Global Surface Mining is using mining technology and applying it to a number of civil construction projects to avoid expensive drilling and blasting.
Hitting hard rock on a construction site can grind productivity to a halt. It can slow down road building, rail construction, tunnelling and excavation, often leading to a need for drilling or blasting.
Sometimes drilling and blasting isn’t an option, as it would cause too much disruption to nearby traffic and damage nearby infrastructure. It can also be expensive and time consuming, requiring multiple teams and safety experts on site.
One solution to these potential issues comes from the mining world, namely the use of equipment traditionally used in surface mining. Global Surface Mining (GSM) is using the Wirtgen 2500 Surface Miner (SM), a machine that functions similar to a road profiler, but with much more cutting power to slice through hard rock.
Damian Nice, Operations Manager for Global Surface Mining, says the selective mining machines are able to cut through materials in half a metre-thick layers at a time.
“The system is more efficient than drilling and blasting as it minimises disruption to other activities. For example, if you’re working close to an existing road and the traffic needs to continue flowing, the surface miner can cut material without any disruption to traffic,” Mr. Nice says.
“When drilling or blasting is involved, there’s also the chance for fly rock to damage nearby infrastructure. Because of this, using a surface miner to clear rock is much safer with no explosives needed and fewer interruptions to traffic.”
Because the machine only requires one operator, Mr. Nice says it is cheaper and safer than the equivalent drill and blast or excavation crews.
ON THE ROAD
GSM has assisted civil construction projects around the country with their fleet of surface miners. Fulton Hogan, which was looking for an alternative to rock breaking on the section of the Foxground and Berry Bypass section of the Princes Highway upgrade in NSW, called in GSM to assist with excavation of the rock.
“The rock along the alignment was very consistent and hard. Initially Fulton Hogan had drilled and blasted in some areas and employed rock breakers elsewhere. The blasting caused damage to the rock in the walls and the rock breaking was very slow and expensive,” Mr. Nice says.
The key objectives for the project were to keep the existing road safely open at all times, minimise the damage to the underlying rock in the batters and floors, eliminate over-excavation, increase production to improve the project program and reduce overall costs.
To do so, GSM mobilised a 2500 SM, which rapidly milled the rock up to the edge of the existing Princes Highway. Around 95 per cent of the material produced by the surface miner was crushed to a size less than 100 millimetres, creating a material that was recycled and used along the alignment in fill areas.
The 2500 SM with GPS control was able to trim the floor of the road to subgrade level without disturbing the underlying rock, meaning they were able to eliminate any over excavation and additional cost of subgrade preparation.
Mr. Nice says the initial scope of the project was 50,000 cubic metres, but due to the success and cost efficiency of the surface miners, the scope of the project was increased to 140,000 cubic metres.
Similarly, in 2015 GSM were contracted by the Northern Territory Department of Infrastructure to excavate rock along the Tiger Brennan Drive duplication alignment. The rock varied from soft free dig material to relatively hard phyllite with interbedded sandstone and porcellanite.
Traditional drilling, blasting or rock breaking were problematic alongside the busy road and so a 2500 SM was brought in. It was able to achieve similar results as the Berry Bypass interchange project.
Mr. Nice says the process for rail projects is very similar, especially when hard rock is getting in the way of cutting down to a foundation.
GSM had been contracted by mining and civil construction company NRW to assist excavating the rock cuttings along the Roy Hill rail alignment.
Traditional methods had been employed on the project by NRW to remove the rock, including drilling and blasting through the hard granite. This would create blast affected material below the required level of the rail line embankment. NRW would them remove the blasted material before sourcing approved fill material to build the level back up to the design’s required level.
Mr. Nice says this method was costly, in particular when the blasts became shallow or when rock breakers were brought in to trim areas that hadn’t been blasted properly.
GSM mobilised two 2500 SMs to cut through the rock where shallow blasting had become too expensive and to provide thin cuts in previously blasted ground. The surface miners were able to accurately mill the rock to the required level, which Mr. Nice says eliminated the need for any back filling.
The machines have been used all around Australia, thanks to their size and weight. The 2500 surface miners weigh around 90 tonnes in transport, which Mr. Nice says allows them to be sent to projects where they are most needed.
German built and designed, the Wirtgen surface miners are being upgraded by GSM to help it fit in these Australian projects.
“We’ve developed a dust suppression system to minimise how much dust is created. Ensuring dust on projects is reduced as much as possible as this important for projects in built up areas and urban spaces.”