What we asked

1. Underground coal mines will need to go deeper to access coal seams, which could possibly increase the risks to the operations. What risk management strategies is the Australian coal industry preparing to prevent hazards such as roof collapses as mining gets deeper and what further management strategies would you like to see in place?

2. Longwall expansions are being flagged for underground coal mines in both Queensland and New South Wales. Despite attempts to seamlessly incorporate mining infrastructure with present mining operations, commissioning delays can be common. How can suppliers, consultants and coal companies work together to reduce delays in sourcing and commissioning major longwall moving equipment?

Mining Consultancy Services (Australia) managing director Jack Steenekamp

1. The coal mining industry has globally and locally progressed significantly over the last few decades in interpreting and predicting geological and geotechnical conditions in future underground workings. This has mainly been driven as safety improvement initiatives but also to improve productivity and to support the decrease in unit production cost and the unnecessary cost and delays caused by recovery.

The majority of underground mining operations in Australia have a formalised and stringent system of predicting conditions and geological anomalies based on interpretation and modelling of exploration and drilling data. This information is transferred to a hazard management plan and overlain on the envisaged mine plan.

This document is generally presented and discussed with all relevant parties prior to mining the area and also available for review in the mines’ systems and on noticeboards.

Subsequent to mining in development panels, the plans are adjusted based on actual findings and underground survey to ensure up-to-date information is available to prepare for retreat mining and to utilise when this mining occurs.

Various technologies have been and are progressively developing to improve the management of roof and ribs, and the cutting face in the case of longwall operations. In general, roof and rib support techniques and technologies have progressed to include in many cases the installation of roof and in some cases rib mesh as well as long tendons or cable anchors as part of primary support.

This practice prevents the possibility of fracturing and spalling as soon as possible after mining. While full-column grouting, W-straps and additional support can be installed efficiently as secondary support with purpose-built attachments during periods of non-production, the installation of roof and rib support traditionally only possible with secondary support activities can be installed as part of the primary production process without impacting heavily on development rates.

Production equipment has also progressively been adapted to assist with roof and rib control. In-place bolter-miners have progressively been adapted to ensure primary bolting occurs as close as possible to the cutting face with the positioning and orientation of bolting rigs and shovel and loading configuration, e.g. east-west conveyors and shovel angles.

Improved functionality and automation of bolters supports better installations and auto-cycles and cutting height limits improve roof control through more accurate mining horizons.

Similarly, progressive automation of longwall equipment and systems has been instrumental in curtailing inconsistent operational practice such as powered roof support settings and horizon control.

The progressive optimisation of powered roof support design, stiffness and configuration, for example minimum canopy-tip-to-face and optimised prop-free-front distances, with operational practices and cycles as one-web-back, have improved roof and face control capability in longwall panels.

Risk management of roof, rib and face stability is dependent on accurate and timely information to implement effective controls proactively, and with purpose-built equipment and supporting technologies or processes.

The underground coal mining industry has progressed significantly in both these areas, however improved accuracy of reporting and capturing of relevant information by operational personnel during mining would further improve immediate management of the risk and in the prediction and control of mining conditions in future mining areas.

Communication technologies from underground to surface and end-of-shift reporting options have also improved over the past couple of years to include Wi-Fi technologies and on-line systems. This allows for in-time and accurate data transfer and reporting for next-shift and longer term preparation and management of these risks.

Research to develop a polymer-based spray-on alternative to steel mesh, with a suitable continuous miner-mounted strata mapping or scanning system to capture any geological features before application of the polymeric skin as well as further automation of bolting, mesh handling and cutting, are in progress. These technologies have proven successful in a workshop or laboratory environment, however, the challenge is to implement these practically and sustainably in an underground environment without impacting negatively on production rates and to get general acceptance within the industry.

Balanced front-end loading of mining projects, to include sufficient and timely geological and geotechnical information during the design and planning phases and in advance of mining, remains a robust risk management approach. MCS is of the opinion that this is one of the key factors to develop an optimised safety-focused and cost-effective strategy for future mining operations.

2. The global mining industry in general and similarly the coal mining industry in Australia have experienced a huge increase in demand for equipment and services since the turn of the global financial crisis.

Although traditional suppliers and service providers and entrants to the industry have been attempting to keep up with this increased strain on demand, the development of projects and expansion and extension of existing operations have caused a demand in excess of supply.

There are conflicting opinions on this trend continuing in the foreseeable future and beyond.

However, while it does, the only way to manage this effectively and secure supply and service provision is to plan accurately and in advance with sufficient lead time for notification and order placement to acquire equipment and materials and engage the correct skills and resources.

Similarly, the timely engagement of consultants to conduct and complete relevant studies, designs and schedules and to work closely with operators, suppliers and service providers, will allow for sufficient lead time to ensure the acquisition and provision of equipment and services, ranging from mine establishment to longwall moves.

Palaris Mining managing director John Pala

1. Australia is at the forefront in many areas of technical capability. This will be a feature into the future across geotechnical, geological interpretation, ventilation and gas management, greenhouse abatement strategies, improved equipment automation and remote operation capabilities.

Many of the features of modern longwalls have been driven through the increasing expectations of Australia mine operators, for example automation systems, improved ground control and anti-collision systems.

Another noteworthy aspect of technical improvement is the increasing influence of Chinese technology in areas such as top coal caving and overburden grout injection.

This is likely to increase with further investment in our industry.

I expect the combination of the technical advances together with increasing sophistication in a range of risk management tools such as “functional safety” and “safety case” will ultimately be used as part of integrated management strategies as mining gets deeper.

2. The fundamental issue with longwall moves is that there are so many variables which impact the operating schedule of a longwall that it is practically impossible to develop a schedule that can guarantee the window of time when move equipment will be needed.

Longwall moves dates always move around. This can be a dilemma even within the same coal company.

So this is essentially a financial and risk management strategy by each operation to weigh up the cost of longwall standing idle versus procurement of sufficient equipment to avoid delays.

These economic assessments are always undertaken as matter of routine by sites when considering risk-reward “trade-offs” of capital purchases.

In this climate of increased revenues – particularly for hard coking coals – justification for spare equipment should be somewhat easier that in the past.

This article appeared first in the June issue of Australian Longwall.