Behavior of circular footing resting on laterally confined granular reinforced soil

Abstract

Three dimensional physical laboratory models were examined to investigate the influence of soil confinement on circular footing behavior resting on granular soil. A total of 23 model footing tests were performed. Nine hollow cylinders with various heights and diameters were installed around the footing model for soil confinement purpose. Square geogrid layers were placed at different depths beneath the bottom edge of the cylinder. Different parameters such as height, diameter, and depth of the cylinder were studied. Moreover, number, width, and position of the geogrid layers were, also, investigated. The response of a non-confined footing model was set as reference for comparison purpose. The results showed enhancement in the bearing capacity of the soil as well as a reduction in its settlement in all used configurations compared with the reference case. It is, however, observed that on increasing the number of geogrid layers more than one layer had a small significant effect on the footing behavior. Moreover, placing geogrid layers underneath the cylinders improves the bearing capacity up to 7.5 times that of the non-confined case. Footing with cylinder of a diameter nearly equal to the footing diameter behaves as one unit like a deep foundation. This behavior pattern was no longer observed with large cylinder diameter and small height. Finally, the study ends up with recommendations for selection of cylinder dimensions to maximize the bearing capacity. The benefits of using geogrid layers were also highlighted.

Behavior of Vertically Confined Square Footing on Reinforced Sand under Centric Inclined Loading

“…Keeping economy in view, confinement technique is one of the suitably applicable methods that have been accepted to enhance the bearing capacity of footing and reduce settlement to permissible limit. In the past few years different materials such as geocell, un-plasticized polyvinyl chloride (Upvc) cylinder, semi flexible vertical reinforcement, mild steel casing, plastic hollow cylinder, timber box have been used as confiner and shown notable improvement in bearing capacity of footing ( Rajgopal et al [25], Sawaaf and Nazer [30], Jha [18], Krishna et al [21], Elsaied [13], Amarasinghe et al [2]). Mandal and Manjunath [23] used geogrid and bamboo sticks as vertical reinforcement elements and studied their effect on the bearing capacity of a strip footing.…”

Model studies of plus and double box shaped skirted footings resting on sand

“…El Wakil [14] reported that the bearing capacity of the footing was directly and inversely proportional to the skirt depth and the relative density respectively of the sand. The use of skirts for improving the load-settlement response of circular footing on reinforced sand was explored by Elsaied et al [15]. Based on 23 laboratory small scale model tests, it was concluded placing geogrid layers below the skirted footing improves the bearing capacity up to 7.5 times in comparison to the unconfined case.…”

Experimental and numerical studies of skirted hexagonal footings on three sands

“…In recent years, experimental research on skirted footings such as strip [5][6][7], square [4,[8][9][10][11][12], circular [6,[13][14][15][16][17][18][19][20][21][22][23] and rectangular [12], subjected to vertical or inclined loads, has been reported. Numerical studies on skirted footing such as strip [6], square [10] and circular [6] were reported in the literature.…”