A new scheme has been launched for the Technical Approval of foundation piles with certification. To this end, a collaboration has been set up between the approval operators SECO and Buildwise, the certification operator BCCA and independent experts in the field of foundation piles. The development of this scheme was initiated at the request of the sector itself.
Situation until now
In Belgium, the calculation of the theoretical bearing capacity of foundation piles should be based on the provisions of NBN EN 1997-1, the Belgian Annex (ANB) to that document and, until recently, Buildwise Dimensioning methods Nr. 12 and 19. In these Dimensioning methods, the use of certain favourable factors (installation factor, model factor, safety factor) was been linked to the presence of a quality system, compliance with information sheets published by Buildwise and carrying out loading tests on instrumented piles.
New development: ATG with certification
However, compliance with these quality conditions was not verified by an independent third party. This possibility has now been integrated into the new document “Buildwise Dimensioning method Nr. 20” through the use of Technical Approval (ATG) with certification.
These changes have an immediate impact on the design of screw piles with soil displacement, CFA piles and micropiles, but also in future, on other foundation and anchoring systems. In order to limit market disruption as much as possible, it has been decided to process all requests grouped by type and to publish them together at the same time. In the 1st phase, the work was devoted to screw piles with soil displacement.
The initial process for obtaining an ATG with certification consists of two parts: technical approval and certification.
The technical approval relates to the technical requirements of the product in the intended field of application. During certification, the quality system is audited in order to assess whether the producer can guarantee quality on a continuous basis.
In order to guarantee equivalence between all the files, a UBAtc Technical Approval Guideline and a BCCA Application Regulation for certification (TRA) have been drawn up.
An initial review was carried out for all files submitted:
- The calculation method used (according to the Buildwise Dimensioning method 20) has been verified via a reference calculation (Benchmark).
- To be able to justify the improved coefficients, the producer could also carry out loading tests on the instrumented piles. This test data has been analysed to verify compliance with the requirements of the UBAtc Technical Approval Guideline.
- The producer’s quality system was audited, after which any remarks were followed up with an action plan.
- To verify the application of internal procedures and work instructions, on-site inspections were carried out during which the execution of certain piles was monitored.
Following the evaluation described above – based on the rules described in the UBAtc Technical Approval Guideline and the TRA – 12 ATG dossiers (screw piles with soil displacement) from 8 different producers have now been approved and published as texts on 02/05/2023.
From now on, the follow-up phase of these files will begin with audits, technical checks and on-site checks.
On 25/5/2023 the concerned parties, represented by the Groupement Belge de Mécanique des Sols et de la Géotechnique-Belgische Groepering voor Grondmechanica en Geotechniek (GBMS-BGGG), BCCA, Buildwise, SECO and ABEF held an information session to explain the ATG framework and clarify design implications from the perspective of clients, design offices, general contractors and contractors of deep foundation.
The ATG texts can be consulted on the UBAtc website (in French and Dutch only): foundation piles – BUtgB-UBAtc
The Buildwise Dimensioning method Nr. 20 may be consulted on the Buildwise website (in French and Dutch only): Directives pour l’application de l’Eurocode 7 en Belgique selon la NBN EN 1997-1 ANB. Partie 1 : dimensionnement géotechnique à l’état limite ultime (ELU) de pieux et de micropieux sous charge axiale à partir d’essais de pénétration statique (CPT). (buildwise.be)