Snowy 2.0 teams are monitoring a surface depression that has emerged above the headrace tunnel at Tantangara.
The integrity of the tunnel has not been compromised, and tunnelling is continuing while work to remediate the surface depression above tunnel boring machine (TBM) Florence is carried out. There is a safety exclusion zone around the surface depression.
Ensuring the safety of the Snowy 2.0 workforce and members of the public is the priority for Snowy Hydro and principal contractor Future Generation Joint Venture.
The Snowy 2.0 teams are conducting geophysical investigations of the area and continuing grouting operations and probing from the TBM.
As previously indicated, the ground conditions encountered by the TBMs on Snowy 2.0 have been highly variable, ranging from very loose, sandy ground to extremely hard rock in fluctuating groundwater conditions.
TBM Florence is transitioning from soft material into harder rock conditions.
Tunnel boring machine (TBM) Florence continues excavating the Snowy 2.0 headrace tunnel at Tantangara following successful reinforcement works.
As anticipated, the ground conditions encountered by the TBMs on Snowy 2.0 have been highly variable, ranging from soft, sandy ground to extremely hard rock.
The Snowy 2.0 teams have been working collaboratively to safely navigate the softer ground conditions experienced at Tantangara, including high groundwater inflows.
As part of the tunnelling process we probed in advance of the TBM, identifying the soft ground ahead, and then consulted with our expert design consultants to plan for stabilisation works. TBM Florence has been specifically designed to encounter these variable ground conditions.
Consolidation grouting around the perimeter of the headrace tunnel, and internally, the installation of steel ribs to reinforce the concrete segmental lining in the soft zone, have been carried out to ensure stability and manage groundwater inflows. Additional instrumentation to monitor ground performance has also been installed.
Successful execution of the reinforcement works by Snowy 2.0 principal contractor Future Generation Joint Venture (FGJV) is enabling the TBM to carefully thrust off the segments and move forward.
Snowy Hydro expects variable and soft ground conditions to occur in sections of the very long 17-kilometre headrace tunnel. Further ground improvement works – a typical tunnelling process – will be carried out where required so the TBM can safely advance.
Snowy Hydro and its Future Generation Joint Venture partners are working towards the successful delivery of Snowy 2.0.
Click here for images of TBM Florence and the reinforcement works.
Snowy Hydro is again trialling the use of unmanned submersible vehicles to monitor the condition of hard to access Scheme assets.
While the Snowy Scheme is one of the civil engineering wonders of the modern world, many of its assets are difficult to reach due to the Snowy Mountains terrain and the challenges associated with the sheer volume of water flowing through the Scheme.
With the help of Perth-based company Synaya, the Civil Engineering and Dam Safety team are using a Mini Remotely Operated Vehicle (ROV) to conduct inspections of some of our hard to access assets, such as the Guthega Surge Tank and Island Bend intake structure.
The ROV is a small, submersible vehicle operated from the surface of the water via a tether. Equipped with miniature high-resolution cameras, lights and video recording equipment, they can be used to assess the condition of underwater civil assets. The information they collect determines future inspection frequencies, maintenance requirements and accurate scoping of projects.
The Mini-ROV, a Seabotix LVB150 weighing approximately 12 kilograms, was used as part of a successful trial where a variety of tests were performed to assess its manoeuvrability, visibility and access. Results showed that these observation vehicles reduce the safety risk to staff by eliminating the need for someone to physically enter tunnels for inspections, reduce the environmental impact associated with dewatering assets and they also reduce the need for extensive outage times.
It also provides access to extensive visual data, which can be referenced in the future to more accurately assess what stage of the asset’s lifecycle it’s in.
Using technology of this kind is not new for Snowy Hydro; in 2013, we used a larger unmanned underwater vehicle to inspect multiple tunnels within the Scheme for maintenance. We were awarded an Australian Business Award for Innovation and also broke a world record for the longest, unmanned underwater tunnel inspection. We have also trialled the use of unmanned aerial vehicles, or drones, to inspect our assets from the air.
In future, this unmanned technology will continue to be used to inspect difficult to access assets of the Scheme ensuring the safety of our people and keeping our assets in peak condition.