Bearing capacity of tension steel piles in thinly inter-layered soils: numerical Class-A prediction vs. field measurements

This study investigates the bearing capacity of tension piles and pile-soil interaction during loading. Discrepancies between predicted and measured bearing capacities in previous tests motivated the study, where analytical methods showed considerable scatter and uncertainties in design. A large-scale field test was conducted on three additional adjacent tension piles (Pile 1, 2 and 3), featuring extensive fibre-optic strain measurements. Concurrently, a numerical Class-A prediction was developed beforehand to analyse pile-soil interaction and predict bearing capacity, utilising hypoplastic and visco-hypoplastic models for the thinly inter-layered subsoils. The fibre-optic measurements revealed significant locked-in bending strains post-installation, prior to loading. The results showed a correlation between pronounced bending strains and lower load-bearing capacity. Numerical predictions were compared with the field measurements, providing good agreement with Pile 1, which exhibited minimal installation-induced bending and thus represented an idealised case. This comparison offered valuable insights into tension pile failure mechanisms and load capacity. This research enhances understanding of tension pile behaviour in complex soils and underscores the necessity of optimising installation methods to improve load-bearing capacities.