Numerical modelling of the uplift process and breakaway of circular surface footings

Compared to compression, modelling the uplift process of a surface footing is extremely challenging due to transient, coupled and highly non-linear soil behaviour and due to the complex interaction between the footing and soil. This paper presents a numerical finite element modelling approach to address these challenges by employing the modified Cam-Clay constitutive model for soil and a cohesive element-based hydro-mechanical interface between the footing and soil. The numerical results agree well with physical modelling data from centrifuge tests, exhibiting both rate dependency of uplift resistance and the occurrence of the rapid drop in resistance known as ‘breakaway’. Based on the verified numerical model, the effect of uplift rates on the resistance and the underlying mechanism of the breakaway phenomenon are discussed in detail. A sensitivity study of the interface model was conducted to demonstrate the key parameters and recommend appropriate value ranges.