A mesh of support and safety

A Western Australia researcher has developed a mesh and cable product that can absorb energy in underground mining, revolutionising safety standards in the industry. Jessica Darnbrough writes for Australian Mining.

It has long been understood that underground mining operations involve a partic­ular level and type of risk not encountered in other industries.

Last year, a Western Aus­tralian researcher developed a mesh and cable product that suc­cessfully increased the level of underground mine safety.

Professor Yves Potvin from the Australian Centre for Geo­mechanics developed a High Energy Absorption (HEA) mesh to tackle the challenges in deep and high stress mining condi­tions and mechanised mining.

“Development mining in high stress environments can lead to severe conditions,” Potvin told Australian Mining.

“HEA mesh is designed to promote efficient load-sharing between the surface support and the reinforcement.

“As the rock surface moves it pulls the mesh, which is con­tained by the cable web.

“In comparison to existing ground support systems such as mesh and shotcrete, HEA mesh is cost-effective, flexible, can be rapidly installed and is capable of supporting heavy loads.”

These features present an effective force in addressing extreme ground conditions such as high energy seismic events and squeezing ground.

Potvin described the HEA mesh as a cable bolt that was laced and overlaid with a sheet of regular or crinkled weld mesh.

Mine the issue

According to Potvin, the prod­uct had to withstand seismic effects and rockbursts.

“When the rock mass is stiff or when mining progresses near seismically active geological struc­tures, rockburst can become a serious hazard,” Potvin said.

“At the other end of the spec­trum, when the rock mass is weak and ductile, squeezing ground and high convergence become the challenge that must be managed during and after development mining.”

In order to combat the prob­lem, Potvin developed a strong and deformable surface support system. Although other surface sup­port systems were available to the industry, Potvin recognised a weakness in each of the designs.

Most of the other products available overlapped in certain areas, which meant companies were doubling up on materials, slowing the rate of mechanical installation.

After developing and testing several prototypes, Potvin lucked on to a design that effectively absorbed energy during under­ground mining.

According to Potvin, the design had five to eight times the load capacity of its competi­tors as well as two to three times the elongation.

Furthermore, the HEA mesh was proven to have two to three times the energy absorption.

“The HEA mesh demon­strated superior performance in squeezing ground and rockburst prone ground,” Potvin said.

“Support systems commonly used in ‘normal’ ground condi­tions fail to work in extreme conditions because they have clear weaknesses.

“A miss-match of the defor­mation or load bearing capac­ity between the reinforcement and the surface support often results in early failure.

The con­nections between the bolts and the surface support and the over­lap of mesh sheets are other well known weak areas of common support systems.”

Potvin said minesite trials have proven the mesh system is particularly effective in transfer­ring the load from the surface support to the reinforcement, eliminating any weaknesses.

Fit for purpose

Professor Potvin and the Aus­tralian Centre for Geomechan­ics are currently attempting to market the underground mesh system to geotechnical engineers and underground mines.

“The product will undergo further laboratory and field tri­als early this year to refine the effectiveness of the cable mesh technology, but I expect the prod­uct to be readily embraced by the industry once it is launched,” Potvin said.

According to Potvin, com­mercial considerations are cur­rently being established includ­ing supply and demand. With the industry currently suffering from a downwards trend, Potvin is considering extending the use of the mesh to include deeper mining proj­ects where the seismic risks and safety conditions are greater.

Last year, Potvin’s mesh and cable product won the Ready for Market category in the West­ern Australia Inventor of the Year Awards.

The Ready to Market cate­gory is open to organisations and individuals that have devel­oped a product or service that is ready to be licensed, manu­factured or marketed but needs funding to take that step.

Selected from three category finalists, Potvin said he was delighted to win the Ready for Market Category award.

“We are pleased to be acknowledged by the Depart­ment of Industry and Resources and Inventor of the Year pro­gram for our innovation in tech­nology and design,” Potvin said.

• Professor Yves Potvin

Australian Centre for Geomechanics

08 6488 3300

www.acg.uwa.edu.au

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