Finite element modeling of partially embedded pipelines in clay seabed using Coupled Eulerian–Lagrangian method

Abstract

Vertical seabed penetration and lateral movement of deep-water offshore pipelines are simulated using the Coupled Eulerian–Lagrangian (CEL) approach in Abaqus finite element (FE) software. Abaqus CEL has been used in some previous studies to simulate large-deformation behavior of offshore pipelines; however, the effects of strain rate and strain-softening on undrained shear strength (su) have not been considered. In this study, the effects of these factors are critically examined. The available built-in models in Abaqus CEL cannot account for these factors directly, especially the strain rate; therefore, the development of user subroutines is required. In the present study, a simple but realistic soil constitutive model (published by Zhou and Randolph in 2007) that considers the effects of strain rate and strain-softening on su is implemented in Abaqus CEL. The effects of FE mesh size and shear band formation on penetration resistance are discussed based on a comprehensive FE simulation. Lateral analyses are performed for “light” and “heavy” pipes in clay seabed having a linearly increasing undrained shear strength profile for smooth and rough pipe–soil interface conditions. The FE results are compared with previous theoretical, numerical, and centrifuge test results. Based on the present FE analyses, it is shown that, similar to the remeshing and interpolation techniques with small strain (RITSS) technique developed at the The University of Western Australia, the Abaqus CEL can successfully simulate the response of partially embedded pipelines in deep-water clay seabed, provided strain rate and softening dependent clay models are implemented. A methodology to implement such a model using Abaqus user subroutine is also presented.

Large deformation finite-element modelling of progressive failure leading to spread in sensitive clay slopes

“…Therefore, numerical issues related to mesh distortion or mesh tangling, even at very large strains, are not expected anywhere, including the zones around the failure planes. Note that Abaqus CEL has been used in previous studies for other applications such as quasi-static penetration of spudcan foundations and offshore pipelines (Qiu et al, 2011;Tho et al, 2012;Dutta et al, 2015). Its performance has also been validated by comparing the results with the remeshing and interpolation technique with small strain (RITSS) for static and dynamic problems (Tian et al, 2011;Wang et al, 2013).…”

Numerical Investigation of Dynamic Pipe–Soil Interaction on Electrokinetic-Treated Soft Clay Soil

“…The water has the depth of 0.055m and the soil has the depth of 0.105m. The data were 12 obtained based on small-scale modelling by Dutta et al (2014), this was scaled by a multiplier factor of 40 to represent the large-scale experiment conducted by Dingle et al (2008).…”

“…Detail analyses with regards to vertical penetration of pipeline have been discussed by (Dingle et al 2008;Dutta et al 2014). However, the dynamic analysis investigates further the EK effect on the pipe under the same and also different conditions for a non-EK treated soil and EK treated soil.…”

Modelling large plastic deformations of cohesive soils using sequential limit analysis

“…A number of other advanced numerical approaches are available for the analysis of geotechnical problems involving large plastic deformations. These include the material point method, [31][32][33][34] smoothed particle hydrodynamics, [35][36][37][38] and the distinct element method, [39][40][41][42][43][44] although at present the most widely used approaches are FE-based methods such as the arbitrary Lagrangian-Eulerian, 45,46 remeshing and interpolation technique with small strain (RITSS), [47][48][49][50] and coupled Eulerian-Lagrangian (CEL) [51][52][53][54][55][56][57][58] techniques. The RITSS method originally developed by Hu and Randolph 47 is an improved arbitrary Lagrangian-Eulerian approach that divides a large-deformation problem into a series of small-deformation FE analyses.…”