Geomechanical substantiation of the Oleniy Ruchey deposit underground mining in a protective pillar of the Niorkpakhk open pit

Abstract

The location of significant volumes of the lower level reserves close to an open pit which produces the adjacent Niorkpakhk deposit considerably complicates underground mining of the Oleniy Ruchey rockburst-hazardous deposit. The progress of underground excavations into the under-pit space is permitted if the undermined rock thickness and open pit walls remain stable. 3D numerical studies of stress-strain state have indicated particularities in deformation such as increase in undermined thickness stability under high tectonic stresses. The parameters of safe mining of temporary inactive reserves were scientifically substantiated. The boundaries of maximal development of underground mining were determined. The stability of overlying rocks and open pit walls is maintained by forming an advance of overlying sublevels relative underlying ones under 45° angle and providing the monitoring for the undermined rock mass. The mining method in a protective pillar the authors propose allows increasing reserves of the first mining stage by 76.9% and avoiding decrease in production volumes when mining operations terminate.