Subsidence interactions related to longwall mining of the upper and lower Kittanning coalbeds

The U.S. Bureau of Mines, in an effort to improve coal conservation and utilization, is currently investigating longwall panel layouts to maximize coal recovery and minimize interactive problems in multiple-seam operations. When longwalling coalbeds in ascending order, subsidence of the overlying strata is an interactive problem that may influence the stability of the gate roads and longwall panels in the upper mine. To control interactive problems, two fundamental design approaches involved either offsetting of superimposing the gate roads and longwall panels. This paper involves analytical predictions and underground observations of longwall development ground control problems at a south-central Pennsylvania coal mine where gate road superpositioning was practiced