Hi-tech canary could save miners’ lives

Researchers at the Commonwealth Scientific and Industrial Research Organisation in Australia have developed a new technology capable of predicting hazards in coal mines.

Researchers at the Commonwealth Scientific and Industrial Research Organisation in Australia have developed a new technology capable of predicting mine collapse or the release of deadly gases into a mine.

The ‘hi-tech canary’ can reportedly set alarm bells ringing at the first sign of danger.

‘The technology, which operates remotely, will make mining safer and improve the way mines are designed in the future,’ said CSIRO research group leader Mark Berry.

‘By enabling miners to deal quickly with hazards, the technology will save mining companies millions of dollars in lost production costs, with mines losing up to $1 million a day whenever work stops. This amounts to hundreds of millions of dollars every year in Australia alone.

The technique has been tested at 15 underground coal mines in Queensland, New South Wales (NSW) and China.

‘The technique, called microseismic analysis, centres on the fine measurement of seismic waves generated in rock under stress from mining,’ said Mr Berry.

The research team developed instruments and data processing and visualisation tools for the analysis, which can be conducted up to 700 metres from the mining area.

Arrays of geophones pick up the seismic waves. Geophones are devices with a wire coil inside a magnetic field. Seismic waves cause the coil to move in the field, generating a voltage. Signals from the geophones pass via cable to CSIRO’s data acquisition system, where they are amplified and recorded.

‘Different kinds of rock failure have different seismic radiation signatures, so geophysicists can differentiate between shear and tensile failure,’ said CSIRO scientist Dr Xun Luo.

‘By comparing parameters, including amplitude and arrival times of P (fast, longitudinal) and S (slow transverse) waves, we can pinpoint the location and orientation of the fracture,’ said Dr Luo.

Microseismic monitoring also provides estimates of the size of the fracture and the energy of the seismic waves generated.

‘At one site, an underground coal mine in central Queensland, engineers were concerned that mining would reactivate a fault through the coal seam, causing the mine’s roof to collapse.

‘We detected no significant seismicity in the fault zone. Daily reports of weak seismicity meant mining could proceed without interruptions that could have cost the company millions of dollars,’ said Dr Luo.

In another case, a NSW colliery faced the risk of fire from sudden, unpredictable methane gas emissions during mining. Microseismic monitoring by CSIRO correlated periodic, low frequency seismic waves with some emissions. The emissions are said to have lagged the seismic waves by three days.

In the future, microseismic analysis will enable miners to predict gaseous emissions and evacuate personnel if necessary.

According to CSIRO, the theoretical knowledge gained from the project will put more geotechnical science into mine design, enabling engineers to come up with safer plans.

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