ACCESS TO SEAM FROM SURFACE FOR UNDERGROUND COAL MINING

Overview

The means of gaining access to the coal seam from the surface is a matter to be decided early in the planning process and which can greatly affect the future operations for the whole life of the mine.
Decisions need to be made regarding the:

• Type and function (e.g. coal haulage, personnel and/or materials transport, ventilation only)
• Number
• Size
• Location
• Construction method

of access openings, and possibly timing (not all may be required at the start of operations).
Note that, in Australia at least, legislation requires 2 independent means of access able to be traversed by personnel, so that there is always an alternative means of egress (commonly referred to as a second egress or emergency escapeway) from the mine available in the event the primary means becomes unavailable for any reason In addition to this requirement, the accesses must be adequate to allow for:

• Sufficient ventilation quantities at acceptable ventilation pressures and costs
• Efficient and safe transport of personnel and materials into and out of the mine
• Installation of adequate services (e.g. electric power, water and usually compressed air reticulation systems and pumping or "waste water" reticulation system).
• Coal transport at the required rate
• Handling water make and spillage which occurs within the access

These requirements may be conflicting and some compromise is usually required, particularly when cost is taken into account. Lack of available capital may be a limiting factor and there may be time constraints (minimizing time to start of production so cash flow becomes available as soon as possible) which prevent the optimum design being installed.
It must also be decided if the accesses should allow for future expansion at this stage. The capital costs are very high and there are likely to be pressures to reduce costs pending commencement of production and subsequent positive cash flows. However carrying out modifications and/or extensions to mine accesses at a later stage within an operating mine can be particularly disruptive and expensive at a time where high fixed costs are present.