Figure opposite shows a general layout of punch longwall mining. The aim of this method is to mine coal form the highwall of an open cut operation, in which the stripping ratio is far outweighs the production cost of coal mined.
The method consists of driving a set of headings in to the coal seam from the highwall of an open cut operation. The two headings are driven a predetermined distance (say 3 000 m) and are then connected to form a panel. Longwall face equipment is subsequently installed across the panel as shown in Figure 1. The coal is mined by retreating back toward the highwall until a short distance from the entry. This section of coal is left to act as a barrier pillar to protect the highwall.
Punch longwall mining is carried out using single entry gateroads as the they are only used by one panel. The adjacent panels can be similarly extracted with fresh entries being driven adjacent to the previous mined out panel leaving a barrier pillar of suitable width to provide safe retreating of the new panel as shown in Figure 2 opposite.
The extracted coal is transported out and piled at the ramp whereit is transported by the most convenient method used by the mine.
This system of mining is suited to mining reserves which would otherwise will be difficult to mine with the conventional mining methods.
The features of this system of mining include:
- The system requires no transport, conveyor drifts, shafts, complex ventilation systems or main headings as in conventional underground mining methods, hence this benefit provides cheaper, faster, simpler access and commencement of longwall mining.
- Gaining knowledge about mining, geological, and other information is quickly achieved at an early stage.
- This method is flexible as the infrastructure can be easily relocated.
- The development of gateroads on future panels is separate from the current longwall panel due to the use of barrier pillars.
- Requires less manpower and the method is suitable for contract work.