Loosely Skirted Circular Foundation under Different Loading Conditions: Performance, Mechanism, and Limitations

The term loosely skirted foundation is used to describe the geogrid skirts that are positioned beneath the footing. This technique enhances soil performance and reduces costs when compared to rigid skirted footings. The present study examines the performance of loosely skirted circular footings on poorly graded sand with and without horizontal reinforcement layers inside the skirt rooms. The footings are subjected to loading eccentricities, (e) of 0, 0.08 D and 0.16 D, where D is the diameter of the footing. The depth of the skirt (L) was adjusted to values of 0.5 D, 1 D, 1.5 D, and 2 D. The number of geogrid layers (N) was varied based on the skirt depth. The spacing between horizontal reinforcements (Y) was evaluated at 0.25 D, 0.5 D, 0.75 D, and 1 D. The loosely skirted circular footing without lateral reinforcement within the skirt demonstrated optimal performance at L/D = 1.5, enhancing bearing capacity by 111.64%, 91.5%, and 76.3% and reducing settlement by 57.1%, 52.7%, and 51%, respectively, for e/D = 0, 0.08, and 0.16. Concerning the loosely skirted circular footing with lateral reinforcement within the skirt, the optimal performance was observed at L/D = 2 and the minimum spacing reinforcement was evidenced at Y = 0.25 D, which enhanced the bearing capacity by 235.6% and 224%, respectively. The results revealed that the best performance was obtained for the loosely skirted circular footing without lateral reinforcement within the skirt, with enhancements of 111.64%, 91.5%, and 76.3% in the bearing capacity and reductions of 57.1%, 52.7%, and 51% in the settlement at e/D = 0, 0.08, and 0.16, respectively. Conversely, the best performance for the loosely skirted circular footing with lateral reinforcement inside the skirt was observed at L/D = 2 and the minimum spacing reinforcement Y = 0.25 D, with enhancements of 235.6%, 224%, and 194% in the bearing capacity and reductions of 72.2%, 67.2%, and 68% was noted at e/D= 0, 0.08, and 0.16, respectively.