ABSTRACT
This paper investigates the influence of stope geometry irregularity on stope sloughing and dilution. A comprehensive dilution database including mine design and geotechnical data from a local mine in Kazakhstan was established. The stopes were categorized into three shape classes depending on the extent of the irregularity, simple, semi-complex and complex geometry. First, numerical modelling was performed and the results suggested that the stope with complex geometry was found to have the highest effect on sloughing and dilution in terms of strength factor and tension. Next, the Rock Engineering System (RES), was used to define the dilution index (DI) for each category of stope geometry. The results revealed that the stope category had the most significant effect on the dilution index. In addition, the stability numbers corresponding to the stopes in this study was calculated and the accompanying stability graph was plotted for comparison purposes. The plots of the dilution index and stability number for all of the stope categories showed good correlations. This indicates that the DI can not only quantify the effect of stope geometry irregularity, but also can be used to evaluate the stope dilution.
In mining projects it is of paramount importance for geotechnical engineers to reduce the costs, minimize wastes, avoid dilution and improve production. As mining progresses deeper, unfavorable ground conditions can be found leading to unplanned poor stope performances. The stope hangingwall sloughage has been recognized as the dominant source of unplanned dilution in open stope underground mines (Urli and Esmaieli, 2016). Because of that, an extensive amount of research related to open stope dilution and sloughing, has been carried out over the past few decades. The stope geometry (shape, size, dimensions and orientation) is one of the key parameters influencing the level of unplanned dilution in open stope mining (Potvin, 1988, Stewart, 2005, Pakalnis, 2015, Vallejos et al., 2017, Heidarzadeh et al., 2019). Other factors include: the induced in-situ stresses, the blasting patterns, the surrounding rock mass properties, and operational needs.
