Application of Eurocode 7 to the design of flood embankments (C749)
This guide provides national guidance for practitioners in the UK and Ireland on the design of flood embankments to EN 1997 Eurocode 7: Geotechnical design. The aim is to improve clarity on key issues relating to the design of flood embankments, which are not addressed in detail by the current EN 1997. These include:
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- risk categories for flood embankments
- modification of partial factors on the basis of consequence
- distinction between different design situations
- design water levels and pore water pressures
- applicability of ULSs.
The need for this guide was identified by the CIRIA-led UK and Ireland Backing Group for the International Levee Handbook (ILH) project. Where appropriate this guide provides cross references to the extensive guidance included within the ILH.
The guide covers the design of new flood embankments and significant modification of existing embankments in the UK and Ireland. It does not cover assessment of existing embankments or the design of new flood structures, though brief discussion is provided on the importance of detailing the interface between flood embankments and associated structures.
Section 2.3 of the guide presents a risk classification for embankments, which may be used to determine the level of design and construction supervision applied to a scheme, and the associated adjusted partial factors that may be used in design. Differentiation is also made between risk categories and EN 1997 Geotechnical Categories, which can be used to determine the level of ground investigation and analysis undertaken on a scheme.
The guide presents a summary of the typical embankment design process and at each stage identifies the relevant requirements of EN 1997 and provides guidance on how these requirements may be implemented. Particular detail is provided in Section 3 in relation to determining the appropriate design situation for flood embankment and in Section 4 the guide outlines the approach to establishing design values of water levels of water pressures, which are a critical input for flood embankment design. Section 5 outlines the approach to assessing each of the critical ultimate limit states applicable to flood embankments and includes tables of partial factors to be used based on the UK and Irish National Annexes to EN 1997.
During preparation of this guide a number of opportunities for further research development were identified and the guide concludes with recommendations for further work that could be undertaken to improve the design of flood embankments to EN 1997.
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This guide reflects thinking at the time of writing (September 2014) from a range of practitioners including members of Evolution Groups working towards the revision of EN 1997 planned for 2020. Subject to feedback from users in the UK and Ireland, this guide is likely to be updated. CIRIA is establishing a Community of Practice through which such feedback will be sought. The guide will, ultimately, be superseded by the publication of the revised EN 1997. Further details can be found on the CIRIA website at www.ciria.org/ILH