Geotechnical precursors to large-scale ground collapse in mines

Analysis of instances of large-scale ground collapse in underground and open pit mines shows that geotechnical precursors to rock mass failure appear over time. Recorded geotechnical precursors in cases of ground collapse larger than 100 000 tonnes were examined. Results indicated that a sequence leading to rock mass collapse existed. Ground movement was observed at the periphery of each impending collapse over extended periods, in some case years. Months before collapse, the main precursor is deterioration of ground conditions. In hard rock mass, within weeks before collapse, precursors in the form of high stress signs were noticed in close proximity to the centre of the eventual collapse area. Hours before the collapse, the most common precursors were rock noises and large falls of ground close to the centre of the imminent collapse. (C) 2001 Elsevier Science Ltd. All rights reserved.