Pile-Soil Interaction During Installation in Carbonate Sand
Author
Pariyar, Nabin
Term
4. term
Education
Publication year
2026
Submitted on
2026-11-19
Abstract
This thesis investigates how particle breakage governs the drained mechanical behaviour of a crushable carbonate sand from the South China Sea and how this process affects the installation of driven piles in such deposits. The work is divided into an experimental part and a numerical part. In the experimental programme, six consolidated drained triaxial tests are carried out at nominal relative densities of 30, 60 and 80 % and effective confining stresses of 200 and 500 kPa. These tests are used to analyse strength, dilatancy and stiffness, while particle breakage is quantified by sieve analyses and microscopic examination. The results show that peak strength is controlled by dilatancy, which is suppressed at higher stress levels due to grain crushing, and that the constant-volume friction angle is approximately 41°. The extent of breakage is found to be governed mainly by the initial density rather than by the plastic work input. In the numerical part, the laboratory data are used to calibrate a breakage-enhanced wave equation model of pile driving. The simulations indicate that particle breakage reduces soil resistance, particularly at the pile toe, but that the crushed soil also increases the elastic toe displacement (toe quake), so the pile does not necessarily become easier to drive. Overall, the study improves understanding of pile–soil interaction in carbonate sands and provides a basis for more reliable assessments of drivability, blow count and stresses during pile installation.
Dette speciale undersøger, hvordan partikelbrud styrer den drænede mekaniske adfærd af en knusbar karbonatsand fra Det Sydkinesiske Hav, og hvordan dette påvirker installationen af nedrammede pæle i sådanne aflejringer. Projektet er opdelt i en eksperimentel del og en numerisk del. I den eksperimentelle del udføres seks konsoliderede, drænede triaxialforsøg ved nominelle relative densiteter på 30, 60 og 80 % samt effektive indeslutningstryk på 200 og 500 kPa. Forsøgene bruges til at analysere styrke, dilatans og stiffness, og partikelbrud kvantificeres ved sigteanalyser og mikroskopisk undersøgelse. Resultaterne viser, at toppstyrken er styret af dilatans, som undertrykkes ved højere spændingsniveauer på grund af kornknusning, og at friktionsvinklen ved konstant volumen er omkring 41°. Brududviklingen styres primært af den initiale densitet frem for det plastiske arbejde. I den numeriske del anvendes laboratorieresultaterne til at kalibrere en brudforbedret bølgeligningsmodel for pæleramning. Modelleringen indikerer, at partikelbrud reducerer jordmodstanden, især ved pælespidsen, men at den knuste jord samtidig øger spidsens elastiske forskydning (toe quake), så installationen ikke nødvendigvis bliver mere let. Tilsammen bidrager studiet til en bedre forståelse af pæle–jord-interaktion i karbonatsand og giver grundlag for mere pålidelige vurderinger af drivbarhed, slagantal og spændinger under pæleinstallation.
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Keywords