Non-Linear Clay Soil Model for Lateral Pipe-Soil Interaction

This paper describes implementation and application of nonlinear lateral soil models for pipeline lateral buckling analysis. Several lateral soil models have been developed in the past and the model developed by Verley is often referenced in pipeline on-bottom hydrodynamic stability analyses (see [11], [13]). The Verley’s model includes the build up of soil passive resistance as a function of small cyclic lateral motions and it is implemented in the PONDUS software (developed by MARINTEK) for on-bottom stability analysis as well as the DNV-RP-F109. However, the Verley model does not include the build up of additional soil berm resistance due to large cyclic in-place lateral motions applicable for lateral thermal buckling behaviors. The effect of additional soil berm resistance from large cyclic motions has been investigated by other research projects, such as the SAFEBUCK JIP [5]. In this paper, a complete non-linear lateral soil models with inherent soil berm resistance including both effects are formulated. The soil model combines the Verley model, the models described in DNV-RP-F109, and the berm model from SAFEBUCK’s results. The DNV and Verley’s model are used to model soil resistance in small amplitude cycle continued by the berm model after breakout achieved during large amplitude cycle. The new model is compared with PONDUS to validate the results of Verley and DNV model. The soil model is implemented inside SIMLA software [15] to enable finite element analysis. An example application of the model to pipeline global buckling analysis is then presented.