| A finite element (FE) package is developed to represent the impacts of mining on strata deformation and the resulting groundwater regime. Included in the graphical user interface are all aspects of model assembly, composure, execution, and examination of the resulting response. The package uses fast element meshing, optimal renumbering and advanced data search algorithms to maximize run speed, ease storage requirements and to provide a robust and versatile tool for the evaluation of mining related impacts on groundwater resources.;The model is used to evaluate the anticipated groundwater response in a variety of environments. An evaluation of hazardous groundwater inflows in the North China Basin is completed to define the mechanisms of catastrophic inrushes. Sensitivity studies replicate the observed precursive events and define intersection of mining-induced shear-deformation lobes, with the underlying overpressured aquifer as the likely trigger. Inrush mitigation methods, including provision of mining-concurrent backstowing and pillar and strata destressing, are evaluated to define potential impacts. Backstowing is shown to exacerbate inrush potential, and destressing is demonstrated to relieve the potential by more uniformly distributing induced stresses.;Evaluation of hydrologic response in the overburden around longwall panels establishes the relationship between panel depth, barrier pillar width and amounts of stream water loss and panel inflows. Intersection of the shear-extension zone with the ground surface is shown capable of precipitating stream capture, with the severity of this effect strongly linked to panel depth, location, and overburden stratigraphy, relative to the channel. The retention of a reduced width pillar directly underlying the streambed is shown to reduce hydrologic impact for shallow panels as a zone of horizontal compression develops in the streambed. Mining effect diminishes with increased panel depth. Topographic influences on behavior are shown to be significant. Panels located sub-valley develop zones of increased hydraulic conductivity that enhance recharge from upland areas and may increase stream recharge and local groundwater levels. For sub-hilltop mining, changes in hydraulic conductivity are at depth and primarily affect behavior local to the panel. Penetrating zones of extension, that reach close to the ground surface, also influence shallow water supplies. This effect is decreased where low conductivity layers are present in the stratigraphy, that isolate aquifer units, and where recharge is high.;The influence of surface and underground mining activities on groundwater resources are shown to be strongly dependent on the location specific parameters of topography, stratigraphy, excavation morphology and sequencing. These disparate variables may be readily accommodated on a case-specific basis using the computational package developed in this work. |
