Mine Site Specific Longwall-Induced Permeability Changes: A Case Study

Mine site specific numerical models using representative hydraulic properties of various overburden strata have been developed to investigate the effect of underground excavations on change in permeability in overburden strata. The developed models have been calibrated and validated against the mine site subsidence and mine water inflow data. The paper compares results obtained from a 3D finite element modelling with a 2D discrete element modelling. Each technique is demonstrated to have unique capabilities; the continuum method has efficiencies that allow three dimensional simulation while the discontinuum approach allows for the initiation and propagation of fractures allowing for the calculation of permeability from first principles. The comparative results between 3D simulation and 2D simulation are in good agreement. It has been noted that a well-defined 2D model can also represent the 3D numerical model in order to quantitatively estimate the height of connected fractures. The increase on the longwall panel widths causes the height of enhanced permeability to increase.