Detection of stress redistribution in a complex isolated coal pillar with active SVT technology

The detection of stress redistribution in a mining area is essential for forecasting and preventing coal burst disasters in underground mining practices. Active seismic velocity tomography (SVT) is an effective way of investigating large-scale regional stress distribution. Active SVT technology was applied to a complex isolated coal pillar twice to assess coal burst hazard level and to guide the design of de-stress measures as well as to verify their de-stress effect. Test results show that high stress concentration existed in scattered zones along the boundary of the coal pillar rather than in the whole coal pillar. Qualitative comparison of the two SVT tests conducted before and after implementing de-stress measures indicates (1) if high-density wave sources and receivers are appropriately arranged, the spatio-temporal detection precision of active SVT technology could be sufficiently high to identify the de-stress effect of a single deep-hole roof blasting or a group of coal seam blasting upon their completion; (2) The implementation of de-stress measures in the isolated coal pillar area helped drive the stress concentration away from the de-stressed area to the adjacent area instead of fully eliminating the stress concentration. This stress-driving effect indicates that a possibly advisable strategy of coal burst control in the isolated coal pillar area could be driving stress concentration to the area further away from the area of high production activities rather than attempting to eliminate stress concentration.