Design of Barrier Pillar for Highwall Stability in Punch Longwall Mining: A Numerical Modelling Approach

Punch longwall mining technique is a highly economical method of extracting coal deposit existing beyond the critical depth of open pit mine. As the entries to longwall project are driven and maintained into the highwall, it's stability is of paramount importance for the sustenance of punch longwall project.

The subsidence resulting from longwall retreat should not affect the highwall of the open pit, from the floor of which punch longwall is started. A safe barrier pillar left between the highwall and the last line of extraction by longwall retreating assumes significance in that respect. A case study of one opencast mine operating in Southern India was taken up, where punch longwall project is planned, for arriving at safe barrier width. Studies were carried out using 3D disticnt element modeling.