Ultimate Bearing Capacity of Square/Rectangular Footing on Layered Soil

Abstract

As per the literature the developed bearing capacity equations consider homogeneous soil beneath the footing. But in actual practice the soil below the footing is anisotropic and mostly layered. Therefore a layered profile of soil must be considered while deriving equation for the footing resting over layered soil. The paper present the bearing capacity equation for square/rectangular footing resting over layered soil using punching shear failure mechanism following projected area approach. At ultimate load punching shear mechanism has been adopted. The punching shear failure surface developed in the dense sand has a parabolic shape when full mobilization of shear force into the failure surface is taken into consideration. For analysis, it is considered that a frustum of the pyramid is formed in dense sand below the footing which is considered to be a linearized curve. The bearing capacity expression is derived considering certain assumptions. Stresses acting on the part of the pyramid are determined and by applying the integration for whole pyramid the bearing capacity equation is derived using the upper and lower layer properties as boundary limit. Finally the parametric study is carried out and the results are compared with the equations of the square/rectangular footing available in the literature.