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4.3.2.
Analyzed waste rock
The waste rock analyzed in this section corresponds to large run of mine (ROM)
samples obtained from the open pits of two mines located in high mountainous areas
in the central region of Chile. These materials are coarse, with angular to sub-
angular shape, obtained by the blasting of hard porphyritic rocks. These rocks have a
compressive strength of about 120 MPa, and a specific gravity of solids G
s
of 2.7 to
2.8. In general, the waste rock is loaded by mine trucks of large tonnage,
transported and then dumped in different sectors of the dump, in layers of limited
thickness (about 50 m) according to a pre-established placement plan.
The results shown in Figure 4.2 correspond to those obtained with ROM waste
rock (ROM WR) and crushed and leached waste rock. ROM WR was obtained from
a sampling of about 50 tons directly from a dump. A portion of these materials was
crushed to create a second sample. The third sample was taken from a trench dug in
a waste rock platform subjected to forced leaching over a period of two years.
Percent passing
# 200
# 4
8 "
100
Waste Rock Grain Size Distribution (GSD)
ROM WR (original from field)
Leached WR (original from field)
ROM WR (homothetic 8")
Leached WR (< 8")
Leached WR (homothetic 8")
Crushed WR (< 8")
Crushed WR (homothetic 8")
90
80
70
60
50
40
30
20
10
0
0.01
0.1
1
10
100
Particle diameter (mm)
Figure 4.2.
Grain size distributions of waste rock analyzed
The macrogranulometric analyses (integral grain size distribution) shown in
Figure 4.2 made it possible to determine the maximal sizes of the particles, which
vary in general between 30 cm and 100 cm (12” and 40”). Below 8 cm (3”), these
materials present fine contents (particles passing through the 200 ASTM sieve)
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