Load/settlement prediction for large-diameter bored piles in Mercia mudstone

A semi-empirical method has been developed which can predict the characteri stics of large-diameter, bored, cast in situ piles in Mercia mudstone, at e very stage of loading up to the ultimate state. The analysis is based on ma thematical representation of: (a) the mobilization of shaft resistance and end bearing with increasing pile settlement; (b) the variation in load shar ing between the pile shaft and base; (c) where present, the additional infl uence of compressible soil debris on settlement at pile base level; and (d) the effect of nonlinear stress-strain behaviour of concrete on pile compre ssion, hence settlement. The predictive method has been validated against a large database of full-scale pile tests in Mercia mudstone and other cohes ive soils. The database comprised test piles with or without instrumentatio n and having a wide range of diameters and lengths. In every case, the pred ictive capability is judged to be accurate and satisfactory. The method is also capable of dealing with special circumstances whereby a pile is specif ically constructed to support load purely in shaft resistance or end bearin g. The improved predictive capability of this method, in pile analysis, is expected to result in a more cost-effective construction.