Highwall mining of thick,steeply dipping coal–A case study in geotechnical design and recovery optimization

Highwall mining of thick(up to 30.48 m) steeply dipping(20° or more) coal seams provides many chal lenges, both geotechnically and operationally, as seam dips near or in excess of highwall mining machine capabilities are encountered. Maximizing coal recovery while maintaining highwall stability requires innovative techniques with regard to web and barrier pillar layout, depth of penetration, and choice of mining horizon within the seam. Stability of highwall mining slopes, openings, and pillarsare typically analyzed using the ARMPS-HWM program, as well as LAMODEL, UDEC and SLOPE/W modeling.Highwall stability can be maintained, and highwall mining production optimized by applying design cri-teria in creative ways, including alternating miner penetration depths and initiating mining of thick seams toward the bottom of the seam. Highwall mining of thick, steeply dipping coal requires careful planning and execution, including close cooperation between geotechnical design engineers, the mining company, and the highwall mining contractor. This paper describes the application of creative design techniques to a specific pit arrangement at the Westmoreland Kemmerer Mine, Kemmerer,Wyoming. Highwall mining was accomplished by UGM ADDCAR Systems, LLC on a contract basis.