Investigating the unseen flow of concrete in deep foundation construction-PPT Presentation

PPT Presentation

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The presentation investigates how fresh concrete flows during deep foundation construction and how flow restrictions can generate defects in reinforced bored piles. Such defects may require costly investigation and remediation and can reduce a structure’s lifespan, reliability, and performance. These risks are increasingly important as foundations become larger and deeper and concrete pours extend.<br /><br />The researchers model fresh concrete in OpenFOAM as a homogeneous Bingham fluid. Its flow behavior is governed by yield stress—the stress needed to initiate flow—and plastic viscosity, which describes resistance to flow after initiation. Both properties affect concrete’s ability to flow, fill the pile, displace support fluid, and move sediment.<br /><br />Observations and simulations show that concrete initially flows mainly horizontally from the tremie, then shifts toward vertically dominated flow. Restricted or bulging flow can produce “mattressing” defects. Flow patterns vary with distance from the tremie, and purely horizontal flow at the start is associated with more severe mattressing.<br /><br />Defect severity depends on concrete workability, the size of the cover zone, and other restrictions to flow. Lower-workability concrete and smaller cover zones can contribute to more severe defects; multiple restrictions compound the effect. The presentation uses severity grids to illustrate how these factors interact.<br /><br />The research highlights numerical modelling as a useful tool for understanding and predicting concrete flow. Measuring slump-flow and slump-flow velocity on site could provide input for modelling actual concrete batches. The authors recommend considering concrete flow behavior alongside structural requirements and adopting a holistic pile-design process involving structural engineers, geotechnical engineers, and contractors.

Keywords

fresh concrete

deep foundation

bored piles

Bingham fluid

yield stress

plastic viscosity

tremie

mattressing defects

numerical modelling

slump-flow