Automated procedure to derive convex failure envelope formulations for circular surface foundations under six degrees of freedom loading

• Published in: Computers and geotechnics 2021-09, Vol.137, p.104174, Article 104174
• Main Authors: Suryasentana, Stephen K., Burd, Harvey J., Byrne, Byron W., Shonberg, Avi
• Format: Article
• Language: English
• Subjects: Automation; Bearing capacity; Combined loading; Degrees of freedom; Failure; Failure analysis; Failure load; Finite element method; Foundations; Mathematical models; Numerical modelling; Offshore engineering; Procedures; Soil-structure interaction
• ISSN: 0266-352X; 1873-7633
• DOI: 10.1016/j.compgeo.2021.104174

Failure envelope formulations are typically employed to assess the ultimate capacity of foundations under combined loading and for incorporation in macro-element models. However, the complex interaction between each load component, especially for six degree of freedom (6DoF) loading, means that determining satisfactory formulations is often a complex process. Previous researchers have identified this difficulty as an obstacle to the adoption of the failure envelope approach in foundation engineering applications. To address this issue, the paper describes a systematic procedure for deriving globally convex failure envelope formulations; the procedure is applied to a circular surface foundation, bearing on undrained clay, in 6DoF load space. The formulations are shown to closely represent the failure load combinations determined from finite element analyses for a variety of loading conditions, including non-planar horizontal-moment loading. An example macro-element model based on the proposed formulation is described; the macro-element model provides a close representation of the foundation behaviour determined from a separate finite element analysis. A key aspect of the paper is that it demonstrates an automated process to determine well-behaved failure envelope formulations. The automated nature of the process has considerable advantages over the manual procedures that have previously been employed to determine failure envelope formulations.