Interwell area design procedure to generate safe zones in rockburst-hazardous conditions of Talnakh deposits

Abstract

Stoping at rockburst-hazardous deposits Talnakh and Oktyabrsky should be carried out within protected zones to prevent dynamic events induced by rock pressure. Until the 2000s, the main method of generation of safe zones was construction of protection capping by means of advanced cutting of aguard bed in the  roof of an ore body. Later on, the destressing drilling method was introduced. This approach to relaxation of ore bodies from stresses ensures formation of a self-developing local destress zone possessing high yielding. The latter prevents accumulation of elastic energy in adjacent rock mass. Borehole erosion transforms round cross-sections to ellipsoids, and, consequently, the width of the interwell space decreases. As the spacing of boreholes reduces, the intensity of failure in the interwell area grows. The borehole destressing technology is used in sulfide ore cutting with backfilling. Effectivization of the borehole destressing technology is discussed. The main stages of this method implementation in rockburst-hazardous mines in the Talnakh ore province are described. The absence of an engineering procedure to calculate drillhole spacing in destress drilling is emphasized. The general provisions of such procedure to take into account the key features of the geomechanical borehole–interwell area system are substantiated. The approach to determination of critical stresses for deformation to take place in the interwell area is shown. Destress drilling widely uses Solo Sandvik and Simba Atlas Copco drill rigs for ring drilling of holes with diameters of 64–89 mm.