Empirical observations of dilution in panel caving
RL Castro, PS Paredes
The extraction of ore in panel caving operations also involves the coextraction
of non-economic material, known as dilution. Forecasting,
avoiding, and understanding the mechanics of dilution is critical to longterm
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.