Evaluation of N c Factor of Bearing Capacity Equation

Abstract In geotechnical engineering, the assessment of the ultimate capacity of shallow foundation for clay according to general bearing capacity theory depends mainly on the N c factor, moreover, there are some theories adopted to estimate this factor, so the suitability of each method can be verified after compare it with the practical finding, due to the difficulty or impossibility of performing full-scale practical work, this leads to a lack of research in this topic. The purpose of this paper is to assess the N c factor from small and large-scale foundations. In this paper, experimental work is performed on a model footing in remolded clay, and a finite element analysis is performed using Plaxis program for undisturbed and remolded clay, from the results of this study, it can be observed that the N c factor should be normalized with the footing width. The N c factor for small-size footing is lower than large-size and in the range between (3 to 4.5), while for a large-size foundation, the N c factor value depends on the foundation size and starts from (4.5) and reaches about (6.5). The N c factor equals about (2.4) for small model footing in remolded clay and this value is considered outside of the suggested range which is (4 to 6.18) for fully saturated clay at undrained conditions.