Full-scale Testing and Numerical Modeling oF Axial and Lateral Soil Pipe Interaction in Deepwater

Thursday, 18 December 2014
Mohammad Sarraf Joshaghani and Aram M.Raheem, University of Houston, Houston, TX, United States
A thorough understanding of the behavior of deep sea pipes is crucial for off-shore oil & gas industry. During the service life, network of oil and gas pipelines that connect the floating platforms to the subsea wells in deepwater undergo significant changes in temperature and pressure resulting in high shears, strains and movement. These pipelines laid on the very soft seabed become susceptible to large movement and lateral buckling resulting in global instability of the entire system. Hence, it is of paramount importance to address the aforementioned issues through combined numerical modeling and experimental study of various conditions in the field. Modeling this behavior needs to take into account the complex interactions between pipe, water, and soil (which, in this case, will be a saturated porous media). Physical experiments can be challenging as the undrained shear strength is very low of the order of 0.01 kPa. In this research, we have performed large-scale experiments as well as numerical modeling. Several full-scale models have been designed and constructed to investigate the behavior of various types of pipes (steel, plastic) on the simulated clayey sea bed (undrained shear strength ranged from 0.01 kPa to 0.11 kPa). Axial and lateral pipe soil interactions have been characterized, and appropriate mitigation solutions for axial walking and lateral buckling have been proposed. On the numerical modeling front, the pipe-soil behavior is simulated using the Coupled Eulerian Lagrangian (CEL) and Arbitrary-Lagrangian-Eulerian (ALE) formulations.