FORMULATION OF EQUIVALENT STIFFNESS FOR SEMI-INFINITE ELASTIC SUBGRADE AND ITS APPLICATION

Equivalent stiffness equations in the normal and tangential direction at the bottom and walls of a semi-infinite elastic ditch were formulated by employing the principle of energy equivalence and Mindlin’s displacement equations in a semi-infinite elastic body subject to a concentrated force acting in the interior of the semi-infinite elastic body. Similar equivalent stiffness equations were formulated by Boussinesq’s and Cerriti’s displacement equations due to a concentrated force acting on the surface of a semi-infinite elastic body. Equivalent stiffnesses pertinent to a wide range of soil have been determined by these equivalent stiffness equations. Finally, some applications in analyzing the interactions between the superstructure and the foundation and the subgrade of tall and super tall buildings were illustrated by examples.