Mining Institute, Kola Science Center, Russian Academy of Sciences, Apatity, Russia:

I. E. Semenova, Head of sector, Candidate of Engineering Sciences, i.semenova@ksc.ru
I. M. Avetisyan, Senior Researcher, Candidate of Engineering Sciences

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.

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