Relative stress conditions in an underground pillar, Homestake Mine, Lead, SD

Abstract

Abstract Personnel from the Spokane Research Center, a division of the national Institute for Occupational Safety and Health (NIOSH), have been investigating the use of three-dimensional seismic tomography to detect hazardous ground conditions and monitor the mechanical integrity of a rock mass. This technique was used to determine relative stress in an underground pillar on the 7400 level of the Homestake Mine, Lead, SD. Low velocities, which are interpreted as identifying areas of low stress, were associated with boreholes, segments of haulageways, and the corner of an adjacent pillar. High velocities, which are interpreted as identifying areas of high stress, were identified in the northeast part of the pillar. High stess can result in enough seismic activity to cause unsafe conditions for miners, such as ground falls. The importance of identifying highly stressed areas in a pillar is that engineers can evaluate the mining cycle and determine the best approach to excavating such areas, or use destressing or preconditioning techniques to relieve the stress. In the field of rock mechanics, the benefits of using three-dimensional seismic tomography to identify high stress are that (1) the technology is noninvasive, (2) it is reliable, (3) it allows a series of surveys to be conducted over time, (4) it is less expensive than conventional methods, (5) it is time efficient, and (6) it allows researchers to evaluate and monitor a large rock mass (as much as 2 million cubic meters of rock)