Underground mining: Breaking new ground

 As New Zealand continues its Inquiry into the Pike River Coal disaster, the same question keeps coming up – could this tragedy have been avoided. 

Could the changes underground, and the leaking of gas have been monitored and prevented?

History has shown that finding trapped miners is almost like finding a needle in a haystack, especially in the case of the trapped Chilean miners.

These miners have now taken it upon themselves to sue the Government of Chile for not ensuring high mining standards and safer mines.

A new development in seismic detection is paving the way for significantly enhanced mine safety standards throughout the world. 

Dubbed the SP2, it is a sophisticated seismic monitor with multiple applications including identifying potentially dangerous changes in underground structures, detecting trapped miners at depths of more than 300 metres, as well as locating deep deposits of flowing oil and water.

The SP2 detects micro seismic signals generated in underground strata that would normally be masked by major mining activities. 

Weaknesses forming around underground shafts as well as open pit faces can now be identified – potentially preventing collapses or wall slippages. 

Its unique ability to ‘see through’ noise means it is able to filter out extraneous signals produced by everyday mining activities, and therefore be used during normal mining operations. 

At a mine in Derbyshire, UK, an earlier version of the SP2 successfully predicted a rock outburst occurring over four months before the event itself.

Independently verified by the University of Liverpool, the device was set up and data monitored over several months. 

At 22 weeks before the event it accurately identified a cluster of increased micro-seismic activities, and at 18 weeks had pinpointed where the collapse was likely to take place. 

Preferring to believe their existing monitoring devices, which did not pick up these signals, the mine owners chose to ignore these warnings and the subsequent collapse, exactly as predicted, caused the closure of the mine and financial losses of more than £1 million. 

Fortunately, unlike mine collapses in Chile, New Zealand, and frequently China, no-one was trapped or injured in the accident.

Another major strength of the SP2 is its ability to locate deposits of flowing liquids deep in the underground strata that are generating seismic energy. 

Movements can be monitored, thereby not only aiding excavation activities, but also indicating where breaches might occur. 

Water underground is a serious hazard, as recent events in some of Queensland’s underground coal mines show. 

At Anglo American’s Grasstree coal mine, three miners had to quickly climb onto heavy equipment after an on-site storage dam broke its banks, sending 36 mega litres of water gushing into the underground tunnels.

Tests performed in deep mines recently have highlighted the speed at which the new technology identifies and locates all seismic activity. 

Features found included moving water which, when plotted in 3D, indicated a waterfall as well as seismic stress releases due to mining operations. 

This kind of knowledge allows mine owners to take action to re-plan their mining activities and reduce the likelihood of an accident.

Philip Shaw of SureWave Technology, who has spent the last decade developing the SP2, realised the science behind strata monitoring and signal detection could hold the key to locating personnel underground. 

With the string of recent mining disasters around the world it is clear that rescue teams have no easy way to detect trapped miners. 

In the case of Chile’s mine collapse in October 2010 it took 17 days for the miners to be located. 

It also required a multi-national effort, with many experts from across the globe flooding to the Chilean underground gold mine.

In New Zealand, the rescuers are still yet to fully enter the mine, and it took many days for robots to locate the bodies of the 29 miners. 

No technology has been sophisticated enough to accurately locate anyone trapped underground – that is, until now.

A demonstration at Patriot’s Federal #2 Mine in West Virginia, USA earlier this year proved the SP2 was able to accurately locate simulated trapped miners at a depth of 316m. 

The ‘trapped’ miners tapped the shaft wall with a commonly-used wooden crib block and immediately their location was picked up in real time. 

The demonstration was documented by Dr Keith Heasley, Mining Professor at the West Virginia University, who confirmed the successful test. "I was pleased to clearly see the signal from the miners pounding on the roof from that depth. This system performed much better than other systems I have seen," Heasley said.

Shaw added that "we are confident our technology would be able to locate miners to a depth of up to 600m". 

Weighing in at less than 60 kilograms, the portable device can be set up and running within a matter of hours, saving vital time for emergency rescue teams. 

As the New Zealand Inquiry into Pike River has stated, the time between the incident and eventual arrival and preparation of the rescue teams was crucial, with response times lacking.

Multiple sensors mean that an area of more than one kilometre can now be covered, providing significant ‘visibility’ for rescue efforts. 

No other technology is known to produce such advanced data of this kind, making it a unique safety device in accident prevention as well as a powerful rescue tool. 

Not only can it potentially save many lives, but mining companies are set to save millions in lost time. 

By being able to identify these underground weaknesses, planned activities can be adjusted to reduce or prevent downtime and lost production, as well as aid the planning of future activities. 

Since appearing in the September issue of Australian Mining, this technology has mostly recently been used in the rescue and recovery efforts in Wales, where four miners lost their lives in an underground coal mine.

 

To keep up to date with Australian Mining, subscribe to our free email newsletters delivered straight to your inbox. Click here.