This work deals with the types of nonlinearities of the sea bed ground, those arising in offshore pile activities. The iteration methods of nonlinear ground computer calculation were proposed. The modification of Murzenko" s model (1966) was given with the account of plastic strenthening-disstrenthening and. dilatation. This nonlinear-elastic approach is an effective one in solving the problems when offshore platforms" and port facilities" design takes large pile displacements into an account. The results of calculations of test experiments showed a satisfactory convergence.
Steel tube pile foundations are widely used for port hydro technical construction and for shelf platform erections for oil-gas extraction. The piles accept considerable horizontal loads from its upper part exerted by waves and ice. Calculation and pile foundation design techniques are highly requires because of the high costs and reliability of offshore structures. Lengthy piles and complex variable geological conditions give rise to a set of nonlinear factors affecting "the pile-ground" system interaction. It" s very important to take into account the pile disconnection and its sliding along the ground, pile spatial work along with formations of diverse stress states, pile group effect, in the ground. The paper presented describes the techniques of ground rigidity calculations required for pile evaluation accounting physical and geometrical nonlinearities. The techniques developed afford to combine the calculations of "the upper structure - pile group - ground".
At large pile displacements an immence deformation is developing in the ground, and the hypothesis accepted small deformations becomes untrue. Here it is used the non-linearelastic approach based on nonlinear dependence between stresses and strains taken to be common in all points in the ground rook. Elastic and non-elastic deformations are not divided and empiric "stress - elastic-plastic deformation" relationship is used.
