::.. Radio Imaging in Australia... Using Radio Tomography to Image Coal Seams..::

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DownLoad Application Notes Radio Imaging NEW Link to discussion forum Image structure between boreholes Electromagnetic Tomography, also known as Radio Imaging Method (RIM) gives an image of the rock between two bores or mine drives. Technically it gives the conductivity distribution of the ground between a transmitting antenna and receiving antenna . The method is similar to a medical CT Scan, however our access around the feature of interest is often limited to boreholes or roadways either side of the target. Thus we acquire a 2D image that represents a slice through the target. The image below gives a typical shot of what we can see. Image showing Coal Seam Structure The darker Blue is Coal, the interburden is shown as yellow to green. This image also shows the coal seam. The blue colour again is coal
Equipment
There are two parts to the Rim system Borehole RIM2 system The hand carried RIM2020 system. RIM2 transmitter probe: Both systems contain H field antennas operating at frequencies of 2.5 to 992kHz. The RIM2 system measures both amplitude and phase data by means of a control unit. This unit couples and synchronizes the borehole transmitter and receiver. The RIM2020 system measures only amplitude information. The RIM2 probes are 4m long and 45mm wide, enabling a wide selection of holes diameters to be surveyed. They are connected to winches via 550m of milspec kevlar reinforced fibre optic cable. The use of fibre optic cable greatly improves the signal to noise ratio and effectively isolates the tools as point source transmitters and receivers. The Queensland and New South Wales Mines Departments certify both the RIM2 and RIM2020 tools Intrinsically Safe.
Radio Imaging Theory
The radio signal loses strength (attenuated) as it propagates through the earth. The signal attenuation is a function of the transmission frequency and the electrical conductivity of the media. By setting up a transmitter at one point and a receiver at another it is possible to measure the signal loss and/or phase change along the path between the two points. By collecting many overlapping raypaths it is possible to invert the attenuation distribution into an image by use of specialised processing software. The diagrams below shows the RIM signal attenuation. The picture on the right shows typical raypath coverage between 2 boreholes.


A radio signal at a specific frequency travels further through low conductivity media (limestone, coal, potash, meta-sediments, granite) than through materials with high conductivity (shale, mudstone, clay, ore zones etc). Therefore a conductive ore within a resistive host acts as an excellent RIM target. The data are processed using the state of the art Imagewin from CMTE in Australia. This package is specifically designed for electromagnetic tomography data and contains algorithms such as weight clamping and central weighting to enhance the tomography dataset. DownLoad Application Notes Talk to SSI about your in Mine OR Cross HOLE INFORMATION ISSUE email or Phone Link to Information Request Form
Applications: Radio Imaging is used in a wide variety of mine applications. Follow the links to either: Above ground coal applications Underground coal applications Metalliferous applications Link to Information Request form

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