In this paper a new soil resistance prediction method to study pile group -soil Interaction behaviour under quasi-static horizontal loading IS discussed. The soil is Inhomogeneous with elasto-viscoplastic behaviour. The soil model accounts for the nonlinearities such as slip page, plastic strengthening, pile group effect, consolidation. The offshore cylindrical piles with large deflections at the mud line (y/ro > 0.01) are considered. The Flow Line Method IS described for the estimation of kinematic fields around circular Pile segment. The principles presented here form a basis on which a numerical solution technique can be developed for pile-Soil-pile Interaction problem. The Flow Line Method assumes that the axial strain rate field around the pile can be estimated from the maximum normal stress field and relies on the lower bound (static) solution of the theory of plasticity, which IS found In the global coordinate system. Then we can estimate the shear strain rate and shear stress fields In the local coordinate system (Pile segment IS fixed) according to the upper bound (kinematic) solution. A successive approximations method for the mixed elasto - viscoplastic Indentation problem on the base of variational equations IS developed. The piles can be analysed by the finite element (FEM) or finite difference methods. A computer program DISC IS compact and unexpensive to allow parametric studies to be undertaken. There IS a good agreement between the computed and field observed values.
The large deflections of offshore Piles produce the complex physical and geometrical nonlinearities such as Pile group effect, slippage, consolidation and so on. Present guidelines assumes the nonlinear contact models (p-y curves) Which generally are based on the results of Pile load tests performed to deflection/diameter (y/2ro) ratios < 0.40 and at frequencies w< 0.5s-1(Codes of USSR Ministry at Gas Industry, 1985).