Article Business Practice Laboratories

Eurocode 7 the Attachments

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Tags: Eurocode 7 Geotechnical Investigations

An update on progress

John Powell – Technical Director Geolabs and Independent Consultant
David Norbury – Independent Consultant

We trust that by now all readers are aware that, in addition to the two parts of Eurocode 7*, there are a number of other Standards which are required to make up the complete set for use in ground investigations and geotechnical design practice.  There are the National Annexes that go with the two parts, and then there are a number of attachments which are called up in Eurocode 7 Part 2.  These are not all yet available, and this article provides an update on the current position in 2011.

A number of the Standards have been published and implemented into UK practice, as listed in Table 1.  At the same time as implementation, the corresponding parts of any conflicting BS have been withdrawn, hence Clauses 3.2 and 3.3 of BS 1377 Part 9 no longer exist and should not be referred to in specification, practice or reporting and BS5930 has undergone two sets of amendments as highlighted in Table 1

Table 1                        Standards published and implemented at the time of writing

Standard number Coverage of Standard Comment
BS EN ISO 22475/1 Sampling and groundwater measurement Implemented. Changes incorporated in BS5930+A2
BS 22475/2 Qualification of enterprises and personnel Now published as normative British Standards.
BS 22475/3 Conformity assessment of enterprises and personnel
BS EN ISO 22476/2 Dynamic probing Implemented
Clauses 3.2 and 3.3 of BS 1377 Part 9 withdrawn. Changes incorporated in BS5930+A2
BS EN ISO 22476/3 Standard Penetration test
BS EN ISO 22476/10 (TS) Weight sounding test Implemented; not widely used in UK
BS EN ISO 22476/11 (TS) Flat dilatometer test
BS EN ISO 22476/12 Mechanical CPT Implemented but no action as no precedent BS
BS EN ISO 14688/1 Soil description Implemented. Changes incorporated in BS5930+A2
BS EN ISO 14688/2 Soil classification
BS EN ISO 14689/1 Rock description and classification

That is a total 11 standards to date that are available for use in the UK.  The implementation of these has not been straightforward and some key issues will require further work at national and European level.

However, the story does not end there as a number of other Standards listed in Table 2 have now been drafted, commented upon and have finalised text and are due to be published shortly, and possibly this year.

Table 2                        Standards that will shortly be published

Standard number Coverage of Standard
22476 – Field testing /1         Electrical Cone and piezocone penetration tests
/4         Ménard Pressuremeter
/5         Flexible dilatometer
/6         Self boring p/meter
/7         Borehole Jacking test
/8         Full displacement p/meter
/9         Field vane test
22282 – Geohydraulic tests /1         General rules
/2         Water permeability test in borehole without packer
/3         Water pressure test in rock
/4         Pumping tests
/5         Infiltrometer tests
/6         Closed packer systems

This list comprises a further 13 standards that will need to be implemented into national practice within 6 months of publication.  That will require a major effort by industry at a time of difficult trading conditions.  This is not a happy coincidence in timing.

There are also a number of other Standards, (20 or so) which are further from publication, but which are called up in EC7 Part 2.  The date of publication of these Standards is not known, but is likely to be within two to three years.

And that is still not the end of the story.  Work has begun in other areas of investigation and testing on Standards which are not, at this stage, referred to in Eurocode Part 2; that omission will be corrected as the Standards are published.
The UK mirror committee (B/526/3) is charged with the implementation of all these Standards in a timely manner, but we cannot do this alone.  We can publish news editorial as the above listed Standards come into circulation, but we need the help of industry.  In particular, we aim to encourage volunteers to digest and publish critical but helpful summaries of the new Standards.  This was carried out for those Standards already implemented (22476/2 and 22476/3, 14688/1, 14688/2 and 14689/1) and the relevant articles were published in Ground Engineering.  The take up of these was still slow, and we will all need to do better in the years to come.  The main reason for this is that if we do not implement smoothly and rapidly we will be operating parallel systems of old and new. This will be inefficient and cause errors and misunderstandings.

Finally, readers should note that there are maintenance and feedback systems in place for getting standards corrected and amended.  This is not an easy or rapid process, but if you have any critical comments please submit these officially to BSI (cc to authors) and they will find their way to B/526/3 for action.  It is not intended that the Eurocodes and the attachments will be fossilised as at the time of publication, and so UK industry can provide a positive lead in Europe to making these Standards better.

NOTE to READERS – amendments to the DP and SPT EN ISO Standards are shortly to be published; whilst the changes in these align closer to UK practice,keep your eyes open for these and other changes.
*Note that Corrigenda have been issued for both Part 1 (2009) and Part 2 (2010) of EC7

Article Contaminated Land Data Management Laboratories

NHBC’s Role in Developing Hazardous Sites

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Tags: brownfield data Investigations NHBC

NHBC (National House-Building Council) is the standard setting body and the leading warranty and insurance provider for new and newly converted homes in the UK. Our role is to work with the house-building and wider construction industry to provide warranty, risk management and compliance services that raise the standards of new homes, and to provide consumer protection to new homebuyers.

Approximately 80% of new homes built in the UK each year are registered with NHBC and benefit from our 10-year warranty and insurance policy called Buildmark. Around 1.6 million homes are currently covered by Buildmark policies and over the past 40 years, NHBC has protected more than 30% of all existing homes in the UK.

In 1999 Buildmark was extended to provide the homeowner with protection cover against the issue of a statutory notice. This was done in the anticipation of Part 2A, which came into force a year later.

The NHBC Foundation

The NHBC Foundation was launched in 2006 in partnership with the BRE Trust. Its remit is to provide the necessary data and intelligence to develop long-term solutions to industry challenges which lie ahead and lead debate and thinking among industry experts. The NHBC Foundation facilitates research and development, and shares pragmatic and relevant guidance and good practice to the homebuilding industry.

Though much of the NHBC Foundation’s research is focused on the challenges of the Government’s 2016 zero carbon homes target, published works do include ground related issues such as ground source heat pumps, the risks associated with basement construction and the efficient design of piling for housing.

NHBC Standards

The 2011 NHBC Standards, effective from 1 January 2011, introduced for the first time a new chapter for low or zero carbon technologies (Chapter 3.1). It also included an update to Chapter 4.1 – Land quality on managing ground conditions, and a major update to Chapter 4.6 – Vibratory and ground improvement techniques, as well as reference to the introduction of Eurocodes in place of British Standards.

The latest update to the NHBC Standards continues our corporate mission to work with the house-building and wider construction industry to provide guidance, inspection and technical services to raise the standard of new build UK homes to protection homeowners. The identification of geotechnical risk assessment and the implementation of robust site investigations and geotechnical and remediation designs are therefore essential to NHBC, our developer customers and ultimately the homeowner.

Chapter 4.1 Land quality – managing ground conditions

Chapter 4.1 was first published in 1998 and, since that time, few changes have been made. The Chapter has now been updated to reflect recent technical changes and developments, made to reflect the changes to British Standards and the development of European Standards. It now includes technical guidance produced since the Chapter was last revised and better aligns the process for assessing contaminated land with the Government’s guidance document CLR 11 (Contaminated Land Report 11): Model Procedures for the Management of Land Contamination (2004).

Chapter – CH4.6 Vibratory ground improvement techniques

The update to Chapter 4.6 reflects changes and innovations in ground improvement techniques. It outlines current industry practice, provides additional guidance on the suitability of ground to be treated, clarifies the objective of vibro treatment, and updates the range of suitable stone fill for vibro column materials by permitting the use of suitable recycled aggregates. It now also references Eurocode EC7 (BS EN 1997 – Geotechnical Design).

The new Standards reflect the EU wide transition to Eurocodes for the design of structural elements following the withdrawal of the existing British Standards in March 2010. It is proposed that the Building Regulations in England and Wales will be revised in 2013, with the structural Eurocodes becoming the standard reference document for demonstrating compliance. In the interim, the Public Contract Regulations 2006 require Eurocodes to be used for the design and construction of publically funded building projects.

For geotechnically challenging sites, such as those where vibro improvement, piling or engineered fill is required, the management of geotechnical risk is likely to be enhanced by adherence to EC7. Additionally, in the UK, the British Standard for Earthworks (BS6031:2009) has also been extensively revised and is now compatible with the Eurocodes. These documents set out the requirements for assessing the geotechnical suitability of the ground for development and the execution of stabilisation works and foundations.

Some of the changes include:

  • References to the 15 kPa absolute limit on soft clay strength has been dropped
  • The 30 kPa limit on soft clays is maintained as not being generally acceptable unless the suitability of the treatment can be demonstrated, taking due account of the impact of group effects, ground heave and settlement
  • Requirement to consider inundation settlement risk issues of poorly compacted fill
  • Requirement to consider surcharging settlement effects
  • References to chalk or clay fills have been omitted and replaced with the generic ‘loose or un-engineered fills’
  • Requirement to consider effects on ground gas and contamination
  • Recycled aggregates can be used subject to compliance with BRE Digest 433 or other suitable guidance, such as WRAP
  • Validation testing is required of treated ground to confirm that the proposed load-settlement performance has been achieved
  • Requirement to produce validation reports confirming that the proposed load settlement performance of treated ground has been achieved
  • Clarification that plate load tests on stone columns alone are not acceptable to NHBC for treatment validation

 

Land Quality Endorsement (LQE)

For housing developments on major Brownfield sites requiring significant geotechnical and contamination remediation, NHBC has increasingly noted that many of the sites developed for housing in the UK are remediated by specialist remediation companies, landowners, private developers, regeneration specialists, development agencies and similar companies.

These organisations are responsible for or own contaminated land and are remediating them for residential development. However, they are not themselves NHBC registered builders or developers, and are therefore outside NHBC risk management processes and may not be aware of NHBC’s requirements.

NHBC introduced Land Quality Endorsement (LQE) in 2005 as a consultancy service providing technical risk management for sites being remediated befoere residential development. LQE allows the assessment of contaminated and brownfield sites against the requirements of the NHBC Standards.

This determines the suitability of these sites for Buildmark cover in advance of the formal registration of residential properties. Sites are assessed against the requirements of NHBC Standards Chapter 4.1, including a review of geotechnical and foundation proposals alongside contamination assessments.

The pre-registration assessment of sites affected by contamination and the remediation adopted will potentially enhance the marketability of a site by reducing the potential risks to the builder or developer, whilst saving time and effort.

Article Business Practice Data Management Executive Safety

Establishing Ground Rules

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Tags: construction ground HSE Investigations

Concerns over the place of Ground investigations in relation to CDM led John Banks and Mouchel Parkman to raise queries with HSE and an APS Legal Adviser. We print below the critical exchanges for the benefit of all those who may encounter similar concerns/ problems.

From John Bans (Technical Director of Mouchel Parkman and Finance Director of APSt) to staff at Mouchel Parkman

“I have attached a copy of the legal advice received from The Association for Project Safety relating to the application of CDM Regulations to Ground Investigations. The reason for asking for a specific ruling was the attitude of the Contractor who despite being informed (via structure and correct ICE Conditions of Contract) that we expected them to be Principal Contractor, moaned about the fact once appointed.  The work is small in scale: 3 days trail pitting, then a break and then returning to undertake the boreholes for 3 weeks.

You will note that the ruling supplied states that it is the project that is important (building schools [and in fact most projects] generally takes longer than 6 weeks to construct)

I know I have started this before but note that:

  • All Ground Investigations, allied to a larger project will have a construction period of no longer than 6 weeks (and generally that is the only reason we are doing them), need a CDM Co-ordinator and Principal Contractor

The only exception is where we are undertaking Ground Investigations and there is no final project (seeing if a site is within Part 11A, etc)”

 

The APS Legal Advisors had responded to John’s enquiries as follows:
“The issue in this query centres around the definition of a project. This is defined in regulation 2 as “a project which includes or is intended to include construction work and includes all planning, design, management or other involved in a project until the end of the construction phase”.

The ground investigation is part of a larger project. The definition of a project extends to include the planning and design, which is taking place at the same time as the ground investigation. It would be artificial to treat the ground investigation works as separate from the project as a whole.

The difference between treating the ground investigation as part of a notifiable project, and treating it as a stand alone project which is not notifiable, need not be very great.  The ground investigation contractor would of course have the duties of a principal contractor, but contractors have duties under CDM2007 in any event if their work is not notifiable (see regulation 13).

Because of the limited nature of the works, the health and safety file would not need to be lengthy or elaborate. The health and safety plan would deal with the specific risks only. Similarly the health and safety file would not need to cover more than the residual risks arising out of the ground investigation works or which have become apparent as the result of those works.”

The Mouchel Parkman Compliance manager had also sought the views of the HSE at Rose Court via infoline and received the following.

“You are correct in every respect. The ground investigation works are part of the notifiable part of the project. It is not unusual for ground investigation works to take place early, perhaps long before the appointment of the Principal Contractor who will be undertaking the management of the main construction phase. However, it is still part of the same overall project.

As the project is notifiable, and the ground investigation is part of the notifiable project, there needs to be a Principal Contractor (PC) appointed. If the only work being carried out on site is the ground investigation, then I do not understand why the ground contractor thinks they are not competent to act as PC- for themselves. The role of PC is essentially to co-ordinate the construction work on site, to ensure that it is carried out safely. I assume the contractor feels confident enough to do their own work safely.  There will be a requirement to fence off the site, liaise and co-ordinate with the school/client to ensure safety to children, staff and the nearby public, and ensure welfare facilities. Their construction phase plan will only need to go as far as covering their involvement at the site. At the end of their work, presumable they relinquish the role of PC, which is subsequently taken up by the PC for the main construction phase plan.

If there will be other contractors working at the same time as the ground investigation contractor, I can understand their reluctance if they have not been in a position to manage other contractors before, and they may not have personnel capable or competent to do this task. Otherwise, acting as PC for their own work only, should not create any extra demands.

Ref: Article taken from APS newsletter/ October 2007