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Tunnel project plays key role in Australia’s Sydney orbital network

Tunnels Article April 18, 2005
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A series of major road improvements is addressing the problem of increased numbers of vehicles and its attendant congestion in Australia. The most recent is the Lane Cove Tunnel Project, which will provide a controlled-access link from the M2 Motorway to the Gore Hill Freeway, just north of Sydney. In addition to twin 3.6-km tunnels, the project widens 3 km of the Gore Hill Freeway from four to six lanes. The project also will provide a number of valuable improvements to the arterials and local roads as it reduces traffic and improves access east of the Lane Cove River on the surface streets.

Sydney has developed a long-term vision to meet its transport needs. Some of its key strategies related to vehicular traffic include meeting the needs of the growing and changing community, improving air quality, safeguarding the environment, reducing car dependency, making space for cyclists and walkers and preventing accidents. A number of significant roadway projects have been initiated in the last 15 years. A network of seven motorways will link to form a ring, or a “Sydney orbital” network, around the metropolitan area, totaling about 110 km. The completion of the network will reduce travel time and remove trucks and through traffic from local roads, creating a safer and less congested urban environment.

The design and construction of the final link in Sydney’s orbital motorway network commenced December 2003 with the Lane Cove Tunnel Co. (LCTC) reaching financial closure with the Roads and Traffic Authority of New South Wales (RTA). LCTC engaged the Australian contractors Thiess and John Holland (TJH) to deliver the $1.1 billion project under a design-build contract. Parsons Brinckerhoff (PB) is TJH’s lead design consultant.

LCTC will have a 33-year concession to operate and maintain the facility and recover its investment through a fully electronic tolling system. The project involves funding, building and operating a 3.6-km twin tunnel and associated roadworks to connect the M2 Motorway with the Gore Hill Freeway, providing a much-needed high-capacity link from the north to the city.

Survey creates results

Design began in December 2003 and is now over 90% complete. The tunnel was designed using a three-dimensional MX model. The design process was highly controlled and automated with much of the work progressing simultaneously. Survey information was fed directly into the three-dimensional model. Alignments, cross sections and setting out data were directly extractable for both the surface and underground design and construction. Automatic referencing files helped coordinate the roadway design with the structural components including bridges and retaining and noise walls.

The eastbound and the westbound vehicular tunnels are 3.6 km long and vary in depth up to 50 meters underground. The eastbound tunnel comprises two lanes at the entry portal expanding into three lanes. The third lane becomes an exit ramp lane near the eastern end of the tunnel. The westbound tunnel is made up of two lanes at the portal which are met by a single lane entry ramp from the Pacific Highway to form three lanes which are carried for the remainder of the tunnel.

Tunnel ventilation will be provided by a longitudinal ventilation system for each of the main lane tunnels, supplemented by mid-tunnel supply and exhaust to augment the main system during congested traffic conditions. Normal ventilation generally runs in the direction of traffic with the exception of part of the exit ramp and portals where the airflow is in the opposite direction to avoid portal emissions.

Over the 8.5-km project link there is a series of changes to the surface roads. The 3.5 km of surface roadway on top of the tunnels will be returned to local roads. The 3-km segment of the Gore Hill Freeway is being widened from four to six lanes. The Reserve Road interchange will be significantly modified as right-hand ramp entrances and exits are replaced by left-hand entrances and exits.

The project entails widening or modifying more than 16 bridge structures. Over 40 new retaining walls will be constructed totaling more than 30,000 sq meters, with many as high as 11 meters. Almost 4 km of new and relocated existing noise walls will be constructed, with many as much as 4 meters high.

The project is designed to strict safety standards. The tunnels and roadway will be managed from a state-of-the-art control center, where traffic operations will be closely monitored, with intervention when necessary. There will be direct links to the NSW fire brigade, police and emergency services. Closed-circuit television cameras will be located every 60 meters, traffic management detectors every 40 meters and emergency egress at a maximum spacing of 120 meters for the main lanes and ramps.

The tunnels will be outfitted with electronic variable message signs, radio rebroadcast, emergency exits and cross passages. Fire extinguishers and emergency phones will be located at least every 60 meters. A deluge system capable of delivering 10 l/s per sq meter over a 60-meter roadway segment is a key part of the response to a major fire.

Interesting enough

The design objectives of the project are not only to improve mobility for vehicles, public transport, cyclists and pedestrians, but to improve the corridor and make the travel experience aesthetically pleasing and interesting where possible, as well as enhance the surrounding area and existing vegetation. The project employs landscape treatment, materials and finishes that are ecologically sound and minimize maintenance.

A framework urban design and landscape plan was prepared in early 2004 in consultation with four city councils and other relevant authorities. The plan presented an integrated urban design solution that was reflected in the final design and is consistent with the design principles established in the Environmental Impact Statement and relevant planning documents. Design principles included reinforcing a sense of place at key locations, providing architecture that enhances the journey and the surroundings and reinforces the various bushland and other environments along the route.

Specific geographic components of the project, in both the built form and landscaped areas, will provide integration and interaction with the engineered solutions. These built elements include the tunnel portals, the bridges, retaining walls, noise walls, tolling roadside equipment, the control building and surface substations. Pedestrian and cycle elements include footpaths and paving, pedestrian crossings, street furniture and fixings. Landscape elements include the proposed treatment, finishes and materials of exposed surfaces.

Environmental management was an important aspect of planning, designing and delivering the project as well, covering matters such as controlling noise and dust, identifying and protecting areas of environmental significance and traffic management. The project had to gain approval and licenses from the Environment Protection Authority. Environmental management reports and construction method statements are available to the public.

Community involvement also is an important part of the project development, from planning to delivery of the constructed facility. Local communities are provided with relevant and timely information before and during construction, through community liaison, via the Internet on a project website, through a public display center and other measures. As part of community involvement policy, TJH developed and utilized an extensive community involvement program to ensure residents and businesses were consulted and received information about work taking place in their local areas.

Quick and concise

Construction began in May 2004. In June, the first of seven 300-kW roadheaders began excavating the 800,000 cu meters of rock needed to complete the project. The tunnels are being predominantly excavated in Hawkesbury Sandstone, a good tunnel medium. The roadheaders weigh over 100 tons and are capable of excavating up to six linear meters of tunnel a day.

The three-dimensional model of the tunnel design is fed directly into the roadheader’s laser guidance system for precise excavation. Since excavation began, the contractor has exceeded the record for underground construction three times, most recently when 4,000 cu meters of excavation was accomplished by one roadheader in one week.

The excavation is estimated to be completed in early 2006, and then the tunnels will be outfitted with traffic management and mechanical and electrical systems. Surface construction also began in 2004.

More than 104,000 vehicles per day are projected to use the Lane Cove Tunnel in its opening year. The project will allow for faster journey times between the city and Sydney’s developing northwest sector. The Sydney orbital network will be fully operational, resulting in reduced traffic on the local roads above the tunnels, less noise and improved air quality, as well as improved bus service. There also will be a cycleway across the project that will form part of a continuous bicycle route northwest of Sydney Harbour.

The completion of the Lane Cove Tunnel Project in 2007 will mark an important engineering achievement in designing and delivering a major transportation infrastructure facility with minimum impact to the traveling public. It represents an important outcome in congestion, environmental and safety management.

About the author: 
Rozek is a project design director for Parsons Brinckerhoff, Sydney, Australia.
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