Pile Length Optimization in Fixed Template Offshore Platform Using Risk Reduction Approach

Document Type : Original Research Article


1 Ph.D. student of university of Qom

2 Assistant professor, University of Qom

3 3Assistant Professor, University of Qom


The purpose of risk management is managing the uncertainties by considering activities for identifying, assessing, monitoring, and reducing the impact of risks. Three strategies may be used to deal with the kind of risks that exist in projects: risk acceptance, risk transfer, and risk reduction. Events that can affect the economical goals of a project must be identified and evaluated so that they can be appropriately managed. Fixed jacket-type offshore platform (JTOP) as an expensive and necessary structure in energy facilities. in this research, the effect of knowledge increasing on the risk reduction and cost optimization for  JTOP is studying. This paper focuses on optimizing the pile length of the fixed jacket-type offshore platforms and reducing the conservative design by using the risk reduction approach. Fixed offshore platform in South Pars Gas Fields of Iran as a case study.Increasing the Geotechnical knowledge and reducing the pile lengths is performed as considering similar geotechnical study at this regions and pile dynamic driving test (PDA), updating the pile bearing capacity base on increased knowledge for geotechnical data, and finally assessing the result based on inplace analyzing Pile driving result shows increasing the longterm soil bearing capacity, So first of all the required strength and parameters extracted from the existing data with analyzing and comparing where to adjust and matches with the lower limit of the theoretical equations. Finally, this new assumption is used for optimizing the pile length design.  This research shows that that the numerical analysis and assumptions that have been used in the design procedure are conservative and a proper risk management program with the knowledge increasing could have resulted in risk reduction. The analysis process that has been used in the present research leads to the pile cost reduction by 11% that is considerable for stakeholders in such an expensive structure. The most important innovation in this paper is the use of the results of pile driving operation for optimal pile design because, in pile driving operation, piles with design diameter are used.


[1]Chen, J.Y., Matarak, B.A., carpenter, J.F., and Gilbert, R.B., (2009), Analysis of Potential Conservatism in Foundation Design for Offshore Platform Assessment, Final Project Report Prepared for the Minerals Management Service.
[2]Tang, W.H., and Gilbert, R.B., (1992), Offshore Pile System Reliability, Final Report to American Petroleum Institute (Project PRAC 89-29).
[3]Murff, J. D., and Hamilton, J. M., (1993), PUltimate for Undrained Analysis for Laterally Loaded Piles, Journal of Geotechnical Engineering, ASCE, Vol. 119, No. 1, pp. 91-107.
[4]Murff, J.D., Lacasse, S., and Young, A.G., (1993), Discussion and summary on foundation elements, system and analysis, Proceedings of an International Workshop Assessment and Requalification of Offshore Production Structures, New Orleans, Louisiana, pp. 151-165.
[5]Pelletier, J. H., Murff, J. D., and Young, A. C., (1993), Historical Development and Assessment of the Current API Design Methods for Axially Loaded Piles, Offshore Technology Conference, Houston, Texas, OTC 7157.
[6]Aggarwal, R.K., Litton, R.W., Cornell, C.A., Tang, W.H., Chen, J.H. and Murff, J.D., (1996), Development of pile foundation bias factors using observed behavior of platforms during Hurricane Andrew, Offshore Technology Conference, Houston,Texas, OTC 8078, pp. 445-455.
[7]Bea, R.G., Jin, Z., Valle, C. and Ramos, R., (1999), Evaluation of reliability of platform pile foundations, Journal of Geotechnical and Geoenvironmental Engineering, ASCE, Vol. 125, No. 8, pp. 695-704.
[8]American Petroleum Institute, (2000) Recommended practice for planning, designing and constructing fixed offshore platforms, 21st ed., Washington, D.C.
[9]SACS Suite program, (2011), version 5.3.
[10] Werner, S. D., Dickenson, S. E., and Taylor, C. E., (1997), Seismic Risk Reduction at Ports: Case Study and Acceptable Risk Evaluation, Journal of Waterway, Port, and Coastal Engineering, American Society of Civil Engineers, Vol. 123, November-December, pp. 337-346.
[11] PDI, (2010), GRLWEAP Manual for Windows, 30725 Aurora Road, Cleveland, OH 44139 USA: PDI.
[12] CAPWAP Signal Matching, Art of Foundation Engineering Practice (GSP 198), p. 534–553.
[13] Randolph, M.F., and Gourvenec, S., (2011), Offshore Geotechnical engineering, Spon Press, London.
[14] Stevens, R., Wiltsie, E. & Turton, and T., (1982), Evaluating Drivability for Hard Clay, Very Dense Sand, and Rock, Offshore Technology Conference.
[15] Colliat, J., Vergobbi, P. and Puech, A., (1993), Friction Degradation And Set-Up Effects In Hard Clays Offshore Congo And Angola, Offshore Technology Conference.
[16] Skov, R., Denver, H., (1988), Time-dependence of bearing capacity of piles, The 3rd International Conference on Application of Stress-wave Theory to Piles, Ottawa, Canada, pp. 879–888.
[17] Svinkin, M.R., and Skov, R., (2000), Set-up effect of cohesive soils in pile capacity, The 6th International Conference on Application of Stress-wave Theory to Piles, Sao Paulo, Brazil, pp. 107–111. [18] Svinkin, M.R., (1996), Setup and relaxation in glacial sand-discussion, Journal of Geotechnical and Geo-environmental Engineering – ASCE, 122 (4), pp. 319-321