Estimate end bearing resistance of a circular foundation using small strain and large deformation finite element modelling

Accurately predicting the end bearing resistance of the foundation is important for its design and application. This research compares the results of a circular foundation end bearing resistance in uniform clay from small strain finite-element (SSFE) analysis and large-deformation finite-element (LDFE) analysis, with focus on the effect of soil stiffness. Results show that the soil stiffness has little influence on the bearing capacity of a shallow foundation with a shallow failure mechanism; for a deeply buried foundation, however, a deep flow mechanism is developed, and the failure zone is influenced by the soil stiffness. It is found that, for a shallow foundation, artificially increasing the soil stiffness in SSFE analysis allows for obtaining the end bearing capacity at a smaller displacement without sacrificing accuracy; while employing increased soil stiffness for deeply buried foundations may lead to inaccurate results. For penetrating problems, e.g., pile installation and CPT (cone penetration test), SSFE analysis may underestimate the end bearing resistance factor without considering the installation effect.