Centrifuge and numerical study of shallow and embedded foundations on dry sand under combined loading conditions

Abstract

The present paper examines the behaviour of shallow and embedded foundations under combined vertical, horizontal and moment (𝑉, 𝐻, 𝑀) loading in dry sand. For such foundation systems, the use of interaction diagrams offers an alternative to the conventional bearing capacity analysis. Such diagrams have been extensively used in the past for various types of foundations (shallow, skirted, spudcan, embedded, etc.). The effect of embedment has also been studied thoroughly both experimentally (1g – ng tests) and numerically, however mostly for foundations in cohesive soil. The present study examines the response of such foundation systems of embedment ratios between 𝐷/𝐵 = 0 ÷ 1 in cohesionless material. Initially, an experimental study was conducted at the ETH geotechnical drum centrifuge using three different foundation systems subjected to displacement controlled vertical push loading but also to combined loading conditions. The foundation in all cases was square shaped of width 𝐵 = 2.8𝑚 (prototype scale) investigating three different 𝐷/𝐵. The results of the experiments were then used to calibrate the numerical models focusing on the foundation level, using PLAXIS 3D program. The later were used to conduct a detailed parametric study applying various combinations of 𝑉, 𝐻, 𝑀 loading. The results are presented in the form of interaction diagrams and are further validated against similar published failure envelopes. These results show the evolution of the failure surface with respect to embedment ratio and contribute to a better understanding of the response of such foundation systems.