A comparison between theoretical and numerical ultimate failure domains for pile groups

Multiaxial strength envelopes have been recently proposed as a rational approach for the design of pile foundations subjected to inclined and eccentric loads, leading to more economical solutions with respect to standard methods applied in the design practice. Theoretical solutions based on the application of the Upper-Bound (UB) and Lower-Bound (LB) theorem of Limit Analysis have been proposed to derive the ultimate failure domain of pile groups. In this paper, theoretical predictions for a 4×1 pile group embedded in a homogeneous clayey soil deposit are validated against the results of numerical analyses carried out with the Finite Element code Abaqus. To take into account the nonlinear behaviour of reinforced concrete piles, a damaged plasticity model was used for the concrete, while the reinforcing bars were modelled as equivalent elastoplastic shell elements. The soil was modelled as a standard elastic-perfectly plastic material with a Tresca failure criterion to represent the undrained soil behaviour in a total stress analysis.