Punch Longwall Mining

This is a rather specialized type of mining which is only applicable where a seam is exposed at the highwall of an open cut mine which has reached the economic limit for open cut mining. It could also be applied where a seam has an extensive natural outcrop, but there are no instances of this in Australia known to the writer.
Two roadways or sets of roadways are driven into the seam from the highwall (or outcrop) to the maximum practical distance to form gate roads and are then connected by driving the longwall installation roadway.
The longwall is then retreated back towards the surface, leaving only a pillar of coal sufficient to prevent the highwall being destabilized.
The longwall is then recovered and the process repeated, possibly using a roadway remaining from the previous block, if available, as one of the gate roads.

Punch mining into an open cut highwall

In this way a large area of coal can be recovered, beyond the open cut limit, without the need for major investment in infrastructure (shafts, main roadways, etc), the coal produced being delivered into the open cut where other necessary facilities (coal prep plant, surface transport loading facilities, stockpiles, etc) already exist.
The term punch mining is only applied where a series of such longwall blocks is extracted, each in effect being a small underground mine. It is not used to describe the case of a large underground mine being developed by driving the mine access from a highwall or outcrop.
Any method of mining could actually be used to extract coal in this way, but it has been included in the longwall section as the method has been developed for use with longwall equipment.