Numerical analysis of ultimate bearing capacity of strip footings near slopes

The footing placed on the top of a slope is common in geotechnical engineering practice. However, few studies were performed to study the bearing capacity and the failure mechanism of footing-slope systems. In this study, discontinuity layout optimization (DLO) is adopted to study the effects of geometry of the slope, soil properties and footing location on the limit load and the critical collapse mechanism. Evaluations are provided concerning the recommended estimating methods in present codes both at home and abroad. The results show that the ultimate bearing capacity decreases as the increasing slope height and slope angle, but the effects can be neglected when the slope height exceeds a critical value; the ultimate bearing capacity increases as the increasing soil strength. The failure slip becomes shallower with high soil cohesion, while the failure slip develops deeper with the increase of friction angle. The bearing capacity increases with the normalized footing distance of from the crest of slopes, and there is a critical normalized distance that makes the effect of slopes can be negligible. The specified value for the minimum distance suggested by the China Code for design of building footing is smaller than the critical distance with high soil strength and large slope angles, and the effect of slopes on the bearing capacity should be considered; conversely, the recommended designed distance tends to be conservative for low soil strength and small slope angles. In AASHTO code, the ultimate bearing capacity values for cohesiveless soil are reliable, but only face failure mode is considered; the recommended design chart is contrary to theoretical solution in cohesive soil. The normalized footing distance from the crest of slopes is underestimated in AASHTO code.