Roof sounding device - A loose rock detector

The US Bureau of Mines has developed a method and device designed to detect loose rock material in underground mines. The technology is designed to be an aid to mine workers in detecting hazardous roof conditions in underground mines which can complement or replace the traditional roof sounding techniques where the miner relies on experience to determine whether rock conditions are sound. The leading cause of accidents and fatalities in underground mines is falls of loose rock pieces or rock slabs from the mine roof. In previous research the Bureau of Mines found that loose rock, when impacted, vibrates at a much lower frequency than intact rock material. A major problem in determining rock stability using this technique has been the repeatability of the impact signal. This difficulty has been greatly reduced in the current design by measuring the power spectra contained in two separate frequency bands of the signal produced by striking the rock in question. The ratio of the energy contained in each band is computed. This process minimizes any striking force differences, producing accurate, repeatable results for solid rock as well as loose, drummy material. The prototype has been successfully tested in a variety of underground environments including coal, uranium, molybdenum, silver, and salt. The technology has ben investigated by the US Mine Health and Safety Administration and the Department of Energy for use in detecting detached tunnel lining areas in nuclear repositories. The paper will discuss the technique, applicable results, and future applications