a method is presented for the analysis and prediction of single pile behaviour under maintained loading, based on the use of hyperbolic functions to describe individual shaft and base performance. When these functions are combined, and elastic pile shortening is added by a relatively simple procedure, an accurate model is obtained. By a simple method of linkage, which relies on the fact that a hyperbolic function of the type described requires only definition of its origin, its asymptote and either its initial slope or a single point on the function, conventional 'elastic' soil parameters and ultimate loads may be used to describe total performance. By means of the changing slope of such functions, this method also reflects well in the increase of soil moduli at low strains. Examples are given from back-analysis of some fully instrumented and other cast-in-place pile test results, to demonstrate that good agreement with all recorded features can be achieved using the model. Extensive use has confirmed its validity for maintained load tests in a wide range of soils. Provided that piles have been made to settle sufficiently under load, so that the latter part of each relationship is well defined beyond the stage where shaft friction is close to a constant value, all the main relevant parameters can be determined with good accuracy in back-analysis. The derived data may then used to predict behaviour of piles in similar circumstances on other sites or of piles of different diameter in the same soils. Subject to the conditions described in the Paper, the method has far-reaching implications for design, construction and testing techniques.
