Issues to be Considered

In no particular order, issues which should be considered are:

• Accesses are very expensive so their number and size (cross section and length) need to be minimized from a capital cost point of view
  
• Excavated material has to be disposed of on surface which also suggests minimizing the number and size of accesses
  
• Accesses carry the total mine airflow and the lower the resistance to flow the better, hence the size and number of accesses need to be maximized from a ventilation point of view (but length still to be minimized) – note that the power cost for ventilation is incurred 24 hours a day every day of the mine's life with rare fan stoppages for particular purposes
  
• If the resistance to ventilation flow in the accesses is very high, extra roadways may be required throughout the mine to keep the overall resistance down to practical levels. If development mining is not profitable it may be more economic to excavate larger or increase the number of accesses instead
  
• Desirability of keeping personnel and supplies transport in a separate access to coal haulage, and the desirability of keeping both in intake airways
  
• Full extraction of coal cannot be carried out within an area around any access to ensure it remains stable – first workings only within the shaft or drift pillar. This area of sterilized coal needs to be minimized or located to coincide with an area where coal is already sterilized for other reasons

Areas of coal sterilised by shaft or drift pillars

Vertical Shaft

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Drift

• Strata/stress conditions – any access has to remain stable with minimum maintenance costs, for the life of the mine (in most cases), so locating accesses within potential adverse strata or stress conditions should be avoided
  
• Size of equipment to be installed in the access or to be transported through it - the opening size not only needs to be large enough to fit the equipment in, but the effect of the equipment on the cross sectional area needs to be considered from a ventilation perspective.
  
• Position within the lease – to one end (or side) or located centrally within the lease. There are both benefits and disadvantages in all options.
  
• Means of personnel transport – travelling time, need to change from one type of transport to another.
  
• Physical limitations on surface sites – avoid flood prone areas, site to be easily accessible for employees, materials supply to site and coal transport away from site.
  
• Social limitations on surface sites – effect on local populations from noise, dust, visual pollution, traffic
  
• Heritage/cultural limitations on surface sites
  
• Zoning limitations on surface sites – non-industrial zonings, water catchment areas, etc
  
• Availability of services – water and electric power supplies, disposal of waste water
  
• Areas for disposal of waste rock
  
• Timing – a minimum two accesses are required to be interconnected before any major development can take place, so they need to be reasonably close.
  
• Provision for handling water and/or spillage made within the access
  

Note that not all the accesses have to be located at the same place if there are benefits in separating them.