Bearing Capacity and Settlement of Skirted Shallow Foundations on Sand

The behavior of axially loaded skirted shallow foundations resting on sand was studied using an extensive numerical analysis. Surface, pier, and skirted square foundations resting on sand with different shear strength properties were utilized in the analysis. A physical model testing, although on much smaller scale, was also carried out to support the numerical analysis results. The effects of foundation size, shear strength of sand, and skirt depth on bearing capacity and settlement of skirted foundations were assessed. The results of this study revealed that skirted foundations exhibit bearing capacity and settlement values that are close, but not equal, to those of pier foundations of the same width and depth. The enhancement in bearing capacity of shallow foundation increases with increasing skirt depth and decreasing relative density of sand. Settlement reduction may exceed a value of 70% in the case of having skirt-depth/foundation-width of 2.0. Charts and equations are presented to estimate bearing capacity and settlement of skirted shallow foundations in terms of those of surface foundation and skirt-depth/foundation-width.