Undrained capacity of circular shallow foundations under combined VHMT loading

Abstract

Wind turbine (WT) foundations are generally subjected to large combined vertical, horizontal, moment, and torsional (VHMT) loads. The available investigations of the ultimate limit states of WT foundations focus predominately on unlimited-tension soil-foundation interfaces that are more appropriate for offshore settings. However, the interfaces for onshore WT foundations are generally unable to resist tensile loads. To address this omission, a zero-tension interface is used to investigate the VHMT failure envelope of circular shallow foundations under undrained soil conditions using finite element analysis. The effects of soil strength heterogeneity and foundation embedment were investigated. The results show that torsional loads reduce the VHM bearing capacity of circular foundations. The foundation embedment is also found to significantly increase the foundation bearing capacity. A full 4-D analytical expression for the VHMT failure envelope has been proposed based on the calculated failure envelopes.

Undrained capacity of circular shallow foundations on two-layer clays under combined VHMT loading

“…Crust correction factors of uniaxial capacities (He and Newson, 2022a, 2022b): (a) V ult and (b) M ult .…”

“…A swipe test is able to track the whole or a portion of a failure envelope. Refer to He and Newson (2022b) for more details of probe tests and swipe tests. Two typical failure envelopes obtained using the swipe and probe tests are shown in Figure 4.…”

“…Normalized 3-D failure surfaces (He and Newson, 2022a, 2022b): (a) VHM at T = 0, (b) VHT at M = 0, and (c) VMT at H = 0.…”

“…Failure envelopes for different types of foundations (e.g. strip (Bransby and Randolph, 1998; Fathipour et al, 2022), rectangular (Gourvenec and Randolph, 2003) and circular (Suryasentana et al, 2021) foundations), homogeneous (Taiebat and Carter, 2010) or non-homogeneous (He and Newson, 2022b; Wu et al, 2022) soils, and zero-tension (Shen et al, 2016) or unlimited-tension (Gourvenec and Randolph, 2003) interface conditions have been previously investigated under undrained soil conditions. These studies have been primarily confined to a single layer soil with a uniform or linearly increasing soil undrained shear strength profile.…”