| Underground Coal Applications |
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Notes
Coal seams can work as excellent conductors of radio signals in certain frequency bands and in these cases can act as wave guides. The thorectical treatment is beyond what we can show here at this stage but the waveguiding can extend our range in a very useful way.
We use the waveguide phenomena to transmit signals across longwall blocks that may be up to 250m across.
The RIM20/20 operates in the 22.5 to 992.5kHz range, allowing a large range of frequencies to be chosen depending on the width of the longwall and the expected attenuation rate of the target.
The following pictures show the crew setting up for a RIM 2020 survey underground. The "TXA" is the RIM antenna. This is being positioned at a set distance off the tunnel side "rib" or tunnel face.
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| Interpreted RIM2020 Image |
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The picture above shows a tomographic image of a dyke within a coal seam obtained from a survey in an Australian longwall mine. This is a plan view of the longwall block between the maingate (top) and tailgate (bottom). The dyke appears as the red and yellow colours within a uniform background of the coal seam. It is possible the dyke is faulted midway across the panel.
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| Coal - In Seam Borehole Surveys |
Where the target is not between developed roadways, such as in advance of a development roadway, a borehole RIM system called RIM2 can be used in horizontal boreholes drilled away from the development headings.
The underground RIM2 system consists of a separate borehole transmitter and receiver probe that can be pushed along horizontal boreholes to distances of up to 250m. The probes are connected to a control unit via milspec fibre optic cables to eliminate the chance of the cable acting as a radiating antenna. The RIM2 system operates at frequencies ranging from 2.5kHz to 900kHz, and in seam can transmit radio signals through more than 250m of coal.
All the RIM2 equipment is certified Intrinsically Safe by both the Queensland and NSW Mines Departments for use in Underground Coal Mines.
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Application Notes
Link to Information Request form
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