“As a company, we had no real knowledge of grouting technology. We would drill the faults underground and another contractor would grout them but I could see that the product they were using was not always giving the best results,” he said.

“Around the same time, one of our clients asked if we would consider doing the full job for their operation; up until then, we specialised in drilling and reinforcement installation for consolidation. So I researched and sourced a system capable of mixing and applying grout. The product itself was good but the technical support was nowhere near as comprehensive as we needed.”

Then McPhedran came across Multigrout Australia managing director Bruce Grant.

“The Multigrout system had traditionally been used in civil tunnelling but I soon learned that Bruce was committed to getting it into the mining industry as well and that gave me cause for hope,” he said. “Finally, I had found a guy who had some idea what he was doing and who could give us the support we needed as our company expanded into the grouting game. We trialled the system with a few of our customers, and Multigrout Australia provided the training and phone support.”

Multigrout is a high-performance grout injection system originally used in civil applications for groundwater control and ground strengthening but recently adapted to the longwall mining industry. Capable of producing stable grouts with minimal bleeding or water loss, the system can be used over a wide range of water-cement ratios and, according to Grant, has enhanced penetration capabilities and improved consolidation effects compared to traditional cement-based grouts.

“There have been numerous cases where traditional cement grouts have performed poorly which can pose a significant safety and investment risk to companies,” he said. “The primary advantage that Multigrout has over others on the market is its versatility in a wide range of strata conditions to penetrate and completely fill joint structures, enhancing the characteristics of the ground mass.”

Marketed by Elkem ASA Materials in Norway and introduced to Australia in 2001, the system is made up of four material components – ordinary Portland microfine or ultrafine cement, a microsilica-based additive known as GroutAid, a super-plasticiser and a time-controlled, mineral-based cement known as Blocker Grout. GroutAid is believed to increase the efficiency of injection grouting by improving the plastic and hardened properties of the grout, allowing it to be injected into soils and cracks in rock and concrete, while Blocker Grout works as a troubleshooting product in difficult ground and “water fighting” conditions.

Grant said Multigrout is attracting increasing interest from coal mining companies, although he stressed it is still very much early days.

“There has been a great lack of knowledge and understanding of high-performance grouting, particularly in the underground mining industry, and we will be working with the market to improve that knowledge and demonstrate exactly what can be achieved with the right product,” he said.

In the meantime, McPhedran and his team have used the system on contracts at contracts at several Queensland coal mines including Oaky Creek, Newlands and Moranbah North, however he believes they are yet to realise its full potential.

“We have definitely taken a step up when it comes to our fault consolidation work. Every fault we deal with has different characteristics and we believe have found a system that is capable of coping with those variations,” he said.

“Multigrout is a very specific product that you can successfully work with if you have the right gear and the right method of applying it. We believe the additives in it make it a much superior, workable alternative to what is generally available on the market. We have to have a grout that stays “alive” for a reasonable amount of time so we can pump it into the fairly long holes and varied ground that we encounter underground.

“The next step for us is refining the design and application of the product and that will be a long process because every fault is different and every mine’s needs are different.”

Australia's Mining Monthly