Insight into numerical characteristics of embedded finite elements for pile-type structures employing an enhanced formulation

A number of problems encountered in the field of computational geotechnics requires the modelling of numerous pile-type structures embedded in a three-dimensional soil continuum. Traditional modelling approaches to this problem result in computational costs that must be regarded as unbearable for most practical purposes. As an attractive alternative, we propose an enhanced embedded FE model with implicit interaction surface (EB-I) where coupling between the contacting domains is realized by an implicit surface-to-volume (2D-to-3D) coupling scheme. As a novelty, the latter implements a non-linear interface constitutive model that allows for explicit consideration of endpoint interaction , but does not represent a constraint for the solid mesh generation. As the slender structure is discretized employing the Timoshenko beam theory, shear deformability is explicitly considered, as opposed to earlier EB-I-type models reassessed in this paper. The credibility of the proposed EB-I is numerically validated on the basis of comparative studies. It is found that the 2D-to-3D coupling scheme generally improves the well-posedness of the resultant global stiffness matrix, making the proposed EB-I computationally competitive to geometrically simplified line-to-volume coupling schemes. Future lines of research are carefully addressed throughout this work and include the normal stress recovery technique as well as applications to large-scale simulations.