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Abstract: During installation of a displacement pile, the soil around the pile is heavily distorted. The resulting changes in soil density and stress state around the pile determine the ultimate pile capacity. In most finite element models, the installation phase is not explicitly modelled. In this paper the full installation phase is modelled in two different ways, in a numerical code capable of large deformations. In the first approach the pile is fixed and the soil flows around the pile. This modelling approach requires somewhat unrealistic boundary conditions and requires that the results for the pile installation are for a non-stationary phase of the calculation, whereas formally only the values at the stationary full penetration phase are reliable. A second modelling approach has been introduced to overcome these limitations. In the new approach the initial conditions are set as a stress level, increasing linearly with depth, resulting from a gravity loading stage, and a stepwise penetration of the pile into the soil is prescribed. This approach updates the geometry of the problem domain and keeps updating the convective terms in a fixed mesh. Results are compared with experimental results from centrifuge tests. Although both models show the development of large effective vertical stress below the pile base and porosity change near the pile shaft, also differences with the experimental results are found. Especially the stiffness response during pile installation is difficult to model correctly. [Copyright &y& Elsevier]

This paper presents the determination of virtual micro-forming limit diagrams from two types of numerical simulations based on the finite element method: one with modelling of the full tool for micro-deep drawing and a thin blank with geometric imperfections, based on a defined roughness; and a second called "reduced simulation" where different deformation paths were simulated with appropriate boundary conditions by introducing the same type of geometric imperfections on aluminium 1050A (99.5%). A new test for detecting the onset of necking, called the "change of slope" criterion has been defined. Several methods based on histograms to represent the distributions of major and minor strains, have been used to determine the strain at the onset of necking. The numerical micro-forming limit diagrams (MFLD) were then compared to one obtained experimentally. [ABSTRACT FROM AUTHOR]