Abstract: “The goal of this study is to prepare a new proposed method for the estimation of pile critical length in clayey soil for offshore structures. For this purpose the dolphin of Khor Al-Amaya berth No. 8 (in the Arabian Gulf, south of Iraq) is taking as a case study which subjected to dynamic load using the interface finite element method. A computer program has been written by Fortran 90 language to get the required solution. The (p-y), (t-z), and (q-z) curves which are adopted by American Petroleum Institute (API) are used to find normal, and tangential interface moduli and end bearing modulus. To get the required results, the Subspace Method is carried out for free vibration analysis and the Newmark method is adopted in direct integration time domain. The obtained results are compared with both elastic and Matlock and Reese solutions proved that the interface solution gives higher response values of vertical pile other than the two solutions because of the nonlinear effects of the inter”

Keywords: *Department of Civil Engineering / Basrah University-Iraq