Effects of restraining conditions on the bearing capacity of footings near slopes

Abstract

In evaluating the ultimate bearing capacity (qu) of a strip footing adjacent to a slope, conventional correction formulas for the effect of load eccentricity may not be applicable because these formulas were developed exclusively for footings situated on horizontal grounds, where loads eccentric to opposite sides of the footing yield identical results for qu. In this study, loading tests and analyses are conducted on a strip footing placed adjacent to a model slope with various slope angles. The experimental evidence shows that a load eccentric toward the heel of a footing leads to an increase in bearing capacity, whereas the analytical results based on conventional formulas show the opposite trend. To address this discrepancy, an approach is proposed that uses a bearing capacity correction formula for a footing with a setback from the crest of the slope. Results of a comparative study show that the experimental values for bearing capacity factor Nγ(test), with full corrections for load inclination, load eccentricity, and footing setback are comparable to the theoretical solutions. Furthermore, fully corrected values for Nγ(test) for the fixed footing approximately follow the line of the upper boundary; those for the free-rotating footing follow the lower boundary of the theoretical solutions reported in the literature. This discrepancy is due to the different failure mechanisms induced by the restraining conditions of the footing which have yet to be considered in engineering practice.