A magnetic sonde to measure distance and hence movement through rock and mine fill material.

What is it about?

A prototype sonde was developed to establish whether distance and, hence, movement can be measured over short ranges via low-frequency electromagnetic fields. An initial trial under laboratory conditions demonstrated that the principle could be used for measurements through air, though the measurements were affected by temperature and by vehicle movements outside the laboratory. Subsequent field trials at an abandoned mine produced measurements through up to 20 m of rock that were very close to the surveyed distances. Finally, a two-week trial of settlement monitoring undertaken in a roadway in the harsh underground environment of Boulby salt and potash mine confirmed the potential of the technique for accurate measurement of convergence and separation.

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Why is it important?

The sonde discussed in this paper was a prototype developed in the 1990s. With the advent of internet of things technologies, this sonde may be very useful for monitoring settlement in mine fill and tailings storage facilities.