Girponickel Institute LLC, Saint-Petersburg, Russia

A. V. Trofimov, Head of Geotechnique Laboratory, Candidate of Engineering Sciences
A. P. Kirkin, Researcher at Geotechnique Laboratory, KirkinAP@nornik.ru
A. E. Rumyantsev, Chief Specialist at Geotechnique Laboratory, Candidate of Engineering Sciences
A. V. Kolganov, Researcher at Geotechnique Laboratory

The stress–strain analysis of rock mass is an obligatory stage of a mineral access project. It is often difficult to investigate stresses and strains because of the great depth of ore occurrences, and for this reason, the initial stress assessment is only possible when studying damages of walls in exploratory and geotechnical boreholes. Another method of the stress–strain behavior investigation at rockburst-hazardous deposits is core discing. This method allows determining the degree of rockburst hazard and the maximal stress which leads to the formation of discs, but it is impossible to reveal the directions of the active stresses. In this case, it is possible to assess the level of the stresses by damages of borehole walls. It is known that a damage zone appears in the direction which is perpendicular to the action of the maximal stresses, and it becomes possible to determine both the value and direction of stresses. Detection of damage zones and their spatial orientation uses the method of acoustic borehole imaging. The article presents the processed data of acoustic imaging of geotechnical borehole walls in the field of a polymetallic ore deposit of intrusive genesis. From the data on the size and spatial orientation of plastic deformation zones, the primary assessment of the initial stresses is carried out. The verification of the results used the finite element-based modeling. The stress state was mostly tectonic and governed by the high-rate regional fault. The value of the maximal horizontal stress reached 70 MPa in some areas.

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