The Australian Coal Association Research Program research into the analytical method, ongoing for the past three years, has been conducted by Seedsman Geotechnics director Dr Ross Seedsman.

Seedsman will introduce the general concepts in free seminars at the University of Wollongong on February 11 and at the Queensland town of Emerald on February 25.

Seedsman told International Longwall News the analytical method was not a replacement for the empirical approach, and both methods could be used together by geotechnical engineers to achieve a range of better outcomes.

“A good design engineer looks at his or her problem in more than one way,” he said. “And up until now we have had only one method of doing it.”

While acknowledging the empirical method is based on precedent and practice, and is also very conservative in most but not all cases, he said the analytical method would be another tool that goes into a geotechnical engineer’s toolbox.

He said the analytical method forces the geology to be looked at first and the main benefit will be to optimise the roof support.

“Your recommended support will be closer to the one that is needed. It makes the whole development process more efficient because you install what you need and only what you need at once as opposed to installing something that may not be up to the job, then monitoring and noticing it is falling down and trying to remediate,” he said.

Noting the empirical method has a number of strong advocates, Seedsman said the analytical method should not be seen as an alternative and both approaches should be run in parallel.

Drawing from the whole geotechnical engineering discipline, and in particular the work conducted in the deep metal mines of Canada and the civil road tunnels in Sydney, Seedsman said the purpose of the ACARP research was to make the analytical method widely usable by geotechnical engineers.

“We have refined a number of analyses that have been validated against current mining practices and allow for the specification of bolting densities during development and also for support of the main gate and the tailgate during longwall retreat,” he said.

To make the analytical method easy to use, a flowchart will be provided which guides the engineer through a series of calculations and equations to be made at certain steps.

While this might sound complicated, Seedsman said applying the newer logical method at a minesite was a lot easier than he originally anticipated.

Using a laptop with Microsoft Excel installed, the necessary calculation equations can be programmed into spreadsheets.

“The risk to the research project was that the analyses couldn’t be done in spreadsheets on a minesite and the engineers would have to go to consultants to get some of the stuff done because it was just going to be too complicated,” Seedsman said.

“But it’s actually turned out to be remarkably amenable to spreadsheets on minesites.”

With a lot of the mathematical calculations accounted for through spreadsheets, Seedsman said a couple of days of training could suffice for geotech staff to pick up some of the sophisticated engineering concepts used in the analytical method.

“The key to good rib and roof support design is understanding the rock mass underground and not the complexity of the calculations,” he said.

On the benefits of the analytical system, Seedsman said it was very applicable to greenfield sites where there is less precedential information to work from.

He also said the analytical method could assist in the quest for faster development.

“You are potentially putting in less support because you are putting in optimised support right away, meaning faster development, lower costs and better planning,” he said.

“You will be able to conduct feasibility studies and prefeasibility studies with a much better guess of your development cost.”

Seedsman has some 30 years of experience in the coal mining industry with the last 10 years as a self-employed consultant.

He has provided consulting services to most of Australia’s coal companies including Xstrata Coal, BHP Billion Mitsubishi Alliance, Gujarat NRE and Centennial Coal, including the redesign of the company’s Mandalong longwall mine.

Some of the subjects to be covered in the seminars include tests for compressive, tensile and shear failure in the roof and rib, suspension designs to prevent roof and rib collapse and reinforcement designs to prevent delamination.

For more information contact Seedsman at: sgpl@hotkey.net.au