Journal of the Southern African Institute of Mining and Metallurgy
On-line version ISSN 2411-9717
Print version ISSN 0038-223X
The extraction of ore in panel caving operations also involves the co-extraction of non-economic material, known as dilution. Forecasting, avoiding, and understanding the mechanics of dilution is critical to long-term planning. The models of dilution that are currently in use in panel caving operations are those by Laubscher (1994), who postulated that dilution is due to gravitational flow and depends on the height of interaction, the column height, and the draw uniformity. This paper presents a back-analysis of extraction and dilution behaviour at Codelco's El Salvador and Andina Divisions, which use panel caving as a mining method. This analysis was conducted in order to review the existent dilution entry mechanisms and calculation methods. Three sources of dilution were identified. The first source is 'gravitational dilution', which is due to gravitational flow and mixing as dilution migrates by gravity from a sector located above the panel under analysis. The second source of dilution is 'caving dilution', which occurs when an air gap is formed in a large area and a sudden propagation of a hang-up occurs, inducing early ingress of waste into the production level from a level above. The third mode observed is 'lateral dilution', which occurs when the panel is located next to an exhausted sector and the broken material enters the draw column early during draw. In the last two cases, dilution could migrate large distances horizontally. The mine data indicated that draw and caving strategy are key for long-term planning of large panel caves.
Keywords : panel caving; dilution entry; gravity flow mechanics; draw control; uniform draw.