Experimental Study of Skirted Square Foundations Resting on Sand for Improvement of Foundation Settlement and Bearing Capacity

This study employed physical modeling to examine the performance of skirted square foundations installed in sand. The effects of the ratio of skirt depth to foundation width, side roughness, and shear strength of the sand on the behavior of skirted foundations were considered. The performance of the skirted foundations was compared with those of embedded and surface foundations. The results showed that settlement was greater for the embedded foundations than for the skirted foundations. The application of a skirt for a surface foundation decreased the settlement and satisfactorily increased the bearing capacity and subgrade reaction modulus. A decrease in the shear strength of the sand and an increase in the skirt depth increased the bearing capacity and decreased the settlement of the surface foundations. The ratio of the bearing capacity of the skirted foundations to that of the surface foundations was 2.3- to 5.1-fold, depending on the embedment ratio (L/B). This ratio for the subgrade reaction modulus was 1.2- to 5.3-fold. Several diagrams have been introduced to estimate the decrease in settlement and increase in the bearing capacity of surface foundations with the application of skirts.