Note: This study was part of a broader project Suction Caissons: Model Tests (MMS Project #362)
Despite advances in the field, more research is needed to explain the mechanics and working properties of suction caissons, especially those with aspect ratios greater than three. Several design issues have arisen in recent years regarding suction caisson installation and capacity, including (Clukey 2001):
- Interaction between horizontal and vertical components of inclined loads on the padeye of a caisson, and which component governs total capacity.
- Effects of suction installation on skin friction between the caisson and surrounding soil.
- Reverse end-bearing forces on the caisson during uplift.
- Differences in axial capacity between undrained and drained loading conditions.
- Set-up time and excess pore pressure dissipation, and their effects on uplift capacity.
An ongoing research project with the Offshore Technology Research Center, jointly funded by U.S. Minerals Management Service and a number of offshore companies, at the University of Texas at Austin and Texas A&M University at College Station, is currently underway to investigate the behavior of suction caissons. This work is focused on suction caissons with large aspect ratios in normally consolidated clay resembling typical deposits in the Gulf of Mexico. The goal of the project is to address important design issues using observations from laboratory model tests and analytical modeling to develop a better understanding of suction caisson mechanics. Additional goals defined during the course of the project are to examine:
- Differences in axial uplift capacity for caissons inserted by self-weight versus those inserted by suction pressure.
- Behavior of the internal soil plug during insertion and uplift.
- Repeatability of model tests.
- Comparisons with previous model suction caissons experiments.
Described herein are suction caisson laboratory testing facilities at the University of Texas, data reduction methods, and experimental results from model caissons tested to failure by axial pullout. Similar tests by other researchers are addressed through a literature review. Conclusions from the testing are drawn, as well as recommendations for further research.
Related Publications: 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
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)