Geomechanics substantiation of pillars development parameters in case of combined mining the contiguous steep ore bodies

Abstract

Purpose. Determining the actual dimensions of the protecting and crown pillars of ore bodies by seismic survey and assessing the possibility of rock mass collapse and fracturing at the lower levels of the Zhairemskoye field. Methods. An integrated approach is used, which involves the analysis of complete ore bodies development during the combined mining. To determine the geological strength index (GSI) and rock mass rating (RMR), the mass structure is studied, as well as the survey is executed of rock fracturing on the contours of mine workings at levels of +288, +240, +192, +144 m. In addition, the physical and mechanical properties of rocks are refined using the RocLab software. Using the numerical modelling of the self-caving process, when mining the protecting and crown pillars, the processed results of numerical modelling are analysed and the possible zones of the mass deformation are assessed based on the Phase2 software. Findings. It has been determined that during the mining of ore bodies 4 and 6, protecting pillars between the quarry and the underground mine, crown pillars between the levels up to the level of +144 m, the rock displacements are possible along glide surfaces. It has been revealed that the haulage workings of levels +240 and +192 m fall into the zone of possible displacements influence, and the rock pillar between ore bodies 4 and 6 will be exposed to inelastic deformations during the mining of crown pillars to the level of +144 m. It has been found that after the crown pillar development between the levels of +240 and +192 m for ore body 6, the rock pillar destructions are possible between ore bodies 4 and 6, since during the modelling, displacements of more than 2 mm are observed. In this case, the destruction processes are possible in the rock pillar upper part. Originality.A geomechanical assessment of the rocks tendency to caving is given and problem areas of stability during the mining of ore bodies 4 and 6 in the Zhairemskoye field are identified. Practical implications. The stable parameters of protecting and crown pillars have been substantiated, which is an important aspect in the design/efficient technology of mining the contiguous ore bodies. Keywords: engineering seismic, ore body, pillar, level, iron, manganese