Abstract
Previous land use may have a significant effect on the hydrogeology of an area. Sites where extensive deep and opencast mining activities have taken place are often characterised by complex groundwater regimes. Many of the vast areas of disused and derelict terrain resulting from these activities, have now been developed as landfills. As landfill sites may constitute a major source of groundwater contamination, the hydrogeology of a site must be understood prior to the design and construction of disposal facilities.A heavy reliance is currently placed upon the ability of predictive groundwater models to simulate flow behaviour, irrespective of the hydrogeological setting. The applicability of most of these models to extensively mined strata is questionable. In addition, many researchers place little emphasis upon the development of an accurate conceptual model. This is indicative of an overconfidence in the ability to characterise most groundwater systems, by the direct input of hydrogeological data into numerical models.
This thesis describes the hydrogeological investigation of the largest landfill facility ever developed in Scotland, situated within the former opencast site at Greengairs near Airdrie, Lanarkshire. A detailed conceptual model is developed for the site which is based on various stages of interpretative study, inclusive of a comprehensive assessment of water quality and groundwater flow relationships. A full hydrological assessment of the site catchment is presented, which identifies the magnitude of surface water/groundwater interaction relative to a large surface water feature in the area. A review of groundwater flow theory and modelling techniques is presented, as is an attempt to develop a computer model which simulates groundwater flows through the various forms of 'channels' afforded by deep mining activities.
This work illustrates the degree, time permitting, to which a conceptual groundwater model can be developed. In particular, the reliability of the Soil Conservation Service runoff procedure to produce an accurate representation of catchment behaviour, in quantitative terms, is demonstrated, as is the vital importance of detailed field observations for hydrological studies. A sufficient level of evidence is presented to suggest that the conceptual modelling phase of a hydrogeological investigation, is an essential prerequisite to numerical modelling studies and should not, in any circumstances, be omitted.
This study concluded that the primary mechanism for groundwater movements in worked coal measures strata, will relate to the artificial features associated with deep mining activities. A secondary level of 'pathways' for groundwater movements is provided by the presence and associated characteristics of discontinuities within the rock mass. The ratio of artificial, subsurface features, beneficial to fluid movements, to the fracture dominated flowpaths within unmined strata, will determine the 'weighting' that can be applied to the n influence of each mechanism for flow. Neither Darcian or Discrete Fracture Network modelling approaches, permit the level of interaction afforded by these features to be incorporated within a groundwater model. However this work has shown, for the first time, that graphical computer programs, designed for the simulation of water networks, may provide the basis for the development of a model which is 'truly' representative of flow behaviour in extensively mined coal measures strata.
Many aspects of this study, and in particular the conceptual modelling techniques presented, contribute significantly to knowledge concerning the hydrogeological characteristics of worked coal measures. Recommendations for further research studies are included.
| Date of Award | Apr 1997 |
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| Original language | English |
| Supervisor | Ian Spence (Supervisor) & Kehinde Oduyemi (Supervisor) |