The challenge of seafloor characterization for deepwater facilities is that the mooring foundations, subsea well trees and flowlines are spread over large areas (tens of thousands of feet across), while the cost of obtaining high-quality geotechnical data for the seafloor is high. Therefore, information from a handful of soil borings is typically extrapolated over thousands of feet to design foundations. This extrapolation leads to uncertainty that could potentially lead to excessively conservative designs or to unreliable designs.
The objective of this research was to develop a reliability-based methodology to design suction caisson foundations with typical seafloor characterization data and to apply this methodology to optimize geotechnical investigation programs. The following tasks were completed in order to meet this objective:
- Quantify effect of spatial variability in soil properties on design for suction caissons.
- Calibrate and quantify uncertainty in design method for suction caissons.
- Develop a reliability-based design methodology for suction caissons.
- Quantify the added value of site characterization data and foundation installation information in reducing uncertainty in suction caisson design.
This research utilized and synthesized the results from a handful of related OTRC projects, including:
- Suction Caisson Model Testing by Olson, Rauch and Gilbert;
- Suction Caisson Predictive Modeling by Aubeny and Murff;
- Suction Caisson Finite Element Modeling by Tassoulas;
- Suction Caisson State-of-Practice by Murff (and API); and
- Mooring System Reliability by Zhang and Gilbert.