An application of numerical methods to the prediction of strata methane flow in longwall mining

Abstract

This research describes an application of numerical methods for the prediction of strata methane flow into workings around a logwwall coal face employing methane drainage. This method of methane predic- tion was developed by solving the time-dependent gas flow equation using the finite element analysis. Having obtained the gas pressure distribution throughout the finite element mesh, a mass flow equation was derived to calculate methane flow rate for a given mining boun- dary. A computer program for the prediction of methane flow was then developed by devising appropriate modifications and additions to a finite element package originally written for heat flow by PAFEC limited. Stress analysis was also carried out in order to provide an understanding of stress fields around a longwall face to evaluate the induced permeabilities under these stress fields. Three main routines of the original package required modifica- tions to accommodate the solution of a different equation. These we- re element routines, solution routines and flux calculation routines. These routines, after modification, were used to simulate advance and retreat longwall mining, with and without drainage. Several different sensitivity tests were carried out by changing parameters such as borehole pressure, length, and spacing in order to aid the planning of methane drainage systems for longwall mining.