The U.S. Bureau of Mines, in cooperation with a central Utah coal mine operator, began a study in July 1988 into longwall gateroad designs applicable to deep, bump-prone mine conditions. Prior to the study, four adjacent longwall panels, incorporating a variety of panel entry configurations using "yielding" chain pillars, experienced severe bumps and coal outbursts at the face and in the tailgate pillars during panel extraction, resulting in several lost- time accidents and a fatality. To quantify those factors primarily responsible for bump occurrences during panel retreat, a field investigation was initiated to confirm the anticipated performance of a two-entry gateroad system employing a large, nonyielding chain pillar design. Hydraulic borehole pressure cells and roof-to-floor closure (convergence) measurement stations were installed to monitor gateroad abutment loading and entry closure during panel extraction. Study results indicate that very high confinement of the coal seam by strong roof and floor members existing across the entire property, in conjunction with overburden depths in excess of 1,600 ft, provides for bump-scale energy storage not only in gate pillars, but along the entire periphery of the active mining area. Insufficient gate pillar designs were also identified as possibly enhancing the occurrence of bumps in the tailgate and adjacent face areas.
Proc. 9th Int'l Conf. on Ground Control in Mining. West Virginia Univ., Dep. Min. Eng., 1990, PP. 142-149