BASIC MINE PLANNING
S.Narayana Moorthy

BASIC MINE PLANNING
Have you considered these?
A Hard look
Any consideration to be given.
Major thrust

Mine planning is all about including all phases of working an ore body/mineral deposit to its economical limits. Enormous thinking and forethought go into this. Still the site personnel at the operational level get surprises and need to guard for any contingency. This article examines some aspects which appear very basic but can pose real challenges.

Now, to cite an example, an intricate limestone deposit is worked. The priority is the daily/monthly recovery targets. In a large-scale working, feeding to a major plant many things don't even get noticed and with the thrust on the limestone as a raw material, the target is for limestone and the term reject consists of all material other than the acceptable grade in the plant. Consequently the economics is based on the yield from run off mine plus rejects sent to the dump. The economics could also vary if the material supply only augments other sources and some sort of flexibility in the grade is allowed.

The danger lurking here is exploiting only good grade and passable grade and leaving out all other material either as blocks or sending to a dump. If the recovery is not considered economical, the dump grows and most of the material is compacted and could be lost.

On the other hand, for the working of a non-captive mine or one which meets only part of the suppliers and can have its own decision making, the economics change. Here the overhead is directly proportional to the recovery. A very close look is given to the reject category and what is considered SALEABLE material gets a thrust. The economics of the mine undergoes a drastic change.

An outsourced mine could have different yardsticks compared to  a captive mine.

An intricate deposit undergoes immense structural deformation and it has been seen that the exposures offer opportunities when closely looked into. A limestone mine with calcite veins and dolomite blocks yields the following:

Calcite
Limestone of cement grade or plant acceptable grade
Magnesia limestone for other uses
Even the quartzite yields possibilities

Each of this material has different market value and the overall performance of the mine could bring about surprising results. Mineral conservation gets the thrust automatically and every bit out of the run off mine gets a closer look and segregated.

Here is where the  necessity to create different stacks/ yards for varying grades come and the working undergoes a radical change. The reserves are exactly measured, values assessed and planning gets a priority and working becomes a on-site-daily assessed affair.

The geologist and the surveyor get into the act, mining becomes totally commercial as different from that of a  captive mine. The site personnel then have the necessity to know many things which otherwise would not even come to their knowledge.

Have you considered these?

Mining lease area and mineralized zone
Where the dumps would be located and how many segregation points
Levels of the mine and distances
How many workings can yield material that can be directly loaded and dispatched?
How many blocks come under high recovery, medium recovery, low recovery and total reject?
What  is the threshold value
Proportions of all these with reference to the run off mine

Quartzite could be hard to drill, limestone a better penetration, dolomite/magnesia limestone may not need much drilling at all and overburden could be tricky.

The locations of the blocks and the volume from each block.

The levels play a major role in realistic calculations for the haulage in particular. The market determines the economics of working different bands and the levels at which these occur play a very important role in  day to day working.
Often the volume/tonnage of the end product may lead to a false sense of comfort.

A very hard look therefore is needed at:

The nature of the deposit and working results in the adjoining mines if available
The nature of the overburden to be handled and the distances to move it for disposal
Administration involved in maintaining different dumps
Segregation at the dumps and multiple handling

Unless the volumes are adequate to have independent working blocks, it becomes necessary to plan frequent movement of available equipment to different working blocks. This not only disturbs a planned working, but adds to the maintenance woes and unpredictable availability.

The working timings necessarily have to meet the requirement at the plant which is the main consumer and the secondary marketing proportions suitably planned. PLANNING THEREFORE BECOMES A VERY TRICKY AFFAIR BALANCING THE VOLUMES. The optimal use of the equipment may not be achieved perhaps and this could focus on the realization from other material. The vagaries of the structure would call for real forethought and adequate inventory to keep up delivery schedules.

UTILIZATION OF AVAILABLE RESOURCES BECOMES THEREFORE A NECESSITY AT THE OPERATIONAL LEVEL AND PERSONNEL AT THE OPERATIONAL LEVEL NEED TO HAVE FLEXIBILITY TO ADAPT TO SURPRISES.
 

And consideration to be given at:

Do the performance relate to the targets?
Are the dispatches consistent with the projections?
Is there any queuing at the loading end or idling for want of supporting equipment?
Proper yard and stack area demarcation done for different quality stacks
How is the re-handling at the dump carried out?
Formation and maintenance of different dumps
Who does the quality reconciliation and at what intervals?
Is there any rejection of the supplied material on account of quality?
Protection from nature (rain etc)
Is there any procedural and documentation delays?

Daily

Have you considered these?

Major thrust areas are:

under-utilization of equipment
need for development and maintenance
protection against uncertainties
quality audits
proper feedback from commercial departments