Precision roadheader and rockbolting on WestConnex 20 Dec 2018

With the last two sections of the AUD$16.8 billion WestConnex highway project in Sydney now awarded for the M4-M5 Link and its Rozelle underground interchange, the most significant road infrastructure project in Australia is on track for being fully opened to traffic in 2023.

Full scope of the Sydney WestConnex project

At about 30km in length, WestConnex comprises the widening and extending underground of the M4, duplicating of the M5, and connecting the two underground motorways to provide a long overdue and seamless free-flowing western bypass of Sydney’s central business district for motorists.

The majority of the ground conditions along the route comprise Sydney sandstone, a geological formation favourable for tunnelling. It was decided that due to accessibility difficulties for the construction equipment and impact on the surrounding area, and its population, the tunnelling works would be completed utilising roadheader equipment as opposed to tunnel boring machines and supported with rockbolts and shotcrete.

Excavation of the highway project tunnels began in 2015 when excavation of the 5.5km twin-tube three-lane tunnels on the M4 underground section between Homebush and Hubberfield was awarded in 2016 to the CPB Contractors/Samsung/John Holland JV using 21 roadheaders and 11 Robodrill bolting rigs across four construction access sites. Construction also included 50 cross passages connecting the parallel highway tunnels making a total tunnelling effort of around 14km.

A roadheader at work

The first roadheader was commissioned and started tunnelling on the M4 phase of the project in July 2016. With the 21 roadheaders operating, production was running at an average of about 25m to 30m per week. Rockbolting support required that clusters of bolts were positioned and installed quickly and accurately each day and within each shift.

With excavation completed in December 2017, the project team is moving on to mechanical and electrical fit-out and road deck pavement work is progressing.

The 9km of twin three-lane tunnels for the new M5 underground highway, from Kingsgrove to a new St Peters Interchange (Fig 1), was awarded in 2016 to the CPB Contractors/Dragados/Samsung JV. Excavation is nearing completion after reaching peak production with 20 roadheaders and 11 Robodrill bolters working on a 24hr/day, 7day/week basis from construction sites at St Peters Interchange, Arncliffe, Bexley and Kingsgrove. The M5 project includes excavations of some 75 cross passages.

Shotcreting to provide immediate support

For the excavation work on both contracts, a major contribution has been the software and hardware guidance systems supplied by specialist tunnel construction support software developer and provider VMT.

To ensure the roadheaders excavate the designed tunnel profile and that bolters position their tunnel support correctly, accurate and reliable navigation systems have been required. This is where the VMT expertise came in. Having bid to provide navigation systems for both WestConnex M4 and M5 tunnel contracts, VMT was extremely pleased to be awarded both contracts. The challenge for VMT was to deliver, commission and support some 57 navigation systems between May 2016 and 2019.

The navigation equipment contracts required VMT to supply:

• TUnIS navigation equipment for all roadheaders and bolters
• TUnIS office servers and software for each site office for the collection, analysis and management of machine data.
• Permanent service on site for system commissioning and support, plus training of surveyors, site engineers and operators.

Positioning a rockbolt as part of the tunnel support operation

While development processes try to take into account all feasible problems to ensure a smooth running of the hardware and software when in use, real life situations often challenge those.

In terms of performance, the VMT engineers on site agreed that with the newly developed TUnIS Roadheader software being used for the first time (it was previously SLS software), the project was one of the biggest challenges faced to date. However, it was proven that the programmers had completed a great job to deliver the software before start of tunnelling.

In terms of the new hardware, previous hardware used on roadheaders had become obsolete, and needed to be updated. The particular environment in tunnels and the continual vibration of the excavation machines had to be accounted for and again to date all hardware has proven to be reliable.

One of the biggest challenges for VMT has been the number of machines to install, survey and to commission and this was quite an intense operation. Having completed the installation the second part of the process was to train all the people how to use it. With operators, surveyors, electricians and engineers all involved with maintaining the VMT guidance equipment, more than 100 people were required to learn the systems from VMT engineers.

Breakthrough of one of the roadheaders on the M5 road tunnel

Offering roadheader navigation systems since 2005, the existing VMT system could not originally meet WestConnex requirements to collect, analyse and manage data from all roadheaders and bolters. Furthermore, the need to integrate the data output of the navigation systems with the main office monitoring software, which was also internet connected, meant that - with such a huge number of units in operation across the duration of the projects - VMT needed to effectively redesign the new navigation systems. This meant that significant development of the basic roadheader navigation system was required.

Having to involve virtually all of the company’s staff, this development process was a significant challenge for VMT and required cooperation with the roadheader and bolter machine manufacturers so that the main machine body utilises the VMT navigation system to position the roadheaders and bolters at the correct location for precise profiling for the roadheaders and accurate installation of bolting patterns with the operators having the knowledge that the machine body is located precisely.

The type and range of information that the systems are required to collect and process includes not only positional data and profile data but also operations data such as power consumption, hydraulic pressures and other operational factors that can be used to monitor machine performance remotely. Information such as the path of the cutterhead in relation to the face and the pre-designed profile of the tunnel cross-section was also collected for post-excavation analysis which would enable cutter effectiveness in relation to the local geology to be established and the accuracy of the cut to the required profile to be understood. This information could also be used for operator training purposes.

Finished three-lane tunnel profile

Commenting on the WestConnex projects Alexander Höfer, VMT Product Manager for the contracts said: “The WestConnex projects have been very much the biggest challenge faced by the VMT staff to date. However feedback from the tunnelling teams has been excellent and our staff both in Australia and at the head office in Germany can be proud of our achievements. What we at VMT can say is that we played our part and played it well. My congratulations go to the whole team.”

Commenting on the progress to date VMT Project Engineer, Dan McPhail said: “As with all underground construction projects, there have been challenges, but the VMT equipment provided, installed and supported by the onsite team has worked extremely well in the conditions of the WestConnex operations. The teamwork between our own staff and the contractor has proven to be a major factor in the successes achieved to date.”