Bearing Capacity Evaluation of Skirted Reinforced Sand Slopes by Physical Modeling

Foundations are sometimes located either on a sloped surface or near the crown of a slope. Obvious examples can be seen in the footings of bridges abutments, foundations near excavations, retaining walls, and electric transmission towers built on mountain slopes. When the footing is placed near the edge of sloping ground, the bearing capacity may be significantly reduced, depending on the location of the footing concerning the slope. Therefore, the bearing capacity and stability of a slope is one of the most important research issues in geotechnical engineering. The adjacent soil's bearing capacity and the slope's stability can be increased by installing continuous confining structures like skirts. Skirted foundations are a type of shallow foundation with internal or lateral skirts made of steel or reinforced concrete. Using a skirt due to confinement of the soil beneath the foundation and transmitting the shear Failure at the level of the skirt tip. In this research, a series of laboratory tests were conducted on strip footing models adjacent to sand slope whit one side vertical skirt to evaluate the load-settlement response subjected to vertical compression loading. The effects of skirt depth (Hs) and setback distance (b) of the model on the bearing capacity and settlement of skirted foundations were studied. The results of the model tests have shown that using skirts improves the bearing capacity and settlement values of skirted foundations compared with shallow foundations without a skirt. The ultimate bearing capacity of skirted foundations increases up to about 104 to 232% with increasing the ratio of skirt depth to foundation width. To investigate the effect of setback distance on the skirted foundation behavior, three different distances of footing from crest to the width of the footing of 0, 1, and 2 were used. The results showed that the increase in the ratio of the distance of footing from the crest to the width of footing caused to increase in the ultimate bearing capacity of only footing. The results showed when the skirted footing is placed directly at the crest (b=0), increasing the depth of skirts leads to a significant increase in the bearing capacity. By increasing the edge distance from the slope crest to the footing, the effect of utilized skirts decreases. The Settlement Reduction Factor (SRF) decreased from 4 to 72% with the increase in the depth of the skirt and with a decrease in setback distance. Furthermore, the effect of a single-side skirt strip foundation resting on the top of the sand slope was investigated on the values of foundation tilting and failure mechanism. Evaluating results showed that strip footing near the slope has a clockwise tilt angle and after using one single skirt the tilt angle got changed. It was observed that in setback distance b/B=0 under s/B=15% with an increase in skirt depth (Hs=1b, 3B), the reduction values of footing tilt were from 46 to 24%, respectively. In the end, utilized skirts affect the failure mechanism and dependent on skirt length and setback distance change the failure pattern of the soil, face failure to toe, or base failure.