Identification of modulus of subgrade reaction for a pile foundation

This paper deals with the identification of modulus of subgrade reaction n(h) far a sandy soil. The initial evaluation of n(h) is determined in the laboratory based on Terzaghi's method The evaluated value of n(h) is verified numerically by means of the finite element method. However, the results of numerical analysis in terms of the displacements did not match exactly to the experimental results. This-fact was attributed to an inadequately determined value of n(h). The difference between the results of numerical analysis and experimental outcomes formed the basis for identifying the true value of n(h) in the framework of sensitivity theory, The difference in horizontal displacement is associated with the first variation of lateral deflection, while the difference between the initially evaluated value of n(h) and its true value is related to the first variation of modulus of subgrade reaction n(h). All discrete points located on the load-displacement curves determined in the laboratory are examined in the framework of sensitivity analysis, Consequently the proposed identification method of n(h) is capable of determining both the tangent and the secant constant of modulus of subgrade reaction n(h).