A methodology for risk-based management of the remaining life of structures in vertical mine shafts through integrated structural inspection and maintenance

Abstract

Mine shaft structures play a crucial role in mining operations, and their structural integrity is essential for ensuring operational safety. However, these structures deteriorate over time because of various factors such as corrosion, cracking, structural damage and structural ageing. The structural deterioration impacts on production, safety, and the environment. Estimating their remaining life is critical for preventive maintenance planning and ensuring continued operation. Corrosion significantly affects steel structures, leading to accelerated deterioration and potential catastrophic failures. Regular Structural Inspection and Maintenance Management (SIMM) programmes are essential to detect and address wear, preventing failures, and extending shaft lifespan. Challenges persist in managing corrective measures for mine shaft maintenance, hampering data reliability and informed decision-making. The disconnect between structural inspection results and maintenance systems leads to unaddressed defects and inadequate tracking of critical maintenance in Computerised Maintenance Management Systems (CMMS). This gap hampers informed decisionmaking regarding life cycle cost (LCC) and life of mine (LoM) estimation. This dissertation aims to bridge the gap by integrating structural inspection and maintenance data with CMMS, proposing the Integrated Structural Inspection and Maintenance Management System (iSIMM) and prognostic and risk/economics-based maintenance decision-making model for improved structural maintenance in the mining industry. The research journey starts by exploring mine shaft intricacies and the SIMM, followed by an extensive literature review on structural health and monitoring, covering corrosion, ageing, maintenance, and regulatory requirements. It progresses to developing an iSIMM and a maintenance decision-making model. Validation through a case study at Harmony Gold Mine confirms the practical application of these models in real mining environments. The research findings underscore the potential extension of mine shaft structures’ lifespan by timely replacement of degraded parts, ensuring continuous operations without significant disruptions. Investors have the opportunity to assess risks and returns for possible mine life extension. The implementation of an integrated inspection system enhances visibility into required maintenance for the mine shaft structures, facilitating effective monitoring of maintenance progress and structural condition changes affected by proper upkeep. Proactive monitoring and management practices contribute to 3 reducing LCCs by employing risk-based inspection and condition-based maintenance strategies for optimal maintenance. Moreover, the prognostic and risk/economics-based maintenance decision-making model aids in estimating mine life and supports resource planning. Predictive modelling plays a vital role in determining replacement costs, contributing to future budget planning efforts. The credibility and dependability of the findings are based on the analysis of reports from third-party structural engineering inspections conducted over the past decade. These findings have been verified through physical inspections, in-depth discussions with both mine engineers and contracted structural engineers, and consultations with the engineering teams responsible for performing regular shaft examinations.