R. Beemer, A. N. Bandini-Maeder, J. Shaw, Ulysse Lebrec, M. Cassidy
Calcareous sediments are prominent throughout the low-latitudinal offshore environment and have been known to be problematic for offshore foundation systems. These fascinating soils consist largely of the skeletal remains of single-celled marine organisms (plankton and zooplankton) and can be as geologically complex as their onshore siliceous counter parts. To enable an adequate understanding of their characteristics, in particular, their intra-granular micro-structure, it is important that geotechnical engineers do not forget about the multifaceted biological origins of these calcareous sediments and the different geological processes that created them. In this paper, the 3D models of soils grains generated from micro-computed tomography scans, scanning electeron microscope images, and optical microscope images of two calcareous sediments from two different depositional environments are presented and their geotechnical implications discussed. One is a coastal bioclastic sediment from Perth, Western Australia that is geologically similar to carbonate sediments typically used in micro-mechanics and particle crushing studies in the literature. The other is a hemipelagic sediment from a region of the North West Shelf of Australia that has historically been geotechnically problematic for engineers. The results show there is a marked difference between coastal bioclastic and hemipelagic sediments in terms of geological context and the associated particle micro-structures. This brings into question whether a coastal bioclastic calcareous sediment is a good micro-mechanical substitute for a hemipelagic one.
{"title":"The Granular Structure of Two Marine Carbonate Sediments","authors":"R. Beemer, A. N. Bandini-Maeder, J. Shaw, Ulysse Lebrec, M. Cassidy","doi":"10.1115/OMAE2018-77087","DOIUrl":"https://doi.org/10.1115/OMAE2018-77087","url":null,"abstract":"Calcareous sediments are prominent throughout the low-latitudinal offshore environment and have been known to be problematic for offshore foundation systems. These fascinating soils consist largely of the skeletal remains of single-celled marine organisms (plankton and zooplankton) and can be as geologically complex as their onshore siliceous counter parts. To enable an adequate understanding of their characteristics, in particular, their intra-granular micro-structure, it is important that geotechnical engineers do not forget about the multifaceted biological origins of these calcareous sediments and the different geological processes that created them. In this paper, the 3D models of soils grains generated from micro-computed tomography scans, scanning electeron microscope images, and optical microscope images of two calcareous sediments from two different depositional environments are presented and their geotechnical implications discussed. One is a coastal bioclastic sediment from Perth, Western Australia that is geologically similar to carbonate sediments typically used in micro-mechanics and particle crushing studies in the literature. The other is a hemipelagic sediment from a region of the North West Shelf of Australia that has historically been geotechnically problematic for engineers. The results show there is a marked difference between coastal bioclastic and hemipelagic sediments in terms of geological context and the associated particle micro-structures. This brings into question whether a coastal bioclastic calcareous sediment is a good micro-mechanical substitute for a hemipelagic one.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124431894","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Gravity installed anchors (GIAs) are the most recent generation of anchoring solution to moor floating facilities for deepwater oil and gas developments. After the installation of GIAs, the anchors are connected with the floating facility via the mooring lines, which interact with the anchors at the shackle and influence the keying and diving performance of GIAs. In the present work, a three-dimensional large deformation finite element (LDFE) model is established using the coupled Eulerian–Lagrangian method to investigate the performance of embedded mooring lines during keying and diving of GIAs. To verify the efficiency of the LDFE model, comparisons with the plasticity models are performed. Then, a parametric study is undertaken to quantify the relationship between the drag force Ta and drag angle θah at the shackle and the drag force T0 and drag angle θ0 at the mudline, in terms of the frictional coefficient, drag angle at the mudline and soil strain rate and strain softening. It is demonstrated that the drag angle at the mudline has the most significant effect on the performance of embedded mooring lines and hence the keying and diving of GIAs.
{"title":"Performance of Embedded Mooring Lines During Keying and Diving of Gravity Installed Anchors","authors":"Yanbing Zhao, Haixiao Liu","doi":"10.1115/OMAE2018-78034","DOIUrl":"https://doi.org/10.1115/OMAE2018-78034","url":null,"abstract":"Gravity installed anchors (GIAs) are the most recent generation of anchoring solution to moor floating facilities for deepwater oil and gas developments. After the installation of GIAs, the anchors are connected with the floating facility via the mooring lines, which interact with the anchors at the shackle and influence the keying and diving performance of GIAs. In the present work, a three-dimensional large deformation finite element (LDFE) model is established using the coupled Eulerian–Lagrangian method to investigate the performance of embedded mooring lines during keying and diving of GIAs. To verify the efficiency of the LDFE model, comparisons with the plasticity models are performed. Then, a parametric study is undertaken to quantify the relationship between the drag force Ta and drag angle θah at the shackle and the drag force T0 and drag angle θ0 at the mudline, in terms of the frictional coefficient, drag angle at the mudline and soil strain rate and strain softening. It is demonstrated that the drag angle at the mudline has the most significant effect on the performance of embedded mooring lines and hence the keying and diving of GIAs.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130664922","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Offshore Wave Energy Converter (WEC) farms are widely deployed as regards the individual isolated devices aiming at maximum wave energy absorption and facilitating installation and power transmission. This paper summarizes the theory behind the hydrodynamic interactions of diffracted waves by a large array of vertical cylinders. The latter exhibits some remarkable hydrodynamic interference effects — near resonant modes — in waves causing large loads in adjacent elements of the array. Numerical results concerning the exciting wave loads for a variety of different array configurations of truncated and bottomless cylinders are presented and the free surface elevation around the elements of the array is evaluated pointing out the near trapped modes.
{"title":"Wave Diffraction on Arrays of Vertical Truncated Cylindrical Bodies","authors":"S. Mavrakos, I. Chatjigeorgiou, D. Konispoliatis","doi":"10.1115/OMAE2018-78287","DOIUrl":"https://doi.org/10.1115/OMAE2018-78287","url":null,"abstract":"Offshore Wave Energy Converter (WEC) farms are widely deployed as regards the individual isolated devices aiming at maximum wave energy absorption and facilitating installation and power transmission. This paper summarizes the theory behind the hydrodynamic interactions of diffracted waves by a large array of vertical cylinders. The latter exhibits some remarkable hydrodynamic interference effects — near resonant modes — in waves causing large loads in adjacent elements of the array. Numerical results concerning the exciting wave loads for a variety of different array configurations of truncated and bottomless cylinders are presented and the free surface elevation around the elements of the array is evaluated pointing out the near trapped modes.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"256 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131889047","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Water wave interactions with floating deformable bodies is an interesting coupled problem finding important applications, as in the case of the responses of large floating structures and platforms of shallow draft and wave-ice sheet interaction. In this work we consider interactions of waves with floating elastic structures in enclosed or partially enclosed basins, as e.g. lakes, bays, reservoirs and harbors. Related applications include the wave induced deflection of floating marinas, solar energy platforms, ice covered lakes, etc. When enclosed or partially enclosed basins are considered, the hydroelastic interactions may be triggered due to the formation of standing waves. These standing waves or seiches have been documented in several occasions. In many cases the seiche effects in terms of wave amplitudes are small, but extreme catastrophic seiches have also occured. This fact suggests that the integrity of a floating structure might be compromised due to an extreme seiche. The main aim of this study is the analysis and simulation of hydroelastic standing waves. Towards this aim a configuration comprising of a constant depth basin, partially covered by a large, thin, floating elastic plate is studied. Shallow-water conditions, typical for the analysis of long waves are considered. The study focuses on the identification of the main resonant frequencies, which is important concerning the design of the considered floating structures. The problem is treated by a semi-analytical method based on the shallow water model by Stoker (1957), in conjunction with modal series expansions. Indicative results are presented illustrating the effects of the main parameters characterising the system, like the dimensions and rigidity of the structure, the clearances and the bathymetry.
{"title":"Resonances of Floating Elastic Structures in Enclosed Shallow-Water Basins","authors":"T. Papathanasiou, K. Belibassakis","doi":"10.1115/OMAE2018-77529","DOIUrl":"https://doi.org/10.1115/OMAE2018-77529","url":null,"abstract":"Water wave interactions with floating deformable bodies is an interesting coupled problem finding important applications, as in the case of the responses of large floating structures and platforms of shallow draft and wave-ice sheet interaction. In this work we consider interactions of waves with floating elastic structures in enclosed or partially enclosed basins, as e.g. lakes, bays, reservoirs and harbors. Related applications include the wave induced deflection of floating marinas, solar energy platforms, ice covered lakes, etc. When enclosed or partially enclosed basins are considered, the hydroelastic interactions may be triggered due to the formation of standing waves. These standing waves or seiches have been documented in several occasions. In many cases the seiche effects in terms of wave amplitudes are small, but extreme catastrophic seiches have also occured. This fact suggests that the integrity of a floating structure might be compromised due to an extreme seiche. The main aim of this study is the analysis and simulation of hydroelastic standing waves. Towards this aim a configuration comprising of a constant depth basin, partially covered by a large, thin, floating elastic plate is studied. Shallow-water conditions, typical for the analysis of long waves are considered. The study focuses on the identification of the main resonant frequencies, which is important concerning the design of the considered floating structures. The problem is treated by a semi-analytical method based on the shallow water model by Stoker (1957), in conjunction with modal series expansions. Indicative results are presented illustrating the effects of the main parameters characterising the system, like the dimensions and rigidity of the structure, the clearances and the bathymetry.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133877850","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this study, a new design wave analysis method for estimating the extreme slow-drift motion of floating offshore structures is introduced. Here, the design wave refers to the irregular incident wave of short duration that induces the extreme response of desired return period. The present method is composed of following four steps: linearization of the dynamic system, probabilistic analysis of the Volterra series, generation of the design waves, and the fully-coupled nonlinear time-domain simulations. In generating the design waves, the conditioning of the most likely extreme response profile is suggested. The method was applied to a deep-water semi-submersible platform, and the results appeared to be promising compared to the full-length nonlinear simulations.
{"title":"Design Wave Analysis for the Extreme Horizontal Slow-Drift Motion of Moored Floating Platforms","authors":"D. Lim, Yonghwan Kim","doi":"10.1115/OMAE2018-78582","DOIUrl":"https://doi.org/10.1115/OMAE2018-78582","url":null,"abstract":"In this study, a new design wave analysis method for estimating the extreme slow-drift motion of floating offshore structures is introduced. Here, the design wave refers to the irregular incident wave of short duration that induces the extreme response of desired return period. The present method is composed of following four steps: linearization of the dynamic system, probabilistic analysis of the Volterra series, generation of the design waves, and the fully-coupled nonlinear time-domain simulations. In generating the design waves, the conditioning of the most likely extreme response profile is suggested. The method was applied to a deep-water semi-submersible platform, and the results appeared to be promising compared to the full-length nonlinear simulations.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126023126","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
With increased activities in natural gas transportation and offshore exploration in the past decades, assessment of sloshing in liquefied natural gas (LNG) tanks has become an important practical issue. In this paper, we focus on the deterministic calculation of the coupled sloshing and ship motions in regular wave conditions. An in-house numerical code is used to solve the seakeeping problem coupled with the sloshing dynamics. The numerical method adopts a weakly nonlinear approach using impulse response functions for the seakeeping problem. Nonlinear Froude-Krylov and hydrostatic forces are directly evaluated in the time domain. A three-dimensional finite difference method is applied to solve the sloshing problem. The numerical method is validated by comparing with experimental results in the literature. The developed numerical method is used to analyze the nonlinear effects of wave heights.
{"title":"Nonlinear Effects of Wave Heights on Coupled Sloshing and Seakeeping Responses","authors":"Xin Wang, M. Arai, G. Karuka","doi":"10.1115/OMAE2018-78232","DOIUrl":"https://doi.org/10.1115/OMAE2018-78232","url":null,"abstract":"With increased activities in natural gas transportation and offshore exploration in the past decades, assessment of sloshing in liquefied natural gas (LNG) tanks has become an important practical issue. In this paper, we focus on the deterministic calculation of the coupled sloshing and ship motions in regular wave conditions. An in-house numerical code is used to solve the seakeeping problem coupled with the sloshing dynamics. The numerical method adopts a weakly nonlinear approach using impulse response functions for the seakeeping problem. Nonlinear Froude-Krylov and hydrostatic forces are directly evaluated in the time domain. A three-dimensional finite difference method is applied to solve the sloshing problem. The numerical method is validated by comparing with experimental results in the literature. The developed numerical method is used to analyze the nonlinear effects of wave heights.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"118 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126042816","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To support a lighthouse, a trestle and other structures, screw pile has been used as the foundation for more than a hundred years. Because of its efficient installation, high bearing capacity and other advantages, increasing attention has been paid to use it as the offshore wind power foundation. In this research, laboratory test was conducted to study the influence of screw pitch and the diameter of helix on the lateral bearing capacity of single-helix pile, considering the effect of the installation. The results of the single-helix pile were compared with that of steel pipe pile and other methods. According to the test, helix diameter has negligible effect on the lateral bearing capacity of helical pile, but the pitch of helical influence that significantly because of more disturbance of soil.
{"title":"Study on the Lateral Bearing Capacity of Single-Helix Pile for Offshore Wind Power","authors":"H. Ding, Wang Le, Puyang Zhang, Conghuan Le","doi":"10.1115/OMAE2018-77391","DOIUrl":"https://doi.org/10.1115/OMAE2018-77391","url":null,"abstract":"To support a lighthouse, a trestle and other structures, screw pile has been used as the foundation for more than a hundred years. Because of its efficient installation, high bearing capacity and other advantages, increasing attention has been paid to use it as the offshore wind power foundation. In this research, laboratory test was conducted to study the influence of screw pitch and the diameter of helix on the lateral bearing capacity of single-helix pile, considering the effect of the installation. The results of the single-helix pile were compared with that of steel pipe pile and other methods. According to the test, helix diameter has negligible effect on the lateral bearing capacity of helical pile, but the pitch of helical influence that significantly because of more disturbance of soil.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"25 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124025922","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. Qiao, Muren Bao, Jun Yan, Zhou Daocheng, Li Yugang
With the development of marine resources going to deeper water depth, the mooring system design becomes more important. Predicting the embedded trajectory of drag anchor during the installation process is very significant for calculating the ultimate pullout bearing capacity of drag anchor and the mooring system design. Firstly, the initial angle and embedded depth of drag anchor are assumed. Secondly, the drag anchor penetrates a unit displacement along the direction parallel to the anchor fluke at each incremental step, and the specific position information (horizontal, vertical, angle) could be obtained. Thirdly, the ultimate bearing capacity of drag anchor at this incremental step could be calculated using the two-dimensional and three-dimensional finite element model which considering the contact friction between the drag embedment anchor and seabed clay. And then, the new specific position information could be obtained according to the mechanical equilibrium equation of inverse catenary. Finally, the whole drag anchor embedded trajectory could be obtained when the drag angle between the anchor fluke and seabed tends to zero as a limit state. In this paper, a method of predicting embedded trajectory based on the finite element analyses of bearing capacity of drag anchor is established, which could be used as a reference for the practical engineering.
{"title":"A Method to Predict Embedded Trajectory Based on the Finite Element Analyses of Bearing Capacity of Drag Anchor","authors":"D. Qiao, Muren Bao, Jun Yan, Zhou Daocheng, Li Yugang","doi":"10.1115/OMAE2018-77167","DOIUrl":"https://doi.org/10.1115/OMAE2018-77167","url":null,"abstract":"With the development of marine resources going to deeper water depth, the mooring system design becomes more important. Predicting the embedded trajectory of drag anchor during the installation process is very significant for calculating the ultimate pullout bearing capacity of drag anchor and the mooring system design. Firstly, the initial angle and embedded depth of drag anchor are assumed. Secondly, the drag anchor penetrates a unit displacement along the direction parallel to the anchor fluke at each incremental step, and the specific position information (horizontal, vertical, angle) could be obtained. Thirdly, the ultimate bearing capacity of drag anchor at this incremental step could be calculated using the two-dimensional and three-dimensional finite element model which considering the contact friction between the drag embedment anchor and seabed clay. And then, the new specific position information could be obtained according to the mechanical equilibrium equation of inverse catenary. Finally, the whole drag anchor embedded trajectory could be obtained when the drag angle between the anchor fluke and seabed tends to zero as a limit state. In this paper, a method of predicting embedded trajectory based on the finite element analyses of bearing capacity of drag anchor is established, which could be used as a reference for the practical engineering.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132214867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The role played by the curvature of the body surface on the hydrodynamics of water entry with high horizontal velocity component is investigated experimentally. The study is a part of a research activity finalized at the understanding of the aircraft ditching problem. In order to avoid scaling effects which may prevent the development of ventilation/cavitation phenomena, the study is carried out at full scale velocity. Measurements are presented in terms of pressures and loads whereas some underwater visualizations are used for the interpretation of the data. Both a convex and concave body surface are considered and comparisons with the flat plate data are established. In the case of a concave shape, a quite complicated flow with large air entrainment develops beneath the plate. The air entrainment causes a general reduction of the pressure peak at the middle, whereas the pressure peaks recorded at the side probes are about in line with those found for the flat plate in the same conditions. The total hydrodynamic load acting normal to the plate grows more regularly but the maximum load is essentially the same as that measured in the flat plate case. For the convex shape, the pressure probes located in the middle of the plate get wetted well before the ones at the side and the pressure peaks at the sides are much lower than those in the middle. The reduced pressures at the sides cause a reduction of the total loading in the normal direction compared to flat and concave plates.
{"title":"Effect of Surface Curvature on the Hydrodynamics of Water Entry at High Horizontal Velocity","authors":"A. Iafrati","doi":"10.1115/OMAE2018-78438","DOIUrl":"https://doi.org/10.1115/OMAE2018-78438","url":null,"abstract":"The role played by the curvature of the body surface on the hydrodynamics of water entry with high horizontal velocity component is investigated experimentally. The study is a part of a research activity finalized at the understanding of the aircraft ditching problem. In order to avoid scaling effects which may prevent the development of ventilation/cavitation phenomena, the study is carried out at full scale velocity. Measurements are presented in terms of pressures and loads whereas some underwater visualizations are used for the interpretation of the data. Both a convex and concave body surface are considered and comparisons with the flat plate data are established.\u0000 In the case of a concave shape, a quite complicated flow with large air entrainment develops beneath the plate. The air entrainment causes a general reduction of the pressure peak at the middle, whereas the pressure peaks recorded at the side probes are about in line with those found for the flat plate in the same conditions. The total hydrodynamic load acting normal to the plate grows more regularly but the maximum load is essentially the same as that measured in the flat plate case. For the convex shape, the pressure probes located in the middle of the plate get wetted well before the ones at the side and the pressure peaks at the sides are much lower than those in the middle. The reduced pressures at the sides cause a reduction of the total loading in the normal direction compared to flat and concave plates.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"74 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121376438","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
As offshore oil and gas fields mature on the Grand Banks, offshore Newfoundland and Labrador, marginal field subsea tie-backs are necessary to maintain production levels. Existing untrenched flowline lengths have been limited by the assumption that iceberg contact equates to flowline failure. However, extended tie-backs will be necessary to develop stranded resources. To potentially reduce the number of failure cases, we can consider a better definition of failure that accounts for the pipeline response due to iceberg-soil-pipeline interaction events. Reducing the failure rate from free-floating iceberg contacts alone can significantly increase safe tie-back lengths. This paper examines the flowline response from impacts with free-floating icebergs using large deformation finite element analysis. The plane strain pipe-soil interaction response is first simulated for pure vertical loading and compared against analytical bearing capacity theory. The influence of non-associativity in the soil constitutive model is demonstrated with respect to predicting the pipe drained penetration resistance in dense sands. Oblique vertical-horizontal plane strain pipe-soil interaction is also investigated, and it is shown that the vertical penetration resistance is reduced when the pipe trajectory deviates from pure vertical, consistent with published interaction diagrams. Lastly, the fully coupled interaction scenario of free-floating iceberg-pipe-soil interaction is simulated, showing the effects of the pipe wall thickness and soil strength. The numerical modelling procedures are described and the soil constitutive model that incorporates dense sand behavior is detailed.
{"title":"Simulating the Response of Untrenched Flowlines due to Iceberg-Flowline-Soil Interaction","authors":"Kenton Pike, Andrew Blundon","doi":"10.1115/OMAE2018-78128","DOIUrl":"https://doi.org/10.1115/OMAE2018-78128","url":null,"abstract":"As offshore oil and gas fields mature on the Grand Banks, offshore Newfoundland and Labrador, marginal field subsea tie-backs are necessary to maintain production levels. Existing untrenched flowline lengths have been limited by the assumption that iceberg contact equates to flowline failure. However, extended tie-backs will be necessary to develop stranded resources. To potentially reduce the number of failure cases, we can consider a better definition of failure that accounts for the pipeline response due to iceberg-soil-pipeline interaction events. Reducing the failure rate from free-floating iceberg contacts alone can significantly increase safe tie-back lengths.\u0000 This paper examines the flowline response from impacts with free-floating icebergs using large deformation finite element analysis. The plane strain pipe-soil interaction response is first simulated for pure vertical loading and compared against analytical bearing capacity theory. The influence of non-associativity in the soil constitutive model is demonstrated with respect to predicting the pipe drained penetration resistance in dense sands. Oblique vertical-horizontal plane strain pipe-soil interaction is also investigated, and it is shown that the vertical penetration resistance is reduced when the pipe trajectory deviates from pure vertical, consistent with published interaction diagrams. Lastly, the fully coupled interaction scenario of free-floating iceberg-pipe-soil interaction is simulated, showing the effects of the pipe wall thickness and soil strength. The numerical modelling procedures are described and the soil constitutive model that incorporates dense sand behavior is detailed.","PeriodicalId":106551,"journal":{"name":"Volume 9: Offshore Geotechnics; Honoring Symposium for Professor Bernard Molin on Marine and Offshore Hydrodynamics","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128446858","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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