Numerical Analysis for The Response of Skirt Circular Shallow Footing Resting on Sandy Soil under Pure Vertical Dynamic Loads

Abstract

In this paper, the dynamic response of a circular skirt foundation resting on sandy soil subjected to pure vertical dynamic load was analyzed numerically using finite element software, PLAXIS 3D 2020. The linear elastic model was adopted to describe the behavior of the shallow concrete circular foundation with (1m) diameter and (0.2 m) thick and the soil underneath, with and without skit. Different skirt’s length to diameter ratios (L/D) (0.25, 0.5, 0.75, and 1.0), in addition to different skirt thicknesses (0.1, 0.15, and 0.2 m) were anticipated. A harmonic pure vertical load was applied on the foundation with an intensity of (10 kPa) at different frequencies of (10, 30, and 100) Hz. The results show that, in dry sand, skirts improve the foundation performance effectively by increasing its load carrying capacity and reducing the dynamic amplitude, particularly when the skirt (L/D) ratio becomes higher. Furthermore, increasing the applied load frequency decreases the dynamic amplitude due to increasing the inertia forces for both footing and underneath soil. However, the increase in the skirt’s thickness does not influence dynamic amplitude, and it can be neglected for design purposes.