The London District Surveyors Association (LDSA) has announced publication of a new version of its design document for piles in London Clay which is widely used by building control across the capital’s 32 boroughs.
The main change to the Guidance Notes for the Design of Straight Shafted Bored Piles in London Clay document is the inclusion of design guidance to Eurocode 7.
“The guidance is aimed at designers of piles in London Clay and is used by surveyors assessing the designs,” said Arup senior engineer Stuart Pennington, who led the work to update the 2009 document.
“The update adds more recent changes in practice, such as the use of larger rigs, wider use of tremies to pour concrete and the need for base cleanliness on larger diameter piles.”
According to Pennington, surveying departments have been struggling to analyse pile designs undertaken using the limit states that are called for in EC7 alongside conventional designs that use working stress.
“The pre-face of the 2009 document called for an update to be produced in the future to include EC7 design guidance,” said Pennington. “At the time there were not enough site examples available to demonstrate the EC7 design approach. It has been a challenge to give a Eurocode method to mirror the working stress approach to result in a similar design but we have used data gathered on real projects to validate the guidance.”
Nonetheless, LDSA president Anthony Oloyede said in the foreword of the new document that it is not a design manual and designers must use their own professional judgement as to the suitability of the standards and use more stringent criteria if appropriate.
The document was first published in 1999 based on research undertaken by Arup director Dinesh Patel, who also undertook the 2009 update.
Patel has worked with Pennington over the last nine months to develop the update and the work has been reviewed by the Federation of Piling Specialists with input from Keltbray Piling managing director Stuart Norman and Balfour Beatty Ground Engineering technical director Mark Pennington.
According to Patel, the new guidance has been positively received by building control. “The new document will aid assessment of EC7 pile designs and will help surveyors have a clear understanding of current best practice.”
- The LDSA has made the new guidance freely available and is available for download as a PDF document by clicking on the link in the related files box below.