Ultimate Bearing Capacity of Circular Footing on Layered Soil

The bearing capacity equations developed in literature consider homogenous soil below the base of the footing. But in actual practice soil mass is non homogenous and anisotropic. Therefore, while deducing the expression of the bearing capacity in case of circular footing resting over layered deposits, one has to take into account for a layered profile of soil. The paper presents the theoretical equation for the bearing capacity of a circular footing resting on layered soil profile using punching shear failure mechanism following projected area approach. The punching mechanism has been adopted while at ultimate load the mechanism of punching shear failure developed in dense sand has a parabolic shape when full mobilization of shear force into failure surface is taken into consideration otherwise punching failure is the actual failure while punching in the lower layer continues to a larger extent depending upon the loading at interface. For the analysis part frustum is considered to be a linearize curve for the actual shape of failure and a bearing capacity expression is deduced adopting certain assumptions. Stresses acting on the frustum have been analyzed and after series of integration bearing capacity equations is generalized. The proposed bearing capacity equation has been derived as a function of upper and lower layer properties. Finally the parametric study is carried out. The results of the parametric study were compared with the available equations in literature for the circular footing. Further, the results were validated with the experimental results reported in literature by other investigator.

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