Progress Reports: June 2005 December 2004 June 2004 December 2003 June 2003 December 2002 June 2002 December 2001Suction Caissons and Vertically Loaded Anchors
Finite Element ModelingOBJECTIVE: 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 DURATION: 6 years
PROJECT PLAN FOR YEAR 6 (2004-2005):
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 literatureIn 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
PRINCIPAL INVESTIGATOR (S) & OTHERS INVOLVED IN PROJECT:
PI(s): John L. Tassoulas.
Others: Graduate Student.
Date: June 2005
Project Title: Suction Caissons: Finite Element Modeling
MMS Project: 362 TO Numbers: 16169/35980
PI: John L. Tassoulas
COTR: A. Konczvald
Estimated Completion Date: September 30, 2005
Project Description: This project is aimed at using and documenting a computational procedure developed recently for the analysis of suction caissons in clayey soils under monotonic axial (tensile) and lateral loads considering the effects of installation.
Progress: A finite-element procedure is currently being applied to simulations of tests conducted at the C-CORE Centrifuge Facility (Memorial University of Newfoundland, Canada) on suction-caisson models (Cao 2003). Developed in the course of recent OTRC-supported research (under the supervision of J.L. Tassoulas), the computational procedure simulates the entire process followed in 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 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. Ppore-water flow obeys Darcy’s law and frictional contact is accounted for at soil-caisson interfaces. Calibration and verification of the procedure have already been carried out successfully (Vásquez 2000, Maniar 2004) on the basis of simulations of laboratory 1-g tests (OTRC Projects supervised by R.E. Olson and A.F. Rauch) on small-scale suction-caisson models in normally-consolidated clay and earlier 1-g tests (OTRC Projects supervised by R.E. Olson) in overconsolidated clay. In parallel with the centrifuge test simulations, the computer program in which the procedure has been implemented is undergoing documentation while a straightforward user interface is being prepared for input preparation.
Reports & Publications:
Maniar, D.R., and Tassoulas, J.L. (2005). “Simulations of Suction Caisson Behavior under Axial and Inclined Loads.” Research Report, Offshore Technology Research Center, in preparation.Vásquez, L.F.G., and Tassoulas, J.L. (2005). “Axial Capacity of Suction Caissons in Overconsolidated Clay: Computational Modeling.” Research Report, Offshore Technology Research Center, in preparation.
Date: December, 2004
Project Title: Suction Caissons: Finite Element Modeling
MMS Project: 362 TO Numbers: 16169/35980
PI: John L. Tassoulas
COTR: A. KonczvaldEstimated Completion Date: September 30, 2005
Project Description: This Project is focused on the development of a computational procedure based on the finite element method for the analysis of suction caissons in clayey soils under monotonic axial (tensile) and lateral loads considering the effects of installation.
Progress: We have completed the formulation, implementation and evaluation of a technique for numerical simulation of installation and pull-out of suction caissons subjected to axial and lateral loads. The technique consists of (1) axisymmetric finite-element computations for installation and axial pull-out, and (2) a hybrid approach that transfers the state of the soil-caisson system at completion of installation (carried out by our axisymmetric finite-element computations that incorporates special computational features for handling the installation process) to a three-dimensional finite-element model based on (the general-purpose computer program) ABAQUS for further analysis of caisson behavior under lateral loads. Results from tests of model caissons installed by self-weight and suction in normally consolidated soils, conducted in a complementary OTRC project under the supervision of A.F. Rauch and R.E. Olson, compare very well with our computational estimates (Maniar 2004). Currently, we are applying our technique to simulations of centrifuge and other available tests on suction caissons. Also, we are documenting our software for axisymmetric finite-element analysis of installation and axial pull-out and preparing a guide for preparation of ABAQUS input files for three-dimensional computations.
Reports & Publications:
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.R., 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.R. 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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Date: June 2004Project Name: Suction Caissons: Finite Element Modeling
Project Number: 362 Task Order: 16169
Principal Investigators: John L. Tassoulas
Estimated Completion Date: September 2005
Project Description:
This project is focused on the development of a computational procedure based on the finite element method for the analysis of suction caissons in clayey soils under monotonic axial (tensile) and lateral loads considering the effects of installation.
Progress:
An evaluation of a hybrid approach of transferring the estimated state of the clay in the soil tank to the three dimensional FEA model of the suction caisson in the soil has been completed. The state of the clay is estimated by an axisymmetric finite element analysis procedure that incorporates special computational features for handling the installation process. The three-dimensional finite-element model being used to analyze the response of suction caissons to lateral loads is based on the general-purpose computer program ABAQUS. Results from tests of model caissons installed by self-weight and suction in normally consolidated soils, conducted in a complementary OTRC project under the supervision of A.F. Rauch and R.E. Olson, compare very well with our computational estimates. Furthermore, analyses have shown that the soil-tank interface (during preparation of the test bed by kaolinite slurry consolidation) affects the initial (prior-to-caisson-installation) state of stress in the clay significantly, thereby influencing the measured caisson capacities under both axial and lateral loads. Friction between the tank wall and the soil has been taken into account in the most recent calibration of the computations, and this adjustment has brought numerical results and experimental data to very good agreement.
Reports & Publications:
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
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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., “Finite-Element Modeling of Suction Piles,” Ph.D. Dissertation, Department of Civil Engineering, The University of Texas at Austin, in preparation.
Date: December 2003
Project Name: Suction Caissons: Finite Element Modeling
TEES Project Number: 32558-58877 MMS Task Order: 16169 MMS Project Number: 362
Principal Investigators: John L. Tassoulas
Estimated Completion Date: September 30, 2004
Project Description:
This Project is focused on the development of a computational procedure based on the finite element method for the analysis of suction caissons in clayey soils under monotonic axial (tensile) and lateral loads considering the effects of installation.
Progress:
We have extended and applied our computational procedure to the analysis of suction caissons subjected to combined axial and lateral loads. This was accomplished by transferring the state of the clay, as estimated by our axisymmetric finite element analysis computer program (with special features for handling the installation process) to a three-dimensional finite-element model within the framework of the general-purpose computer program ABAQUS. We have continued to use the bounding-surface soil plasticity model as a user-supplied routine in ABAQUS. This hybrid approach is promising. Comparisons with results from tests of model caissons installed by self-weight in normally consolidated soil, conducted at OTRC under the supervision of A.F. Rauch and R.E. Olson, have shown very good agreement. Currently, we are examining our procedure in comparison with results from lateral-load tests of caissons for which suction was used during the installation process.
Reports & Publications:
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.
Date: June, 2003
Project Name: Suction Caissons: Finite Element Modeling
Project Number: 32558-58877 Task Order: 16169
Principal Investigators: John L. Tassoulas
Estimated Completion Date: September 30, 2004
Project Description:
This Project is focused on the development of a computational procedure based on the finite element method for the analysis of suction caissons in clayey soils under monotonic axial (tensile) and lateral loads considering the effects of installation.
Progress:
We have continued the comparison and calibration of our procedure with data from tests of model caissons in normally consolidated soil carried out at OTRC under the supervision of A.F. Rauch and R.E. Olson. Our computations of the axial pullout capacity of model caissons are within about 15% of the measured values. Furthermore, the computed and measured values of the pore-water pressure at the end of the installation process are in reasonably good agreement. The time required for reconsolidation of the clay disturbed during caisson penetration according to our simulations is about the same as in the laboratory tests. Also, we have made progress in our work on a three-dimensional finite element analysis capability (for caissons subjected to combinations of axial and lateral loads). We are completing the development of a procedure by which the state of the clay, as estimated by our axisymmetric finite element analysis computer program with special features for handling the installation process, will be transferred to a three-dimensional finite element model built within the framework of the general-purpose computer program ABAQUS for computations of caisson response to combined axial and lateral loads. The bounding-surface soil plasticity model used in our calculations to date will be employed as a user-supplied routine in ABAQUS.
Reports & Publications:
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.
Date: December 2, 2002
Project Name: Suction Caissons: Finite Element Modeling
Project Number: 32558-58877 Task Order: 16169
Principal Investigators: John L. Tassoulas
Estimated Completion Date: September 30, 2004
Project Description:
This Project is focused on the development of a computational procedure based on the finite element method for the analysis of suction caissons in clayey soils under monotonic axial (tensile) and lateral loads considering the effects of installation.
Progress:
We have initiated the comparison and calibration of our procedure with data from tests of model caissons in normally consolidated soil carried out at OTRC under the supervision of A.F. Rauch and R.E. Olson. Currently, we are investigating the effect of clay consolidation after completion of the caisson installation process on the axial pullout capacity. We have also begun work on a three-dimensional finite element analysis capability (an extension of the existing axisymmetric version) for caissons subjected to combinations of axial and lateral loads.
Reports & Publications:
Vásquez Chicata, L. F. G., and Tassoulas, J. L., “Computational Procedure for the Analysis of Suction Piles,” CD-ROM Proceedings of EM2000, Fourteenth Engineering Mechanics Conference of the American Society of Civil Engineers, Austin, Texas, May 21-24, 2000.
Vasquez Chicata, L. F. G., “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 Caisson Behavior,” CD-ROM 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.
Date: June 2002
Project Name: Suction Caissons: Finite Element Modeling
Task Order: 16169 Project Number: 58877
Principal Investigators: John L. Tassoulas
Estimated Completion Date: September 2004
Project Description:
This project is focused on the development of a computational procedure based on the finite element method for the analysis of suction caissons in clayey soils under monotonic axial (tensile) and lateral loads considering the effects of installation.
Progress:
We have overcome difficulties that we encountered when we applied an earlier version of the computational procedure to consolidation studies of very soft clayey soils in which tests of suction caissons are currently being conducted within the framework of another OTRC project. The difficulties were associated with the treatment of large deformation implemented in the procedure. A robust alternative formulation suitable for early stages of slurry consolidation is now functional in our procedure. Furthermore, we have undertaken a brief examination leading to a simple representation of the effects of aging on soil consolidation. A simple scheme for adjusting the finite-element mesh in a neighborhood of the caisson tip (rim) during the installation process in order to avoid use of excessively distorted finite elements is nearing completion. In this scheme, a priori definition of the penetration path will no longer be required. We expect that this computational refinement will produce better approximation of the state of stress in the soil that, in turn, will lead to improved estimation of both axial and lateral capacities.
Reports & 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.
Date: December 17, 2001
Project Name: Suction Caissons: Finite Element Modeling
Task Order: 16169 Project Number: 58877
Principal Investigators: John L. Tassoulas
Estimated Completion Date: September 2004
Project Description:
This project is focused on the development of a computational procedure based on the finite element method for the analysis of suction caissons in clayey soils under monotonic axial (tensile) and lateral loads considering the effects of installation.
Progress:
We have overcome difficulties that we encountered when we applied an earlier version of the computational procedure to consolidation studies of very soft clayey soils in which tests of suction caissons are currently being conducted within the framework of another OTRC project. The difficulties were associated with the treatment of large deformation implemented in the procedure. A robust alternative formulation suitable for early stages of slurry consolidation is now functional in our procedure. Furthermore, we have undertaken a brief examination leading to a simple representation of the effects of aging on soil consolidation. A simple scheme for adjusting the finite-element mesh in a neighborhood of the caisson tip (rim) during the installation process in order to avoid use of excessively distorted finite elements is nearing completion. In this scheme, a priori definition of the penetration path will no longer be required. We expect that this computational refinement will produce better approximation of the state of stress in the soil that, in turn, will lead to improved estimation of both axial and lateral capacities.
Reports & 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.