Punch through of spudcan foundation in sand overlying clay

PU CH-THROUGH OF SPUDCA FOU DATIO I SA D OVERLYI G CLAY TEH KAR LU ATIO AL U IVERSITY OF SI GAPORE 2007 PU CH-THROUGH OF SPUDCA FOU DATIO I SA D OVERLYI G CLAY TEH KAR LU (B. Eng. (Hons.), UTM) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF CIVIL ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2007 Acknowledgements Ever since embarked on this journey, the experience has been so fascinating and rewarding. My heartfelt thanks go out to both of my supervisors, Prof. Leung Chun Fai and Prof. Chow Yean Khow, for providing me with the best opportunities to learn, grow and progress. Their timely advices, patience and encouragement motivated me to think outside the box. I would like to acknowledge the financial support of the NUS research scholarship (which otherwise, I would not have pampered myself every morning with caffè e latte), and NUS research grant RP 264-000-167-112 for the research equipment expenses. I wish to warmly thank all the officers of the Geotechnical Engineering Laboratory and Centrifuge Laboratory - Mr. Wong, Mr. Tan, Mr. Shen, Mr. Foo, Mr. John Choy, Shaja, Mdm. Jamilah and Mr. Loo. Without your help, I could not have tamed the giant Centrifuge. Not forgetting to mention the officers of the CE Department who responded to my enquiries with friendly smiles. I treasure deeply the friendship built up within the geotechnical research group. The research life could be unimaginable dull and helpless without their friendly companions, particularly Kheng Ghee, Pang, Okky, Yonggang, Liangbo, Yen, Xiying, Chen Xi, Haibo, Xie Yi, Chee Wee, Cheng Ti, Eddie, Sindhu, Karma, Krishna, Wang Lei, Ali and Prof. Phoon (of course). I am also grateful to Colin Nelson, Paul Handidjaja, Nancy Chan, Matthew Quah, Dr. Foo and Julian Osborne for sharing their invaluable practical experiences with me. Your words have never stopped pushing me to think hard on how to link the (idealized) academic research findings to practical application. One of the best moments in my research journey was the opportunity of performing research at the Centre for Offshore Foundation Systems (COFS), The University of Western Australia (UWA), co-supervised by Prof. Mark Cassidy under the sponsorship of Keppel Offshore and Marines, Singapore which is greatly acknowledged. My sincere gratitude to Mark, Prof. Randolph, Christophe, Dave and i Shazzad for all the fruitful discussions; Monica for arranging my temporary stay; Bart, Don, Neil, Frank, David and Gary for their hard work making sure my experiments ran smoothly; Top, Han Eng, Xiangtao, Frank, Mark, James, Susie and KK Lee for warming up my (winter) stay with the flames of friendship. I embarked on another memorable journey when Dr. Dave White kindly provided me an opportunity to visit Schofield Centre, Cambridge in August 2006. Working with Dave, a star researcher with a deep sense of humility, is always inspiring and enjoyable. His invaluable guidance and encouragement cultivate my ‘addiction’ to seeking for wisdom. I would also like to acknowledge the generosity of Prof. Bolton and Prof. Schofield with their time for discussion; and the friendliness shown by Johnson, Alec, Fiona, Anama and Tom. Spending a short period of time (September 2006) at Oxford University working under Prof. Guy Houlsby and Dr. Byron Byrne was another enlightening experience where I start looked into the behaviour of skirted foundation, keeping up with the latest development in the industry. Thanks also go out to Thanasis, Oliver and Philip for demonstrating how the East (Chow Mein) and West (British beer) could coexist harmoniously (in a stomach) all the time. I would definitely not be who I am today without my supportive family. I am deeply indebted to my dad, mum and sister for loving me without reservation and standingby like nothing in the world that is more important than me. For all the sacrifices they made to fill my life with love and happiness, I dedicate this work to my beloved parents and sister. ii Table of Contents Acknowledgements i Table of Contents Summary List of Tables iii viii x List of Figures List of Symbols xi xix Chapter 1: Introduction 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Jack-up rig and spudcan foundation Foundation hazards of spudcan in sand overlying clay 1.2.1 Punch-through during installation 1.2.2 Scour-induced punch-through Differences between conventional shallow foundation and spudcan Evaluation of spudcan vertical bearing capacity Needs for further research Objectives and scope of study 1.6.1 Spudcan bearing capacity in sand 10 1.6.2 10 Spudcan bearing response in sand overlying normally consolidated (NC) clay 1.6.3 Failure mechanism of spudcan foundation in sand overlying NC clay 1.6.4 Estimation of spudcan bearing resistance profile in sand overlying NC clay Outline of thesis 10 11 11 Chapter 2: Literature Review 2.1 Bearing capacity in sand 19 2.1.1 21 2.1.2 2.2 Effects of conical base and base roughness on bearing capacity in sand Scale effect and progressive failure on bearing capacity in sand 2.1.3 Selection of strength parameter for sand bearing capacity 2.1.4 Summary Bearing capacity in sand overlying clay 2.2.1 Basis of analysis 2.2.2 Experimental investigation 23 25 28 29 30 30 iii 2.2.3 Analytical design model 32 2.2.3.1 Projected area method 2.2.3.2 Method by Yamaguchi (1963) 2.2.3.3 Method by Hanna and Meyerhof (1980) 33 35 36 2.2.3.4 Method by Love et al. (1987) 2.2.3.5 Method by Okamura et al. (1998) 2.2.3.6 Kinematic upper bound approach 2.2.4 Numerical analysis 38 39 42 43 2.3 2.4 2.2.4.1 Burd and Fryman (1997) 2.2.4.2 Shiau et al. (2003) Bearing failure mechanism in sand overlying clay Spudcan bearing capacity in sand overlying clay 43 45 45 48 2.5 Concluding remarks 51 Chapter 3: Spudcan Bearing Capacity in Sand 3.1 Experimental investigation of spudcan penetration in sand 3.1.1 Spudcan failure mechanism – Half spudcan penetration test 74 75 75 3.2 3.1.1.1 Experimental set-up, sample preparation and testing procedure 3.1.1.2 Soil flow patterns induced by spudcan penetration 3.1.1.3 Comparison between spudcan and flat footing bearing failure mechanisms 3.1.2 Spudcan bearing capacity profile – Full spudcan penetration test 3.1.2.1 Experimental set-up, sample preparation and testing procedure 3.1.2.2 Spudcan load-penetration response Design framework for spudcan bearing capacity in sand 83 84 3.3 3.2.1 Bearing capacity factors accounting for conical angle 3.2.2 Strength-dilatancy relationship for spudcan bearing capacity 3.2.3 Validation of proposed design framework Concluding remarks 84 87 92 93 77 79 81 81 Chapter 4: Spudcan Penetration in Sand overlying C Clay 4.1 Centrifuge model test 4.1.1 Spudcan penetration test conducted at NUS 114 115 4.1.2 4.1.3 118 120 Spudcan penetration test conducted at UWA Penetration test of miniature penetrometers iv 4.2 4.3 4.4 4.5 4.6 Soil strength profile of sand overlying NC clay 121 4.2.1 4.2.2 Calibration test of piezocone Typical piezocone and ball resistance profiles in sand overlying NC clay 4.2.3 ‘Stratigraphy’ effect on soil strength interpretation 4.2.4 Deriving su profile 121 123 Performance of spudcan penetration into sand overlying NC clay 4.3.1 Typical spudcan penetration resistance profile 4.3.2 Surface deformation and pore pressure development induced by spudcan penetration 4.3.3 Displacement versus load control mode 4.3.4 Effects of overlying sand layer thickness 129 130 130 4.3.5 4.3.6 Effect of spudcan diameter Effect of overlying sand relative density 134 135 4.3.7 Discussions and summary 4.3.7.1 Critical depth, dcrit 4.3.7.2 Governing factors 4.3.7.3 Limiting H/D, H*/D 136 136 137 139 125 127 132 133 Comparisons between experimental results and predictions using existing methods 4.4.1 Selection of design strength parameter 4.4.2 Comparisons between measured and predicted spudcan bearing profiles 4.4.3 Comparisons between measured and predicted q0 and qmax 140 143 Generalization of spudcan penetration resistance profiles Concluding remarks 145 146 141 142 Chapter 5: Failure Mechanism of Spudcan Penetration in Sand overlying C clay 5.1 Centrifuge model tests and image processing analysis 5.1.1 Half spudcan penetration test in sand overlying NC clay 5.1.2 Image processing analysis 174 174 177 5.2 Revealing failure mechanism of spudcan penetration in sand overlying NC clay 5.2.1 Soil flow mechanism 5.2.2 Soil displacement contours and deformation of imaginary marker strips 5.2.3 Shear strain distribution 5.2.4 Spudcan failure mechanisms 5.2.4.1 Failure mechanism for q0 178 179 181 184 185 185 v 5.2.4.2 Failure mechanism for qmax 5.3 5.4 5.2.4.3 Failure mechanism for spudcan bearing capacity in underlying clay Effect of thickness ratio on spudcan failure mechanism 5.3.1 Failure mechanism for q0 5.3.2 Failure mechanism for qmax 5.3.3 Failure mechanism for spudcan bearing capacity in underlying clay Concluding remarks 186 188 189 189 189 191 192 Chapter 6: Spudcan Bearing Capacity in Sand overlying C Clay – Design Framework, Procedures and Validation 6.1 Design consideration 6.1.1 Surface bearing capacity, q0 6.1.2 6.2 6.3 6.4 6.1.1.1 Determination of φ1 6.1.1.2 Determination of K Maximum bearing capacity, qmax 214 215 217 6.1.2.1 Shear resistance in sand, Qs,max 6.1.2.2 Determination of Qc, max 219 221 225 225 6.1.2.3 Determination of φ2 6.1.2.4 Determination of ψ, R and r 6.1.3 Bearing capacity in underlying clay 6.1.3.1 Determination of Nc 6.1.3.2 Determination of h Design procedure for calculating spudcan bearing capacity 6.2.1 Spudcan bearing capacity in sand, qsand 6.2.2 Spudcan bearing capacity in clay, qclay 6.2.3 210 212 227 228 229 229 230 231 Spudcan bearing capacity in sand overlying NC clay 6.2.3.1 Surface spudcan bearing capacity, q0 231 231 6.2.3.2 Maximum spudcan bearing capacity, qmax 6.2.3.3 Spudcan bearing capacity in underlying clay Validation of proposed design framework Concluding remarks 232 233 233 237 Chapter 7: Conclusions 7.1 7.2 Introduction Summary of findings 260 260 7.2.1 260 Spudcan bearing capacity in sand vi 7.2.2 Spudcan bearing response in sand overlying NC clay 7.2.3 7.3 261 Failure mechanism of spudcan foundation in sand overlying NC clay 7.2.4 Estimation of spudcan bearing capacity profile in sand overlying NC clay Recommendations for further research 7.3.1 Further validation of the proposed design framework 7.3.2 Utilizing penetrometer penetration resistance profile to predict spudcan bearing capacity profile 7.3.3 Skirted foundation to mitigate spudcan punch-through 262 7.3.4 267 References Investigation of spudcan bearing capacity in multi-layered soil 263 264 264 265 266 269 vii Summary Spudcan installation in sand overlying clay is subjected to potential punch-through hazard. Punch-through failure occurs when the applied load exceeds the maximum bearing resistance of the upper sand layer causing the spudcan to plunge into the underlying clay. The risk of the failure remains as the predicted spudcan penetration responses are often found deviated from the field performance, highlighting the need of reappraisal of the existing design methods. The present study aims to enhance the level of understanding of the spudcan bearing resistance in sand overlying normally consolidated (NC) clay through centrifuge modeling. A priori study was first conducted focusing on the development of bearing resistance-depth profile and bearing failure mechanism for spudcan installation in sand. The findings propose some modifications to the conventional assessment of the spudcan bearing capacity profile in sand to account for the effects of conical base, size-induced stress level, progressive failure and pre-yield sand compression. Similar study performed in sand overlying NC clay reveals that the bearing ratio of the two soil layers and the ratio of spudcan diameter to the upper sand layer thickness emerge as the main factors governing the development of spudcan bearing resistance in the layered soil. The experimental findings also provide evidence of the continuous change in spudcan foundation failure mechanism with penetration depth. Adopting limit equilibrium theory, a novel design framework involves analyses performed at several prescribed spudcan levels is proposed to predict the complete viii Chapter –Conclusions . Besides a comprehensive design procedure to guide the designer to calculate q0, qmax and bearing capacity in the underlying clay, the determination of input parameters for the calculations is outlined to avoid ambiguous implementation. The ability of the design framework to predict the overall spudcan bearing response in sand overlying NC clay was validated using a database comprising of centrifuge test results obtained from the present study as well as existing studies. In general, the constructed theoretical profiles show good agreement to those obtained experimentally. The simplified bearing resistance profile is therefore useful for identifying the potential of punch-through hazard during spudcan installation or operational period. 7.2 Recommendations for further research Some possible areas that worth further exploration are discussed here. These include the improvement of the present proposed design framework, alternative approach to predict spudcan bearing capacity in sand overlying clay, mitigation of spudcan punchthrough and extension of the analysis for the case of two-layered soil to multi-layered soil. 7.3.1 Further validation of the proposed design framework The design framework proposed in the present study was validated using the database comprising solely centrifuge test results. These tests were conducted using spudcan diameter of equal to or less than 14 m on samples which mostly consist of dense sand overlying soft clay. Besides using a larger model spudcan, more experimental work could be phased in to extend the study to incorporate (i) loose sand overlying soft clay; and (ii) loose sand overlying strong clay. The test results are believed to further justify the geometric parameters derived empirically. Apart from using experimental 264 Chapter –Conclusions . data, validation using field data would further enhance the practical application of the proposed design framework. 7.3.2 Utilizing penetrometer penetration resistance profile to predict spudcan bearing capacity profile A sound analytical solution will not guarantee a good estimation of spudcan bearing capacity without a reliable input of soil strength parameters. In fact, this is a common problem found in offshore industry in obtaining a set of high quality soil strength parameters owing to the environmental and cost-saving factors. Alternatively, in view of the fact that some of the in-situ SI penetrometers such as piezocone, ball and T-bar share a similar penetration mechanism as the spudcan, utilizing the readings of these penetrometers to shed lights on the spudcan penetration behaviour is deemed feasible. To adopt this alternative approach, a thorough understanding of the performance of spudcan and penetrometer in different types of soil profiles and how they differ from each other should be established. For instance, Erbrich (2005) discussed that owing to the differences in penetration rate, dimension and geometry, the variations that could possibly exist between T-bar and spudcan penetration resistances are mainly due to the effects of drainage and strain rate on clay characteristic as well as soil wedge trapped underneath the spudcan (Lu et al., 2001). Apart from this, the stress level induced strength variation could vary the penetrometer and spudcan resistance profiles developed in the sand to a considerably large extent considering the huge dimension of spudcan and its limited penetration in sand. For two-layered soil, Teh et al. (2007) made some additional suggestions to account for the effects of stratigraphy and trapped soil wedge. 265 Chapter –Conclusions . Similar approach has been applied to pile design (Eslami and Fellenius, 1997; White and Bolton, 2005). In view of the fact that this approach could reduce the reliance on the soil strength parameters and provide indication for the potential of spudcan punchthrough prior to its installation, more research should be conducted to realize the application feasibility to the spudcan design. 7.3.3 Skirted foundation to mitigate spudcan punch-through There is an increasing interest in the use of skirted foundation for its ability of providing uplift capacity (Bransby and Houlsby, 1999) and larger lateral resistance against the horizontal environmental loads (Cassidy et al., 2004). The skirted foundation consists of a shallow foundation with a thin skirt at its circumference which looks like an upturned bucket. Teh et al. (2006b) investigated the penetration resistance profiles developed by the skirted foundations with different skirt length on loose sand and clay with flat and irregular surface. The results indicated that the vertical resistance increased marginally when the annulus of the skirted foundation began to penetrate the soil and significant increase in resistance revealed only when the base of the top-plate made contact with the soil. Knowing that the skirted foundation bearing resistance is calculated as the sum of the side resistance on the inside and outside of the skirt, and the end bearing on the annulus rim (Houlsby and Byrne, 2005a,b), the findings indicated that the end bearing resistance constitutes a major portion of the overall foundation resistance. 266 Chapter –Conclusions . Conceptually, one way to mitigate the punch-through hazard in sand overlying clay formation is to replace the use of spudcan with skirted foundation with skirt height preferably equals to or larger than the upper sand layer thickness. When the base-plate of the foundation making contact with the sand surface, the annulus rim has reached the underlying clay and therefore reduces the end bearing resistance. Although the overall bearing resistance becomes lesser and the foundation is expected to found at a deeper depth, it diminishes the development of a peak bearing resistance as shown by the spudcan while penetrating the upper sand layer. This enables a smooth installation of the foundation in seabed formation consisting of strong overlying weak soil. 7.3.4 Investigation of spudcan bearing capacity in multi-layered soil It is aware that the actual seabed formation is anisotropic and multi-layered in nature. The conventional approach for spudcan analysis in multi-layered soil is divided into stages in which for each stage of analysis, calculation was performed on a simplified two-layered soil assuming the most likely failure mechanism (SNAME, 2002b). The knowledge of the spudcan bearing capacity in two-layered soil could be, therefore, extended to the case of multi-layered soil. Nevertheless, it was demonstrated by Teh et al. (2006c) that different assumed failure mechanism could lead to significant variation in the calculated bearing capacity profile. Therefore, more experimental studies to gain insight of the failure mechanism developed in the multi-layered soil would be useful to establish a proper design guideline. Apart from performing experimental work, numerical analysis is regarded as one possible option to evaluate spudcan bearing capacity in multi-layered soil. However, further studies are required to ensure the accuracy of the numerical analysis for large 267 Chapter –Conclusions . strain simulation. For similar input parameters, Kellezi and Stromann (2003) revealed that adopting different existing numerical software led to a great variation in the evaluated bearing capacity. For this instance, data obtained from experimental studies or field monitoring would be useful to make suggestion of a suitable soil model and modeling technique used for spudcan analysis in multi-layered soil. 268 References Ahmadi, M.M. and P.K. Robertson. Thin layer effects on the CPT qc measurement. Can. Geotech. J., 42, pp. 1302-1317. 2005. Arumongkol, J. Centrifuge modeling of single pile subjected to compression and tension in clay. Ph.D. Thesis, National University of Singapore. 2004. Atkinson, J. An introduction to the mechanics of soils and foundations. England: McGraw-Hill. 1993. Baligh, M.M. and R.F. Scott. Analysis of wedge penetration in clay. Géotechnique, 26(1), pp. 185-208. 1976. Baglioni, V.P., G.S. Chow and S.N. Endley. Jack-up foundation stability in stratified soil profiles. In Proc. 14th Offshore Technology Conference, Vol. 4, Paper OTC 4409, pp. 363-384. 1982. Bolton, M.D. The strength and dilatancy of sands. Géotechnique, 36(1), pp. 65-78. 1986. Bolton, M.D. and C.K. Lau. Vertical bearing capacity factors for circular and strip footings on Mohr-Coulomb. Can. Geotech. J., 30, pp. 1024-1033. 1993. Bransby, M.F. and M.F. Randolph. Combined loading of skirted foundations. Géotechnique, 48(5), pp. 637-655. 1998. Brown, J.D. and W.G. Paterson. Failure of an oil storage tank founded on a sensitive marine clay. Can. Geotech. J., 1, pp. 205-214. 1964. Burd, H.J and S. Frydman. Discussion for bearing capacity of footings over twolayered foundation soils. Journal of Geotechnical Engineering, ASCE, 122(8), pp. 699-700. 1996. Burd, H.J and S. Frydman. Bearing capacity of plane-strain footings on layered soils. Can. Geotech. J., 34, pp. 241-253. 1997. Cassidy, M.J. and G.T. Houlsby. Vertical bearing capacity factors for conical footings on sand. Géotechnique, 52(9), pp. 687-692. 2002. Cassidy, M.J., B.W. Byrne and M.F. Randolph. A comparison of the combined loading behaviour of spudcan and caisson foundations on soft normally consolidated clay. Géotechnique, 54(2), pp. 91-106. 2004. Caquot, A. and J. Kerisel. Traite de mecanique des sols. Paris: Gauthier-Villars. 1949. 269 Cheong, J. Physical testing of jack-up footings on sand subjected to torsion. Honours Thesis, The University of Western Australia. 2002. Chung, S. F. and M.F. Randolph. Penetration resistance in soft clay for different shaped penetrometers. In Proc. 2nd Int. Conf. on Site Characterization, Porto, Vol. 1, pp. 671-678. 2004. Chiba, S., T. Onuki and K. Sao. 1986. Static and dynamic measurement of bottom fixity. In The jack-up Drilling Platform, ed by L.F. Boswell, pp. 307-327, London: Collins. 1986. Chua, K. and W.H. Craig. Foundation stability of jack-up drilling rigs. Report to Marine Technology Directorate and Shell Expro, Manchester University. 1987. Craig, R.F. Soil Mechanics. London: Chapman & Hall. 1992. Craig, W.H. and K. Chua. Deep penetration of spudcan foundations on sand and clay. Géotechnique, 40(4), pp. 541-556. 1990. Das, B.M. and K.F. Dallo. Bearing capacity of shallow foundation on a strong sand layer. In Civil Engineering for Practicing and Design Engineers, Vol. 3, pp. 417438, New York: Pergamon Press. 1985. Davisson, M.T. Settlement histories of two pile supported grain soils. In Proc. Conf. on Performance of Earth and Earth-Supported Structure, Lafayette, Indiana, ASCE, Vol. 1, pp. 1155-1167. 1972. De Beer, E. The scale effect in the transposition of the results of deep-sounding tests on the ultimate bearing capacity of piles and caisson foundations. Géotechnique, 13(1), pp. 39-75. 1963. De Beer, E. Bearing capacity and settlement pf shallow foundations on sand. In Proc. Symp. on Bearing Capacity and Settlement of Foundations, Dept of Civil Engineering, Duke Univ., Durham, North Carolina, ed by A. Vesic, pp. 15-43. 1967. Dean, E.T.R., R.G. James, A.N. Schofield, F.S.C. Tan, and Y. Tsukamoto. The bearing capacity of conical footings on sand in relation to the behavior of spudcan footings of jackups. In Predictive Soil Mechanics: Proc. Wroth Memorial Symp, ed by G.T. Houlsby and A.N. Schofield, pp. 140-161, London: Thomas Telford. 1993. Dembicki, E. and W. Odrobinski. A contribution to the tests on the bearing capacity of stratified subsoil under the foundation. In Proc. 8th Int. Conf. on Soil Mech. and Found. Eng., Vol. 1.3, pp. 61-64. 1973. Dutt, R.N. and W.B. Ingram. Jack-up rig sitting in calcareous soils. In Proc. 16th Offshore Technology Conf., Paper OTC 4840. 1984. Edwards, D.H., L. Zdravkovic and D.M. Potts. Depth factors for undrained bearing capacity. Géotechnique, 55(10), pp. 755-758. 2005. 270 Erbrich, C. T. Australian frontiers – spudcans on the edge. In Proc. Int. Sym. on Frontier in Offshore Geotechnics, Perth, pp. 49-74. 2005. Eslami, A. and B.H. Fellenius. Pile capacity by direct CPT and CPTu methods applied to 102 case histories. Can. Geotech. J., 34, pp. 886-904. 1997. Finnie, I.M.S. Performance of shallow foundation in calcareous soil. Ph.D Thesis, The University of Western Australia. 1993. Finnie, I.M.S. and M.F. Randolph. Punch-through and liquefaction induced failure of shallow foundations on calcareous sediments. In Proc. Int. Conf. on Behaviour of Offshore Structure, BOSS’94, Boston, pp. 217-230. 1994. Forkiewicz, A. Upper bound to bearing capacity of layered soils. Can. Geotech. J., 26, pp. 730-736. 1989. Fretti, C., L. Presti, C.F. Diego and S. Pedroni. A pluvial deposition method to reconstitute well-graded sand specimens. Geotechnical Testing Journal, 18(2), pp.292-298. 1995. Fryman, S. and H.J. Burd. Numerical studies of the bearing capacity factor, Nγ. Journal of Geotechnical Engineering, ASCE, 123(1), pp. 20-29. 1997. Goh, T.L. Stabilisation of an excavation by an embedded improved soil layer. Ph.D Thesis, National University of Singapore. 2003 Golder, H.Q. The ultimate bearing pressure of rectangular footings. J. Institution for Civil Engineers, Vol. 17, pp. 161-174. 1941. Green, A.P. Plastic yielding of metal junctions due to combined shear and pressure. J. Mech. Phys. Solid. 2(3), pp. 197-211. 1954. Habib, P. Essais de charge portante de pieux en modèle réduit, Ann. Inst. Tech. Bat. Trav. Publ., Paris, Vol. 6, pp. 361. 1953. Hancox, M. Jack-up Moving. Ledbury, England: Oilfield Publications Limited. 1993. Handidjaja, P. Personal communication. 2006. Hanna, A.M. and G.G. Meyerhof. Design chart for ultimate bearing capacity of foundation on sand overlying soft clay. Can. Geotech. J., 17, pp. 300-303. 1980. Hansen, J. B. A revised and extended formula for bearing capacity. Danish Geotechnical Institute Bulletin No. 28. 1970. Heikkilä, J. Geometric Camera Calibration Using Circular Control Points. IEEE Transactions on Pattern Analysis and Machine Intelligence, 22(10), pp. 1066-1077. 2000. 271 Hossain, M. S., Z. Mehryar, Y. Hu, and M.F. Randolph. Deep penetration of spudcan foundation into NC clay. In Proc. Int. Conf. Offshore Mechanics and Artic Engng., Vancouver, OMAE2004-51154. 2004. Hossain, M.S., Y. Hu, M.F. Randolph and D.J. White. Limiting cavity depth for spudcan foundations penetrating clay. Géotechnique, 55(9), pp. 679-690. 2005. Hossain, M.S., M.F. Randolph, Y. Hu and D.J. White. Cavity stability and bearing capacity of spudcan foundations on clay. In Proc. Offshore Technology Conference, Paper OTC 17770. 2006. Houlsby, G.T. and C.P. Wroth. Calculation of stresses on shallow penetrometers and footings. In Proc. IUTAM/IUGG Symp. Seabed Mechanics, Newcastle upon Tyne, pp. 107 – 112. 1983. Houlsby, G.T. and C.M. Martin. Undrained bearing capacity factors for conical footings on clay. Géotechnique, 53(5), pp. 513-520. 2003. Houlsby, G.T. and B.W. Byrne. Design procedures for installation of suction caissons in clay and other materials. Proc. Institution of Civil Engineers, Geotechnical Engineering, 158(2), pp 75-82. 2005a. Houlsby, G.T. and B.W. Byrne. Design procedures for installation of suction caissons in sand. Proc. Institution of Civil Engineers, Geotechnical Engineering, 158(3), pp. 135-144. 2005b. House, A.R., J.R.M.S. Oliveira and M.F. Randolph. Evaluating the coefficient of consolidation using penetration tests. Int. J. of Physical Modelling in Geotechnics, 1(3), pp. 17-25. 2001. Hunt, J.R. Opportunities for improvement, contractual, technical and operational. Presentation slides for OGP/CORE Workshop: The jack-up drilling option – Ingredient for success, Singapore. 2005. Jaky, J. The coefficient of earth pressure at rest. J. Soc. Hungarian Architects and Engrs, 78 (22), pp. 355-358. 1944. Jacobsen, M., K.V. Christensen and C.S. Sorensen. Gennemlokning af tynde sandlag. Vag og Vattenbyggaren 8/9, pp. 23-25. 1977. James, R. G. and H. Tanaka. An investigation of the bearing capacity of footings under eccentric and inclined loading in sand in a geotechnical centrifuge. In Proc. Symp. Recent Advances in Geotechnical Centrifuge Modeling, University of California, Davis, pp. 88-115. 1984. Jamiolkowski, M., C.C. Ladd, J.T. Germaine and R. Lancellotta. New developments in field and laboratory testing of soils. State-of-the art report. In Proc. 11th Int. Conf. on Soil Mechanics and Foundation Engineering, San Francisco, pp. 57-153. 1985. 272 Jamiolkowski M.B., D.C.F. Lo Presti and M. Manassero. Evaluation of relative density and shear strength of sand from cone penetration test (CPT) and flat dilatometer (DMT). In Soil behaviour and soft ground construction, ed by J.T Germaine, T.C. Sheahan and R.V. Whitman, ASCE, GSP 119, pp. 201-238. 2003. Kenny, M.J. and K.Z. Andrawes. The bearing capacity of footings on a sand layer overlying soft clay. Géotechnique, 47(2), pp. 339-345. 1997. Kimura, T., O. Kusakabe, K. Saitoh, N. Fuji and A. Shidai. Anisotropic effect on bearing capacity and settlement. In Proc. 6th Asian Regional Conf. Soil Mechanics and Foundation Engineering, Vol. 1, pp.31-34. 1979. Kimura, T., O. Kusakabe and K. Saitoh. Geotechnical model test of bearing capacity problems in centrifuge. Géotechnique, 35(1), pp. 33-45. 1985. Kulhawy, F.H. Some thoughts on the evaluation of undrained shear strength for design. In Predictive Soil Mechanics: Proc. Wroth Memorial Symp, ed by G.T. Houlsby and A.N. Schofield, pp. 394-403, London: Thomas Telford. 1993. Kusakabe, O., H. Yamaguchi and A. Morikage. Experimental and analysis on the scale effect of Nγ for circular and rectangular footings. Centrifuge 91, pp. 179-186. 1991. Kutter, B.L., A. Abghari and J.A. Cheney. Strength parameters for bearing capacity of sand. J. Geotechnical Engineering, ASCE, 114(4), pp. 491-497. 1988. Kraft, L.M. and S.C. Helfrich. Bearing capacity of shallow footing, sand over clay. Can. Geotech. J., 20, pp. 182-185. 1983. Kellezi, L. and H. Stromann. FEM analysis of jack-up spudcan penetration for multilayered critical soil conditions. In Proc. BGA Int. Conf. on Foundations, ICOF 2003, Dundee, Scotland, pp. 410-420. 2003. Lee, F.H., T.S. Tan, C.F. Leung, K.Y. Yong, G.P. Karunaratue and S.L. Lee. Development of Geotechnical Centrifuge Facility at the National University of Singapore. Centrifuge 91, ed by H-Y. Ko and F.G. McLean, pp. 11-17. Rotterdam: A.A. Balkema. 1991. Hight, D.W. and Leroueil, S. Characteristic of soils for engineering purpose. In Characterisation and Engineering Properties of Natural Soils, ed by T.S. Tan, K.K. Phoon, D.W. Hight and S. Leroueil, pp. 255-360, Balkema. 2003. Lunne, T., P.K. Robertson and J.J.M. Powell. Cone penetration testing in geotechnical practice. London: Blackie Academic & Professional. 1997. Leung, C.F., K.L. Teh, Y.K. Chow, Foo, K.S. and.C.K. Quah. Evaluation of SNAME methods in predicting spudcan punch through. Jack-up Asia Conf., Singapore. 2006. 273 Love, J.P. Model testing of geogrids in unpaved roads. DPhil. Thesis, University of Oxford. 1984. Love, J.P., H.J. Burd, W.E. Milligan and G.T. Houlsby. Analytical and model studies of reinforcement of a layer of granular fill on a soft clay subgrade. Can. Geotech. J., 24, pp. 611-622. 1987. Lu, Q., Y. Hu and M.F. Randolph. Deep penetration in soft clay with strength increasing with depth. In Proc. 11th Int. Conf. on Offshore and Polar Engineering, Stavanger, Norway, pp. 453-458. 2001. Madhav, M.R. and J.S.N. Sharma. Bearing capacity of clay overlain by stiff soil. Journal of Geotechnical Engineering, ASCE, 117(12), pp. 1941-1948. 1991. Magnan. J.P., N. Droniuc and Y. Canepa. The calculation methods for the bearing capacity of shallow foundations. In Int. Sym. Identification and determination of soil and rock parameters for geotechnical design, on shallow foundations and on ground improvement, Vol. 2, pp. 79-154. 2004. Martin, C.M. Physical and numerical modeling of offshore foundation under combined loads. DPhil. Thesis, University of Oxford. 1994. Martin, C.M. User guide for ABC - Analysis of Bearing Capacity. Report No. OUEL 2261/03, Department of Engineering Science, University of Oxford. 2003. McClelland, B., A.G. Young and B.D. Remmes. Avoiding Jack-up Rig Foundation Failures. In Proc. Symp. Geotechnical Aspects of Coastal and Offshore Structures, Bangkok, pp. 137-157. 1981. Meyerhof, G.G. The bearing capacity of sand. PhD Thesis, University of London. 1950. Meyerhof, G.G. The ultimate bearing capacity of foundations. Géotechnique, 2, pp. 301-332. 1951. Meyerhof, G.G. The ultimate bearing capacity of wedge-shaped foundation. In Proc. 5th Int. Conf. Soil Mechanics and Foundation Engineering, Vol. 2, pp. 105-109. 1961. Meyerhof, G.G. Ultimate bearing capacity of footings on sand layer overlying clay. Can. Geotech. J., 11, pp. 223-229. 1974. Meyerhor, G.G. and A.M. Hanna. Ultimate bearing capacity of foundations of layered soils under inclined loads. Can. Geotech. J., 15, pp. 565-572. 1978. Michalowski, R.L. and L. Shi. Bearing capacity of footings over two-layer foundations soils. Journal of Geotechnical Engineering, ASCE, 121(5), pp. 421428. 1995. 274 Michalowski, R.L. and L. Shi. Closure to bearing capacity of footings over twolayered foundation soils. Journal of Geotechnical Engineering, ASCE, 122(8), pp. 701-702. 1996. Myslivec, A. and Z. Kysela. The bearing capacity of foundation. Amsterdam: Elsevier. 1978. Nagtegaal, J.C., D.M. Park and J.R. Rice. On numerically accurate finite element solutions in the fully plastic range. Computer Methods in Applied Mechanics and Engineering, 4, pp. 153-177. 1974. Nater, P., J. Laue and S.M. Springman. Modeling of shallow foundations on homogenous and layered soils. In Proc. 15th Int. Conf. Soil Mechanics and Geotechnical Engineering, Vol. 1, pp. 755-760. 2001. Ng, T.G. Cyclic behaviour of spudcan footing on sand. Ph.D Thesis, National University of Singapore. 1998. Okamura, M., J. Takemura and T. Kimura. Centrifuge model test on bearing capacity and deformation of sand layer overlying clay. Soils and Foundations, 37(1), pp. 7388. 1997. Okamura, M., J. Takemura and T. Kimura. Bearing capacity predictions of sand layer overlying clay based on limit equilibrium methods. Soils and Foundations, 38(1), pp. 181-194. 1998. O’Loughlin, C. and B.M. Lehane. Measure and prediction of deformation patterns beneath strip footings in sand. Research report No. C:1751, Department of Civil and Resource Engineering, University of Western Australia. 2003. O'Loughlin C., B.M. Lehane and D.J. White. Optical measurement of soil movements beneath shallow foundations on sand. In Proc. 13th European Conf. on Soil Mechanics and Geotechnical Engineering, Prague, Vol. 2, pp. 767-772. 2003 Osbourne, J.J. Are we good or are we lucky? Managing the mudline risk. Presentation slides for OGP/CORE Workshop: The jack-up drilling option – Ingredient for success, Singapore. 2005. Osbourne, J.J. and J.M. Paisley. SE Asia jack-up punch-throughs: The way forward? In Proc. Int. Conf. Offshore Site Investigation and Geotechnics, London, pp. 301306. 2002. Ovesen, N.K. Centrifuge testing applied to bearing capacity problems of footings on sand. Géotechnique, 25(2), pp. 394-401. 1975. Ovesen, N.K. Panel discussion in Session - The use of physical models in design. In Proc. 7th Int. Conf. on Soil Mechanics and Foundation Engineering, Vol. 4, pp. 318-323. 1979. 275 Perkins, S.W. Bearing capacity of highly frictional material. Geotech. Testing J., 18(4), pp. 450-462. 1995. Perkins, S.W. and C. Madson. Bearing capacity of shallow foundations on sand: A relative density approach. Journal of Geotechnical and Geoenvironmental Engineering, 126(6), pp. 521-530. 2000. Potts, D.M. and L. Zdravkovic. Finite element analysis in Geotechnical Engineering: Application. London: Thomas Telford. 2001. Pu, J.M.L. and H.Y. Ko. Experimental determination of bearing capacity in sand by centrifuge footing tests. Centrifuge 88, pp. 293-299. 1988. Purwana, O.A. Centrifuge model study on spudcan extraction in soft clay. Ph.D Thesis, National University of Singapore. 2007 Randolph, M.F. and G.T. Houlsby. The limiting pressure on a circular pile loaded laterally in cohesive soil. Géotechnique, 34(4), pp. 613-623. 1984. Randolph, M. F, R. J. Jewell, K. J. L. Stone and T.A. Brown. Establishing a new centrifuge facility. Centrifuge 91, pp. 3-9. 1991. Randolph, M.F. RATZ manual version 4-2 for load transfer analysis of axially loaded piles. 2003. Randolph, M.F. and S. Hope. Effect of cone velocity on cone resistance and excess pore pressure. In Proc. Int. Symp. on Engineering Practice and Performance of Soft Deposits, Osaka. 2004. Randolph, M.F., M.B. Jamiolkowski and L. Zdravkovi. Load carrying capacity of foundations. In Proc. Skempton Memorial Conf., London, Vol. 1, pp. 207-240. 2004. Randolph, M.F., M.J. Cassidy, S. Gourvenec and C. Erbrich. The Challenges of Offshore Geotechnical Engineering. Invited State of the Art Report, 16th Int. Conf. on Soil Mechanics and Geotechnical Engineering, Osaka, Japan, pp. 123-176. 2005. Rankine, W.M.J. On the stability of loose earth. Phil. Trans. Roy. Soc., London, 147(2), pp. 9-27. 1857. Renzi, R., J. F. Corte, G. Rault, G. Bagge, M. Gui and J. Laue. Cone penetration tests in the centrifuge: Experience of five laboratories. Centrifuge 94, pp. 77-82. 1994. Shiraishi, S. Variation in bearing capacity factors of dense sand assessed by model loading tests. Soils and Foundations, 30(1), pp. 17-26. 1990. Shiau, J.S., A.V. Lyamin and S.W. Sloan. Bearing capacity of a sand layer on clay by finite element limit analysis. Can. Geotech. J., 40, pp. 900-915. 2003. 276 Skempton, A.W., A.S. Yassin and R.E. Gibson. Théorie de la force portante des pieux. Annales de l’Institut Technique du Bâtiment et des Traveaux Publics, 6, pp. 285-290. 1953. Sloan, S.W. and M.F. Randolph. Numerical prediction of collapse loads using finite element methods. Int. J. Numerical and Analytical Methods in Geomechanics, 6, pp. 47-76. 1982. SNAME. Guidelines for site specific assessment of mobile jackup units. Society of Naval Architects and Marine Engineers, Technical and Research Bulletin 5-5A, New Jersey. 2002a. SNAME. Commentaries to guidelines for site specific assessment of mobile jackup units. Society of Naval Architects and Marine Engineers, Technical and Research Bulletin 5-5A, New Jersey. 2002b. Sweeney, M.S., R.M. Webb and R.H. Wilkinson. Scour around jackup rig footings. In Proc. Offshore Technology Conference, Paper OTC 5764, pp. 171-180. 1988. Steward, D.P. Lateral loading of piled bridge abutments due to embankment construction. Ph.D Thesis, The University of Western Australia. 1992. Stewart, D. P., R. S. Boyle and M.F. Randolph. Experience with a new drum centrifuge. Centrifuge ’98, Tokyo, Japan, Vol. 1, pp. 35-40. 1998. Tan, F.S.C. Theoretical and centrifuge modelling of conical footings on sand. Ph.D Thesis, University of Cambridge. 1990. Tani, K. and W.H. Craig. Development of centrifuge cone penetration test to evaluate the undrained shear strength profile of a model clay bed. Soils and Foundations, 35(2), pp. 37-47. 1995. Tatsuoka, F., S. Zhou, T. Sato and S. Shibuya. Evaluation method of liquefaction potential and its application. Report on seismic hazards on the ground in urban areas, Ministry of Education of Japan, Tokyo. 1990. Tatsuoka, F., M. Okahara, T. Tanaka, T. Tani, T. Morimoto and M.S.A. Siddeque. Progressive failure and particle size effect in bearing capacity of footing on sand. ASCE Geotech. Special Publication, No. 27, pp. 788-802. 1991. Taylor, R.N., R.J. Grant, S. Robson and J. Kuwano. An image analysis system for determining plane and 3-D displacements in soil models. Proc. Centrifuge’98, pp. 73-78. 1998. Tcheng, Y. Foundation superficielles en milieu stratifié. In Proc. 4th Int. Conf. on Soil Mechanics and Foundation Engineering, London. Vol. 1, pp. 449-452. 1957. Thanadol, K. Behaviour of embedded improved soil berm in an excavation. Ph.D Thesis, National University of Singapore. 2003. 277 Teh, K.L, C.F. Leung and Y.K. Chow. Performance of miniature CPTU in sand overlying NC clay through centrifuge modeling. In Proc. Int. Conf. on Physical Modelling in Geotechnics, Hong Kong, pp. 299-304. 2006a. Teh, K.L., B.W. Byrne and G.T. Houlsby. Effects of seabed irregularities on loads developed in legs of jack-up unit. Jack-up Asia Conf., Singapore. 2006b. Teh, K.L, C.F. Leung, Y.K. Chow, P. Handidjaja and C. Nelson. Analysis of spudcan installation through loose sand into clay. Jack-up Asia Conf., Singapore. 2006c. Teh, K.L., C.F. Leung and Y.K. Chow. Some considerations for predicting spudcan penetration resistance in two-layered soil using miniature penetrometer. In Proc. 6th Int. Offshore Site Investigation and Geotechnics Conf.:Confronting New Challenge and Sharing Knowledge, London, pp. 47-52. 2007. Terzaghi, K. Theoretical Soil Mechanics. New York:Wiley. 1943. Tomlinson, M.J. Foundation design and construction. London: Longman. 1986. Tsukamoto Y. Drum centrifuge tests of three-leg jack-ups on sand. Ph.D Thesis, University of Cambridge. 1994. Ueno, K., K. Muira and Y. Maeda. Prediction of ultimate bearing capacity of surface footings with regards to size effect. Soils and Foundations, 38(3), pp. 165-178. 1998. Ueno, K., K. Muira, O. Kusakebe and M. Nishimura. Reappraisal of size effect of bearing capacity from plastic solution. Journal of Geotechnical and Geoenvironmental Engineering, 127(3), pp. 275-281. 2001. Valsangkar, A.J. and G.G. Meyerhof. Experimental study of punching coefficient and shape factor for two-layered soils. Can. Geotech. J., 16, pp. 802-805. 1979. Vesic, A.S. Bearing capacity of shallow foundations. In Foundation Engineering Handbook, ed by Winterkorn and Fang. New York: Van Nostrand Reinhold. 1975. Wang, M.C. Discussion for bearing capacity of footings over two-layered foundation soils. Journal of Geotechnical Engineering, ASCE, 122(8), pp. 700-701. 1996. White D.J. An investigation into the behaviour of pressed-in piles. Ph.D Thesis, University of Cambridge. 2002. White D.J. Foundation Engineering. Lecture Note: Module 4D5, University of Cambridge. 2005. White, D.J. and W.A. Take. GeoPIV: Particle Image Velocimetry (PIV) software for use in geotechnical testing. Cambridge University Engineering Department, Technical Report D-SOILS-TR322. 2002. 278 White, D.J., W.A. Take and M.D. Bolton. Soil deformation measurement using particle image velocity (PIV) and photogrammetry. Géotechnique, 53(7), pp. 619631. 2003. White, D. J. and M.D. Bolton. Comparing CPT and pile base resistance in sand. Proc. Institution of Civil Engineers, Geotechnical Engineering, 158(1), pp. 3-14. 2005. White D.J., M.F. Randolph and B. Thompson. An image-based deformation measurement system for the geotechnical centrifuge. Int. J. Physical Modelling in Geotechnics, 5(3), pp. 1-12. 2005. White, D.J., K.L. Teh, C.F. Leung and Y.K. Chow. A comparison of the beraing capacity pf flat and conical circular foundations on sand. Provisionally accepted by Géotechnique. 2007. Whitlow, R. Basic soil mechanics. England: Prentice Hall. 2001. Wood, D.M. Soil behaviour and critical state soil mechanics. New York: Cambridge University Press. 1990. Yamaguchi, H. Practical formula of bearing value for two layered ground. Proc. 2nd Asian Reg. Conf. Soil Mechanics and Foundation Engineering, Tokyo, Vol. 1, pp. 176-180. 1963. Young, A.G. and J.A. Focht. Sub-surface hazards affect mobile jack-up rig operations. Soundings, McClelland Engineers, Houston. 1981. Young, A.G., B.D. Remmes and B.J. Meyer. Foundation Performance of Offshore Jack-up Drilling Rigs. Journal of Geotechnical Engineering, ASCE, 110(7), pp. 841-859. 1984. Zhu, F., J.I. Clark and R.Phillips. Scale effect of strip and circular footings resting on dense sand. Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 127(7), pp. 613-621. 2001. 279 [...]... estimation of spudcan bearing capacity in sand, (ii) investigate spudcan bearing response in sand overlying NC clay, (iii) establish the failure mechanisms of spudcan foundation in sand overlying NC clay, and (iv) devise a design framework to estimate spudcan bearing capacity profile in sand overlying NC clay Some parts of the present study were conducted in collaboration with the Centre for Offshore Foundation. .. q foundation bearing resistance/ capacity q0 spudcan bearing capacity in sand overlying clay at d = 0 qc measured cone tip resistance qcalculated theoretical calculated foundation bearing capacity qclay surface clay bearing capacity qmax maximum spudcan bearing capacity in sand overlying clay qmeasured experimental measured foundation bearing capacity qnom nominal bearing pressure qsand sand bearing... 2.30 Analysis of spudcan bearing capacity in sand overlying clay using projected area method (after SNAME, 2002b) Figure 2.31 Analysis of spudcan bearing capacity in sand overlying clay using punching shear method (after SNAME, 2002a) Figure 2.32 Spudcan bearing resistance profiles in saturated sand overlying clay (after Craig and Chua, 1990) Figure 3.1 Drum centrifuge at The University of Western Australia... complete spudcan bearing capacity profile taking into consideration the characteristics of the spudcan foundation would be of practical interest 8 Chapter 1 – Introduction * It is worth highlighting that a good understanding of spudcan bearing capacity in sand and clay respectively forms the backbone in investigating the bearing capacity in a layered soil system The research on spudcan in clay seems... installation of jack-up rig is carried out during calm weather where the environmental load is minimal and this allows the process to be accomplished within a period of 1 to 3 days depending on the seabed profile 1.2 Foundation hazards of spudcan in sand overlying clay The performance of spudcan in homogeneous soil can often be predicted with a certain degree of accuracy (Hancox, 1993) For instance, spudcan. .. stability of the spudcan may be threatened by the seabed scouring phenomenon Spudcan installation in sand overlying clay site is geotechnically challenging Depending on the thickness of the overlying sand layer, the spudcan performance could turn out to be unstable though its final penetration lies between the two distinct conditions The foundation stability could be threatened by the possibility of punchthrough... List of Figures Figure 1.1 Worldwide utilization rate of offshore rigs Figure 1.2 Nomenclature of jack-up rig Figure 1.3 Examples of spudcan configuration Figure 1.4 Distribution of seabed with sand overlying clay formation Figure 1.5 Footing bearing capacity profile in strong overlying soft stratum (after Young et al., 1984) Figure 1.6 Spudcan penetrations under self weight and total preload in sand overlying. .. safe and economic use of mobile jack-up structures is still hindered by the limited understanding on the installation of the large conical spudcan footings in the seabed The stability of spudcan foundation is predominantly governed by the soil condition of the site Particularly, a site consisting of sand overlying clay is known to cause probable foundation hazards to the spudcan foundation and hence... penetrometer shaft diameter D′ effective diameter of circular /spudcan footing in contact with seabed H thickness of upper sand layer Heff thickness between the footing base and the sand- clay interface H*/D limiting H/D where qu = qsand L length of rectangular footing R radius of underlying clay surface area subjected to combined loading V′spud volume of spudcan embedded in soil ab ball net area ratio xix ac piezocone... possibility of punchthrough during installation and scour-induced punch- through In fact, such layered soil formation is commonly found in the regions of active jack-up rig operation as shown in Figure 1.4 (modified from Osborne, 2005; Handidjaja, pers comm.) 1.2.1 Punch- through during installation Spudcan penetration in sand overlying clay may potentially trigger a bearing capacity problem when the . 7.2.1 Spudcan bearing capacity in sand 260 vii 7.2.2 Spudcan bearing response in sand overlying NC clay 261 7.2.3 Failure mechanism of spudcan foundation in sand overlying NC clay 262 . 2.3 Bearing failure mechanism in sand overlying clay 45 2.4 Spudcan bearing capacity in sand overlying clay 48 2.5 Concluding remarks 51 Chapter 3: Spudcan Bearing Capacity in Sand . Analysis of spudcan bearing capacity in sand overlying clay using punching shear method (after SNAME, 2002a) Figure 2.32 Spudcan bearing resistance profiles in saturated sand overlying clay