Prediction of pile settlement using simplified models

Modelling soil nonlinearity in pile settlement analysis often requires numerical analysis based either on 1-dimensional “t-z” curves or even multi-dimensional constitutive models, which may not be appealing to geotechnical engineers. A number of alternative approaches are available that take advantage of simplified constitutive models and analytical methods to develop solutions that are suitable for spreadsheet calculations. This paper investigates the error introduced by the assumptions in two such models. A theoretical “t-z” curve is developed based on a simplified constitutive model and a new approximate approach developed that incorporates nonlinearity for both shaft and base resistance. This is compared to the predictions of a linear elastic – perfectly plastic method using an informed choice of linear elastic stiffness. A basic sensitivity study is carried out comparing the two approaches with a 1-dimensional numerical solution.