Institute of Mining, Ural Branch, Russian Academy of Sciences, Ekaterinburg, Russia:

Sashurin A. D., Head of Geomechanics Department, sashour@igd.uran.ru
Panzhin A. A., Academic Secretary, Candidate of Engineering Sciences, panzhin@igduran.ru
Kharisov T. F., Junior Researcher, Underground Mine Geomechanics Laboratory, Timur-ne@mail.ru
Knyazev D. Yu., Junior Researcher, Underground Mine Geomechanics Laboratory, knyazev@igduran.ru

In mining high-grade quartz veins, it is strictly required to produce pure quartz concentrate and to reduce loss and dilution of the useful mineral component. Compliance with the requirements, in accordance with the specifics of quartz production, is in many ways dependent on stability of mine openings. It is known that mine support pressure mainly grows due to displacement of wall rocks toward the axis of a mine opening (convergence) in the course of the working face advance. The results of numerous studies into the mechanism of this process in an elastic rock mass allow optimizing stability of mine openings. On the other hand, the mentioned process in a post-limiting stress state rock mass yet remains to be studied. This article describes findings of investigation of support pressure in the working face area in the post-limiting state rock mass. The investigations involved in situ measurements of rock deformation in the face areas with the spacings conformable with the cross-section dimension of an opening in terms of drivage a mine shaft using a combination technology in a hard rock mass in the post-limiting stress state. Based on the accomplished measurements and using FSP-1 Trends program to construct nonlinear regression equations and function–factor trends, the mathematical model describes the change in the absolute deformation of wall rocks in the course of the working face advance. The mathematical model produces an exponential dependence of the convergence factor α* and the ratio between the distance to the face, L, and the radius of the mine opening, R. The values of the factor α* determined in the postlimiting stress rock mass differ significantly from the same factor values obtained earlier for the elastically deforming rocks. The comparative analysis of the changes in α* in the host rock mass of Kyshtym quartz deposit subject to elastic deformation and in the rock mass in the post-limiting stress state shows significant difference between the two processes, which is to be accounted for when selecting support design and installation procedure.

Work is executed at financial support of the Ministry of education and science of the Russian Federation (project RFMEF160714X0026)

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