Joint analysis of rock mass stress state and elasticity modulus during shaft sinking

The article presents an innovative procedure for the joint stress–strain and elasticity modulus analysis in high-strength rock masses with spacing from a few to tens meters. The procedure includes measurement of elastic convergence of rock walls due to deeper penetration of the foot of a vertical shaft and the analysis of measured displacements of check points along the shaft cross-section perimeter with subsequent two-stage solution of an inverse geomechanical problem. In the first stage, in the lobed diagram of measured displacements of check points, the azimuths of axes of the principal horizontal stresses in surrounding rock mass are determined. In the second stage, the process of deeper penetration of the shaft foot is modeled with different scenarios of the rock mass stress–strain behavior set as varied principal horizontal stresses at the known azimuths of their main axes. Then, the model and in-situ measurement results are compared using the analysis of variance ANOVA. The wanted variant of the stress–strain behavior and the associated modulus of elasticity, such that deviation of the actually measured displacements of check points from the model values is minimal, is identified by the extremum analysis of the experimental diagrams. The procedure was successfully tested in Vspomogatelny and Skipovoi vertical shafts of the Tenth Anniversary of Independence of Kazakhstan mine within Donskoy Mining and Processing Plant, in qualitatively different geological conditions: high-strength rock mass areas categorized as unstable and stable. In unstable rocks, the measured elasticity modulus Е = 3,5 ± 0,7 GPa made 6 %–16 % of the elasticity modulus in samples. In the stable rock mass, the measured modulus Е = 36,6 ± 7,7 GPa almost coincided with the elastic modulus of samples.

Balek A.E., Ozornin I.L., Kayumova A.N. Joint analysis of rock mass stress state and elasticity modulus during shaft sinking. MIAB. Mining Inf. Anal. Bull. 2020;(3-1):21-36. [In Russ]. DOI: 10.25018/0236-1493-2020-31-0-21-36.

The study was supported within the framework of State Contract No. 07500581-19-00, Project No. 0405-2019-0007.

Balek A.E.¹, Dr. Sci. (Eng.), leading researcher, e-mail: balek@igduran.ru,
Ozornin I.L.¹, Head of Underground Structures Geomechanics Laboratory,
Kayumova A.N.¹, Cand. Sci. (Eng.), Researcher,
¹ The Institute of Mining of the Ural branch of the Russian Academy of Sciences, 620075, Ekaterinburg, Russia.

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