First workings are conducted for two main reasons:
- To develop the pillars, bords and/or panels to enable their subsequent extraction, and
- To develop multiple main entries for access to the coal reserves. These entries are supported in the long term by the pillars consequently formed.
The number of development headings driven in any area of workings can vary between two and eight. This is
dependent primarily on the purpose of development, and the second method of working together with the following factors:
- Mine capacity,
- Pillar and /or pillar and panel system relating to depth of working, productivity and panel extraction system,
- Number of continuous miner units operating,
- Coal clearance system,
- Men and material transport, and
The size of the pillars and headings driven during the first working stage is restricted by statutory requirements of a particular State. In NSW the size of the pillar is restricted to a minimum of 1/10 of the depth, and the width of the bord to 5.5 m. Special exemptions are required for driving bords (roadways) wider than 5.5 m. The roadways are normally driven in rectangular shape.