Published in June 2010 Australian Longwall Magazine
What we asked
1. The Aussie coal industry survived the global financial crisis better than anticipated – what trends do you see now and where are we heading?
2. There are many expansions on the cards while new coal regions are starting to open up. What risks might be overlooked in the haste to increase production and kick off new projects?
Geohart Consultants principal geotechnical engineer-director Wouter Hartman
1. Twelve months on I still see an opportunity for minimising ground control costs which still is a major issue in the rehabilitation schedule for major roadways and intersections.
We still see a need and an opportunity torefine and optimise the use of the Modschock system in ground control quality control. Further work is currently underway in looking at the residual capacity of most rock reinforcement elements which will be a major breakthrough in the technology development.
2. The planning of new projects is always an important part of maximising production. The lack of geotechnical information for most projects has produced some challenges for new longwalls that come online. The problem lies in poor project management and planning in terms of gathering information. The focus has always been on evaluating the resource, and nine out of ten times important geotechnical information is only thought of when a mine plan is being put together and possibly too late in the process, hence the push to get the geotechnical information quite early on in the process.
Seedsman Geotechnics director Ross Seedsman
1. The technical future has not changed – deeper mines. After the recent successes in the Xstrata Queensland operations the expectation is for even higher production longwalls. Higher coal prices should allow the return of pillar workings to mine the faulted coal. Some companies may take on the faulted ground with longwalls – it may be possible so long as a few fundamentals are recognised (see later). It will be interesting to see if pillar extraction with breaker line supports is widely adopted or whether various pocketing strategies are adopted.
One particular concern is the ever-widening knowledge gap between the mining companies and environmental regulators regarding subsidence. While everyone in the community would like to have accurate forecasts of weather, earthquakes or even volcanic activity, we recognise that this is not available and we seek other ways to manage the hazards. At the technical level, scientists and engineers recognise that “accuracy” relates to how close a measurement is to the actual value.
Inparticular, engineers use the term with care when referring to predictions. In this context it is worrying that NSW planning regulators continue to require studies (some need to be detailed) of things that can measured, yet accurate predictions of subsidence deformations for the entire 20-25 years life of a mine (one for which a layout will not be finalised until the last gate road is driven). There is no doubt that there should be constraints on subsidence impacts, but this will not come from unreasonable requirements for accuracy. It will come from a focus on understandingthe tolerance of the surface and the adoption of project-specific subsidence limits. Designing against these limits will force innovation in subsidence engineering, leading to better predictions. Until this approach is adopted, planning for longwalls in NSW will be time-consuming and unpredictable. It is to be hoped that other jurisdictions do not adopt theNSW model.
2. Longwalls are one of several bulk mining systems, all of which have little flexibility to deal with unanticipated geotechnical conditions. The planning of longwall mines is particularly exposed to the horizontal stress paradigm that requires that gate roads be aligned parallel to the major principal horizontal stress so that the maingate roof is stable. Seeking to reduce the horizontal stress in the maingate is only necessary if the rock is relatively weak in comparison to the stress magnitude, and there may be better ways of managing the hazard with the proactive installation of long tendon support. What cannot be managed on high production longwalls is the collapse of the face itself. In recent years, faces aligned within about 20 degrees of the dominant fault/joint structure have experienced a variety of delays related to slabs that cannot pass under the shearer, slides off the face overloading the AFC [armoured face conveyor], and slides leading to increases in tip to face distances and the collapse of the roof. None of these events can be controlled by the longwall supports themselves – regardless of the number of legs and the installed capacity. As a general observation, longwall districts designed to maximise reserve recovery often align parallel to geological structures.
As we move into new coal regions, the hazards of longwalling at shallow depth come back into focus. If these new areas are like the Bowen Basin there is the possibility of very low strength roof and floor.
The early longwalls in the Emerald region, especially Gordonstone, took some time to understand the role of low- strength rock. The roof support technologies now routinely applied at Crinum and Kestrel may be necessary. It has been some time since a longwall face has punched into low-strength floor, but there were some instances in the early days of going underground in the Bowen Basin.
Palaris Mining managing director John Pala
1. If I had been asked this question five weeks ago I would have said that the industry was set for unprecedented growth with significant benefits for the Australian economy. Like most companies associated with the resources industry, we have enjoyed exceptionally strong growth in all areas of service provision, including exploration services, engineering services, underground consultancy, open cut consultancy, sustainability, EPCM [engineering, procurement and construction management] and specialist advisory services. The breadth of activity suggested mining assets at all phases of development were being progressed to new or increased output.
The proposed tax on the mining industry is being viewed with great concern by alllevel of investors in the industry – major mining houses, smaller players and overseas equity investors. A number of the overseas investors I have spoken with have been very surprised at the sudden change; comments like “we thought Australia was politically stable”, “this will affect our confidence to invest” and “we will look more closely atother options”
If implemented, the ramifications of the tax will affect us all. You can’t take $12 billion out of the industry and expect business as usual.
2. The risks are the same as those that occur with any rapid growth
- Inadequate exploration/ poor standards
- Poor quality (veloce) feasibility studies
- Insufficient resources to bring projects online, on time and on budget
- Difficulty in getting trained resources – particularly in remote regions when the asset is in the production phase.
Overall resulting in sub-optimal returns on investments.
The challenge will be to ensure the required rigor and management discipline is maintained so that projects are evaluated and delivered in line with the generally high standards Australian industry has demonstrated to date.
Article continues Monday.
Responses were received during May.
