Saint-Petersburg Mining University, Saint-Petersburg, Russia:

N. A. Belyakov, Associate Professor, Candidate of Engineering Sciences
I. A. Emelyanov, Post-Graduate Student, emelyanov_ia@pers.spmi.ru

Research Center for Geomechanics and Mining Problems, Saint-Petersburg Mining University, Saint-Petersburg, Russia:

K. V. Morozov, Head of Geomechanics Laboratory, Candidate of Engineering Sciences

Reliability of a geomechanical forecast is a major objective when designing and operating an underground structure. Assessment of a forecast reliability can use one of two methods. The first method is geomechanical modeling using a selected model capable of correct description of the behavior and properties of real-life mining subjects. The second method is the in-situ stress measurement. The authors present a processing procedure for the overcoring data, including the multivariant numerical modeling and analytical estimation. The key target of the multi-variant numerical modeling is 3D determination of strain-and-displacement patterns in walls of a test well using an elastic model of rock mass. The proposed procedure works within the framework of elasticity theory since the basis of overcoring is the elastic recovery of an element after drilling, i.e. separation from the main rock mass. The stresses and strains correlate linearly by the Hooke law. The lab-scale test data on the strength and deformation properties of cores from the test well are analyzed. Using the found patterns and measured displacements of walls of a rathole at the stage of the full-scale tests, all linear and angular strains are determined and presented as a matrix (strain tensor). The normal and shear stresses are also determined and presented as tensors. The case-study of processing of the full-scale test data (measured displacements of rathole walls) in apatite–nepheline ore host rock is described.

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