Geomechanical Criteria of Longwall Face Support Selection at Consol Mines

This paper describes geomechanical criteria employed by Consol Energy for selecting mine-specific longwall face supports in the past decade. The criteria include immediate and main roof rock characteristics, floor rock characteristics, critical tip-to-face distance and shield operating range. Detailed roof rock properties from high-density core holes as well as in-mine scope holes are used to evaluate the set load density and shield stiffness required to control the immediate roof and the yield load density required to absorb the load density developed from main roof weighting. Detailed floor rock properties from core holes and in-mine floor bearing capacity tests are used to specify the maximum peak toe pressure as calculated by the Jackson method. The critical tip-to-face distance is evaluated based on the immediate roof rock strength, layering and thickness. The shield operating range is evaluated based on main bench thickness, the presence of thick draw slate, the potential of minor roof falls at the face and transportation restriction. Three case examples representing three different geologic conditions are presented to illustrate the successful application of these geomechanical criteria for selecting longwall face supports within Consol Energy in the past decade.