UBC Theses and Dissertations
Numerical model for corrosion of rock bolts by galvanic minerals in a heterogeneous rock mass Lee, Paul
Corrosion of ground support poses a significant safety risk to underground mines that is difficult to identify and costly to address. The corrosion of embedded ground support elements is undetectable by visual inspection. This leads to unexpected failure typically mitigated by comprehensive rehabilitation that covers any areas suspected of corrosion. Rock bolts are replaced when the visible portion of a rock bolt is judged to be excessively corroded or loss of holding capacity is confirmed by the pull-out test. This thesis investigates the influenced of the mineral electrochemical properties in a heterogeneous rock mass on ground support corrosion. Previous work focused on the uniform corrosion of ground support in wet and dry conditions by empirical experiment in a real or simulated underground mining environment and on the corrosivity classification of environment by various qualitative measures. This thesis approaches the electrochemical influence of rock mass to corrosion of rock bolt by characterization of mineral electrochemical properties, numerical simulation of the galvanic corrosion process, and validation of numerical model by submersion experiment. A procedure for determining the electrochemical properties of minerals was developed with a complementary numerical model for galvanic corrosion of ground support by minerals. Additionally, the simulated numerical corrosion model was validated with a submersion experiment. The numerical model was found to have over-estimated the galvanic corrosion of steel by cathodic mineral, but predicted cathodic protection of steel by anodic mineral. The numerical model did not account for the acid byproducts of oxidized sulphide minerals that resulted in pitting corrosion. These findings allow us to predict galvanic corrosion of steel by minerals and propose a new mechanism for initation of pitting corrosion to by pyrite oxidation.
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