Meshfree Model for Wave-Soil-Pipe Interaction

Wang, Xiao-Xiao (Griffith University Gold Coast Campus) | Tsai, Chia-Cheng (National Kaohsiung University of Science and Technology) | Jeng, Dong-Sheng (Griffith University Gold Coast Campus)

OnePetro 

ABSTRACT

The investigation of the wave-induced soil response is extremely significant for sake of submarine pipelines. Unlike conventional approaches, in this paper, a meshfree model for the wave-seabed interactions around an offshore pipeline is established. The pipeline is considered to be fully buried or partially buried in a trench layer surrounding impermeable walls. The proposed model is validated with the analytical solution, laboratory experiments and numerical models available in the literature. Then, a parametric study is carried out to examine the effects of configuration of a pipeline on the wave-induced soil response in the vicinity of a pipeline.

INTRODUCTION

Submarine pipelines play an extremely important role for the transportation of offshore energy resources that is one of main concerns for offshore engineering. In general, the vulnerability of underwater-laid pipelines may be exposed due to wave-induced liquefaction of underlying seabed soil layers.

Generally, the fluctuating pressures acting upon the seabed due to progressive motion of ocean waves will further induce excess pore pressure and reduce the effective stress within seabed soil. When the excess pore pressure increases, the shear resistance surrounding pipelines may be loss due to the liquefaction of soil. Therefore, the evaluation of the wave-induced soil response is particularly important for offshore engineers involved in the design of protection of offshore pipelines (Fredsøe. 2016).

In the past few decades, numerous investigations for the wave-seabedstructure interactions by using traditional numerical methods, such as finite di_erence method, boundary element method and finite element method, have been reported in the literature. Among these, Cheng and Liu (1986) proposed a boundary integrated model for wave-induced soil response propagating over a pipeline fully buried in a trench layer. Jeng and Cheng (2000) developed a two-dimensional finite di_erence model in a curvilinear coordinate system to examine the wave-induced pore pressures and stresses around a pipeline. The numerical results depicted the significant influence of pipelines on the soil response. Jeng and Lin (2000) proposed a finite element model to examine the wave-induced seabed response in the vicinity of a pipeline in an inhomogeneous seabed. These models were based on the assumption of no slipping at the interface between pipeline and soil. Luan et al. (2008) considered inertial forces and soil-pipeline contact e_ects in their model. It was found from the results that the interface between soil and pipeline significantly a_ected the internal stresses. Dunn et al. (2006) applied the poro-elastoplastic model (Chan, 1988) to investigate the problem of wave-seabed interaction around a fully buried pipeline in marine environments. A three-dimensional finite element model was proposed by Shabani and Jeng (2008) to examine the behaviour of soil under various wave obliquity, soil characteristics and trench configuration. Zhao et al. (2014) adopted new definition of source term in their residual model and applied to the problem of wave-soil-pipe interactions. Duan et al. (2017) proposed a 2D coupled model for wave and current induced soil response around a partially buried pipeline in a trench. They investigated the water-seabed-pipeline interaction under wave and current loading system, and the process was fully coupled.