OTRC Project Summary
|A Computational Procedure for Simulation of Suction Caisson Behavior Under Axial and Inclined Loads
|Minerals Management Service and Industry Consortium
Final Report ID#
|B130(Click to view final report abstract)
Note: Note this study is part of a broader project "Suction Caissons: Finite Element Modeling" (MMS Project 362).
The present work is an extension of the research reported by Vasquez (2000)
and part of a comprehensive research project undertaken at the Offshore Technology
Research Center (OTRC) at The University of Texas at Austin. The
overall project aims at improving current understanding and developing effective
procedures for the design of deep-water anchors (Olson et al., 2001). The
research project focuses on several different topics: laboratory tests on model caissons subjected to axial pullout and inclined loads (El-Gharbawy, 1998;
Luke, 2002; and Coffman, 2003), development of a simplified prediction tool
based on plastic limit analysis (Aubeny et al., 2003a), development of a highly
detailed finite-element computational procedure (Vasquez, 2000; and Maniar
et al., 2003), and reliability-based optimization of geotechnical investigations
(Gambino and Gilbert, 1999; and Gilbert et al., 1999).
Vasquez (2000) presented the development of a finite-element procedure
to simulate the response of suction caissons subjected to axial pullout
under both drained (long-term) and undrained (short-term) conditions. The
procedure was applied to study the laboratory tests reported by El-Gharbawy
(1998). Simulation results obtained for caisson installation process as well as
response of caisson under axial pullout were reported.
The objectives of the present research study are: (1) to develop a computational
framework to simulate behavior of suction caissons and to estimate
their capacities under axial as well as inclined loads, including effects of both
self-weight and suction installation and (2) to simulate laboratory tests, conducted
on model suction caissons at The University of Texas at Austin (Luke,
2002; and Coffman, 2003), in order to calibrate as well as validate the computational
The computational procedure developed in the course of this study simulates
suction caisson installation and estimates the capacities under axial as
well as inclined loads. Suction caisson installation and axial pullout are analyzed
under the assumption of axial symmetry. The soil is modeled with
water-saturated porous finite-elements and the caisson is discretized using (impermeable)
solid finite-elements. The nonlinear behavior of the clayey soil is
modeled through a bounding-surface plasticity model for isotropic cohesive soils, and linear elastic behavior of caisson is assumed. The soil-caisson interfaces
are modeled with a contact algorithm based on a slide-line formulation.
Various remeshing tools are developed to eliminate the need for a priori
specification of the caisson penetration path and to avoid use of excessively
distorted finite elements along caisson-soil interfaces. The remeshing tool is
an improvement over the procedure document by V´asquez (2000) in which the
penetration path defined a priori as located immediately below the caisson tip
and in the axial direction. This predefinition of the path did not account for
the soil movement during caisson installation process. Due to the restriction
on the soil movement, the selected path over (under) estimated amount of soil
within the caisson interior during self-weight (suction) installation. Due to
this the computed capacity might have been affected as it is function of radial
stresses generated within the soil domain during installation process.
The developed formulation is used to obtain results from the simulation
of the caisson installation, and reconsolidation (or setup) of surrounding
soil following caisson installation, and caisson pullout. Three-dimensional
caisson models under horizontal and inclined loads are analyzed using the
ABAQUS/Standard program. The deformed geometry of the caisson-soil system,
stresses within the soil and material state parameters obtained from
axisymmetric simulation of the installation process are specified as initial conditions
to carry out analysis of caisson under horizontal and inclined loads.
In addition, a user-defined material subroutine for the bounding-surface plasticity
model is supplied to the ABAQUS program to model behavior of the
saturated clayey soil. The computed behavior of the caisson is compared with
the observed behavior in the laboratory tests conducted at The University of
Texas at Austin (Luke, 2002; and Coffman, 2003).
Related Publications: Maniar, D.R. and Tassoulas, J.L., “Nonlinear Finite Element Simulation of Suction Caisson Behavior,” CD-ROM Proceedings of EM2002, the Fifteenth Engineering Mechanics Conference, New York, New York, June 2-5, 2002.
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.
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.