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For reliable prediction of deformations and rock stresses in hard coal mining a knowledge of the primary stress state and of changes in stress around workings is essential. Up until now, rock stress has been measured using the triaxial cell and hydrofrac techniques - the former proving unsatisfactory, the latter suitable but insufficient on its own. This project involved use of the hydrofrac technique for repeated measurements before and after shelter longwall working beneath a roadway. Other measurements were taken in a panel with extensive workings, at locations either side of a major tectonic fault, and under the margins of old workings. Some measurements were taken later using the newly developed borehole slot probe technique for comparison with the hydrofrac measurements. The hydrofrac results confirm significant anisotropy in the horizontal stress components. Down to approximately 1100-1200m the horizontal component predominates. Shifts in pressure caused by working are greater in extent and magnitude than was expected. In a direct comparison, results from the two measurement techniques correspond well.

Additional information

Authors: DMT-GESELLSCHAFT FÜR FORSCHUNG UND PRÜFUNG MBH, DMT-Institut für Gebirgsbeherrschung und Hohlraumverfüllung, Fachabteilung Gebirgsschlagverhütung, Bochum (DE);DMT-GESELLSCHAFT FUR FORSCHUNG UND PRUFUNG MBH, DMT-Institut fur Gebirgsbeherrschung und Hohlraumverfullung, Fachabteilung Gebirgsschlagverhutung, Bochum (DE)
Bibliographic Reference: EUR 14669 DE (1993) 72 pp., MF, ECU 4
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