| Summary: | The aim of this thesis has been to analyse and prioritise the geological factors which are prone to risk within British Coal Opencast's site tonnage estimation procedures. Geological variables such as coal seam thickness, specific gravity, washout and old workings deductions have been carefully analysed, using scanning and vectorising software techniques on examples of "ground-truth" recorded from surveyed plans from many worked sites. Techniques such as sensitivity modelling have determined which of the parameters are important in the estimation procedure. Sensitivity modelling has been linked with risk analysis to provide a means to critically review coal tonnage estimation. Statistical, risk analysis and Operational Research methodologies have been developed using commercial and custom written software to analyse and understand the necessary sampling strategies needed to estimate contract tonnages. The reduction of error in a tonnage estimate must be proportional to the increased understanding of the underlying geological variability with increasing sample numbers. A method is demonstrated whereby the optimum number of samples are suggested. However samples which exceed the optimum number do not necessarily increase the accuracy of the estimate proportionately to the extra sampling effort. The rate of this information gain has been modelled using a simulated exploration exercise and the results point towards variability reduction being inversely proportional the square root of the sample numbers. Knowledge gained from the inter-relationship between geological and sampling variability has been recorded, enabling future British Opencast Sites to be drilled and estimated with minimal contract risk. The resulting "Performance Assessment" methodology could be applied to a wider range of mineral exploration activities other than coal applications.
|
|---|
