Major works ramping up on NorthConnex

Initial excavation and tunnel shaft works on the $3 billion NorthConnex project in NSW is now underway, signalling the next phase of this large-scale undertaking.The St Barbara blessing ritual is a tradition carried out on major tunnelling projects around the globe.

St Barbara, the patron saint of those who work underground or in tunnels, has been a key figure for the labourers who undertake such daring projects for centuries.

With major tunnelling works ramping up for the $3 billion NorthConnex project in NSW, a traditional blessing ceremony was carried out last December.

Father Harry Kennedy, assistant priest at the parish in which the twin tunnels of the NorthConnex project are being constructed, carried out the blessing and contributed a statue of the saint, which now sits at the tunnel entrance at the project’s Wilson Road compound.

The ceremony, while spiritual at heart, gives peace of mind to those tackling the project all the while emphasising safety, which is particularly important given its sheer scope.

The NorthConnex project involves the construction of twin nine-kilometre tunnels under Pennant Hills Road, linking the M1 Pacific Motorway at Wahroonga to the Hills M2 Motorway at West Pennant Hills.

Interchanges will be built to the north and south of the project to accommodate connections at either end of the tunnels. When complete, it will link Sydney’s north to the Orbital network and form part of the National Highway route.

The NSW and Federal Governments, Transurban and the M7 Westlink Shareholders will build, operate and maintain the tolled motorway. A Lendlease Bouygues Joint Venture (LLBJV) won the competitive tender to design and construct the project.

Initial excavation and tunnel shaft works at the tunnel’s four entrance sites – the northern interchange, Trelawney Street, Wilson Road and the southern interchange – are underway and major tunnelling will begin in the middle of the year.

NorthConnex Project Director Robert Ioffrida talks to Roads & Civil Works Magazine about the massive scope of the project and the feats required to accomplish this momentous task.

“Every three to four weeks between the end of April and November/December we will be launching a new road header,” he says. “A total of 19 road headers are going to be excavating the tunnel.”

Underground works will continue until this major phase of the project reaches its anticipated completion date in December 2019.

Given the “muffin” profile of the tunnel design, Mr. Ioffrida says tunnel boring machines (TBMs), while considered, were not chosen as the most appropriate machinery for the job.

“The shape of the tunnel doesn’t lend itself to the TBM. Had we used a TBM we would have had to come back for more complex excavation work afterwards,” asserts Mr. Ioffrida.

Precious weeks could be spent constructing the TBMs on site.

On the other hand, the road headers chosen for the project can be put together and ready to work relatively quickly. “For us, using road headers was the most efficient way program-wise,” he adds.

The main tunnels will be built wide enough to allow a third lane in each direction to cater for future traffic requirements.

With a clearance height of 5.3 metres, the tunnels will be the highest in the state and possibly even Australia, according to Mr. Ioffrida.

Once each road header has commenced on site, it will be the most number of the machines used on one road project in Australia.

“If you take the last three major tunnelling projects in NSW and the number of road headers used and add those together, they won’t even amount to this,” says Mr. Ioffrida.

Having 19 large road header machines undertaking excavation work in such a confined space is just one of the many complexities Mr. Ioffrida says makes the project such a challenge.

The nature of the tunnel at such depths (the lowest point being 93 metres below the surface) also brings about some complex engineering conundrums. “At that depth, the stresses in the rock are going to be horizontal, so we have to cater for that which makes the tunnelling process a little bit slower and a lot more challenging,” he says.

Another major challenge is how to successfully move the estimated 2.3 million cubic metres of excavated spoil from site to surface.

The shafts to the surface, 12 by 15 metres in area, are too narrow and deep to bring the spoil up by traditional methods such as gantry cranes and skip bins.

A high-angle conveyor system, typically used in deep mining, has been selected to move the spoil up the shaft.

It is the first time this technology has been used on an infrastructure project in Australia – marking another milestone for the project.

“While it sounds very simple, it’s taken us about a good year to go around the world and put the different technologies to the test and make sure they actually work,” he says.

The spoil will be redistributed for use in select points around Sydney. These include a redevelopment in Sydney’s west and another to the city’s southwest.

A large proportion of the spoil has also been proposed for distribution to the old Hornsby Quarry, which the local council intends to fill and turn into parkland.

This redistribution of spoil serves as one of the projects most significant environmental outcomes, which, Mr. Ioffrida explains, is a main focus point for the project team.

“On this project we’ve set some very high standards,” he says.

The LLBJV is aiming to achieve an “Excellent” rating level under the Infrastructure Sustainability Council of Australia’s (ISCA) Infrastructure Sustainability (IS) Rating Scheme.

“That has not been done before on an infrastructure project of this significance,” adds Mr. Ioffrida.

The project needs to achieve 50 points or higher in some 24 different categories as laid out by the IS Rating Scheme.

These include the likes of waste, ecology, land and management systems. “It could be recycling waste material on site through to the type of lighting that you use or whether or not we use biodegradable fuels,” he says.

Some of these sustainable systems are already implemented on-site.

Acoustic sheds have been built across the tunnel shafts at each of the four major tunnelling sites. These are designed to minimise noise and dust, reducing the impact of excavation work for local residents and businesses.

Mr. Ioffrida explains that achieving such sustainable milestones on the project is added value not just for the workers building the project, knowing they’re undertaking a “green-minded” project, but for asset owners and the public too.

On-site management systems and safety precautions on the project are also setting the bar for infrastructure projects in Australia, particularly through the technological solutions that are being employed.

“The safety and the wellbeing of our people is our number one priority,” says Mr. Ioffrida. “We’re working in a confined space with lots of heavy equipment.” The LLBJV has been working with a technology provider to install safety braking technology on the large tunnelling plant that will be employed below the surface. Should a worker stray into the path of the moving machinery, the sensor-based braking technology will either slow the equipment or bring it to a complete stop.

The tunnel worksites will be fully WiFi accessible. “A lot of tunnel projects have tried to do it in the past but haven’t succeeded,” says Mr. Ioffrida.

He says the LLBJV team is currently working towards making underground WiFi on the project a reality. This will help reduce the need for particular site inspections as tablets and smartphones can negate the need for some individuals to physically be there.

“We’re also employing quite a unique smartcard system,” says Mr. Ioffrida. “All of the workers will have an access card complete with a QR Reader with access or no access to certain areas so people with the right training and the right skills will be in the correct areas.

“This is the first time this type of technology has been used in an infrastructure project and we’re quite happy with how it’s going.”

When finished in 2019, NorthConnex will provide a vital connection for Sydney and NSW, with a particular impact on freight routes.

Mr. Ioffrida says that heavy vehicles will benefit from the project as it provides a vital link for transportation from northern Brisbane or Newcastle through to southwestern Sydney and all the way down to Melbourne.

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