Bearing Capacity and Uneven Settlement of Consecutively Constructed Adjacent Footings Rested on Saturated Sand Using Model Tests

Abstract

The interference of two nearby footings has been challenging due to the lack of suitable construction sites. Therefore, engineers are often forced to place footings at close spacing, which results changing of the ultimate bearing capacity, the settlement, and the tilt based on the considered spacing. In this study, two series of 1 g model test were conducted on two interfering parallel strip footings rested on the Babolsar saturated sand with different safety factors considered for the previously constructed footing (named as the old footing). The footings are loaded unequally and non-simultaneously to simulate mechanism of the new and the old footing with different surcharge and construction orders. The results are presented in the form of non-dimensional interference factors for ultimate bearing capacity and settlement of interfering footings versus isolated footings. It is demonstrated that the interference effect on the performance of isolated footings is considerable. Moreover, by decreasing the S/B ratio (i.e., spacing divided by footing width) from 1 to 0, the settlement ratio increases more than five times. Furthermore, in both series of tests, more than 300% increase in the tilting degree of the old footing was resulted due to the interference with the new footing in the ratio of S/B = 0 compared with S/B = 1. It demonstrates the perilous effect of the old footing tilting caused by the new footing adjacency. Moreover, applying different safety factors for the old footing has no dramatic effect on the tilting of the old footing enforced by the adjacent new footing.