To satisfy flow assurance criteria, it is sometimes required to restrain the pipeline against any movement that could prevent free drainage of the pipeline during a shutdown. Rock dumping of a surface pipeline is a viable restraining solution, provided it is properly designed to withstand lateral (and upheaval) buckling load coming from the pipeline. The available solutions for lateral resistance have been developed for buried pipelines under a flat seabed, and consequently do not take account of the geometry effect relevant to rock berms. They have also been mostly developed for in situ sand conditions, which do not necessarily reflect the properties of the rock or gravel forming the rock berm. In this paper, the lateral resistance of a pipeline buried under a rock berm is investigated using the finite element (FE) method. The developed FE model is validated against the buried pipeline problem with available solution. The effects of geotechnical properties such as friction and dilation angles, and also geometry of the rock berm, are then investigated using the developed model. The findings of this paper are finally discussed towards appropriate engineering design of rock-dumped pipelines.

1. Introduction

Rock-dumping a pipeline on the seabed is often undertaken to provide resistance against lateral buckling of the pipeline. As such, it is essential to have an understanding of the lateral resistance provided by the rock-dump. Experimental and numerical research on the lateral resistance of buried pipelines (Trautmann and O'Rourke, 1983, 1985; Yimsiri et al., 2004; Karimian et al., 2006; Di Prisco and Galli, 2006; Badv and Daryani, 2010) has thus far focused on a flat seabed, and consequently does not take into account the rock-berm geometry effect. In addition, the research has mainly looked at in situ sand, not rock, conditions.

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