This paper presents the process flowsheet and the Excel based assessment tool developed by Torex and their strategic partners at SRK (Canada) and BWB Consulting Services Inc.
Abstract:
Longhole Open Stoping (LHOS) is a widely used mining method. LHOS is considered a “bulk” mining method that is generally applied to steeply dipping deposits. LHOS is generally thought to be a relatively safe and efficient mining method and can be applied in either a transverse or longitudinal orientation with or without backfill.
One of the challenges in designing a LHOS mine is selection of the optimum stope size (height, width, and depth). Larger stope sizes increase the productivity of the stope cycle and reduce the total mine development required to extract the ore. Unit operating costs are reduced with larger stope dimensions. Larger stope sizes introduce geometric simplification of the mining shapes which reduces the selectivity of the method. This could lead to a lower reserve tonnage at a lower head grade. Larger stope sizes also introduce a higher risk of geomechanical instability in the exposed walls of the stope and potentially more unplanned dilution. Decreasing stope size yields greater selectivity, improves ground stability, and reduces the amount of unplanned dilution. These benefits come at a premium in terms of lower stope productivity and higher unit costs.
Selection of the optimum LHOS size has traditionally been done using a combination of empirical, experiential, and analytical methods. This process can be subject to personal and professional bias. Torex Gold Resources Inc. (Torex) initiated a study to create a process and evaluation tool to integrate all relevant design criteria and remove bias from the stope size evaluation process.
