Use of polymers and bentonite for supporting excavation of deep foundations is set to benefit from publication of new guidance next month that aims to improve best practice and share industry knowledge.
Source: Carlos Lam
The Guide to Support Fluids for Deep Foundations document has been jointly developed by the European Federation of Foundations (EFFC), of which the UK’s Federation of Piling Specialists is a member, and the Deep Foundations Institute (DFI).
Awareness of industry need for the guidance came out of the EFFC and DFI’s work on the second edition of the Guide to Tremie Concrete for Deep Foundations, which was published earlier this year.
“Discussions arose about use of polymers and bentonite during work on the tremie guide but we quickly realised that it needed to be a separate subject and a task force was set up to look at the issue,” said Ceecom Consult managing director Chris Harnan, who has been the deputy chairman of the support fluid group since it was set up in 2017.
“The successful use of support fluids requires a basic understanding of geotechnical principals and properties, training, on site experience and, crucially, documentation covering all the areas of use.
“Use of bentonite is fairly well established but use of polymer is still in its infancy in some markets, which is why the guide is essential. The first edition of the guide, which we expect to publish in early 2019, will bring together current knowledge of the behaviour of support fluids and also presents experiences drawn from recent research and case histories from around the world.”
The guide will present current understanding on bentonite, other clays, polymers and blended systems, including the advantages and limitations, in order to allow informed selection of the optimum technical solutions for the conditions on each individual worksite. The document will also include acceptance values for drilling fluids as given in commonly used standards
The guide will include chapters on design considerations, properties of support fluids, raw materials, execution methods and quality control, as well as appendices on excavation stability, support fluid tests and types and properties of pumps.
A second edition of the guide is planned for publication by 2021 and will involve a major research and development project to give recommendations on acceptance values for bentonite, polymer and blended fluids.
According to Harnan, development of the second edition will involve site visits in the US and Europe to around 20 sites to view work, test fluids and concrete and undertake tests on the interface layer to gain real life data for the project.
“We will also be asking contractors to share data on current practices by giving the research team fluid test result information,” said Harnan.
The first edition of the Guide to Support Fluids for Deep Foundations will be made available for the industry free of charge.