Project 8.4.5 – Using GPR to Improve Rehab Soil Characterisation

Monitoring and geochemical modelling at five pilot sites, on undisturbed soils and on opencast spoils, showed that most soils held a large share of the applied salt in the upper unsaturated zone and that salinity built up slowly. Leachate volumes, leachate quality and aquifer mixing ratios were quantified. Irrigation is recommended on alternating pivots and for no longer than ten years in one area.

Sub-seams within the No 2 Seam were characterised at a single test site using lithology, seam thickness, proximate analysis, petrography and geophysical logs, and a paleoenvironmental model was built from them. Wireline logs separated coal from interburden but could not resolve the individual zones, because the physical differences are too subtle. Better sedimentological models gave better reserve and resource estimates.

Geotechnical factors affecting secondary extraction were identified from interviews with collieries already re-mining pillars and with people experienced in stooping, then quantified and ranked against the different aspects of the work. No single factor governs the outcome. Factors interact, so choosing a method and working safely in old workings depends on managing them together across disciplines.