Optimization Study of Pipeline Rock Armour Protection Design Based on Finite Element Analysis

The design of pipeline protection with rock armour berms has been traditionally based on model testing because there has been no closed-form analytical solution available to resolve the complex interaction between the anchor, anchor chain, seabed soil and rock armour. Compared to the costly physical model test, a numerical procedure properly set up allows effective and extensive study on various rock berm configurations. It is expected that better optimized pipeline rock armour protection berm can be designed to offer appreciable savings on project cost. The authors have developed a Finite Element Analysis (FEA) based procedure which can predict the clearance between the anchor fluke tip and pipeline as well as the pushing force on the pipeline during anchor dragging. Both the clearance and pushing force can be used to assess the potential anchor damage to a pipeline with rock backfill protection. The FEA results have been successfully validated against results obtained from physical model tests. A series of numerical tests are performed considering the variations in the trench profile, the armour rock shape, rock particle size and grading properties etc. The protection mechanism of the rock armour berm, with regard to the above factors, is discussed to provide a better understanding for the significance of each parameter in the protection design. Guidelines in achieving an optimized rock berm protection design are also given.