With an ever-increasing population, the northwest district of Sydney is currently believed to be the region with the highest car ownership density per household in Australia. It is expected that over the coming decades, some 200,000 extra residents will arrive in the area taking the population to in excess of 600,000.

One of several TBM breakthroughs on the project

In order to alleviate pressures on the regions road network and ensure, for the first time, a reliable public transport service, the local authorities are currently in the construction phase of the Sydney Metro Northwest project.

Sydney Metro Northwest will be the first fully-automated metro rail system in Australia. It is currently on track to open to customers in the first half of 2019. It will add eight new railway stations and 4,000 commuter car parking spaces. Train services into Sydney city centre will operate every four minutes at peak times and with at least 15 trains an hour at other times.

The construction contract was awarded in June 2013 to the Thiess John Holland Dragados (TJHD) joint venture. The project includes excavation of twin 15km long running tunnels from Bella Vista to Epping. On average, the tunnels are 29m deep and 58m deep at the deepest point. The 6m i.d. running tunnels are being excavated by four TBMs. Once completed these will be Australia’s longest rail tunnels and this is the first project in Australia to use four TBMs simultaneously, with TBMs 1 and 2 launched from Bella Vista to complete 9km to Cherrybrook and TBMs 3 and 4 launched from Cherrybrook to exavate 6km to Epping.

Three tunnelling work sites were established, each of the sites providing support services including power, ventilation, muck handling systems and a cement grout mixing plant. Ground conditions along the route comprise about 60% Sydney sandstone with the remainder being shale. Excavation of the 15km of running tunnels by the four NFM TBMs was completed with a final TBM breakthrough in January 2016.

Segment production in full swing

Segmental lining design and production

While directional control and accuracy of the TBMs was a vital part of the construction project, there was also a need for precise operation throughout the manufacture and supply of tunnel lining segments.

First the correct segments had to be manufactured and then delivered to the right TBM at the right time to ensure smooth uninterrupted progress of all the machines.

There was also a requirement that once installed, the segmental lining at the Epping site had to be monitored to ensure that no post-installation deformation or tunnel movement outside of the pre-set limits of the contract were experienced.

According to Jeremy Glasgow, Project Manager for the project’s Kellyville segment precasting facility: “The original thinking was that we needed to streamline our processes and remove the opportunity for human error as much as possible. With the total of 98,244 segments needed over the whole project, it was worth looking into systems that could not only remove human error but remove actual work required to be undertaken by individuals.”

Having researched available systems on the market, the pre-cast team noted that while there were alternative solutions, at the time there was nothing that appeared to encompass all operations in the same way as the Segment Documentation System (SDS) system from VMT.

Human error removed by VMT systems

Segment production for four consecutive TBM drives

Not only did the SDS system offer an effective way of removing human error and human functions from the production and delivery operation, it also met a requirement from the client to make available certain data throughout the process. It was therefore decided to run the casting yard operations using the VMT SDS system.

Complex demands

What was not fully appreciated at the outset of the segment production process was just how complicated the operation was to become given the scale of the project, with multiple storage yards and job sites and two production carousels.

To maintain high levels of quality assurance the SDS system was designed with significant levels of data protection to ensure only those with authorisation had the necessary access. Given the range and number of personnel requiring access to project data, however, initial set-up of the SDS network had to be revised to allow interface with all different aspects of the process. Had the requirement been fully appreciated at the development stage, it could have been allowed for in the initial design and avoided subsequent additional workload but through close cooperation, the contractor and VMT teams overcame the obstacles.

Precision segmentally lined running tunnel

“This project showed us how challenging it can be to pre-empt how a system needs to work on a site as complex as this,” said Matt Jarvis of VMT, “and also how important it is to involve the right people and ask the right questions before you start. This project also shows that VMT does not simply sell a system and walk away. Once we worked through the initial difficulties, the SDS system did its job very well. We - both the contractor and the VMT team - can be proud of our efforts to confirm the project met its targets in terms of segment production and installation.”

For VMT GmbH, Manfred Messing, Managing Director said: “The Sydney Metro Northwest project was one of those that, despite many years of experience in the various aspects of the tunnelling industry, still managed to teach us all some very interesting and, for future works, important lessons in terms of network connectivity and accessibility in relation to the relatively new SDS system. The fact that in the end our system gave to the contractor what they needed highlights both its flexibility across a range of project complexities and our team’s ability to adapt the system when required.”

Deformation monitoring

For tunnel deformation monitoring at the Epping site, TJHD utilised an in-house software solution for viewing and reporting data. However, to obtain the data in the field they wanted a simple automated hardware solution.

Deformation monitoring of the running tunnels at Epping and beneath existing surface rail infrastructure

Dr Sascha Schneid, Product Management for VMT GmbH developed a TUnIS.deformation ‘light’ concept based the TUnIS Deformation Monitoring software system supplied by VMT. The set-up used a TM30 total station, which showcased the benefits of quality instrumentation, a control box and a hosted web server.

Deformation monitoring at Epping helps to evaluate and assess geometric changes in the tunnel structure, although the system can be used for a variety of monitoring applications. Sensors are installed within the area of influence and their measured values are continuously analysed. When, and if, critical changes occur, warnings and alarm messages (via email, SMS message, or mobile calls), are sent automatically to responsible personnel for immediate action to be taken.

At Epping, prisms were installed on the tunnel structure and monitored using the TUnIS system, detected any movement within. Processed data was then exported in CSV format to the customer’s FTP server for full analysis.

In addition to the system itself, VMT provided system quality control and maintenance, which included, at a minimum, a weekly report on the system status. This assures the customer that the system is working correctly. VMT identifies any errors or shortfall in the monitoring system accuracy, enabling the project team to act quickly.

Ultimately the system provided a low cost, low maintenance and high performance concept that fulfilled all the customer requirements.