Numerical modeling of progressive gob formation in a deep longwall mine

Because the Environmental Protection Agency has identified methane as a greenhouse gas, the degasification of coal bed methane through gob wells has become more critical. It has been observed that the degree of methane emission is closely related to the geomechanical characteristics of coal bearing strata, roof, floor, and surrounding coal seams. As a result, the study of progressive gob formation becomes necessary to understand the mechanism of strata movement and methane emission through gob wells. Several numerical models were developed to simulate gob formation of a longwall mine having similar geologic conditions as the Warrior Basin in Alabama. In addition, monthly production data from 250 gob wells and corresponding face position in each panel were collected from this area to corroborate the results of numerical modeling. This paper describes the techniques for numerical modeling of progressive gob formation and correlate the results with field investigations.