Mortar contact discretisation methods incorporating interface models based on Hypoplasticity and Sanisand: Application to vibratory pile driving

Abstract

A segment-based mortar contact discretisation technique for the analysis of hydro-mechanically coupled dynamic processes with quadratically interpolated finite elements and incorporating advanced interface models is presented. The proposed mortar technique divides the surface pair into finite segments with arbitrary order of integration, allowing, opposite to simpler contact discretisation techniques, for an exact integration of contact stress. The performance of the segment-based in comparison to a (simpler) element-based mortar technique is evaluated by means of simulations of vibratory pile driving model tests in water-saturated sand. For the mechanical modelling of the soil–pile interface either a simple Coulomb friction model, the hypoplastic model with intergranular strain extension, or the elastoplastic Sanisand model is utilised. It is concluded that the segment-based mortar method is superior to the element-based technique in terms of numerical stability if the number of integration points per segment is larger than the number of integration points per element edge for the element-based technique. However, the techniques are found to perform similarly when a comparable number of integration points is used. While the implementation of the segment-based method is found to be more complex in general, the implementation of parallelisation is simpler compared to the element-based mortar method.