Dynamic analysis of wave propagation due to pile installation using numerical simulations

Abstract

This paper discusses the results of a preliminary study of numerical simulations investigating wave propagation during the installation of in-situ driven concrete piles (type Franki pile). Franki piles are cast-in-situ piles that are installed by driving a steel casing into the ground using heavy ramming of a cylindrical hammer. It is a dynamic pile installation process where the hammer directly transfers the dynamic forces to the soil within the installation tube causing high wave propagation through the soil. When installed in groups, the vibrations caused by the driving process of one pile may result in damages to the early-age concrete of adjacent piles. Such complex soil-structure interaction problems can be represented numerically by modelling the pile installation process using realistic parameters (ground conditions, ramming energy etc.). As a preliminary study, a single pile installation is simulated using the FEM software Abaqus. The simulation is based on a Coupled Eulerian-Lagrangian (CEL) approach where the soil is modelled using the hypoplastic constitutive model. The aim is to investigate parts of the installation process regarding the effect of discrete hammer drops. Within the CEL method, the pile hammer is modelled as a Lagrangian part, while the soil is treated as a Eulerian part. The Lagrangian part can move freely through the Eulerian mesh until it encounters Eulerian material. As a result of the simulations, a realistic amplitude pattern can be observed. This can be used as basis for the next phase of the study where the numerical analysis will be validated with the data recorded from field tests.