Transfield/Obayashi have been issued with tender documents with award expected soon and construction to start in the middle of this year.
Another inner city proposal called Metro West is currently being studied. This consists of 4km of twin tunnel rail extension from Redfern to Wynyard with two intermediate stations. Another rail scheme, to extend the rail system to Bondi beach has been shelved.
Two major cable tunnels have just been awarded in Sydney running through the CBD to Redfern. The Energy Australia Tunnel is 1.4km, running from Surry Hills to a new substation at Haymarket. The 3.2m diameter cross section is to be excavated by roadheaders. The Transgrid Tunnel runs from Haymarket to Redfern and is 3.5km long and 3.4m diameter and will be excavated by TBM.
Other state capitals have also seen major tunnel development in recent years. In Melbourne, the much troubled and delayed 3.4km Burnley Tunnel which along with the 1.6km Domain Tunnel, built by the Transfield/Obayashi JV, are a major element of the US$1bn Melbourne City Link which is now open.
The Eastern Freeway extension is currently out to tender and includes a 1.5km long tunnel. The project is a design and construct and is essentially a three lane two-way tunnel but may include a fourth auxiliary lane to connect to the Ringwood interchange.
In Perth the US$107M design and construct Graham Farmer Freeway includes a 1.6km six lane road tunnel constructed by top down cut and cover techniques and was opened in 1998.
The US$6.3M, 1.3km, 2.1m diameter Perth Main Sewer has just been completed. This tunnel from Wembley to Lake Monger forms Section 3 of the Perth Main Sewer Replacement and was excavated by contractor Transfield using a Lovat EPB TBM through the Perth sands.
Another busy area for underground construction in recent years has been Brisbane. A number of major road and bus tunnels are just being completed. This includes the South-East Transit Project consisting of 30km of busway through urban Brisbane with four sections of tunnel about 100m to 150m long and generally 10m wide, and an underground bus station. The Inner City Bypass includes driven tunnels for busway and traffic under Normanby Fiveways, a cut and cover tunnel under the RNA Showgrounds, a driven tunnel under Bowen Bridge Road and a cut and cover tunnel at Breakfast Creek. The Nundah Bypass tunnel via Sandgate Road is some 300m long and 30m wide and consists of two twin-cell cut-and-cover tunnels with ramps and an underground bus station.
The Northern Busway however has been put on hold due to lack of funding. Other road proposals include a 2km traffic toll tunnel from Eagle Farm to Morningside, another toll tunnel from Paddington to West End, and a 5km toll tunnel from Fortitude Valley to Woolloongabba with a submerged tunnel from New Farm to Kangaroo Point.
A major sewer has also just been completed in Brisbane by the Eroc/Obayashi JV. The US$20M North Quay to Breakfast Creek Sewer tunnel is a design and construct job consisting of a 2.4m diameter bored tunnel, 4.5km long with 3.5km in hard rock and 1km in soft ground excavated by TBM, and seven intermediate shafts. The sewer was fully concrete lined with a UPVC corrosion resistant liner.
Other projects currently in planning in Brisbane include a major commercial development in the CBD and other underground space proposals for redevelopment of waste ground and old quarries.
South Australia and Regional New South Wales
In regional areas a major highway tunnel was completed in 1999 as part of the US$72.6M federal funded Adelaide – Crafers Motorway. The 450m long tunnel forms the critical link beneath the Eagle on the Hill on the 7km long six lane highway, 9m high with spans of 14m. The Macmahon Walter Construction JV constructed the section with Connell Wagner providing tunnelling expertise.
The US$183M, 28km Yelgun to Chinderah dual lane highway in northern NSW is part of the US$1.1bn Pacific Highway upgrade, and includes a 140m long bored tunnel at Cudgen Road as the Yelgun bypass and is nearing completion.
Refurbishment of Old Tunnels
The Snowy Mountains Hydroelectric Scheme is considered to be the foundation for civil tunnelling in Australia. This includes some 145km of tunnels and two underground power stations.
This scheme, which celebrated its 50th anniversary last year, was the testing ground for rockbolt and shotcrete support systems and major refurbishment is planned for the Snowy-Geehi and Geehi-Island Bend tunnels this year. Other ongoing refurbishment work in NSW includes the enlargement of a number of 19th century rail tunnels along the coast for electrification, and in Victoria the repair and refurbishment of water tunnels.
Mining
Considering that the civil tunnel development is only a small percentage of the underground construction that takes place in Australia it is still quite extensive. However recent years have seen the development of a huge US$1bn mining infrastructure expansion at the Olympic Dam in Southern Australia and a 1.3km bored conveyor tunnel was completed to cross Port Headland Harbour in Western Australia. A number of major declines have also been constructed as the development for new gold mines at North Parkes and Cadia in New South Wales, and a proposed extension to the old mines at Broken Hill Mine, and Bendigo and Ballarat gold mines in Victoria. Other major metalliferous development has continued in recent years in Tasmania. Major underground development for coal mining has also continued in Central Queensland and NSW.
