Effect of Strength Anisotropy on Failure Envelope of Offshore Shallow Foundations under Combined Loading

Wu, K.; Fan, Q., and Zheng, J., 2015. Effect of strength anisotropy on failure envelope of offshore shallow foundations under combined loading.

The bearing capacity of offshore shallow foundations subjected to combined vertical, horizontal and moment loading is of interest particularly to the offshore geotechnical engineers. This paper reports a finite element (FE) study on the effects of strength anisotropy and foundation embedment depth on the combined bearing capacity. The Tresca failure criterion modified to allow for soil strength anisotropy and coupled with an elasto-perfectly plastic stress-strain relationship is assumed in the analysis which is conducted using the FE software ABAQUS. The undrained bearing capacities of shallow strip foundations under uniaxial vertical (V), moment (M) and horizontal (H) loadings are predicted and compared with available solutions. The V-M-H capacity of embedded foundations under combined loading is represented by failure envelopes in H-M space for various vertical loading levels. The results presented in this paper show that the embedment ratio significantly affects the shape of the failure envelope expressed in terms of loads normalized by the pure moment or pure horizontal load-carrying capacity of the foundation. However, the shape of failure envelope defining the undrained capacity of shallow foundations under horizontal and moment loads is independent of soil strength anisotropy.