Distributed fibre optic sensing for ground monitoring in underground hard rock mining

Authors: John, D; Hoehn, K

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DOI https://doi.org/10.36487/ACG_repo/2465_20

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John, D & Hoehn, K 2024, 'Distributed fibre optic sensing for ground monitoring in underground hard rock mining', in P Andrieux & D Cumming-Potvin (eds), Deep Mining 2024: Proceedings of the 10th International Conference on Deep and High Stress Mining, Australian Centre for Geomechanics, Perth, pp. 391-402, https://doi.org/10.36487/ACG_repo/2465_20

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Abstract:
Managing an underground hard rock mine is an intricate engineering feat, requiring comprehensive oversight. A critical aspect of this management is ground control, focusing on addressing rock instabilities that arise from the mining processes and ore removal. Understanding the geotechnical characteristics of the rock mass and the impacts of mining operations is crucial, yet the capacity to influence ground conditions significantly differs based on the accessibility and the amount of rock at risk of instability. Despite meticulous planning and design, underground mines must be prepared for unforeseen challenges, requiring the deployment of monitoring tools to confirm the stability of specific mine sections. Incorporating cutting-edge distributed fibre optic sensing technology into geotechnical engineering practices offers a way to enhance safety and evaluate ground conditions more effectively. This technology allows for continuous, real-time or near-real-time monitoring along a fibre optic cable; capable of detecting changes in strain, vibration and temperature through alterations in light's intensity, phase, polarisation, wavelength, or travel time within the fibre. Unlike traditional in situ mine monitoring sensors, which are limited by their discrete nature, fibre optic sensing leverages the optical fibre itself, providing a compelling alternative for these applications. An innovative and novel application of this technology was demonstrated by Mining3/CSIRO at an underground hard rock mine located in South Australia, where a distributed fibre optic sensing installation captured detailed strain and temperature measurements in a 500 m deep installation. The system employed durable and cost-effective fibre optic cables within standard HQ diamond drill holes and connected to surface interrogators. The gathered data was processed offsite and integrated into the mine's operational systems for analysis and informed decision-making. This paper presents continuous fibre optic monitoring as an economical, dependable approach that offers critical data to mine managers. It outlines the foundational principles of fibre optic sensing and practical installation considerations for such a system. Distributed fibre optic systems are capable of being installed in deep holes and run over extended distances, in tunnels or on the surface. They provide a comprehensive multi-parameter sensing capability beyond the reach of traditional monitoring tools. Additionally, this paper highlights the potential of fibre optic-based geotechnical monitoring technologies to significantly enhance mine safety and efficiency when integrated into the planning, design, and operational stages of hard rock mines.

Keywords: fibre optic sensing, ground control, underground, hard rock mining, distributed sensing, strain sensing

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