Nonlinear wave effects on the oscillatory pore pressure induced forces on buried pipelines

Abstract

ABSTRACT The present study investigates the influence of nonlinear waves on the oscillatory pore pressure-induced response around buried pipes. The study is carried out considering the applicable wave theories namely: linear, Stokes, cnoidal and solitary wave theories. The soil modelling is based on Biot’s consolidation equations which are solved using Finite Element tool COMSOL Multiphysics. Two case studies are considered for the investigation where the parameters of wave height and water depth are varied respectively for each case study to increase the wave nonlinearity. The hydrodynamic pressure on the seabed is based on the applicable wave theory which is chosen from Le-Mehaute’s diagram. The pore pressures, stresses and forces developed on the buried pipe are evaluated considering different wave theories. As the wave transforms from linear to cnoidal through stokes waves a gradual variation in the wave-induced soil response is observed, whereas the soil response from cnoidal to solitary waves is found to be considerably abrupt. It is observed that the magnitude of these wave-induced forces and stresses due to a solitary wave can be about twice that of a linear wave under a wave crest. Similarly, for the case of pipe under wave trough, linear wave theory gives a very high estimate of uplift force as compared to highly nonlinear solitary waves.