The context of this thesis is the installation of driven piles in clay. Pile driving is an installation method which consists of repeatedly striking the pile head with a mass until desired embedment is attained. Driving brings severe distortions to the soil which has to accommodate for the penetrating pile. At the end of installation, the soil is left in a distressed state, which progressively tends to equilibrium with time, leading to a change in pile capacity. This phenomenon referred to as pile set-up. The objective of this thesis was to implement a numerical model which could account for pile installation and subsequent set-up in clayey soils. Focus was placed on behaviour round the pile shaft. The particularity the developed model is that it accounts for the cycles of shaft-soil shearing occurring during driving. Supported by experimental evidence, the original model developed in this work outlines the following conclusions: • During installation, total stress at pile wall decreases with vertical distance from pile toe (the h/R effect) due to (a) stress relief away from the pile toe and (b) fatigue from the accumulation of driving blows; • After installation, the radial distribution of pore pressure presents a peak a few radii away from the pile shaft. This peak value increases with overconsolidation ratio (OCR) while the pore pressure at the pile wall decreases with OCR; • The shape of pore pressure distribution after installation leads to a short term minimum in radial effective stress (therefore in pile capacity) during set-up. Furthermore, the model yielded the following additional conclusions, which were outside of the scope of the available experimental data: • The soil effective stress response during installation and set-up is mainly governed by overconsolidation ratio, rather than soil strength or stiffness; • There is a critical hammer velocity for which the soil offers maximum adherence to the pile; • Although shaft capacity after set-up was comparable for the open-ended and the closed-ended piles, open-ended set-up time was four times shorter.(FSA - Sciences de l'ingénieur) -- UCL, 201
