Formulation of a Bearing Capacity Equation for a Circular Footing with Vertical and Inclined Loads on Layered Sand

This research work provides a bearing capacity equation for a circular footing placed on dense sand overlying loose sand and subjected to vertical and inclined loading, utilizing the limit equilibrium followed by the projected area approach. For the parametric study, the variables include upper dense sand layer thickness ratio (0.5 to 2.00), friction angle of upper dense sand (41° to 45°) and lower loose sand layer (31° to 35°), and applied load inclination (0° to 30°). The highest and lowest increases in bearing capacity are reported for friction angle combinations of 45°–35° and 41°–31° for various thickness ratios, respectively. For load inclinations of 0°, 10°, 20°, and 30°, bearing capacity is reduced by 43.51%, 72.17%, 85.64%, and 22.62%, 48.56%, 62.17% for friction angles of upper dense and lower loose sand layer combinations of 45° and 35° and at a thickness ratio of 0.5 and 2.0. Considering finite element results, the average deviation of the bearing capacity derived from the suggested equation at surface footing is 7%, 5%, 22%, and 23% for 0°, 10°, 20°, and 30° load inclinations, respectively. The proposed bearing capacity equation yield results that are compared with the available literature, with average deviations of 62%, 50%, 36%, and 36% for load inclination values of 0°, 10°, 20°, and 30°, respectively.