This paper presents the results of a series of field experiments performed to study the effect of installation method on the shaft resistance developed by a pile installed in soft clayey silt. Tests were performed on piles that experienced different levels of cyclic loading during installation. The test results indicate that the radial total stress, pore-water pressure, and shear stress on the pile shaft during installation were strongly affected by the installation procedure; all three were found to increase when the jacking stroke length used during installation increased (or the number of cyclic load applications decreased). However, equalized radial effective stresses that control the long-term pile shaft capacity were found to be insensitive to the installation method. A simple expression that requires the results of a cone penetration test, laboratory measurements of the interface friction angle, and the pile geometry is proposed to calculate the shaft resistance.@en

This paper presents the results of a series of field tests performed to study the effect of soil plugging during installation on the base resistance developed by an openended (pipe) pile in clay. Three instrumented pipe piles were installed in soft clay, and the installation resistance and soil plug development were recorded. The tests revealed that the annular base resistance was equal to the cone penetration test qc resistance and was independent of the soil plug development. In contrast, the soil plug resistance increased from a minimum when the pile was fully coring to a maximum when the pile was fully plugged. A simple expression is proposed that links the plug resistance to the cone penetration test qc value at the specified depth and the incremental filling ratio value developed during installation. This expression is shown to provide reasonable estimates of the plug resistance developed by a large-diameter pipe pile driven into stiff to hard clay in the North Sea. The proposed relationship will be particularly useful for modelling the installation resistance of monopile foundations.@en

The paper presents the results of static tension load tests performed on four closed-ended and one open-ended pile installed at a soft Clay test bed site. The piles sizes ranged from 4m long, 73mm circular steel piles, to 6m long, 250mm square concrete piles. The paper compares the average shaft resistance measured after full and partial equalisation of excess pore pressures set-up during installation, and considers the effect of installation mode, pile type and pile end condition (open or closed ended) on the piles shaft resistance. A number of design approaches from the literature were used to estimate the capacity of the piles at the site. The performance of these is briefly discussed.@en

This paper describes the results of field tests carried out using instrumented piles installed in a very soft estuarine silty clay deposit at Kinnegar, Belfast. The site has been used for a number of years as a geotechnical test bed site and has been comprehensively characterised using both numerous in-situ tests and by mean of an extensive laboratory test program. The instrumented pile used in the investigation was developed at University College Dublin and includes sensors which allow readings of both total radial stress and pore pressure during installation and load testing to be made at a number locations along the pile shaft and at the pile base. The tests were carried out to investigate the effect of pile length on the average shear stress mobilised during installation and load testing. The results are compared to other case histories reported in the literature.@en