Authors: Gabanakgosi, K; Mogorosi, O; Rametlae, K; Boitshepo, B; Barei, OM

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DOI https://doi.org/10.36487/ACG_repo/2135_08

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Gabanakgosi, K, Mogorosi, O, Rametlae, K, Boitshepo, B & Barei, OM 2021, 'Structural data bias assessment at Jwaneng Mine', in PM Dight (ed.), SSIM 2021: Second International Slope Stability in Mining, Australian Centre for Geomechanics, Perth, pp. 159-174, https://doi.org/10.36487/ACG_repo/2135_08

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Abstract:
Successful delivery of a life-of-mine plan largely depends on the reliability and performance of the geotechnical models. Assessments of the reliability of the geotechnical model have therefore become a key focus in managing mining operations. A major risk to the reliability of the geotechnical model is data confidence, and the focus for every mine site is on the key aspects affecting the design and stability of mine excavations. Stability of the mining excavation is controlled in large by geology and structures. In this regard, the confidence in data used to confirm the geology is critical. Pertinent for mines affected by geological structures is an assessment of data bias as structures not appropriately defined could be detrimental to the mine’s stability. Jwaneng Mine’s open pit stability is controlled by steeply dipping bedding daylighting into the pit on the eastern slopes and dipping into the walls on the western slopes. Data confidence in relation to the data collection method has been carried out. This includes spatial resolution, accuracy and precision of the chosen data collection method, as well as bias. Extensive geotechnical data collection through drilling and pit face mapping has been undertaken throughout the life-of-mine. Data collection methodologies have been discussed which informed the data source selection from respective data collection methodologies. Low quality datasets were excluded and assessment was made as to whether significant data gap (spatial) will arise due to exclusion of these datasets. This was, however, not realised as Jwaneng Mine has extensive data coverage, but it presented an opportunity for retrospective assessment of potential data bias. Bias assessment undertaken from the data covered a review of existing drillhole core orientations and mapped discontinuity orientations. Stereonet plots, and 3D plotting of the drillholes, together with discontinuity from geophysical televiewer logs were used for the bias assessment. Evident from the assessment is bias that results from unfavourable drillhole orientation with respect to certain geological structures. The methodology provided a means of proactively realising the gaps and adequately addressing them. This has proven to be valuable knowledge that can be shared with the industry such that mine design studies, as well as operation design reviews, should include it in order to ensure the mine design objectives are successfully delivered.

Keywords: slope design, slope stability, model reliability, data confidence, data bias

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