An Investigation of Failure Envelope for Skirted Foundations in Soft Clay Based on Computer-Aided Analyses

The stability of skirted foundations subjected to combined vertical, horizontal and moment loading is of importance to the offshore engineering. The paper reports a computer-aided study on the effects of strength anisotropy and foundation embedment depth on the combined bearing capacity of skirted foundations. The results show that when the traditional load reference point, i.e. the base center, is utilized, the shape of failure envelope for skirted foundations is strongly dependent on embedment ratio, however independent of soil strength anisotropy. To gain a unified equation to describe the shapes of failure envelopes for skirted foundations with a range of embedment ratios, the searching algorithm for the optimal load reference point is implemented. Based on the optimal load reference point, the failure envelope obtained can be approximated as an ellipse in normalized moment-horizontal load space. Then a closed-form equation is proposed, which can be used to evaluate the bearing capacity of skirted foundations in soft clay considering strength anisotropy effect.