Offshore Technology Research Center

 

OTRC Project Summary

Project Title:

Suction Caissons: Finite Element Modeling

Prinicipal Investigators:

John Tassoulas

Sponsor:

Minerals Management Service and Industry Consortium

Completion Date:

December, 2005

Final Report ID#

B160(Click to view final report abstract)

OBJECTIVE:

Develop a finite element computational procedure for the analysis of suction caissons in clayey soils. The procedure will be will be capable of analyzing both the installed performance and installation of suction caissons. Data from laboratory experiments and any available field data will be used to validate the model. The model can then be used to simulate laboratory or field situations for which no data are available. Such simulated data can be useful in designing further laboratory or field experiments and can provide data that is useful in validating simpler analysis models that can be more practically applied in design.

APPROACH:

A finite-element procedure that describes a suction caisson interacting with soil has been developed The procedure can simulate the entire process followed in laboratory tests including initial soil consolidation, penetration by caisson’s self-weight and further penetration by suction, reconsolidation of the disturbed soil and subsequent application of tensile axial and lateral loads. A formulation of the soil as a two-phase, water-filled, porous medium provides the mechanical framework of the procedure. Elastoplastic behavior of the soil skeleton is described by constitutive equations based on a bounding-surface plasticity theory, pore-water flow obeys Darcy’s law and frictional contact is accounted for at soil-caisson interfaces. Using the procedure, simulations of laboratory tests (OTRC Projects supervised by R.E. Olson and A.F. Rauch) on small-scale suction-caisson models in normally-consolidated and overconsolidated clays have already been conducted with very favorable results.

The validity of the procedure will be further examined by comparing simulations with other available data (laboratory and centrifuge tests and field data). The computer procedure will be simplified (to the extent possible) and documented in order to facilitate the use of the procedure in future research and as a practical tool.

DEPLOYMENT OF RESULTS:

Information resulting from this project will be disseminated by means of presentations at technical conferences, OTRC Reports and refereed journal articles.

PROJECT PLAN:

Scope of Work: The finite-element procedure will be further validated through comparisons of simulations with:
• data from continuing laboratory tests on model suction-caissons (OTRC Project under the supervision of R.E. Olson and R.B. Gilbert)
• existing data from centrifuge tests on model suction caissons
• any field data or observations from full-scale suction caissons that are available in the literature

In addition, the computer procedure will be documented. The preparation of necessary input files will be simplified, described in detail, and automated (to the extent possible) in order to facilitate the use of the procedure in future research and as a practical tool.

Anticipated Results: A final report will document the for conducting finite-element analyses of suction caissons in clayey soils under monotonic axial and lateral loads, and the comparisons of simulation results with experimental and field data.

Related Publications: L. F. G. Vasquez Chicata, “Computational Procedure for the Estimation of Pile Capacity Including Simulation of the Installation Process,” Ph.D. Dissertation, The University of Texas at Austin, December 2000.

Olson, R. E., Rauch, A. F., Gilbert, R. B., Tassoulas, J. L., Aubeny, C. P., and Murff, J. D., “Toward the Design of New Technologies for Deep-Water Anchorages,” Proceedings, Conference of the International Society of Offshore and Polar Engineers, Stavanger, Norway, June 17-22, 2001.

Maniar, D., and Tassoulas, J.L., “Nonlinear Finite Element Simulation of Suction Caissons,” Proceedings, EM2002, Fifteenth Engineering Mechanics Conference, American Society of Civil Engineers, Columbia University, New York, June 2-5, 2002.

Vásquez, L. F. G., Maniar, D. R., and Tassoulas, J. L., “Finite Element Analysis of Suction Piles in Saturated Clayey Soils,” Proceedings, SIAM Conference on Mathematical and Computational Issues in the Geosciences(GS03), Austin, Texas, March 17-20, 2003.

Rauch, A.F., Olson, R.E., Luke, A.M., Maniar, D.R., Tassoulas, J.L., and Mecham, E.C., “Soil Reconsolidation Following the Installation of Suction Caissons,” Proceedings, Offshore Technology Conference, OTC 2003, Houston, Texas, May 5-8, 2003

Maniar, D., Vásquez Chicata, L. F. G., and Tassoulas, J.L., “Installation and Pull-Out of Suction Caissons: Finite-Element Simulation,” Proceedings, OMAE ‘03, 22nd International Conference on Offshore Mechanics and Arctic Engineering, Cancun, Mexico, June 8-13, 2003.

Maniar, D. and Tassoulas, J.L., “Simulation of Suction Caisson Behavior During and After Installation in Normally Consolidated Soil,” CD-ROM Proceedings of EM2003, Sixteenth Engineering Mechanics Conference, American Society of Civil Engineers, Seattle, Washington, July 16 – 18, 2003.

Maniar, D.R., “A Computational Procedure for Simulation of Suction Caisson Behavior under Axial and Inclined Loads,” Ph.D. Dissertation, Department of Civil Engineering, The University of Texas at Austin, August 2004.

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