Journal Article

Evaluation of Rock Burstability with Mechanical Property Testing and Microscopic Image Analysis

Rowe, C. D., Mitri, H. S., Vennes, I., Malki, J.

2025

Overview

Ore extraction at great depths creates high stresses around mine openings which can result in violent rock failure in one of various forms of strainburst. This is especially true with strong and brittle rocks which can store a large amount of strain energy that is suddenly released at failure. The strength and brittleness of rocks have been extensively investigated in the past. The most widely accepted method for the determination of rock burstability is the strain energy storage index obtained from a non-destructive uniaxial load–unload test. However, the results of this method are not always conclusive showing less repeatability when the target test load is changed. This study concerns itself with the introduction of microscopic analysis as a tool to help validate the strain energy index results when burstability cannot be warranted based on mechanical property tests alone. In this study, two types of rocks, namely, basaltic komatiite (BK) and felsic norite (FNOR) obtained from Canadian underground mines are examined. The selection is based on the premise that felsic norite is known to be burstable from the mine experience, whereas basaltic komatiite is not necessarily burstable. A total of 60 mechanical properties tests were conducted including uniaxial compressive strength, Brazilian tensile strength, and load–unload tests. Laboratory tests on FNOR consistently exhibit high burstability; however, the results for the BK tests are not conclusive. To seek explanations for the mechanical rock behavior, 18 thin sections were examined with optical microscopy and image analysis. The findings show the tested BK specimens are dominated by alteration products, and all primary igneous minerals are lost. There is minor quartz, garnet, carbonate minerals, talc, and serpentine, which give the rock its ductile properties. The FNOR specimens are found to be relatively fresh and supported by a strong network of plagioclase with minor pyroxene, biotite, and secondary micas, explaining the higher stiffness. This study demonstrates how optical microscopy can complement mechanical property tests to evaluate burstability of rocks. Highlights Microscopic analysis was introduced to complement rock mechanical tests for the determination of rock burstability. Two types of rocks, namely, basaltic komatiite and felsic norite, were tested using rock mechanical testing and optical microscopy. The basaltic komatiite specimens are dominated by alteration products that are attributed to the rock’s ductile properties. The felsic norite specimens were discovered to be unaltered and characterized by a strong mineral network explaining the high stiffness.

• Publisher: Springer Vienna,Springer Nature B.V
• Subject: Biotite / Brittleness / Carbonate minerals / Carbonates / Civil Engineering / Compressive strength / Earth and Environmental Science / Earth Sciences / Energy / Energy storage / Garnet / Geophysics/Geodesy / Image analysis / Image processing / Komatiites / Laboratory tests / Light microscopy / Mechanical properties / Mechanical tests / Micas / Microscopic analysis / Microscopy / Minerals / Nondestructive testing / Optical microscopy / Optical properties / Original Paper / Plagioclase / Rock / Rocks / Serpentine / Stiffness / Strain / Strain energy / Tensile strength / Underground mines