Vostoktsvetmet, Ust-Kamenogorsk, Kazakhstan:

A. A. Zhirnov, Chief Geotechnical Engineer

Institute of Mining, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia:
Yu. N. Shaposhnik, Leading Researcher, Doctor of Engineering Sciences

S. A. Neverov, Head of a Laboratory, Candidate of Engineering Sciences, nsa_nsk@mail.ru

Mining PRO, Novosibirsk, Russia:
A. M. Nikolsky, Director, Candidate of Engineering Sciences

For Irtysh polymetal sulphide deposit, a 3D geomechanical model of stress state of surrounding rock mass around a mine has been constructed based on the input data on actual in situ stress field measurements. The in situ studies with direct instrumental measurements using the method of slotter borehole drilling outside the influence zone of abatement pressure reveal nearly equicomponent initial stress field with major horizontal forces oriented across the strike of the deposit. The geomechanical modeling describes general condition of underground excavations at operating levels, qualitative and quantitative distributions of stresses, concentration of stresses and formation of large damage area. The most aggravating effect of rock pressure is observed in heavily fractured rock mass at the boundaries of mined-out areas in the footwall and hanging wall of the ore body, as well as in the pillars, floors and roofs of open stopes (voids). It is proved that instability areas dynamically appear in the above-averaged fractured rock mass of Irtysh deposit. Based on the geomechanical analysis of the current geotechnical situation, the numerical modeling of the mine structure elements has been carried out for a mining depth of more than 700 m. The application ranges and safe operation parameters are determined for geotechnologies which are currently in use at the deposit, namely, stoping with shrinkage, sublevel open stoping, sublevel caving and room-and-pillar mining. It has been proved that in heavily fractured rock mass, the mining systems with the current parameters fail to ensure the required safety of mine operation and it is necessary to adjust design parameters of pillars and spans.

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