Predicting the Instability Trajectory of an Obliquely Loaded Pipeline on a Clayey Seabed

• Published in: Journal of marine science and engineering Vol. 10; no. 2; p. 299
• Main Authors: Wang, Ning, Qi, Wengang, Gao, Fuping
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.02.2022
• Subjects: Algorithms; Bearing capacity; clayey seabed; Computer simulation; critical pipe weight; deep-sea pipeline; Elastoplasticity; failure envelope; Finite element method; Instability; Lateral stability; Mathematical analysis; Mathematical models; oblique load; Ocean floor; Pipelines; Pipes; Plane strain; Roughness; Roughness coefficient; Shear strength; Shear stress; Soil; Soil investigations; Soil resistance; Soil stability; Soils; Submarine pipelines; Trajectories; Ultimate loads
• ISSN: 2077-1312; 2077-1312
• DOI: 10.3390/jmse10020299

Predicting the instability trajectory of an obliquely loaded pipeline on the seabed is vital for the global buckling assessment. To numerically investigate the obliquely loaded pipe–soil interactions, a plane strain elastoplastic finite element model incorporating the adaptive meshing technique and the contact-pair algorithm is employed and verified with the existing experimental data and the analytical predictions. The evolution of slip mechanisms within the underlying soil is simulated, indicating the instability direction of the pipe, and the corresponding ultimate soil resistance is closely correlated. It is also indicated that the ultimate load angle is in the positive correlation with the movement angle, the dimensionless embedment of the pipe and the roughness coefficient of the pipe–soil interface. On the basis of numerous simulations, a force-resultant plasticity model including the bearing capacity envelope and the flow rule is proposed for predicting the behavior of a partially embedded pipeline on the clayey seabed. Finally, an explicit expression with respect to the critical submerged weight of the pipe is derived for distinguishing the lateral instability of a pipe between the ‘light’ and the ‘heavy’ mode.