Published in the March 2011 Coal USA Magazine

A further goal is to improve health and safety through the reduced exposure of operators to hazards in the immediate face area.

The initial research and development focus has been to develop the “enabling technologies” necessary to underpin such a high-capacity roadway development system before attempting to incorporate those technologies into the high-capacity system.

A study of the development process at the time resulted in four key enabling technologies being identified, including self-drilling bolts.

A number of ACARP-supported projects have been undertaken or initiated over the past four years to pursue development of those technologies.

With some of those projects now coming to fruition, it is obvious the opportunities afforded by the technologies also create both issues and challenges, related to their introduction and adoption, and ultimate integration into a high-capacity development system.

Member companies of ACARP’s Roadway Development Task Group have provided continuing support to the Ground Support Services Self Drilling Bolt (SDB) project, which is expected to be the subject of extensive underground testing in February-March 2011.

Both “dowel” and tensionable SDBs are being trialled together with an extendable SDB (or tendon alternative) and cut-able SDBs.

In the likely event that the trials are successful, researchers, original equipment manufacturers and operators will then have to contemplate not only how the bolt installation of a two-part resin system can be fitted to a continuous miner, but the implications of current licensing requirements for injection of polymeric strata support materials.

Based on a development rate of 10MPOH and a usage rate of 1 litre per 1.8m roof bolt, approximately 100 litres of resin will require to be supplied to the miner every hour, with the two-part resin being supplied concurrently to each of six injectors located in the roof-and-rib bolting rigs.

Development of the on-board resin distribution system and associated off-miner logistics system is yet to be finalised and will require further underground trials of a fully integrated system before commercialisation can proceed.

The primary aim of the C17018 Automated Bolting and Meshing Installation project being conducted at the University of Wollongong is to develop a continuous miner-mounted bolt-and-mesh handling-manipulating system that feeds self-drilling bolts through to, and to load them into, automated roof and rib bolting rigs (developed by others) and to both feed, place and install steel roof-and-rib mesh sheets ready for bolting.

All components were to be demonstrated as an integrated, programmed system in workshop trials at University of Wollongong this March. Subsequent to that demonstration, the project team aimed to fit the system to a continuous miner for underground trials commencing first quarter 2012.

A second part of the project aims to develop a concept design for a complementary strata-support materials handling system that delivers materials from the panel “track-end” to the continuous miner-mounted bolt-and-mesh handling-manipulating system at a rate which enables the 10MPOH, 20h per day rate to be sustained without interruption.

Preliminary studies have identified that at a support density of four roof bolts and four rib bolts per metre, 23 individual items will be handled, manipulated, and installed with each metre advance (that is, six roof bolts, four rib bolts, 10 bolt washers, one roof mesh, two rib mesh). While the cutting, loading and support cycle of such a high-capacity system is yet to be defined, it is likely that each set of materials (23 items) will have a window of less than 2 minutes within the 6min advance cycle to be positioned in bolting rigs and manipulators ready for installation. Further, at a rate of 10MPOH, 10 sets of the materials will need to be supplied to the face support system every hour, a total of 1.6 tonnes of materials per hour (and approximately 40t per pillar cycle).

Given there is limited real estate available, on-board typical continuous miners for both the bulk storage of materials and the fitment of on-board materials handling devices, it then suggests a system needs to be developed for the bulk storage of materials “off the miner” and the continuous replenishment of materials to the on-board materials handling devices. Further, development of an automated bolt-and-mesh handling system will require development of fully automated, remotely operated bolting systems as operators could not reasonably be expected to continue to manually operate bolters within close proximity to bolt-and-mesh handling devices and moving, rotating bolts and mesh.

Bolting rigs and their automation

The availability and utilisation of real estate on continuous miners is a significant issue and will only be exacerbated as attempts are made to incorporate other developing technologies into an integrated development system.

Continued manual operation of bolting rigs only exacerbates this problem with scarce space being required for operators, as well as exposing operators to the hazards associated with rotating and moving equipment within a confined working environment.

The targeted development rate (10MPOH) will exacerbate this risk due to a doubling or trebling of advance rates (and support installation rates), plus increased exposure to repetitive strain injuries and fatigue-related factors.

The development of self-drilling bolts is a significant step towards addressing those hazards, with the number of human interactions required being dramatically reduced.

Further, the development of push-button or semi-automated control systems reduces risks associated with the inadvertent or unplanned operation of controls.

Ultimately, these hazards will only be fully addressed when automated bolt feeding-positioning devices are developed, together with the ability to remotely operate or supervise all associated controls from a position of safety.

Similarly, the successful development of spray-applied polymers for skin confinement could be expected to drive development of automated bolt-feeding devices and remotely operated bolter controls, so that operators can be removed from the immediate face area while spray application systems are being operated.

Given that rates of 10MPOH are being targeted, it is likely that both cutting, loading, meshing and bolting activities or cutting, loading, spray application and bolting activities will be concurrent operations rather than sequential, particularly where high support densities are being installed.

A limiting factor on development rates in mines where high support densities are required is that of the number of bolting rigs being operated concurrently – bolter rig and continuous miner configurations currently allowing only four roof-bolting rigs and two rib-bolting rigs to be operated concurrently.

The automation of bolting functions and elimination of operator stations could enable a third roof-bolting rig to be incorporated each side of the miner, provided the automated bolt feeding-positioning capability can be maintained to all bolters.

All bolting rigs do not need to be in the same alignment, a third rig could be set back a half-cycle, that is 0.5m.

Alternatively, and depending upon relative roof-and-rib support densities, it may be more appropriate to utilise the space created by removal of the operators’ control station for fitment of a second rib-bolting rig on each side.

The development and application of automated bolt feeding-positioning technologies is likely to require the return of bolting rigs to known or fixed position to allow the bolting manipulator to feed a bolt into the chuck error-free.

That fitment of additional bolting rigs and removal of side slide or tilt may be one means of error-proofing the bolt manipulation function.

The thrust to extend maintenance cycle times and to ruggedise bolter rigs is likely to have increased the “footprint” of bolting rigs, hence limiting the number of bolters able to be fitted. Investigation of alternative designs and materials may be warranted to reduce the footprint and increase the number of bolters able to be fitted.

Further development of automated bolting systems will be necessary to enable operators to be removed from the hazards associated with rotating and moving equipment within a confined working environment, and to fully realise the benefits of automated bolt-and-mesh handling systems currently under development.

Those technologies together should also reduce exposure to repetitive strain injuries and fatigue-related factors resulting from a doubling or trebling of current advance rates (and support installation rates). A further space-related factor is better matching of the number of installed bolting rigs with support-density requirements, through fitment of additional rib or roof bolters as required.