Modeling Subsea Pipeline Movement Subjected to Submarine Debris-Flow Impact

Abstract

Deepwater pipelines are susceptible to destructive impacts from submarine debris flows. Understanding the subsea pipeline movement driven by submarine debris flow is critical to the optimization of pipeline routes and mitigation of submarine geohazards. In this paper, a coupling model of submarine debris flow with pipeline interaction is presented to investigate pipeline movement subjected to debris flow impact. The modeling domain of debris flow is represented by a structured grid system with discretized grid nodes. The dynamic properties of debris flow, such as velocities and heights, are calculated at each grid node. The pipeline is discretized into finite elements. Each element consists of two pipe nodes at the ends. The coordinates of each pipe node are determined using a particle tracking algorithm. The velocities of debris flow at the location of each pipe node are interpolated from the debris flow model and then converted to impact forces applied on each pipe node. An empirical formulation is proposed to estimate the displacements of each pipe node from a given Young’s modulus of pipe material and impact force applied by debris flow. The empirical relationship is developed from a series of numerical simulations conducted with the commercial software ABAQUS. The numerical simulations are performed using a simple model configuration subjected to uniformly distributed impact forces. Later, the coupled model is applied to two schematized cases representing continental shelves with a uniform slope and a sinuous canyon. The effects of the Young’s modulus of pipe material, initial failure height of debris flow, and the number of discretized pipe nodes on pipeline movement are investigated through a series of parametric studies.