The primary focus for this thesis is to investigate the feasibility of highwall mining operations at the Curragh North mine. Highwall mining is best defined as the method whereby underground coal is directly extracted from the coal seam of an open cut highwall in a surface controlled operation by making repeated entries or drives into the seam. Highwall mining has been in use for well over a decade but in this time very few operations have used this technique under a low-wall. It is planned to low-wall mining at Curragh North, other aspects which make this thesis unique is highwall mining up-dip, in close proximity to the MacKenzie River and with a weak alluvium roof and floor composed of tuff.
The basic theories behind highwall mining have been studied which has provided a platform for the development of this thesis. Along with these theories, previous experience gained at other sites has been considered to gain a better understanding of highwall mining. The most important theories used in this thesis include the Highwall Mining Index and the Auger Mining Index. Based on data obtained via borehole drilling, the previously mentioned theories were applied to a site specific case for the Curragh North mine. Through the use of these theories a site assessment of Curragh North was performed in regards to its suitability for highwall mining. This assessment included an initial site assessment, a span stability assessment, a pillar layout assessment and subsidence assessment.
The most important part of this thesis was the pillar design and this was able to be determined based on the Highwall Mining Index parameters. Based on these designs coal reserve calculations were carried out which in turn resulted in a detailed economic and sensitivity analysis. Although highwall mining is still relatively new compared to other types of mining, and is yet to be fully embraced, it is believed highwall mining has a much greater potential in the future when large open pit mines begin to reach there final pits. Further developments in this field will greatly benefit the entire coal mining sector.