4th International Symposium, 'Roofbolting in Mining' Aachen, Germany

THE Institute of Mining Engineering at the Aachen University of Technology in Germany held its 4th International Symposium, “Roofbolting in Mining”, in early June. Like the conference held three years before, this year’s event again drew 350 international experts in the field of rockbolting, who presented over 40 papers on the subject. By Professor Per Martens.

Staff Reporter

These delegates made the journey from around the world to exchange their thoughts and ideas at the event. The two-day conference gave a broad overview of the current developments in rockbolting technology as well as addressing many rock support problems facing different types of mines under many different conditions in the industry today.

This symposium, like each one held annually in Aachen, provides a well-structured and valuable forum for the exchange of information. With many of the experts having a vast understanding of not only their native countries, but extensive knowledge gained from many experiences of working abroad, a large base of knowledge is brought together at this forum. How problems have been overcome in the past, attaining success, future obstacles to be tackled and current strategies are among some of the most important pieces of information being discussed over the two days.

Despite vast differences in economic and geological conditions between countries like Australia, the United States, Germany and South Africa, conference attendees share ideas and approaches throughout the event.

This year’s award for improvement in rockbolting technology was presented to US-based NIOSH for their innovation and achievements in health and safety.

Equipment manufacturers presented latest developments and newest products. J Leeming and S Flook from Joy Mining Machinery, gave an insight into how rapid entry drivage systems are now being applied, under European mining conditions through a presentation of Joy’s newly developed Bolter Miner.

This machine delivers advantages which include drivage rate costs and longwall productivity, and an overall improvement in safety. Leeming and Flook also described the fully integrated mining machine (IMM), currently in trial operations in a USA mine. This machine, which reduces cycle times by combining cutting and bolting operations, could form the basis for future, rapid entry development systems for use in European mining conditions.

Presenters, R Bauer and M Maas from Deilmann-Haniel GmbH, GER, along with K-H Wennmohs of Atlas Copco MCT GmbH, GER, explained their latest technological developments in the area of drilling and anchor bolting. They went on to illustrate that even in the dwindling European coal mining market they have made extensive efforts in developing new products such as a new powerful drifter designed with short length to work in European coal mines. As well as the short length, the jumbo is much narrower, and has new drilling kinematics, new feed systems and drilling controls.

Many of these new systems were developed by using the input from a list of demands developed by DSK Anthrazit Ibbenburen GmbH, detailing European mines need today. This is a great illustration of how the development strategies for new products can advance today, with two companies partnering their expertise while working with a third to develop a unique piece of machinery under very specialised and demanding market conditions.

A unique perspective on the use of hand-operated bolting equipment was presented by T Martin from Schmidt, Kranz & Co GmbH, GER. He depicted the use of hand operated hydraulic roofbolters instead of mechanised rock bolters, or older pneumatic bolting units being used widely in the industry today.

Martin highlighted how many of the rockbolts installed today are set by means of specialised equipment with high investment costs. He then proceeded to show that with the use of a hand-held hydraulic bolter, one can take advantage of the versatility offered by a hand held unit, while at the same time avoiding both the higher overall operating costs associated with pneumatic units, and higher investment costs of mechanical bolters. These hydraulic units are being used across the globe in Western Pennsylvania and Virginia in the US, the Ukraine and in Germany.

The layout or pattern used in the installation of rock support was described by T Lautsch, from RAG Pennsylvania Services Corp, US. He illustrated the different techniques currently in use in the RAG coal mines in the US, Australia, and Germany. K Opolony and N Polysos from Deutsche Steinkohle AG, GER, discussed similar layout themes and new patterns under development from DSK AG. Practices in bolting and cable bolting in Indian mines were also detailed by SK Das from the Indian Institute of Technology, IND. He described how both bolting and cable bolting techniques could be applied in thick seam, coal mining operations using examples from coal mining in India.

Other authors detailed the introduction of roofbolting into other mining operations; ie in coal mines in Sardinia or in a trona mine in the US. H Jurecka from DSK AG pointed out the recent improvements in roofbolting in German coal mines, describing in particular the AVSA, a machine capable of both cutting and bolting simultaneously.

From installation equipment to new developments in bolt, and bolt anchoring technologies, A Campoli from Fosroc Inc, US, outlined the new demands on polyester resins used to anchor deformed rebar rock support. He explained how the effectiveness of resin anchors is dependent upon a complex interaction of many variables including cartridge design, shelf life and resin setting time, each of which, he added, can best be evaluated and the validity of the resins performance be impartially tested through pull failure field testing.

The issues affecting the resin performance itself in the USA applications, surround rapid installation cable systems and other special bolting systems, which in turn demand ever more sophisticated resin performance.

H Bornman from Grinaker, and D Ortlepp and D Stacey from SRK Consulting, South Africa, presented their latest development of a newly designed bolt, Durabar. They showed how the conventional deformed reinforcing bar, woven mesh and cable lacing support methods that have been widely used in deep gold mines are in their opinion quite inappropriate for the support of highly stressed tunnels, under rockbursting conditions. Rather, it is the sense that DurabarTM, cleverly utilises the property of the ductility of ordinary low-carbon steel from which it is made to accommodate the excessive displacement it is subjected to in the case of rockbursts or swelling ground.

Also addressing the high stress issues faced in deep, South African gold mines were LZ Wojno, and JS Kuijpers from CSIR-Miningtek, RSA. They also spoke about how yieldable support units and systems are better able to control the fractured rock around highly stressed excavations in rockbursting conditions. They introduced their yielding cone bolts, which have been developed to effectively deal with the excessive shear deformations experienced in many excavations found at deep levels.

The new developments in rockbolting machinery, cost effective versatile bolting methods, anchoring technology, support layout and the new developments in the supports themselves all lead to more productive low cost bolting but possibly most importantly lead to a much safer mining environment.

Article continues.

Most read Archive


Most read Archive