Arbitrary Lagrangian-Eulerian(ALE) Based Finite Element Simulation Of Displacement Pile In Sand

As one of the important foundations,driven piles are widely used in supporting ports,major bridges,offshore energy platforms,wind turbines and so on.Predicting their limiting capacities and load-displacement behavior under a range of different loading conditions(static,cyclic,axial and lateral load)is critical to many such engineering applications.The ultimate capacities of piles can be predicted through static load tests,but these tests are difficult and expensive to be carried out in offshore engineering.Recent static load test database studies have shown that CPT(cone penetration test)-based design methods can offer reliable estimation for the axial capacities in sands,but the precision and accuracy of these methods still remain to be improved.Obtaining the stresses,displacements and strains of sand accurately during pile penetration can help understand the pile-soil interaction mechanism deeply,reveal the bearing behavior of driven piles,and provide the evidence for establishing a more reasonable capacity calculation method.The Arbitrary Lagrangian-Eulerian(ALE)method available in Abaqus has been employed to simulate highly instrumented calibration chamber tests in which closed-ended piles are penetrated into sand.The stress regime around pile shaft during penetration has been obtained.In addition,the displacement and strain paths of sand have been obtained by using tracer particle method.ALE method can solve mesh distortion that frequently occurred during pile penetration simulations,and tracer particle method can effectively solve the problem of displacement output caused by remeshing.Numerical results of the radial,circumferential and vertical stresses developed during penetration show that sand stresses depend on the relative position to pile tip(vertical distance h/R,radial distance r/R).Immediately below the pile tip,the displacement vectors are nearly vertical,while further away from the pile tip,the displacement vectors have a larger radial component.A transition zone is observed where the displacement vectors rotate from the vertical to the radial direction.The sand undergoes vertical compression and radial extension at the beginning of penetration.When the pile tip passes,the strain direction reverses and radial compression and vertical extension dominate.The simulation results of stresses,displacements and strains are in broad agreement with experimental results,which indicates ALE finite element method is appropriate for pile penetration simulation.