EXTRACTION OF OPEN PIT BOTTOM RESERVES BY ROOM-AND-PILLAR METHOD USING HYBRID BACKFILL

Abstract

For the transition from open pit to underground mining in thin and steeply dipping ore bodies, it is proposed to use the room-and-pillar method with hybrid backfill. The geotechnology assumes bottom-up mining within levels which are generally sequenced top downward. The hybrid backfill is waste rock and rubble concrete. The authors discuss the multivariate problem on the stability of structural elements of the geotechnology with ranking of basic parameters in the field of natural tectonic stresses. The geotechnology safety is proved by the 3D FEM-based stress-strain analysis of the limiting case of mine roof spans. The stress patterns in the structural elements of the technology are determined, and the areas of instability are identified. The rubble concrete pillars effectively ensure mining safety with the discussed technology. The hybrid backfill as against rock fill is a more reliable method of ground control, especially in case of increasing thickness of ore bodies.