PFEM Analysis of Installation Effects on Axial Performance of Jacked Piles in Chalk

TY - GEN

T1 - PFEM Analysis of Installation Effects on Axial Performance of Jacked Piles in Chalk

AU - Ciantia, Matteo O.

AU - Lei, Jiangtao

AU - Monforte, Lluís

AU - Arroyo, Marcos

AU - Gens, Antonio

PY - 2022/2/15

Y1 - 2022/2/15

N2 - Chalk covers areas of the UK and is widespread under the North and Baltic Seas where OWT are currently being installed and where future offshore expansion will be sited. Large piles are often driven in chalk to support OWT and other onshore infrastructure. The installation of pile foundations causes the intact rock surrounding the pile to crush and deteriorates into a putty characterised by a mechanical behaviour very different from the intact chalk. Such complexity is the underlying reason for inadequate current design guidance for pile in chalk which currently relies on empirical methods or partial (wished-in-place) numerical simulations. Installation effects such as grain crushing and pore pressure generation are conservatively estimated (if considered at all), as the change of rock properties around the pile during the installation process cannot be easily quantified. In this paper it is shown how advanced numerical modelling can be used to capture such damaging effects and hence guide the design of pile foundations in chalk. The coupled hydro-mechanical effects developing during pile installation are investigated numerically using a robust and mesh-independent implementation of an elasto-plastic constitutive model for chalk recently reformulated in large strains. The model implemented into an open source Particle Finite Element (PFEM) code, is able to capture the damage of the rock until the formation of a chalk putty layer around the shaft of a small diameter pile. Installation effects are highlighted by comparing the axial performance between wished in place piles and piles which considered the full installation process. The numerical results are then used to critically address the limitation of current design specifications of displacement piles in chalk.

AB - Chalk covers areas of the UK and is widespread under the North and Baltic Seas where OWT are currently being installed and where future offshore expansion will be sited. Large piles are often driven in chalk to support OWT and other onshore infrastructure. The installation of pile foundations causes the intact rock surrounding the pile to crush and deteriorates into a putty characterised by a mechanical behaviour very different from the intact chalk. Such complexity is the underlying reason for inadequate current design guidance for pile in chalk which currently relies on empirical methods or partial (wished-in-place) numerical simulations. Installation effects such as grain crushing and pore pressure generation are conservatively estimated (if considered at all), as the change of rock properties around the pile during the installation process cannot be easily quantified. In this paper it is shown how advanced numerical modelling can be used to capture such damaging effects and hence guide the design of pile foundations in chalk. The coupled hydro-mechanical effects developing during pile installation are investigated numerically using a robust and mesh-independent implementation of an elasto-plastic constitutive model for chalk recently reformulated in large strains. The model implemented into an open source Particle Finite Element (PFEM) code, is able to capture the damage of the rock until the formation of a chalk putty layer around the shaft of a small diameter pile. Installation effects are highlighted by comparing the axial performance between wished in place piles and piles which considered the full installation process. The numerical results are then used to critically address the limitation of current design specifications of displacement piles in chalk.

KW - Chalk

KW - GPFEM

KW - Monopiles

KW - Installation effects

KW - Numerical Modelling

KW - Axial response

KW - PFEM

UR - https://www.scipedia.com/public/Ciantia_et_al_2022a

U2 - 10.23967/particles.2021.004

DO - 10.23967/particles.2021.004

M3 - Conference contribution

SP - 1

EP - 8

BT - Proceedings of the VII International Conference on Particle-Based Methods

A2 - Wriggers, P.

A2 - Bischoff, M.

A2 - Oñate, E.

A2 - Düster, A.

A2 - Zohdi, T.

PB - Scipedia

T2 - VII International Conference on Particle-Based Methods

Y2 - 4 October 2021 through 6 October 2021

ER -