Undrained capacity of shallow octagonal foundations under combined VHM loading

Pengpeng He, Venkatesh Deshpande, Tim Newson

Research output: Contribution to journalArticlepeer-review

Abstract

The foundations of many large onshore and offshore structures are designed to be symmetrical polygons (e.g. octagons). However, the available analytical approaches for the ultimate limit state design of shallow foundations under combined loadings focus predominately on strip, rectangular and circular foundations. Although equivalent inscribed circular foundations have been recommended for foundation design by some guidelines, this simple approximation for octagonal foundations needs to be rigorously assessed due to the high dependence of the failure envelope on foundation shapes. The present study has investigated the general VHM (vertical, horizontal and moment) failure envelope of octagonal foundations under a zero-tension interface for undrained soil conditions using finite element analysis. The effects of soil strength heterogeneity and foundation embedment on the VHM failure envelope have been investigated. Analytical expressions have also been proposed to characterize the failure envelopes for use in design. The results show that octagonal foundations have larger bearing capacity than the corresponding circular foundations, and the difference (around 10%) between them is not negligible. A full 3-D analytical expression for the VHM failure envelope has also been proposed based on the calculated failure envelopes.

Original languageEnglish
Number of pages12
JournalGeotechnical and Geological Engineering
Early online date8 Nov 2022
DOIs
Publication statusE-pub ahead of print - 8 Nov 2022

Keywords

  • Combined loading
  • Failure envelope
  • Finite element analysis
  • Octagonal foundation
  • Zero-tension interface

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