Modified T–Z model—a software for tension piles

Abstract

Pile foundation is one of the common type of foundation used to support structures resting in weak soils and in an offshore environment. Piles are generally subjected to compressive (downward) loads. Hence, the majority of studies on piles are directed towards their behaviour under compressive loads. With the development of tension leg platform (TLP) technology for developing deep offshore oil and gas fields, there is a growing interest in understanding TLP pile foundation. The piles used for TLP foundation are subjected to static pull-out force superimposed by a cyclic tensile force. The review of literature shows that the T–Z method proposed by Sulaiman and Coyle is being used commonly to estimate the load–displacement behaviour of tension piles. Although the method is simple, it suffers from few limitations. This paper critically review the model suggested by Sulaiman and Coyle and presents a modified T–Z model for tension piles. Details of a computer program developed, for the modified T–Z model, are presented in the form of flow-chart and algorithm. The program developed is employed to estimate load–displacement behaviour of a set of field piles. The results are compared with the observed values and with those predicted by the Sulaiman and Coyle method. It is observed that the modified T–Z model provides a better prediction to the observed values than those predicted by the model suggested by Sulaiman and Coyle.