Finite Element Analysis of The Undrained Bearing Capacity Factor Nc of Strip Footing

Abstract—This study explores the influence of soil weight and embedment depth on the bearing capacity factor Nc for strip footings using finite element analysis. Two scenarios were analyzed: a soil body with weight and a weightless soil body, with embedment depths ranging from 0 to 5 meters. The results demonstrate that soil weight significantly increases the Nc factor compared to the weightless case, indicating that the Nc factors proposed by Terzaghi (1943) and Meyerhof (1963), based on weightless soil assumptions, are conservative, particularly for deeper foundations. The Nc factor increases with embedment depth up to a normalized depth (Df/B) of 3.0 for soil with weight, after which it declines, while it stabilizes beyond Df/B=3.0 for weightless soil. Comparisons with past studies show that the derived Nc factors align closely with Meyerhof (1963) and Salgado et al. (2004) for shallow depths but diverge for deeper embedment, exceeding Terzaghi’s and Meyerhof’s values while remaining lower than Skempton (1951) and Salgado et al. (2004). These findings underscore the importance of accounting for soil weight in bearing capacity calculations, particularly for deeper foundations. This work contributes to refining bearing capacity theories and highlights the critical role of soil weight and embedment depth in foundation design. Keywords: Undrained bearing capacity, Nc, Terzaghi, Meyerhof, finite element analysis