Mining solutions company Sandvik has introduced a new ground reinforcement concept for tunnelling and mining applications which the company claims is faster and easier to install than traditional systems while giving better ground support.
The Sandvik Mechanical Dynamic (MD) Rockbolt was designed and developed in Australia by Sandvik Mining’s Newcastle-based Manager for Rock Reinforcement Development Mietek Rataj, and is set to replace a range of ground support systems including resin bolts, stiff splitsets and even cable bolting to a certain degree.
“The problem with resin bolting is that it’s not reliable due to the relatively large-diameter holes which have to be drilled in hard rock mines,” he says.
“This is because the resin is frequently poorly mixed so the bolts are not anchored properly in the rock.
“In addition, their installation can be very slow, and they are relatively rigid two-pass bolts, so they are not suitable for dynamic ground conditions,” Rataj adds.
“In contrast, the MD Rockbolt is a dynamic bolt which is able to yield and withstand changing ground conditions, it’s a one-pass system, with no need for any grouting.”
Sandvik’s MD Rockbolt Product Line Manager Peter Young says the new system is a permanent bolt that is less sensitive to poor ground conditions, such as weak rock mass.
The MD Rockbolts are galvanised, come in 2.4m and 3 m lengths and are rated to hold up to 30 tonnes.
Young says response to the system has been positive.
“We’ve had feedback from one customer that they had an area of ground where they struggled to install just a few resin bolts because the ground was so poor; over that same period of time, they had successfully installed 100 MD Rockbolts,” he says.
“All up, this system saves money and provides significantly better ground support than the alternatives.”
Pricewise, Young says the MD Rockbolts are competitive with other ground bolting systems.
“Resin bolts may be less expensive, but by the time you add in the resin, plus all the time and labour required, and the resin wastage, then our system comes out well in front,” he says.
“They are a direct replacement for resin bolts, so anywhere you can put in these bolts, you can use MD Rockbolots – plus you can put them into very challenging or diffciult situations where other bolts just don’t work.”
Young adds the new concept might even replace cable bolting to a degree.
“There is one application in Australia where a mine Ws able to delay the sintallation of their cable bolts from 25 metres of driveage out to 50 metres,” he says.
Sandvik Mining has released the MD Rockbolt following a two year trial at Victoria’s Fostervile underground gold mine – where the mine was experiencing high levels of deformation in difficult conditions.
Fosterville has since replaced all its resin bolts with MC Rockbolts and the system has gone into use in mines in Mt Isa and Western Australia.
Sandvik adds the system is being trialled in South Australia and Tasmania, as well as mines in Canada and China.
Young says an in-situ dynamic test on the MD Rockbolt was recently carried out at Kalgoorlie Consolidated Gold Mines in Western Australia with results strongly indicating suitability of the system for ground support in seismic conditions.
“Additionally, the WA School of Mines has recently carried out drop testing, and will be releasing its results shortly,” he says.
Find out more about the system on Sandvik Mining’s website.