Background/motivation of the project

Because of the soft soil conditions, the majority of engineered structures in the western part of the Netherlands is founded on pile foundations. In simple terms, a pile is a slender structural element (steel or concrete column) that uses soil-structure interaction to transfer loads to deeper stronger soil layers. The Port of Rotterdam Authority (POR) and Rijkswaterstaat (RWS) are amongst the biggest consumers of piles in the Netherlands. Numerical models capable of modelling pile installation have not yet been developed and thus designers rely on semi-empirical design approaches, using pile class factors linked to in-situ Cone Penetration Test data. Despite the lack of incidence of pile failures, changes to pile design standards (as of January 1st 2017) has resulted in the installation of longer or more piles and increases in both construction time and associated installation risks. The direct impact is an estimated increase in construction costs of 10-20% for all deep foundation projects in the Netherlands. From an economic and environmental perspective, it is attractive to investigate the ‘hidden’ safety factors and incorporate them in the design standards, avoiding oversized pile foundations. Therefore, the mechanisms that govern pile behaviour must be understood. The project is exploring numerous aspects of pile behaviour in sand through the execution and analysis of field tests, laboratory testing and numerical modelling. This comes with the aim of refining the Dutch pile design method and making a global contribution towards the understanding of pile behaviour.


Project goals

This proposal will develop a holistic solution which will improve involving field testing, lab and numerical modelling in conjunction with advanced statistical approaches to provide accurate calculation procedures to determine the axial capacity of a pile.

The aim of the project is to investigate the following aspects:

  1. pile class factors (αp, αs)
  2. qc averaging methods for base resistance
  3. friction fatigue effects on shaft resistance of displacement piles
  4. limiting resistances for assessing pile base and shaft capacities
  5. pile ageing
  6. effects of residual loads as result of pile installation
  7. natural soil variability

Within these aspects, many questions and uncertainties exist. For instance, is a constant αs appropriate for displacement piles where friction fatigue may dominate? Can the limiting base stress and/or shear stress be set at a higher level for normally consolidated sands based on experimental evidence? Is the correlation between αp and penetration into the sand a result of the current averaging method (4D/8D) and should a more appropriate method become adopted? Other important mechanisms to consider are the time-related increase of pile capacity in displacement piles known as pile ageing, the influence of installation conditions across all pile types and also the effect of residual stresses generated during pile installation. Notwithstanding, understanding the influence of these effects is challenging, requiring a multi-faceted approach through the use of field testing, laboratory and numerical simulation.


Partners

The TKI-project Improved Axial Capacity of Piles in Sand is a joint project of:

  • Deltares
  • Technische Universiteit Delft
  • Rijkswaterstaat
  • Havenbedrijf Rotterdam
  • Nederlandse Vereniging Aannemers Funderingswerken (NVAF)
  • Fugro
  • Gemeente Rotterdam


Results (still expanding)



  • No labels

Disclaimer