Estimation of horizontal subgrade reaction coefficient by inverse analysis

The subgrade reaction coefficient of a foundation soil in an open pier has been identified using an extended Kalman filter (EKF) based on measurements taken during in situ horizontal loading tests on a pile. For the in situ tests, the surface clay layer was removed, and the diluvial clay layer was replaced by a rubble mound to reduce the length of the pile above the surface of the foundation deposit. The tests were carried out for both the existing diluvial clay deposit and the replacement rubble mound for purposes of comparing the identified subgrade reaction coefficients in Euler–Bernoulli’s beam equation with nonlinear springs. The measured deflection and the bending moment determined in the tests were used as input data for the inverse analysis. Analysis revealed that the identified subgrade reaction coefficient of the rubble mound is less than that of the diluvial clay under the same level of loading. The numerical results will provide useful information for the future design of open piers and their foundations.