LIMIT ANALYSIS ON EVALUATION OF LATERAL RESISTANCE OF PARTIALLY EMBEDDED PIPES WITH FRICTIONAL PIPE-SOIL INTERFACE

The occurrence of controlled lateral buckling in underwater pipes may be an efficient mechanism in order to relief high compressive stresses developed along its length. Thus, modelling this phenomenon is worthy to evaluate its formation. In the developed model the pipe is treated as a rigid body partially embedded on a deformable soil mass and in order to move laterally, the pipe must overcome the soil resistance and the friction between the soil and structure. This phenomenon is modeled under limit analysis theory and finite element method. Since the pipe movement is known, a limit analysis formulation with prescribed velocities is proposed as an alternative to the force prescription model. Moreover, the friction dissipation is included into limit analysis formulation. From limit analysis continuum formulation, the discretized formulation is derived under 2-D plane strain finite elements and the optimum conditions are solved by contraction and relaxation techniques and Quasi-Newton method. The contact problem is solved by condensation techniques and a complementary problem is solved by Lemke algorithm. By these techniques, the soil lateral resistance is evaluated and compared to frictionless solutions found in literature. Afterwards, the influence of friction coefficient between pipe and soil is considered in horizontal force calculation.