Analysis of soil penetrometer using Eulerian finite element method

Abstract

This thesis investigates the use of an Eulerian Finite Element (EFE) method for modeling penetration in soils. The formulation decouples material and nodal points displacements such that soil flows through a fixed finite element mesh. This approach eliminates problems of mesh distortion associated with conventional Lagrangian formulations but requires special procedures to convect the soil constitutive law and prevent numerical diffusion. The current analyses use the program DiekA, developed at the University of Twente in the Netherlands. Detailed calculations have been performed to investigate the effects of elements size and load/time step size on the stability and accuracy of the numerical simulations. Computed results for undrained penetration in homogeneous clays are similar to prior predictions from approximate steady state formulations such as the Strain Path Method. Further calculations for two-layer systems illustrate the potential of the Eulerian formulation to handle realistic layered soil profiles. A more limited study confirms the complexity of drained penetration in sands, where the predicted tip resistance is affected by soil friction and dilation angles, in situ stresses, and moduli. Further study is needed to establish the role of interface friction and lateral earth pressure. The results in the thesis present a first step towards implementation of more advanced effective stress soil models in EFE analyses of penetration in layered soils.