Advanced Constitutive Models for Offshore Applications on Suction Pile Foundation

Advanced Constitutive Models for Offshore Applications on Suction Pile Foundation

Liao, Kan (TU Delft Mechanical, Maritime and Materials Engineering; TU Delft Offshore Engineering)

Metrikine, A. (mentor)
Pisano, F. (graduation committee)
Tsouvalas, A. (graduation committee)
Askarinejad, A. (graduation committee)
Dijkstra, O.J. (graduation committee)
Rebollo, J. (graduation committee)

Delft University of Technology

Offshore and Dredging Engineering

2020-11-30

The suction pile foundation is a large steel cylinder with an open end and sealed top. This foundation type is widely used in the oil&gas industry and wind energy. Experimental investigation and numerical investigation are the main two methods to understand the performance of the suction bucket foundation. The experimental studies are important and basal for design, but it is time-consuming and costly compared to numerical studies. However, the accuracy of the finite element method(FEM) in geotechnical problems highly depends on whether the soil constitutive models can correctly predict soil behaviour. In our study, we investigate four constitutive models: the Mohr-Coulomb model, the hardening soil model, the NGI-ADP model, and the hypoplastic model. To some extent, advanced soil models can better present soil behaviour than traditional ones. However, it needs more laboratory test data to calibrate the advanced model parameters. The Mohr-Coulomb(MC) model is the most common soil model, which is an isotropic model include few parameters. The hardening soil model exceeds MC model by introducing the stress-dependent stiffness and distinguishing between loading and reload- ing. The NGI-ADP model is mainly used for undrained analysis, and it is an anisotropic model which can exact match with undrained shear strength and stiffness for various failure surfaces. The hypoplastic model has no distinguishing between elastic and plastic strain. It is an inelastic(dissipative) and incrementally nonlinear soil model without the requirement of a yield surface. A soil investigation report of Block 17 offshore Angola is used to calibrate the aforementioned constitutive models. The cone penetration test(CPT), ball penetration test(BPT) and a series of laboratory tests(i.e. direct simple shear, triaxial, and oedometric tests) are exacted from the soil report and interpreted for calibration. Parameter determination procedures for constitutive models are explained. Subsequently, the consistency of the parameter set is validated by numerical simulation of direct shear and triaxial tests. The numerical experiments for a suction pile foundation whose out diameter equals four and aspect ratio equals three are carried out. Four loading cases(i.e. horizontal, vertical tension, vertical compression and vertical-horizontal-moment (VHM) combining loadings) are included in the finite element analysis. The suction pile performance(i.e. deformation and capacity) are compared among the using of different constitutive models. Additionally, the compliance matrices of the suction pile for different soil models are obtained for the structural engineer. The analyses indicated that NGI-ADP model could be the best choice for undrained analysis of suction pile foundation. This model has a robust calibration process, and well simulate the anisotropic strain-stress relationship. Additionally, the finite element results are conservative when modelling by NGI-ADP model. However, this model can not predict the right pore pressure build-up and stress-path, which may be improved by using a well-calibrated hypoplastic model.

Constitutive Model
NGI-ADP
Finite Element Method
PLAXIS 3D

https://doi.org/10.4233/uuid:93aeae21-dd31-4175-b48f-3e30a70d304d

Student theses

master thesis

© 2020 Kan Liao