Abstract
In Yanahara Mine, the sinkages of the roof rock above the iron deposit, induced by pillar extractions, were measured by using the vessels communicated by a flexible tube, rock stresses were measured by means of flatjack and hydraulic fracturing techniques, and the stress changes have been monitored as the pressure changes of the capsules set in rock/pillar. The measurements have been carried out over an extended period of time and a part of stress measurement has been carried out until the mine is abandoned.The induced roof displacements were predicted by numerical analysis using Boundary Element Method which was found to comparatively agree with the measured roof sinkages.The results of the stress measurements suggest that the stresses at the portions near the extracted blocks in the center pillar have gradually decreased with extraction progress while the stresses around the orebody are not significantly changed and the pillar stress at a portion relatively distant from the extracted blocks has slightly increased.
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