Numerical study of suction embedded plate anchor

NUMERICAL STUDY OF SUCTION EMBEDDED PLATE ANCHOR CHEN ZONGRUI NATIONAL UNIVERSITY OF SINGAPORE 2014 NUMERICAL STUDY OF SUCTION EMBEDDED PLATE ANCHOR CHEN ZONGRUI (B. Eng., HUST) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF CIVIL AND ENVIRONMENTAL ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2014 DECLARATION I hereby declare that the thesis is my original work and it has been written by me in its entirety. I have duly acknowledged all the sources of information which have been used in the thesis. This thesis has also not been submitted for any degree in any university previously. _________________ Chen Zongrui 13 August 2014 Acknowledgements First and foremost, I would like to express my deepest appreciation to my supervisors, Professor Chow Yean Khow and Professor Leung Chun Fai for their patient guidance, encouragement and critiques of the research. They have not only introduced me to the field of offshore geotechnics but also have given me advice and unconditional support throughout my candidature. I would also like to acknowledge the scholarship as well as all the facilities provided by the National University of Singapore. Special thanks to Dr. Tho Kee Kiat, who has introduced me to the ABAQUS software and help in this research topic. He always been generous with his time and has constantly been on hand to provide inspiring and fruitful discussions when needed. I wish to extend my warmest thanks to all my colleagues for their persistent friendship and helpful discussions especially Dr. Sindhu Tjahyono, Dr. Sun Jie, Dr. Saw Ay Lee, Dr. Liu Yong, Dr. Zhao Ben, Dr. Ye Feijian, Dr. Tran Huu Huyen Tran, Dr. Li Yuping, Dr. Tang Chong, Mr. Hartono and Mr. Yang Yu. Also, I would like to thank my good friends both in China and Singapore for their support and accompany. Last but not least, I owe my loving thanks to my husband, He Hongbo and my whole family for their unlimited love and support. Without their encouragement and understanding, it would have been impossible for me to finish this work. i Table of Contents Acknowledgements . i Table of Contents .ii Summary vi List of Tables viii List of Figures ix List of Symbols xiv Chapter Introduction 1.1 Offshore oil and gas industry 1.2 Anchor systems . 1.2.1 Anchor piles . 1.2.2 Suction caissons . 1.2.3 Drag anchors 1.2.4 Vertical loaded anchors 1.2.5 Suction embedded plated anchors 1.2.6 Dynamically penetrated anchors 1.3 Suction embedded plate anchor . 1.4 Objectives and scope of study . 1.5 Thesis structure . Chapter Literature Review 21 2.1 Overview . 21 2.2 Uplift capacity of SEPLA . 21 2.2.1 DNV design code . 22 2.2.2 Analytical solutions and empirical solutions . 23 2.2.3 Small strain finite element analysis . 24 2.2.4 Limit analysis theorem solutions . 25 2.2.5 Large deformation finite element analysis . 26 2.3 SEPLA keying process 28 2.3.1 NAVFAC (2012) . 29 2.3.2 DNV (2002) . 29 2.3.3 Wilde et al. (2001) . 29 2.3.4 Song et al. (2005b; 2006; 2009) . 30 2.3.5 Gaudin et al. (2006a; 2006b; 2008; 2009; 2010) and O’Loughlin et al. (2006) 32 2.3.6 Yu et al. (2009) 34 ii 2.3.7 Wang et al. (2011) 35 2.3.8 Yang et al. (2012) and Cassidy et al. (2012) 37 2.4 SEPLA under combined loading . 37 2.5 Summary . 39 Chapter Finite Element Method 47 3.1 Introduction . 47 3.2 Finite element formulations 47 3.2.1 Lagrangian formulation . 48 3.2.2 Arbitrary Lagrangian Eulerian (ALE) formulation 49 3.2.3 Smooth Particle Hydrodynamics (SPH) 50 3.2.4 Eulerian formulation 51 3.3 Numerical model . 53 3.3.1 Abaqus/Explicit 53 3.3.2 The material model 55 3.3.3 The soil sensitivity . 56 3.4 Eulerian finite element model . 56 3.4.1 Domain convergence study 58 3.4.2 Mesh convergence study 58 3.4.3 Pullout rate convergence study 59 3.5 Summary . 60 Chapter Pullout Behaviour of Square Plate Anchor in Uniform Clay 66 4.1 Introduction . 66 4.2 Eulerian finite element model . 67 4.3 Comparison of current results and other approaches 69 4.4 Influence of soil overburden . 70 4.5 Load-displacement curve during pullout process of plate anchor . 74 4.6 Influence of soil rigidity 76 4.7 Conclusion . 82 Chapter Pullout Behaviour of Plate Anchor in Clay with Linearly Increasing Shear Strength . 98 5.1 Introduction . 98 5.2 Existing studies . 100 5.3 Geometry and parameters 103 5.4 Implementation of linearly increasing strength profile in ABAQUS 105 5.5 Effect of soil nonhomogeneity in weightless soil . 106 5.5.1 Shape factor . 110 iii HM after keying, no soil softening 2.5 HM after keying, sensitivity=3 Elkhatib (2006) M/(BLsu) 1.5 0.5 0 H/(BLsu) (c) H-M locus for square plate anchor with B/t=20 Figure 7.14 Interaction curves for square plate anchor with B/t=20 190 Chapter Conclusions and Recommendations 8.1 Introduction The problems related to the application of SEPLAs as a permanent mooring system are investigated by the Eulerian finite element method in this thesis. The pullout behavior of SEPLA in both uniform clay and clay with linearly increasing shear strength are investigated. The keying process and the effect of the suction caisson installation were also assessed in this thesis. The behaviour of SEPLA under combined load after the keying process is studied in this thesis as well. All the problems are illustrated in a logical way and this thesis provides a reference for the design of SEPLA. (1) The complexity of the finite element method This thesis extends the simplified two-dimensional plane strain finite element analysis for studying strip plate anchor uplift capacity to three-dimensional finite element analysis for studying square plate anchor uplift capacity. The Eulerian finite element method is able to simulate the whole pullout process and the failure mechanism is illustrated in this thesis. (2) The soil profile The pullout behavior of square plate anchor in uniform clay is illustrated in Chapter and it is extended to a linear increasing shear strength soil profile in Chapter 5. The difference in behaviour is shown in this thesis. A method to predict the capacity factor of square anchor under different combinations of embedment ratio, soil nonhomogeneity and overburden ratio is proposed. 191 (3) The load complexity The uniaxial uplift capacity of square plate anchor is studied in Chapters and 5. The study is extended to the yield envelop of the plate anchor under a combination of vertical, horizontal and moment loadings in Chapter 7. (4) The behavior of SEPLA at different installation stage Wish-in-place horizontal plate anchor is modeled in Chapters and 5. The installation and extraction of suction caisson as well as the keying process is studied in Chapter 6. The behavior under combined loading after the keying process is investigated in Chapter 7. 8.2 Summary of findings Based on the numerical analysis for the Suction Embedded Plate Anchor, the foregoing study can be summarized as follows. (1) Three types of failure mechanisms are observed during the pullout process with the “immediate breakaway” contact condition. The conventional general failure mechanism and localized full flow mechanism have been extensively presented by early researchers. The Type C failure mechanism defined in this thesis is a partially localized flow mechanism when the overburden ratio is not high enough to form a full flow mechanism. (2) The effect of the soil rigidity index is negligible for both Type A and B failure mechanism. However, the anchor capacity factor is found to increase with increasing value of soil rigidity for Type C failure mechanism. 192 (3) The vertical pullout behavior of SEPLA in uniform clay and clay with linearly increasing shear strength is different. The uplift capacity is lower in soil with linearly increasing shear strength profile as compared to that in a uniform soil with the same undrained shear strength at the initial embedment depth and the same embedment ratio in an idealized weightless soil. When the effect of soil self-weight is taken into account, the capacity factor increases with the overburden ratio up to a limiting value for both uniform clay and clay with linearly increasing shear strength. The limiting capacity factor is identical at 13.1 when the overburden ratio is large enough to force the soil to mobilize the full-flow mechanism. (4) A method to predict the uplift capacity factor for square plate anchor under different combinations of embedment ratio, overburden pressure and soil non-homogeneity is proposed in this thesis. (5) The SEPLA loss of embedment during the keying process is affected by many factors. A smooth contact between soil and anchor will over predict the loss of embedment. The weight and resistance of the anchor shank is efficient in reducing the loss of embedment for SEPLA during the keying process. The loss of embedment increases sharply when the eccentricity ratio e/B is less than 0.5 but it is not sensitive when the eccentricity ratio exceeds 1. The anchor load inclination angle has minimal effect on the ultimate anchor resistance but it affects the loss of embedment. The maximum loss of embedment reduces with reducing pullout angle. 193 (6) The soil flow mechanism is different for the SEPLA during the keying process in uniform clay and in clay with linearly increasing shear strength. The soil flows almost symmetrically around the edges of the fluke after it mobilizes the maximum resistance and the resistance remains constant in uniform clay. However, the SEPLA will mobilize the softer soil in the clay with linearly increasing shear strength after mobilizing the maximum resistance and the soil flow around the upper edge of the SEPLA resulting in a drop of the resistance. (7) The simulation of installation and extraction of the suction caisson which causes the remolding of the soil will reduce the loss of embedment of the SEPLA. The ultimate resistance of SEPLA is about 7% lower when considering the installation by suction caisson because of the remoulding compare to the wish-in-place anchors. (8) The remolding of the soil will not affect the maximum resistance of the wish-in-place horizontal plate anchor but the resistance of the anchor will decease with increasing displacement of the plate. (9) The yield locus for a typical strip and square plate anchor in the short-term condition after the keying process is much smaller than the wish-in-place horizontal plate anchor due to the change of the anchor configuration and the remolding of the soil during the keying process. The shape of the yield locus however does not change. 194 8.3 Recommendations for future studies Some possible areas which are related to the design of SEPLA and worth further exploration will be discussed here. These include the consideration of the effect of aspect ratio, long-term behavior, interaction between SEPLA and mooring line and the behavior of SEPLA under out of plane loading condition after the keying process. 8.3.1 The effect of aspect ratio In this thesis, a square plate anchor is selected to study the vertical pullout behavior of SEPLA in both uniform clay and clay with linearly increasing shear strength. A typical SEPLA is rectangular in shape. A square is an important limiting geometry although not strictly representative of many marine anchors used in practice. The strip plate anchor is another extreme condition and has been extensively studied by previous researchers. The pullout behavior of rectangular plate anchor is expected to be bounded between that of a square and a strip plate anchor. The effect of plate aspect ratio (length/width) needs to be studied for different SEPLA geometry. 8.3.2 Long-term capacity and behaviour of SEPLA All the results presented in this thesis focus on the short-term behavior of SEPLA as it is based on an undrained analysis. The capacity of SEPLA will change after the consolidation of the soil and dissipation of the pore water pressure generated during the undrained analysis. Wong et al. (2012) did model test to study the behavior of SEPLA under sustained loading. They concluded that increase in capacity due to consolidation can be significant for 195 load levels below 80% but failure was found to occur due to strength reduction at low strain rates for a sustained load level of 85%. As the industry intend to apply the SEPLA in permanent mooring systems for floating production facilities (Brown et al., 2010), long-term capacity and behaviour of SEPLA especially the effect of soil consolidation after keying process should be further explored by various parametric study. 8.3.3 Interaction of the SEPLA and mooring line In the field, the keying process of the SEPLA is done from a vessel by changing the position of the vessel while the SEPLA is pulled by a pulley system in the numerical simulation following the procedure of the centrifuge test. A more realistic modeling to represent the real field condition is recommended for further exploration. Most of the previous study for the interaction of mooring line and soil focus on the drag anchor and pointed out that the mooring line will be in a catenary shape in water and inverse catenary shape in soil due to the weight of the mooring line (O’Neill et al., 2003). Further study on the effect of mooring line and soil interaction during the keying process of SEPLA is necessary. 8.3.4 Out of plane loading As the mooring systems are typically designed for anchor line loads that act within the plane of the major axis of the anchor (Gilbert et al., 2009), only inplan load is considered in this thesis. However, if one or more of the mooring lines fail, the remaining anchors will be subjected to out of plane loading condition. The plate anchor will be subjected to six degrees of freedom load: 196 three force components and three moment components. It is important to assess how the out of plane loading can affect the ultimate capacity of the plate. Further study may be carried out to determine the complete yield locus for SEPLA for these loading conditions. 197 Reference ABAQUS (2010). ABAQUS Version 6.10 User's Manuals, SIMULIA. Andersen, K. H. and H. P. Jostad (2002). "Shear strength along outside wall of suction anchors in clay after installation." Proc. 12th Int. Offshore and Polar Engrg. Conf. Andersen, K. H. and H. P. Jostad (2004). "Shear strength along inside of suction anchor skirt wall in clay." Offshore Technology Conference, Houston, Texas, USA. Atkinson, J. H. (2000). "Non-linear soil stiffness in routine design." Geotechnique 50(5): 487-508. Aubeny, C. P., D. J. Murff and J. M. Roesset (2001). "Geotechnical issues in deep and ultra-deep waters." International Journal of Geomechanics - ASCE 1(2): 225-247. Benson, D. J. (1992). "Computational methods in Lagrangian and Eulerian hydrocodes." Computer Methods in Applied Mechanics and Engineering 99(23): 235-394. Brown, R. P., P. C. Wong and J. M. Audibert (2010). "SEPLA keying prediction method based on full-scale offshore tests." International Symposium on Frontiers in Offshore Geotechnics(ISFOG). Perth, Western Australia. Cassidy, M., C. Gaudin, M. Randolph, P. Wong, D. Wang and Y. Tian (2012). "A plasticity model to assess the keying of plate anchors." Geotechnique 62(9): 825-836. Chen, W. and M. Randolph (2007). "External radial stress changes and axial capacity for suction caissons in soft clay." Geotechnique 57(6): 499-511. Chen, Z., K. K. Tho, C. F. Leung and Y. K. Chow (2013). "Influence of overburden pressure and soil rigidity on uplift behavior of square plate anchor in uniform clay." Computers and Geotechnics 52: 71-81. Das, B. M. (1978). "Model tests for uplift capacity of foundations in clay." Soils and Foundations 18(2): 17-24. Das, B. M. (1980). "A procedure for estimation of ultimate uplift capacity of foundations in clay." Soils and Foundations 20(1): 77-82. Das, B. M. and G. Singh (1994). "Uplift capacity of plate anchors in clay." 4th international offshore and polar engineering conference., Golden, Colo. 198 Dingle, H. R. C., D. J. White and C. Gaudin (2008). "Mechanisms of pipe embedment and lateral breakout on soft clay." Canadian Geotechnical Journal 45(5): 636-652. DNV (2002). Design and Installation of Plate Anchors in Clay. Recommended Practice DNV-RP-E302. Ehlers, C., A. Young and J. Chen (2004). "Technology assessment of deepwater anchors." Offshore Technology Conference, Houston, Texas, USA. Einav, I. and M. F. Randolph (2005). "Combining upper bound and strain path methods for evaluating penetration resistance." International journal for numerical methods in engineering 63(14): 1991-2016. Elkhatib, S. (2006). The behaviour of drag-in plate anchors in soft cohesive soils, The University of Western Australia. PhD thesis. Foray P. Y., Alhayari, S., Pons, E., Thorel, L., Thetiot, N., Bale, S. and Flavigny, E. (2005). "Ultimate pullout capacity of SBM’s vertically loaded plate anchor in deep sea sediments". Proceeding of International Symposium on Frontiers in Offshore Geotechnics, Perth, Australia. Gaudin, C., C. D. O'Loughlin, M. F. Randolph and A. C. Lowmass (2006a). "Influence of the installatin process on the performance of suction embedded plate anchors." Geotechnique 56(6): 381-391. Gaudin, C., C. D. O'Loughlin and M. F. Randolph (2006b). "Centrifuge tests on suction embedded plate anchors." the 6th International Conference on Physical Modelling in Geotechnics, Balkema, Rotterdam. Gaudin, C., T. Kien H and S. Ouahsine (2008). "Plate anchor failure mechanism during keying process." International Offshore and Polar Engineering Conference, Vancouver, BC, Canada. Gaudin, C., K. H. Tham and S. Ouahsine (2009). "Keying of plate anchors in NC clay under inclined loading." International journal of Offshore and Polar Engineering 19(2): 135-142. Gaudin, C., M. Simkin, D. J. White and C. D. O'Loughlin (2010). "Experimental investigation into the influence of a keying flap on the keying behaviour of plate anchors." The 20th International Offshore and Polar Engineering Conference, Beijing, China. Gilbert, R. B., C. Lupulescu, C. H. Lee, J. Miller, M. Kroncke, M. Yang, C. P. Aubeny and M. James D (2009). "Analytical and experimental modeling for out-of-plane Loading of Plate Anchors." Offshore Technology Conference, Houston, Texas, USA. Gibson, R. E. (1950). "Correspondence." Journal of Institution of Civil Engineers 34: 382-383. 199 Ha H. Bui, K. Sako, R. Fukagawa, and J. C. Wells (2008). “SPH-based numerical solutions for large deformation of geomaterial considering soilstructure interaction.” The 12th International Association for Computer Methods and Advances in Geomechanics (IACMAG), Goa, India. Hossain, M. S. and M. F. Randolph (2009). "Effect of strain rate and strain softening on the penetration resistance of Spudcan foundations on clay." International Journal of Geomechanics - ASCE 9(3): 122-132. Hu, Y. and M. F. Randolph (1998). "A practical numerical approach for large deformation problems in soil." international journal for numerical and analytical methods in geomechanics 22(5): 327-350. Hu, Y. and M. F. Randolph (2002). "Bearing capacity of caisson foundations on normally consolidation clay." Soils and Foundations 42(5): 71-77. Kumar, J. (1999). "Kinematic slices approach for uplift analysis of strip foundations." International journal for numerical methods in engineering 23(11): 1159-1170. Leffler, W. l., P. R. and G. Sterling (2003). Deepwater Petroleum Exploration and Production. PenWell. Lieng, J. T., A. Kavli, F. Hove and T. I. Tjelta (2000). "Deep penetrating anchor: Further development, optimization and capacity verification." International Society of Offshore and Polar Engineers, Seattle. Martin, C. M. and M. F. Randolph (2001). "Application of the lower and upper bound theorems of plasticity to collapse of circular foundations." 10th International Conference of the Internation Association for Computer Methods and Advances in Geomechanics, Balkema, Rotterdam. Medeiros Jr, C. J. (2001). "Torpedo anchor for deep water." Deepwater Offshore Techenology Conference, Rio de Janeiro. Medeiros Jr, C. J. (2002). "Low cost anchor system for flexible risers in deep waters." Offshore Technology Conference, Houston, Texas, USA. Merifield, R. S., S. W. Sloan and H. S. Yu (2001). "Stability of plate anchors in undrained clay." Geotechnique 51(2): 141-153. Merifield, R. S., A. V. Lyamin, S. W. Sloan and H. S. Yu (2003). "Threedimensional lower bound solutions for stability of plate anchors in clay." Journal of Geotechnical and Geoenvironmental Engineering - ASCE 129(3): 243-253.NAVFAC (2012). Naval Facilities Engineering Command. Handbook for Marine Geotechnical Engineering, California. Neubecker, S. R. and M. F. Randolph (1995). "Profile and frictional capacity of embedded anchor chains." Journal of Geotechnical Engineering - ASCE 121(11): 797-803. 200 O'Loughlin, C. D., A. C. Lowmass, C. Gaudin and M. F. Randolph (2006). "Physical modelling to assess keying characteristics of plate anchors." The 6th International Conference on Physical Modelling in Geotechnics, Hong Kong. O'Neill, M. P., M. F. Bransby and M. F. Randolph (2003). "Drag anchor fluke–soil interaction in clays." Canadian Geotechnical Journal 40(1): 78-94. Qiu, G., S. Henke and J. Grabe (2011). "Application of a Coupled Eulerian– Lagrangian approach on geomechanical problems involving large deformations." Computers and Geotechnics 38(1): 30-39. Randolph, M., M. Cassidy, S. Gourvenec and C. Erbrich (2005). "Challenges of offshore geotechnical engineering." International Conference on soil mechanics and geotechnical engineering. Richardson, M. D. (2008). Dynamically installed anchors for floating offshore structures. School of Civil and Resource Engineering, The university of western Australia. PhD thesis. Rowe, R. K. (1978). Soil structure interaction analysis and its application to the prediction of anchor behavior. Australia, University of Sydney. Rowe, R. K. and E. H. Davis (1982). "The behaviour of anchor plates in clay." Geotechnique 32(1): 9-23. Schwer, L. E. and J. Day (1991). "Computational techniques for penetration of concrete and steel targets by oblique impact of deformable projectiles." Nuclear Engineering and Design 125: 215-238.Song, Z. and Y. Hu (2005a). "Vertical pullout behaviour of plate anchors in uniform clay." International Symposium Frontiers in Offshore Geotechnics, Perth. Song, Z., Y. Hu and M. F. Randolph (2005b). "Pullout behaviour of inclined plate anchors in uniform clay." 11th International Conference of the International Association for Computer Methods and Advances in Geomechanics, Turin, Italy. Song, Z., Y. Hu and D. Wang (2006). "pullout capacity and rotational behaviour of square anchors." the 6th International Conference on Physical Modelling in Geotechnics, Balkema, Rotterdam. Song, Z., Y. Hu and C. Gaudin (2007). "The influence of disturbed zone on capacity of suction embedded plate anchors." 17th International Offshore and Polar Engineering Conference, Lisbon, Portugal. Song, Z. (2008). Pullout Behaviour of Suction Embedded Plate Anchors in Clay. Department of Civil Engineering. Perth, Curtin University of Technology. PhD thesis. Song, Z., Y. Hu and M. F. Randolph (2008). "Numerical Simulation of Vertical Pullout of Plate Anchors in Clay." Journal of Geotechnical and Geoenvironmental Engineering - ASCE 134(6): 866-875. 201 Song, Z., Y. Hu, C. O'Loughlin and M. F. Randolph (2009). "Loss in Anchor Embedment during Plate Anchor Keying in Clay." Journal of Geotechnical and Geoenvironmental Engineering - ASCE 135(10): 1475-1485.Terzaghi, K. (1943). Theoretical soil mechanics. New York, Wiley. Tho, K. K., C. F. Leung, Y. K. Chow and A. C. Palmer (2012a). "Deep cavity flow mechanism of pipe penetration in clay." Canadian Geotechnical Journal 49(1): 59-69. Tho, K. K., C. F. Leung, Y. K. Chow and S. Swaddiwudhipong (2012b). "Eulerian Finite-Element Technique for Analysis of Jack-Up Spudcan Penetration." International Journal of Geomechanics 12(1): 64-73. Tho, K. K., Z. Chen, C. F. Leung and Y. K. Chow (2014). "Pullout behaviour of plate anchor in clay with linearly increasing strength." Canadian Geotechnical Journal 51(1): 92-102. Vesic, A. S. (1971). "Breakout resistance of objects embedded in ocean bottom." Journal of the Soil Mechanics and Foundations Division - ASCE 97(9): 1183-1205. Vryhof (2010). Anchor Manual 2010. V. Anchors and K. a. Yssel. The Netherlands. Wang, D., Y. Hu and M. F. Randolph (2010). "Three-Dimensional Large Deformation Finite-Element Analysis of Plate Anchors in Uniform Clay." Journal of Geotechnical and Geoenvironmental Engineering - ASCE 136(2): 355-365. Wang, D., Y. Hu and M. F. Randolph (2011). "Keying of Rectangular Plate Anchors in Normally Consolidated Clays." Journal of Geotechnical and Geoenvironmental Engineering 137(12): 1244-1253.Wang, D. and C. O'Loughlin (2014). "Numerical study of pull-out capacities of dynamically embedded plate anchors." Canadian Geotechnical Journal. Wilde, B., H. Treu and T. Fulton (2001). "Field testing of suction embedded plate anchors." The 11th International Offshore and Polar Engeering Conference, Stavanger. Wong, P., C. Gaudin, M. F. Randolph, M. J. Cassidy and Y. Tian (2012). "Performance of suction embedded plate anchors in permanent mooring applications." The 22nd International Offshore and Polar Engineering conference, Rhodes, Greece. Yang, M., J. D. Murff and C. P. Aubeny (2010). "Undrained capacity of plate anchors under general loading." Journal of Geotechnical and Geoenvironmental Engineering - ASCE 136(10): 1383-1393. Yang, M., C. P. Aubeny and J. D. Murff (2012). "Behavior of Suction Embedded Plate Anchors during Keying Process." Journal of Geotechnical and Geoenvironmental Engineering (ASCE) 138(2): 174-183.Yu, H. S. (2000). Cavity Expansion Methods in Geomechanics, Kluwer Academic Publishers. 202 Yu, L., J. Liu, X.-J. Kong and Y. Hu (2009). "Three-dimensional numerical analysis of the keying of vertically installed plate anchors in clay." Computers and Geotechnics 36(4): 558-567. Yu, L., J. Liu, X.-J. Kong and Y. Hu (2011) "Numerical study on plate anchor stability in clay." Geotechnique 61, 235-246. Zhou, H. and M. F. Randolph (2007). "Computational techniques and shear band development for cylindrical ans spherical penetometers in strainsoftening clay." International Journal of Geomechanics - ASCE 7(4): 287-295. 203 List of publications Chen, Z, Tho, K. K., Leung, C. F. and Chow, Y. K. (2012) “Eulerian finite element analysis of uplift capacity of plate anchor.” The Twenty-Fifth KKCNN Symposium on Civil Engineering, Busan, Korea. Chen, Z, Tho, K. K., Leung, C. F. and Chow, Y. K. (2013) “Influence of overburden pressure and soil rigidity on uplift behavior of square plate anchor in uniform clay.” Computers and Geotechnics, 52, 71-81. Chen, Z, Tho, K. K., Leung, C. F. and Chow, Y. K. (2013) “Pullout behavior of square plate anchor in clay with uniform and linearly increasing strength.” The Twenty-Sixth KKHTCNN Symposium on Civil Engineering, Singapore. Chow, Y. K, Chen, Z, Tho, K. K. and Leung, C. F. (2013) “Effect of installation of new foundations on adjacent piles.” keynote lecture, International Symposium on Advances in Foundation Engineering (ISAFE 2013), Singapore. Tho, K. K, Chen, Z, Leung, C. F. and Chow, Y. K. (2014) “Pullout behaviour of plate anchor in clay with linearly increasing strength.” Canadian Geotechnical Journal, 51(1), 92-102. Tho, K. K, Chen, Z, Leung, C. F. and Chow, Y. K. (2014) “Enhanced analysis of pile flexural behavior due to installation of adjacent pile.” Canadian Geotechnical Journal, 51(6), 705-711. 204 [...]... padeye 188 Figure 7.14 Interaction curves for square plate anchor with B/t=20 190 xiii List of Symbols A Section area of plate anchor B Width of the plate anchor Cθ Constant which varies with anchor geometry d Chain diameter D Diameter of the circular plate anchor e Anchor padeye eccentricity ef Anchor shank resistance eccentricity ew Anchor shank weight eccentricity En Multiplier giving the... 14 Figure 1.3 Anchor piles (Vryhof, 2010) 14 Figure 1.4 Suction caisson (http://www.delmarus.com) 15 Figure 1.5 Drag anchor (Vryhof, 2010) 16 Figure 1.6 Vertical loaded anchor (Vryhof, 2010) 16 Figure 1.7 (a) Photograph of typical SEPLA Anchor and (b) Schematic of SEPLA (Brown et al., 2010) 17 Figure 1.8 Installation process for Suction embedded plate anchor( Gaudin... anchor position poses other challenges 1.2.5 Suction embedded plated anchors Suction embedded plate anchor (SEPLA) comprises a plate anchor that is penetrated in a vertical orientation using a caisson A typical SEPLA consists of a fluke, a shank and a keying flap (Figure 1.7) The SEPLAs used for Mobile Offshore Drilling Unit (MODU) are usually solid steel plates with widths and lengths ranging from... The SEPLA combines the advantage of suction caissons and vertical loaded anchors With improved geotechnical efficiency, the size and weight of a SEPLA is only approximately 1/3 that of a suction caisson of the same 5 capacity (Brown et al., 2010) Consequently, more plate anchors can be placed on board an anchor handling vessel (AHV) per trip The adoption of a plate anchor mooring system is generally... Effect of soil sensitivity in both uniform transparent soil and NC kaolin clay 139 6.5 Effect of installation and extraction of suction caisson 142 6.6 Parametric studies 143 6.6.1 Effect of anchor unit weight 143 6.6.2 Effect of anchor eccentricity ratio 144 6.6.3 Effect of anchor loading inclination angle 144 6.7 Conclusion 145 Chapter 7 Capacity of Plate. .. capacity of square plate anchor of width B 64 Figure 3.4 Uplift load (F) versus normalized displacement (w/B) curves for convergence study (Anchor width B=0.5m, embedment ratio H/B=5) 65 Figure 4.1 Finite element model for pullout capacity of circular plate anchor 85 Figure 4.2 Normalized uplift load (F) versus displacement (w) responses for circular anchors in weightless soil (Anchor diameter... because of (i) a reduction in the quantity of steel required for the anchor, (ii) the use of smaller AHV vessels, (iii) lesser number of AHV trips required to complete the installation, and (iv) reuse of the suction follower Despite the aforementioned advantages, the final orientation of the plate cannot be assured and the loss of embedment also needs to be considered Additionally, a zone of weakened... installation and extraction of suction caisson results in a lower anchor resistance 1.2.6 Dynamically penetrated anchors Torpedo anchor is a type of dynamically penetrated anchor, which consists of a cylindrical thick wall steel pipe filled with scrap chain or concrete (Figure 1.9) The ballast inside the anchor increases its overall weight and maintains the center of gravity below the center of buoyancy for stability... Horizontal displacement of plate anchor Vmax Maximum vertical load V1 Vertical offset load Wa' Difference between the anchor weight in air and the anchor buoyancy force in soil Y Yield stress α Friction coefficient β Plate anchor inclination to the horizontal γ Soil saturated unit weight η Empirical reduction factor θa Angle of force at the padeye to the horizontal ∆z Loss of embedment during keying... element analysis was conducted in ABAQUS to study the pullout behaviour of SEPLA in uniform clay and in clay with linearly increasing shear strength A new kind of flow mechanism during the pullout of square plate anchor is defined in this thesis as the partially full flow mechanism An approach to predict the uplift capacity of plate anchor under different combinations of embedment ratio, overburden pressure . NUMERICAL STUDY OF SUCTION EMBEDDED PLATE ANCHOR CHEN ZONGRUI NATIONAL UNIVERSITY OF SINGAPORE 2014 NUMERICAL STUDY OF SUCTION EMBEDDED PLATE. gas industry 1 1.2 Anchor systems 2 1.2.1 Anchor piles 2 1.2.2 Suction caissons 3 1.2.3 Drag anchors 3 1.2.4 Vertical loaded anchors 4 1.2.5 Suction embedded plated anchors 4 1.2.6 Dynamically. Effect of anchor unit weight 143 6.6.2 Effect of anchor eccentricity ratio 144 6.6.3 Effect of anchor loading inclination angle 144 6.7 Conclusion 145 Chapter 7 Capacity of Plate Anchor Under