A GEOTECHNICAL SURVEY OF SOME BRITISH COAL MEASURES MUDSTONES, WITH PARTICULAR EMPHASIS ON DURABILITY

Samples of fresh mudstones were obtained from near Tow Law and Kirkhea ton, and of weathered mudstones from near Wrexham. The mineral composi tion of these mudstones was similar, kaolinite being the principal cla y mineral, the clay mineral fraction dominating. Quartz was the chief non-clay mineral present. Some basic geotechnical and index properties were determined. The fresh mudstones from near Tow Law had a low plas ticity, as did the moderately and highly weathered mudstones from near Wrexham. However, the completely weathered mudstones from the latter area possessed intermediate plasticity. The strength of the fresh muds tones from near Kirkheaton was notably higher than that of the mudston es from near Tow Law. Both groups of fresh mudstones displayed signifi cant anisotropy ratios when they underwent axial and diametral point l oad testing. This, no doubt, was due to the influence of lamination. A s durability is one of the most important engineering properties of mu dstone, it was assessed by a number of tests. One cycle slake durabili ty testing did not appear to offer an acceptable indication of the dur ability of mudstones when compared with cyclic wetting and drying, cyc lic freezing and thawing, and geodurability classification. Cyclic sla ke durability testing and comparison with unconfined compressive stren gth would seem to be a more reliable way of determining durability. Bo th fresh and weathered mudstones underwent little expansion when subje cted to swelling tests. However, in the case of the weathered mudstone s, the amount of swelling stress and strain could be related to basic geotechnical properties.