Geoscience Reference
In-Depth Information
Fig. 13.10 Comparison of two
ore/waste dig limits. The left
option is more precise, but less
realistic, and impossible for
the shovel to dig to. Therefore,
a large amount of unplanned
dilution would be expected. The
right option is a smoother dig
limit, easier to dig for the shovel,
but that it may be sub-optimal,
depending on the characteristics
of the mining equipment
Fig. 13.11 Example of an ore
polygon, with 5 vertices and
affecting 19 blocks. The penalty
assigned is a function of the angle
of operation of the shovel
O OO
=
global
profit
digability
profitability. A vertex is randomly selected and moved with-
in a small distance (see Fig. 13.12 ). New profit and penal-
ties are calculated, and the new objective function obtained.
The results are sorted into accepted or rejected perturbations
based on its impact on the objective function, and the process
is iterated until convergence is achieved.
The dig limit selection algorithm can be made semi-auto-
matic if the option of an additional constraint is added manu-
ally, allowing for the technician to account for the limitations
of mining equipment and the value of the material. The dig
limit algorithm works by systematically giving up ore or tak-
ing in additional waste to pay for the increased digability,
i.e., less sharp angles defining the corners of the ore/waste
selection panels.
The initial profit is calculated as the sum of all fractional
blocks that are considered ore (profitable):
ny
nx
∑∑
O
=
frac
P
(,)
ix iy
profit
(,)
ix iy
ix
=
1
iy
=
1
where P represents the profit assigned to each block in the
model, and “ frac ” represents the volume within each profit-
able block.
The initial digability is calculated based on the character-
istics of the mining equipment, taken for example from an
equipment curve, and interpreted as the sum of the penalties
for each angle in the ore/waste polygon, see Fig. 13.11 :
13.6
Summary of Minimum, Good and Best
Practices
nv
=
O
pen
digability
iv
iv
=
1
At a minimum, all short-term models should be updated to
include new data that becomes available. Proper procedures
for validation and checking should be in place, and the com-
plete sequence of updating the model should take less than a
Using simulated annealing, the vertices and angles can be
moved within a small circle (tolerance) to change the angle
that it defines, and thus changing the penalty and overall
 
Search WWH ::




Custom Search