Estimation of open-pit / underground mining cross-effect in complicated geomechanical conditions

Abstract

The paper presents the results of prediction model studies of the stress–strain behavior in Gakman field of Yukspor deposit during hybrid open pit/underground mining under conditions of high tectonic stresses. The mountainous relief, rock mass faulting with a series of weak structures, geometry of the ore body, the actual and design parameters of stopes, and mining operation under the uncaved overlying stratum with three-sided support are taken into account. Based on the multivariate threedimensional stress–strain modeling using the finite element method, geomechanical substantiation of simultaneous open-pit and underground mining was carried out. It has been established that the geomechanical determinants in Gakman field are: – gravitational and tectonic stresses with a significant excess of the tectonic component over the gravitational component; – mountainous relief of ground surface with a significant elevation difference in the study area; – location of underground mining under the uncaved overlying stratum with three-sided support; – faulting of rock mass with a series of weak structures (Gakman fault); – formation of the open pit and crown pillar above underground mine; – significant lag of the mining front on the underlying levels of level + 320 m. The dimensions of the cross-effect zone and crown pillar when the underground operations approach the open pit mine are determined.