The Effect of Aspect Ratio on the Shape Factors of Rectangular Footings on Sandy Soil

Abstract

The dimensional of the footing is crucial parameter affecting the ultimate bearing capacity and failure surface geometry. However, the recommendations found in the literature often conflict with one another. Therefore, in this study, rigorous parametric three-dimensional finite element analyses using PLAXIS 3D with the Hardening Soil (HS) model were conducted to examine the unit weight component of the shape factors (Sγ), the pressure-settlement responses and the failure mechanisms of rectangular footings with an aspect ratio (L/B), defined as the ratio of the length (L) to the width (B) of the footing, ranging from 1 to 10. These analyses were performed four relative densities (Dr) of the sandy soil ranging from 10% to 80%. The results revealed that Sγ values increased with the L/B ratio, peaking at L/B=1.5, followed by a decline as the L/B ratio continued to increase. An increase in the internal friction angle of the soil led to higher Sγ values. This behavior contradicts some earlier studies and is attributed to the three-dimensional interaction of the failure surface, failure surface geometry and displaced soil volume. Furthermore, non-linear regression analysis was performed to produce novel equations to predict Sγ for rectangular footings and unit weight component of the bearing capacity factor (Nγ) for strip footings in sandy soil, demonstrating strong agreement with FE results.

Keywords

• Shape factor
• aspect ratio
• shallow footing
• finite element analysis
• PLAXIS 3D

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