The Effect and Measurement of Horizontal Stress in an Underground Limestone Mine

摘要

Horizontal stress can have a profound effect on the stability of an underground limestone mine. The presence of horizontal stress is usually determined once the mine has been developed and the orientation of headers and crosscuts are well established. Multiple attempts are typically made to control roof falls without reorienting the mine. Once the decision has been made to change the orientation, pillar centers, mine opening widths, and the question of how to determine the correct orientation must be answered. A case history is presented to illustrate how geologic structure, ground conditions and roof falls in adjacent mines, the World Stress Map (Heidbach et aL 2016). in-mine measurement of "cutter" roof orientation, the orientation of strata offset (cats eyes) within borescope holes, and the diametral deviation method of determining horizontal strain from drill core were used to establish the most likely range of horizontal stress. The main headers were re-orientated in a direction parallel to the median of the range of horizontal stress. The crosscuts were angled 60° to the headers to avoid being perpendicular to the horizontal stress direction. Pillar centers and opening widths were increased in the favorable stress direction of the mains and decreased in the less favorable crosscut orientation. The major principal horizontal stress magnitude was estimated using the strain measurements from the diametral deviation method and elastic modulus obtained through testing.