Finite element evaluation of ultimate capacity of strip footing: assessment using various constitutive models and sensitivity analysis

Abstract

Finite element method can be used for computing bearing capacity of shallow foundation with irregular geometry resting on variable subsoil. It is necessary to quantify the parameters affecting the ultimate capacity of footing. This paper presents the results of finite element (FE) analysis of the ultimate failure load of a rough base rigid strip footing resting on c-ϕ soil. The soil is assumed as linear elastic perfectly plastic with Mohr–Coulomb failure criterion and non-associative flow rule. Sensitivity analysis is carried out to examine the ultimate capacity of strip footing considering the strength parameters (c′, ϕ′, and ψ), width of strip footing (B), unit weight of soil (γ), surcharge (q) at the base level of footing, and the deformation parameters (E and ν) as the variables. The study also examines the effect of different material models on the ultimate capacity of the strip footing. The material models considered are Mohr–Coulomb (MC) model, Hardening Soil (HS) model, Hardening Soil model with small-strain stiffness (HSsmall), and Soft Soil (SS) mode-l. It is found from the results of FE analysis that the ultimate load of the strip footing is dependent on the strength parameters, width of footing, unit weight of soil, and surcharge at the base level of the footing. The ultimate capacity is independent of the deformation parameters and will remain almost same corresponding to the material models like MC, HS, HSsmall, and SS. The FE results are compared with the analytical solutions of Terzaghi and Meyerhof. Based on the study, a few suggestions are given in regard to the FE analysis of geotechnical stability problems to obtain the quick results.