Soil-Structure Interaction in Cohesionless Soils during Monotonic Loading
Author
Sjelmo, Åsmund
Term
4. term
Education
Publication year
2012
Abstract
Denne afhandling undersøger jord–konstruktion-interaktion i kohæsionsfri jord under monoton belastning med særligt fokus på sugekassefundamenter til offshore vind. Formålet er at skabe et foreløbigt eksperimentelt grundlag for at vurdere den udrænede respons ved hurtige/impulsive laster fra designbølger. Fire småskalaforsøg blev gennemført med monoton belastning ved stigende belastningshastigheder fra 0,01 til 10 mm/s (tidobling mellem hvert forsøg). En hydraulisk aktuator pålagde forskydning, en lastcelle målte den mobiliserede last, otte poretryksmålere registrerede udviklingen af negative poretryk, og deformationsmålere registrerede vertikale og horisontale bevægelser samt rotationer. Resultaterne viser en stærk sammenhæng mellem belastningshastighed og dannelse af negative poretryk, hvilket påvirker den mobiliserede last og dermed bæreevnen, i overensstemmelse med de observerede bevægelser og rotationer. For at klassificere responsen som drænet, delvist drænet eller udrænet blev afdræningstiden t90 både beregnet og målt; uoverensstemmende resultater indikerer, at afdræning under belastning bør undersøges nærmere, gerne numerisk. Fundene understreger, at hastighedsafhængig jord–konstruktion-interaktion er en vigtig designfaktor for sugekassefundamenter i sand under monoton belastning.
This thesis examines soil–structure interaction in cohesionless soils under monotonic loading with a focus on bucket foundations for offshore wind. The aim is to provide a preliminary experimental basis for assessing undrained response under rapid/impulsive design-wave loading. Four small-scale monotonic loading tests were performed at increasing loading rates from 0.01 to 10 mm/s (tenfold increments). A hydraulic actuator imposed displacement while a load cell recorded mobilized load; eight pore-pressure transducers tracked the development of negative pore pressures, and displacement sensors captured vertical and horizontal movements and rotations. The results indicate a strong correlation between loading rate and the generation of negative pore pressures, which affects mobilized load and hence capacity, consistent with the observed displacements and rotations. To classify the response as drained, partially drained, or undrained, the drainage time t90 was both calculated and measured; inconsistent outcomes suggest that drainage during loading should be investigated further, preferably through numerical analyses. The findings highlight rate-dependent soil–structure interaction as a key design consideration for bucket foundations in sand under monotonic loading.
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