The break even shut-off value will always remain the same as long as the mining and processing cost are unchanged but the height of draw for that shut-off value can change with metal prices. The design parameters which would have the largest impact on the shut-off value would come from the production target, development rate of new draw points, and the average height of draw.

Production Rate

There are many factors which impact the shut-off value but the target production rate is the most important because the production rate will determine whether or not to use a shut-off value. For a panel cave the production rate can be expressed in the following formula:

P = N * A * D * H

P – Production Rate
N – Number of new draw points per period
A – Area of a draw point
D – Average density
H – Average Height of draw

The production rate, along with the number of new draw points opened per period will determine whether there is excess mining capacity. The draw rate will also contribute to whether there is excess mining capacity because it determines how quickly a draw point can be mined. The draw rate and the HOD can be used to calculate the closure rate of draw points. This closure rate should not be higher than the draw point development rate; otherwise there would be no excess mining capacity. Read More.