Increasing sublevel caving (SLC) ore recovery improves productivity by bringing revenue forward and reduces the risk of value dilution due to later stage recovery. Parameters influencing sublevel caving recovery were identified using a combination of self organising maps (machine learning neural networks) and statistics – these advanced analytical methods are available through ProdFinderTM .The analyses are based upon recovery data for 20,000 metal markers installed at the mine over three years, in the early 2000’s:

20,000 metal markers installed at Ridgeway SLC mine in early 2000s (Brunton et al, 2010)

20,000 metal markers installed at Ridgeway SLC mine in early 2000s (Brunton et al, 2010)

Parameters analysed included those related to drawpoint location, drill and blast design, geology, drawpoint geometry, and draw control. To identify parameters influencing recovery, a Self-Organising Map (SOM) technique was adopted. SOM is considered an ideal tool for analysing complex geological and mining datasets, and for extracting relationships and patterns that typically are not evident by other means. The SOM analysis indicated that a number of drill and blast design parameters were directly or inversely correlated to material recovery at the Ridgeway SLC operation. Blasting parameters dominated correlations with recovery when compared to drawpoint and geological parameters.

Charge length, powder factor, PPV breakage criteria, explosive sleep time, and blast detonation issues related to recovery parameters for all levels of recovery. Additionally, the number of blast holes, toe spacing, spacing to burden ratio, and primary detonator location related to total secondary to quaternary recoveries. Non-blasting parameters found to have a significant number of correlations to total extraction zone recovery (including backbreak) parameters include drawpoint width at gradeline and number of thrust faults.

Interpretation of metal marker recovery data

Interpretation of metal marker recovery data (Brunton et al 2010)

Importantly, the analyses indicated that the removal of blast holes resulted in lower extraction zone recoveries. The reduction in the number of blast holes  impacted upon total secondary to quaternary extraction zone recovery either directly (due to factors such as poor fragmentation and limited swell), or indirectly through reduced primary recovery (leading to subsequent lower total secondary to quaternary recoveries).

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Parameters Influencing Full Scale Sublevel Caving Material Recovery at the Ridgeway Gold Mine