New Sandvik bolting system is faster, easier and provides better ground support

By: Sandvik

Date: 25.03.2013

March, 2013: Sandvik Mining has introduced a new concept in ground reinforcement for underground hard rock mines that is faster and easier to install than traditional systems, while giving better, stronger ground support.

New Sandvik bolting system is faster, easier and provides better ground support

Designed and developed in Australia by Sandvik Mining's Newcastle-based Manager for Rock Reinforcement Development, Mietek Rataj, the Sandvik Mechanical Dynamic (MD) Rockbolt replaces a range of ground support systems, including resin bolts, stiff splitsets, and even cable bolting in some instances.

"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," said Rataj.

"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," said Rataj.

"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," he said.

According to Peter Young, Sandvik Mining's product line manager for the MD Rockbolt, the new system is a permanent bolt that is less sensitive to poor ground conditions, such as weak rock mass.

It is easier to install, and there are far fewer issues during installation, so that operators prefer working with it, he said.

MD Rockbolts are galvanised, come in 2.4 m and 3 m lengths, and are rated to hold up to 30 tonnes.

The system is particularly suitable for moving ground conditions as it slides at high load, maintaining high capacity support.

"Similar to a standard friction bolt, the MD bolt is installed in a single pass, with a simple twist to anchor it once it's in the ground," he said.

"Installation is very quick and easy compared with other types of ground support," he said.

"There's no chemical insertion or grout injection required, and no need to come back later to tension up the rebar.

"We've had feedback from one mine 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.

"All up, this system saves money and provides significantly better ground support than the alternatives."

Young said the MD Rockbolts were competitive in price 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 said.

In addition, MD Rockbolts provide a better ground support solution.

"They are a direct replacement for resin bolts, so anywhere you can put in these bolts, you can use MD Rockbolts – plus you can put them into very challenging or difficult situations where other bolts just don't work.

"They may even replace cable bolting to a degree. There is one application in Australia where the mine was able to delay the installation of their cable bolts from 25 metres of driveage out to 50 metres," said Young.

Sandvik Mining fully released the MD Rockbolts onto the market in June 2012, following a two-year product trial at Fosterville, Victoria's largest gold mine (see sidebar for more on Fosterville's experiences with this trial).

This process involved 10 separate trials over two years beginning in January 2009, trialling more than 300 bolts, including several different designs.

In November 2010, MD Rockbolts were first incorporated in Fosterville's ground control plan, ultimately replacing resin bolts in the majority of areas where very high deformation was expected.

In May 2011, a new ground control system was designed around MD Rockbolts for areas of expected high deformation, and by August 2011 they had replaced all resin bolting on site.

Operator feedback on the MD Rockbolts at Fosterville has also been very positive, said Young.

"The operators love the MD Rockbolt, because it is so much quicker and easier to install."

Since then the system has gone into use in mines in Mt Isa and Western Australia, and is being trialled in South Australia and Tasmania, as well as mines in Canada and China.

"There is potential for MD Rockbolts to be used in every hard-rock underground mine in Australia," Young said. "Not only are they quicker and easier to install, they provide much more reliable and consistent installation and performance.

"Recently an in-situ dynamic test on the MD Rockbolt was carried out at Kalgoorlie Consolidated Gold Mines (KGCM) in Western Australia, with the results strongly indicating suitability of the system for ground support in seismic conditions.

"Additionally, the WA School of Mines (WASM) has recently carried out drop testing, and will be releasing its results in the next few weeks," he said.

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