Ice Keel-Seabed Interaction: Numerical Modelling Validation

Phillips, Ryan; Barrett, John; Al-Showaiter, Aiman

doi:10.2523/20696-ms

Cited by 8 publications

(3 citation statements)

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“…Ref 1,10,12) of advanced numerical modelling of ice-soil-pipe interaction using explicit finite element analysis techniques, such as Coupled Eulerian Lagrangian (CEL) analysis and Arbitrary Lagrangian Eulerian (ALE) adaptive meshing. Ref 1,10,12) of advanced numerical modelling of ice-soil-pipe interaction using explicit finite element analysis techniques, such as Coupled Eulerian Lagrangian (CEL) analysis and Arbitrary Lagrangian Eulerian (ALE) adaptive meshing.…”

Section: Coupled Eulerian Lagrangian Methodsmentioning

confidence: 99%

Ice Gouge Interaction with Buried Pipelines Assessment Using Advanced Coupled Eulerian Lagrangian

et al. 2012

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Ice gouging of the seabed is an issue in cold regions where sea ice pressure ridge keels or icebergs can contact the seabed. This creates a design challenge as pipelines must be buried to a sufficient depth to resist loads transferred through the soil to the pipeline. However, as trenching and backfilling is expensive and technically challenging, a goal needs to be to optimize the depth of burial during design.Conventional methods to evaluate the ice gouge loading on a buried pipeline rely on decoupled analysis of the icesoil and soil-pipe responses, which is believed to be a conservative approach and not adequately representative. In this paper, ice gouging is investigated using advanced numerical modelling techniques to reduce this conservatism and better quantify the loads experienced by the pipeline due to ice gouges.The Coupled Eulerian Lagrangian (CEL) finite element method is utilized in a series of comparative studies based upon available centrifuge and full scale test data. The CEL analysis results in relatively smaller sub-gouge deformation depth than the current guidance suggests, based on centrifuge tests. The shallow sub-gouge deformation zone indicated appears to correlate well with the limited amount of full scale test data available. If the less conservative CEL result can be validated, significant burial depth reductions can be achieved.CEL technology originally developed in the early 1960s, however, it has not been widely used until the late 1990s. The soil behaviour in this matter is critical, thus the paper investigates the CEL capabilities to implement geotechnical soil models i.e. Mohr-coulomb soil model. Furthermore, the paper assesses the benefits and limitations of using advanced finite element methods to investigate ice-soil-pipe interaction, highlighting the constraints and the required further developments for the current technology to enable the industry to better evaluate the risk of ice gouging.

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Section: Coupled Eulerian Lagrangian Methodsmentioning

confidence: 99%

Ice Gouge Interaction with Buried Pipelines Assessment Using Advanced Coupled Eulerian Lagrangian

et al. 2012

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“…This material model is capable of capturing the frictional behaviour of sand using effective stress (drained) parameters. The dark region under the leading face of the keel remains unstrained and travels along with the rough keel, as shown by Phillips and Barrett (2011). A simplified material model with a constant residual friction angle and a non-associated flow rule were assumed as the gouging process generates strains much higher than strain observed at critical friction angles.…”

Section: Numerical Analysismentioning

confidence: 99%

“…Altering the angle of attack of the keel will influence scour forces and degree of subscour deformation (Phillips, et al, 2010). A constant keel angle of 30 degrees was considered in this study.…”

Section: Recommendationsmentioning

confidence: 99%

Physical and Numerical Modeling of a Sub-Surface Caisson for Protection of Subsea Facilities against Scouring Icebergs

et al. 2012

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A simple, rectangular sub-surface caisson was evaluated using physical and numerical modeling to develop a method for protecting subsea installations against scouring keels of icebergs on the Grand Banks. This protection strategy was developed to assess the feasibility of the structure as an alternative to costly excavations used to protect subsea equipment on the Grand Backs. The scenario considered was an ice keel (i.e., iceberg) scouring over a buried caisson, avoiding direct contact but with minimal clearance. A centrifuge testing program, consisting of five tests, formed the basis for calibration of a finite element model. The first four centrifuge tests were carried out with water as the pore fluid in order to simulate drained conditions during the keel-soil-structure interaction. In the field, fully drained conditions may not exist; hence the fifth centrifuge test was conducted using a viscous pore fluid to simulate the partially drained conditions. The numerical analyses were conducted using the commercially available finite element software package ABAQUS. This study demonstrated that the Coupled Eulerian Langrangian (CEL) technique is capable of modeling slow keel-soil-structure interaction events in sand. The numerical model performed satisfactorily in simulating the centrifuge tests. The results indicated that such a system can potentially provide the protection needed for subsea installations in ice infested waters. Although this work was based on the conditions encountered on the Grand Banks, the concept would be applicable to other regions. Future work should involve evaluating various ice keel-soil-structure interaction scenarios and attack angles, development of Inspection, Repair and Maintenance (IRM) strategies as well as a detailed assessment of construction and installation issues.

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Resource Development in Arctic Regions

Kenny

Jukes²

2018

Encyclopedia of Maritime and Offshore Engineering

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Hydrocarbon basins in global arctic regions hold significant resources with economic potential to support an array of economic sectors including energy, transportation, petrochemical, agricultural, and manufacturing industries. Due to the harsh physical environment, northern and arctic regions present significant technical and logistical challenges that influence the development of engineering solutions through the design process and may affect the project viability and sanction with respect to technical or economic factors. One of the more significant hazards and extreme loading events encountered is ice gouging due to the interaction of ice features with the seabed subject to environmental driving forces. Trenching and pipeline burial is viewed as one of the most effective mitigation techniques used to promote pipeline serviceability and reduce the risk of pipeline damage; however, there are limitations and constraints with current technologies with respect to the maximum trenching depth and production rates that affect project logistics and economic risk. In addition, there are other physical environmental factors that present challenges including the short open water season, low temperatures, and presence of special terrain characteristics (e.g., hardpan, permafrost, massive ground ice). Current practice used to define system demand (i.e., geotechnical loads) and system capacity (i.e., pipeline mechanical performance) has limitations due to inherent uncertainties with the statistics of physical data sets, experimental techniques, and engineering models used in the analysis. Advancements in computational methods have provided improved engineering tools to analyze these complex nonlinear processes with probabilistic methods providing an objective framework to assess design options with respect to technical, economic, and environmental criteria that meet specified target safety levels. Consideration of cumulative effects, climate change, and sustainability factors add an additional layer of complexity to the engineering framework in terms of social context and political values.

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Ice Keel-Seabed Interaction: Numerical Modelling Validation

Cited by 8 publications

References 0 publications

Ice Gouge Interaction with Buried Pipelines Assessment Using Advanced Coupled Eulerian Lagrangian

Ice Gouge Interaction with Buried Pipelines Assessment Using Advanced Coupled Eulerian Lagrangian

Physical and Numerical Modeling of a Sub-Surface Caisson for Protection of Subsea Facilities against Scouring Icebergs

Resource Development in Arctic Regions

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