Novel methods for characterising pipe-soil interaction forces in situ in deep water

[Truncated abstract] This thesis concerns the establishment of a theoretical understanding for the response of a new class of seabed penetrometers designed specifically for pipe-soil interaction applications avoiding the difficulty of end effects. In view of the perceived need to improve pipeline design guidelines and develop more reliable procedures for estimating the axial interaction between pipe and soil, the study explored toroid and shallow ball penetrometer performance on clays through small strain finite element analyses and physical model testing. Emphasis is placed on the axial interaction in isolation at shallow embedment ratio, but some possible ways of its incorporation into a more general interaction modelling scheme are examined. The concept of toroid and shallow ball penetrometers is first proposed based on the understanding of pipe-soil interactions under undrained vertical and axial loading. Numerical analyses are undertaken using a simple Tresca soil model. The effects of the basic geometry of the pipe, toroid and shallow ball, soil properties and soil flow mechanisms are comprehensively considered, providing convincing evidence to support these novel penetrometers as a basis for determining vertical and axial pipe-soil interactions. It is shown that a toroid penetrometer with a lever arm to diameter ratio (L/D) of 2 provides good agreement with the undrained response of a pipe; the correlations between a shallow ball penetrometer and a pipe with respect to undrained vertical (bearing) and axial (sliding) capacities are also examined.