Summary
Objective
Suction caissons are being used increasingly as seafloor anchorages for deepwater offshore exploration and production platforms. Data are needed to improve and validate analytical models and design practices. Large-scale data are scarce, and available laboratory data do not address all issues important to the design and installation of suction caissons.
The objective of this research is to perform experiments with small prototype suction caissons in normally consolidated clays, such as encountered in the Gulf of Mexico and other offshore locations. The goals include the study of design issues such as the effect of self weight versus suction penetration, limiting ratio of penetration to diameter during suction installation, consolidation (set-up) times after installation, the influence of internal stiffeners on capacity, effects of loading rates on capacity under axial loading, the effect of cyclic axial loading on capacity, range of capacities under lateral loading with differing durations of loading (drained versus undrained loading), effect of mooring line angle on lateral capacity, effect of the mooring line attachment location, and other relevant effects.
These data are being used in companion projects to develop and validate analytical and design methods for this technology. Potential benefits to the offshore industry and regulatory agencies will stem from the greater reliability of future designs.
Approach
Small scale experiments are being conducted in a laboratory. Suction caisson models with a diameter of 100 mm, length of about one meter, and a wall thickness of 0.8 mm (ratio of diameter to wall thickness similar to a full-scale caissons) are being used. The experiments are being conducted in test beds of clay that are made in large tanks. The test bed soil is kaolinite, which was selected to allow deposition from slurry with acceptable consolidation times (about 9 months) and still obtain sediment thick enough to allow testing. The test beds are prepared by mixing the clay and water in an initial tank until the slurry is uniform, and then pumping it into the main tanks. A number of experiments can be performed in a single test bed.
Deployment of Results
The data from these experiments are being used in companion projects to develop and validate analytical and design methods for suction caissons. The experiments and results will be documented in a final report.
The data from these experiments are being used in companion projects to develop and validate analytical and design methods for suction caissons. The experiments and results will be documented in a final report.
Related Publications
Theses
Pedersen, Robert C. (2001), “Model Offshore Soil Deposit: Design, Preparation, and Characterization”, Univ. of Texas, Austin (May).
Mecham, Elliott C. (2001), “A Laboratory for Measuring the Axial and Lateral Load Capacity of Model Suction Caissons”, University of Texas, Austin (December).
Luke, Adam M. (2002), “Axial Capacity of Suction Caissons in Normally Consolidated Kaolinite”, University of Texas, Austin (January).
Coffman Richard A. (2003), “Horizontal Capacity of Suction Caissons in Normally Consolidated Kaolinite”, M.S. Thesis, University of Texas, Austin (December).
Vanka, Sandeep K. (2004), “Laboratory Tests to Estimate Strength Profile of Normally Consolidated Kaolinite”, M. S. Thesis, University of Texas, Austin (December).
Dissertations
El-Sherbiny, Rami M. (2005), “Performance of Suction Caisson Anchors in Normally Consolidated Clay”, Ph.D. dissertation, University of Texas, Austin, August
Publications
Olson, R. E., A. F. Rauch, A. F. Tassoulas, C. P. Aubeny, and W. R. Murff (2001), “Toward the Design of New Technologies for Deep-Water Anchorages”, International Symposium on Offshore and Polar Engineering, Scavenger, Norway, June
Rauch, A. F., Olson, R.E., Mecham, E. C., Pedersen, R.C. (2001). “A Laboratory Facility for Testing Model Suction Caissons.” Proc., OTRC 2001 Intl Conf. on Geotechnical, Geological, Geophysical Properties Deepwater Sediments, Houston, TX, April. pp. 198-216
Pedersen, R. C., R. E. Olson, and A. F. Rauch (2003), “Shear and Interface Strength of Clay at Very Low Effective Stress”, ASTM Geotechnical Testing Journal, Vol. 26, No. 1, paper GTJ200310648-261
Rauch, A. F., R. E. Olson, A. M. Luke, and E. C. Mecham (2003), “Measured Response During Laboratory Installation of Suction Caissons”, International Symposium on Offshore and Polar Engineering, Honolulu, Hawaii, p. 780-787
Luke, A. M., A. F. Rauch, R. E. Olson, and E. C. Mecham (2003), “Behavior of Suction Caissons Measured in Laboratory Pullout Tests”, Proc. OMAE03, 22nd International Conference on Offshore Mechanics and Arctic Engineering, Cancun, Mexico, Paper 37023
Olson, R. E., A. F. Rauch, A. M. Luke, D. R. Maniar, J. T. Tassoulas, and E. C. Mecham (2003), “Soil Reconsolidation Following Installation of Suction Caissons”, Offshore Technology Conference, Houston, paper 15263
Luke, A. M., A. F. Rauch, R. E. Olson, and E. C. Mecham (2003), “Components of Suction Caisson Capacity Measured in Axial Pullout Tests”, Deepwater Mooring Systems: Concepts, Design, Analysis and Materials, OTRC (Offshore Technology Research Center) Specialty Conference, Houston, TX
Olson, R. E., A. F. Rauch, E. C. Mecham, and A. M. Luke (2003), “Self-Weight Consolidation of Large Laboratory Deposits of Clay”, Proc., 12th PanAmerican Conf. on Soil Mech. and Geot. Engr., MIT, Vol. 1, pp. 703-708
Coffman, R. A., R. M. El-Sherbiny, A. F. Rauch, and R. E. Olson (2004), “Measured Horizontal Capacity of Suction Caissons”, Proc., Offshore Tech. Conf., Houston, Paper 16161
Luke, A. M., A. F. Rauch, R. E. Olson, and E. C. Mecham (2005), “Components of Suction Caisson Capacity Measured in Axial Pullout Tests”, Journal of Ocean Engineering, Elsevier (in press)
El-Sherbiny, R. M, Olson, R. E., Gilbert, R. B, and Vanka, S. K. (2005), “Capacity of suction caissons under inclined loading in normally consolidated clay”, Proceeding of the International Symposium on Frontiers in Offshore Geotechnics, Perth, Australia, September
