Analysis of anchor foundation with root caissons loaded in nonhomogeneous soils

Abstract

This paper presents a novel type of deep foundation — an anchor foundation with root caissons, which improve the soil–caisson interaction using penetrating roots. A simplified analytical procedure is proposed for calculating responses of the new anchor foundation subjected to combined vertical, horizontal, and moment loadings. Caisson–soil interaction is simulated by a Winkler subgrade reaction model, with an improved Winkler spring constant to consider the reinforcement effect of roots. The method incorporates limiting soil stress to investigate soil nonlinear behavior and a transfer matrix to represent nonhomogeneous soils, with a passive caisson model accounting for group effects. The effectiveness of the present approach is evaluated by comparison with full-scale field load tests and a finite element analysis on a small-scale anchor foundation to give a preliminary design guideline for the Ma’anshan Yangtze River Bridge in China.