Numerical Analyses of Dip-Slip Fault Rupture-Suction Bucket Interaction
Author
Papavasileiou, Vasileios
Term
4. term
Education
Publication year
2021
Submitted on
2021-06-10
Pages
91
Abstract
This thesis examines how dip-slip fault rupture affects tripod suction bucket foundations for offshore wind turbines. Framed by the question “What is the effect of dip-slip fault rupture on tripod suction bucket foundations?”, the work employs 3D finite element analyses in PLAXIS 3D using the Hardening Soil Model with small-strain stiffness. The numerical model is verified by reproducing free-field responses for both normal and reverse fault ruptures and comparing them against published data. A subsequent parametric study analyzes a tripod suction bucket foundation subjected to reverse fault rupture, with the three legs positioned so that the free-field rupture would emerge beneath each bucket in turn. Two geometries are considered: L/D = 1 (length and diameter of 6.25 m) and L/D = 0.5 (skirt length 3.25 m, diameter 6.5 m). The soil response is evaluated through patterns of plastic shear strain and settlements, and the foundation’s displacements, rotations, and forces are quantified for each bucket. Findings indicate that the presence of the foundation influences rupture propagation and that the tripod must resist horizontal offsets, rotations, and large loads induced by the fault. The most adverse case occurs when the rupture interacts with the middle bucket, which experiences the largest loads and rotations. Reducing skirt length (lower L/D) proves beneficial, as it does not increase tilt or displacement while reducing the imposed loads. The thesis highlights the need for further studies to clarify the complex mechanisms of dip-slip fault rupture–suction bucket interaction.
Denne afhandling undersøger, hvordan en dip-slip forkastningsbrud påvirker tripod sugefundamenter (suction buckets) til offshore vindmøller. Med udgangspunkt i spørgsmålet “Hvad er effekten af dip-slip forkastningsbrud på tripod sugefundamenter?” udføres numeriske 3D-finite element-analyser i PLAXIS 3D med Hardening Soil Model med småtøjningsstivhed. Modellen valideres ved at genskabe frifeltrespons for både normal- og reverse-forkastningsbrud og sammenligne med publicerede resultater. Herefter gennemføres en parametrisk undersøgelse af et tripod sugefundament udsat for reverse-forkastningsbrud, hvor de tre ben placeres, så frifeltbruddet ville fremkomme under hver enkelt bucket. To geometrier analyseres: L/D = 1 (længde og diameter 6,25 m) og L/D = 0,5 (skørtets længde 3,25 m, diameter 6,5 m). Jordens respons vurderes via udbredelse af plastisk forskydningstøjningsfelt og sætninger, mens fundamentets forskydninger, rotationer og laster kvantificeres for hver bucket. Resultaterne viser, at fundamentets tilstedeværelse påvirker brududbredelsen, og at tripod’en udsættes for vandrette forskydninger, rotationer og store laster som følge af forkastningen. Den mest ugunstige situation opstår, når bruddet interagerer med den midterste bucket, hvor de største laster og rotationer optræder. En reduktion af skørtets længde (lavere L/D) er fordelagtig, idet den ikke øger hældning eller forskydning af konstruktionen og samtidig reducerer de påførte laster. Afhandlingen peger på behov for yderligere studier for at belyse den komplekse mekanisme ved interaktion mellem dip-slip forkastningsbrud og sugefundamenter.
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