In mines of Upper Silesia Coal Basin the efficiency of detection of loosened rocks with manual infrared thermometer of RRT-10 type has been tried out and the system for estimation of roof rock quality with rebound hammer. Theoretical relation has been established between loosening thickness and difference of temperatures of loosened and not loosened rocks and this relation was found by measurements to stand in practice. For the geothermic degree of Upper Silesia the approximated range of depth and critical distances have been determined where the air temperature in excavations is approximate to rock temperature and infrared method is of limited application. The experimental relations have been given of rebound index and rebound energy absorption index - when testing with rebound hammer - to the thickness of loosened rock. The results of tests of roof loosenings by infrared thermometer and rebound hammer have been compared and the critical thickness of loosenings detectable with the methods has been given.

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