Stability of Ekofisk Tank: Reliability Analysis

Abstract

The uncertainties encountered in the stability analysis for the foundation of the Ekofisk Tank are formulated in probabilistic terms and used to evaluate the reliability of the foundation design. The major sources of uncertainty are: shear strength of the soil, wave loads, porepressure generation under repeated loads, and methods of analysis. The results show that the conservative assumptions and low safety factor, based on the information available at the time of design, lead to a reliability that is close to those reported for other offshore foundations in the North Sea. About the same reliability is obtained by an estimate made on the basis of current knowledge. This study demonstrates the use of reliability analysis in designs involving complex loadings and inadequate knowledge on soil behavior. The procedures are comparatively simple and may be applied to new designs to help the engineer in making decisions about safety factors.