Numerical Analysis for Failure Envelopes of Shallow Suction Caisson Underwater

Expansion of human territory made it possible to explorer underground space, and now underwater space is considered as alternative dwelling or refuge space. Research on the foundation of offshore structures has been conducted for application to petroleum engineering, and the outcomes are also used for onshore systems. Under ocean environments, the combination of vertical and horizontal loads and moment is imposed to the foundations. In this study, the failure envelopes of the suction caisson foundations under combined loads were investigated based on three-dimensional finite element analysis. The soil condition was assumed undrained, thereby assuming clayey soils. The failure envelops were presented in horizontal load and moment domain for varying vertical load. The failure envelope tended to expand when the magnitude vertical load was reduced. In general, the shape of failure envelope was ellipsoid; the major axis of failure envelope did not rotate when the vertical load changed.