Deep-footing and wide-slab effects in reinforced sandy ground

Quantitative evaluations are performed on two failure mechanisms, namely, deep-footing and wide-slab mechanisms, that dominate the bearing-capacity characteristics of sandy ground reinforced with horizontal reinforcing layers. The improvement contributed by reinforcement, creating a quasi-rigid, wide earth slab immediately under the footing to the bearing capacity is analyzed. The maximization of the bearing-capacity increase of a footing is a matter of optimizing the depth and width of the quasi-rigid earth slab. The results of a total of 105 model tests, including reduced-scale model tests and some centrifuge tests under 15 g, are analyzed using calibrated internal friction angles of sand and an experimentally verified failure mechanism in reinforced sandy ground, namely, the deep-footing mechanism. Back-calculations are performed on the load-spreading angle a, which represents the total effect of the deep footing and wide slab for all the tests. Both linear and nonlinear multiple-variable data regressions are performed to find the relationships between the effect of reinforcing and the factors that control the scheme of reinforcement. The analytical procedure and equation derived in the present study substantiate the prediction of the ultimate bearing capacity of sandy ground reinforced with horizontal reinforcement.