Offshore Technology Research Center

 

OTRC Project Summary

Project Title:

The Pullout Capacity of Suction Caisson Foundations

Prinicipal Investigators:

Roy Olson

Sponsor:

National Science Foundation

Completion Date:

July, 1999

Final Report ID#

B101(Click to view final report abstract)

The experimental program on SCFs at OTRC started in 1991 with the development of a main testing tank and instrumentation system (Malhotra, 1991).  The first set of model tests was conducted in sand and was intended to examine the overall feasibility of the testing program (Pavlicek, 1992).  Efforts were subsequently made to improve the design of the model caisson and extend the scope of tests in sand to include both static and cyclic loading (Jones, 1994).  Improved model caissons were installed using suction successfully in clay (Goldberg, 1994).  The main focus of the project remained on the investigation of the behavior of SCFs for tension leg platforms in water depths of 6,000 to 10,000ft in the GoM.  At these depths, the foundation material is mainly clay and loading of the foundation system is composed of the static uplift loading due buoyancy in addition to cyclic vertical and horizontal loading due to environmental conditions. 

In normally consolidated clay soils of the deep GoM, foundation capacity is derived mainly from increased soil shear strength with depth.  It was therefore deemed necessary to examine the possibility of extending the range of aspect ratios of SCFs beyond that used in the North Sea.  An experimental program was designed to test a set of newly designed and fabricated model foundations, with aspect ratios ranging between 2 and 12.  It was desired to examine the feasibility of installing the model caissons with larger aspect ratios using suction , and to simulate more accurately loading from floating structures than has been done I the past.  To assess the pullout capacity of the model foundation s for TLP applications, the simulated loading was in the form of static vertical tension, cyclic vertical tension, static inclined tension, cyclic inclined tension, and combined vertical and horizontal cyclic tension.  The ultimate goal of the program has been to present to the offshore industry with an understanding of the behavior of the SCFs that is based in the field experience and laboratory modeling.

Related Publications: El-Gharbawy, S., and Olson, R. E., "The Pullout Capacity of Suction Caisson Foundations for Tension Leg Platforms", Proc., ISOPE Conference, Montreal, Vol. 1, pp. 531-536, 1998.

El-Gharbawy, S., and Olson, R. E., "Laboratory Modeling of Suction Caisson Foundations", Proc., ISOPE Conference, Montreal, Vol. 1, pp. 537-542, 1998.

El-Gharbawy, S., and Olson, R. E., "Behavior of Suction Caissons in the Marine Environment", Proc., Offshore Technology Conference, Houston, 1998.

El-Gharbawy, S., and Olson, R.E., "The Cyclic Pullout Capacity of Suction Caisson Foundations," Proceedings, ISOPE Conference, Brest, France, Vol. 1, 1999.

El-Gharbawy, S., and Olson, R.E., "Suction Caisson Foundations in the Gulf of Mexico," Analysis, Design, Construction and Testing of Deep Foundations, J.M. Roesset ed., pp. 281-295, 1999.

El-Gharbawy, S., and Olson, R. E., "Suction Anchor Installations for Deep Gulf of Mexico Applications", Proc., Offshore Technology Conference, Paper OTC 10992, 1999.

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