Unified upper bound solution for bearing capacity of shallow rigid strip foundations generally considering soil dilatancy

Abstract

In light of the upper bound method of a kinematical limit analysis, traditional log-spiral shear zones in the admissible failure mechanism of foundation soil loaded by shallow rigid strip footings are unified by introducing a nonnegative coefficient for the internal friction angle of the soil to generally reflect practical soil dilatancy. While the computed coefficient is generally between 0 and 1 to be compatible with its physical meaning, in many cases it was between 0.5 and 1. The proposed mechanism includes the traditional log-spiral and circular-arc mechanism, and is capable of determining a smaller value of the solution to the bearing capacity than some classic theoretical methods. Based on the proposed mechanism, two bearing capacity factors are refined from the traditional three factors based on the finding that the traditional factors Nq and Nc are not independent of the footing depth and soil cohesion, respectively. A formula including the two items is provided to make the proposed method convenient for use for the practical footings on homogeneous soil.