The EFFC/DFI Guide to Support Fluids for Deep FoundationsÂ-Paper

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The EFFC/DFI Guide to Support Fluids for Deep Foundations, first published in 2019, provides practical guidance for selecting, designing, managing and testing bentonite- and polymer-based fluids used in bored piles, barrettes and diaphragm walls. It covers fluid behaviour and materials, excavation stability, construction procedures, quality control, testing and acceptance criteria. Because standards differ substantially, the guide identifies a need for more consistent industry-wide requirements.<br /><br />An industry-funded Field Research Study (FRS) is collecting data from 20 projects in Europe and North America. It examines supplementary tests and equipment, fluid sampling at different depths, excavation-base cleanliness, concrete-level measurements and the “interface layer” that forms between support fluid and concrete during casting. The study aims to improve understanding of fluid stability, filter-cake formation and fluid interactions with soil, reinforcement and concrete. Its findings, together with academic research, are intended to inform a second edition of the guide.<br /><br />Early results show that bentonite and polymer fluids have distinct density and viscosity characteristics, while measured fluid properties are generally consistent with depth. The study is comparing sampling methods and has successfully recovered interface-layer samples. Initial observations suggest this layer is a complex mixture with no clearly defined boundaries. Its physical and chemical properties remain under investigation.<br /><br />Academic studies are examining polymer-fluid stability, filter cakes and their effects on soil–concrete shear transfer, polymer performance, and the relationship between support fluids and concrete integrity. Important challenges remain, particularly in assessing base cleanliness, concrete levels and filter cakes. Overall, the guide consolidates current industry knowledge while the FRS and related research address gaps needed to improve design, testing and construction practice.

Keywords

bentonite support fluids

polymer support fluids

deep foundations

bored piles

diaphragm walls

fluid testing

quality control

filter cake formation

interface layer

construction practice