Problems with cast-in-situ concrete piles: A study on the possible causes of excessive bleeding

Master thesis (2020)

Authors

J.C. Beute Civil Engineering & Geosciences

Contributors

M. Korff (mentor)
J.H. van Dalen (graduation committee member)
S. Grunewald Concrete Structures - CEG (graduation committee member)
W. Broere (graduation committee member)
F.J.M. Hoefsloot (graduation committee member)
Faculty
Civil Engineering & Geosciences, Civil Engineering & Geosciences
Copyright: © 2020 Jeroen Beute
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Published Date

13-01-2020

Language

English

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Faculty

Civil Engineering & Geosciences

Abstract

First of all, an overview was created of different problems that can occur by the construction of cast-in-situ concrete piles, discussing the mechanisms that cause these problems. From the overview it was concluded that little information is present about the exact cause of excessive bleeding. Two possible causes were identified, excess pore water pressure in the surrounding soil caused by the pile installation and concrete stability, these are further researched. Comprehensive measurement data of the hydraulic head in an intermediate confined sand layer, during the installation of displacement piles, showed a consistent trend. During the descending phase a large increase in the hydraulic head was measured which can be described by volume displacement in the sand layer. In addition, a cumulative effect in the hydraulic head was found at the start of withdrawal of the temporary casing as the excess pore water pressure, resulting from the volume displacement, was not fully dissipated. During withdrawal, two additional pore water pressure increments can be distinguished. The direct increase starting from the onset of withdrawal has been interpreted as being caused by the reaction force of the machine on the ground resulting from the pull up force on the casing necessary to get the casing in motion.
Unfortunately, no conclusive cause was found for the second increase in hydraulic head regarding the processes that take place during withdrawal. This calls for further research as the hydraulic head after withdrawal will influence the interaction between the fresh concrete and the surrounding soil. Then a literature study on (excessive) bleeding in cement based materials was performed to assess how concrete stability influences the initiation of bleeding. The literature study showed that in order to capture the full bleeding phenomenon three processes can be distinguished. Sedimentation, Consolidation and Cement Hydration.