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ENGITECT
Issue
Six - Winter 2000
Introduction
Welcome
to the sixth edition of 'Engitect'. Through your feedback
we are pleased to hear that readers enjoy 'Engitect'.
In this issue we describe some of the major engineering work
carried out for Waitrose Malvern, a recent addition to Waitrose'
portfolio, and also our work over the last 70 years on Euston
House, as well as the regular features such as the caption competition
and the 19th Century construction cartoons
 The
Great Wall of Malvern
The residents of Great Malvern have recently
enjoyed the benefits of a brand new Waitrose store built in
the centre of the town. What shoppers may not appreciate
when they park their cars in the car park is the amount of engineering
work that was necessary in order to create the space in which
the store now lies.
The site was formerly a car park comprising
two terraces cut into a steeply sloping site just to the north
of the main high street. Those of you who know the Malvern
area will recall the steep wooded slopes of the Malvern Hills
around the town.
In order to create a level area for the
store and the car park it was clear that it would be necessary
to cut further into the hillside. In fact some 47,000m3
was excavated. The ground investigation report by Soil
Consultants Ltd found that it would be possible to use much
of the excavated material as fill to make up the car park levels
including a new vehicular access ramp.
A phased construction programme was developed
in conjunction with the construction management contractor,
Costain Construction Ltd., where the excavation was carried
out in stages across the site taking into account the restricted
site confines.
Retaining walls up to 8 metres high were
required to uphold the hillside around the development and to
retain the fill material along the north elevation. These
comprise timber crib walls and reinforced earth retaining structures.
Timber crib walls comprise an interlocking
timber framework which is gradually backfilled with granular
material as the wall is erected. The walls rely on their
self-weight to provide resistance to sliding and overturning,
and the timber is pressure treated with preservative to ensure
longevity. Phi Group undertook the design and installation
of these walls. The reinforced earth retaining structures
comprise granular fill, compacted in layers, over polyethylene
strips laid on the ground as 'reinforcement'. This reinforcement
layer is repeated as the wall is raised. The wall elevation
is faced with Malvern stone with an attractive raised pointing
known locally as 'snake' pointing or more commonly as 'ribbon'
pointing.
 One
particular area of the site presented the design team with a
number of difficulties. The area in question lay on the
site boundary, and a retaining wall some 8,5 metres high, cut
into the declivity, would be required. Just a short way
up the slope lay a 5-storey block of flats. In addition
the requirement to achieve 240 car parking spaces meant that
the excavation could not be cut back at a safe angle to allow
construction of a timber crib wall.
Some form of temporary works was clearly
required to retain the excavated face in the short term so that
the permanent wall in the form of crib wall could be erected.
To make matters worse, however, a spring issued from the ground
near the base of the excavation, and an existing sewer ran across
the site at the top.
Options including reinforced concrete piles
embedded deep in the ground were explored and discounted on
the grounds of cost, due to the presence of rock at a relatively
shallow depth. The final solution was developed by Costain
Construction Ltd., their sub-contractors, Phi Group, and Thomas
Vale, who were responsible for design and installation of sheet
piles.
 The
solution involved the installation of soil nails, which comprise
small diameter holes drilled deep into the embankment, which
are filled with cement grout into which a steel rod id driven.
The 'nails' thus constructed were designed to reinforce and
stabilise the bank and were installed in stages as the excavation
proceeded. Working in this way it was possible to stabilise
the bank at an angle of 600 to the horizontal, whereas
the natural angle of the ground would have been nearer 300.
The steeper slope reduced the space taken to construct the wall
to approximately one third of that required without the nails.
A sheet piled wall was installed at the
base of the excavation because planning requirements dictated
that this section had to be faced with Malvern stone.
Only a limited embedment was possible due to the presence of
rock, so the top of the wall was tied with a soil anchor installed
in a similar way to the soil nails. Once the sheet piles
were in place a timber crib wall was erected to form the permanent
retaining structure, as the nails were designed to act in the
short-term only. The structural form of the wall is illustrated
in the diagram, together with photographs showing the site during
and after construction.
Back
to Top
 Fastrack
Building Comes of Age
Euston
House, a 154,760sq ft storey office block was completed
in 48 weeks from commencement of demolition to occupation. The
building comprises a steel frame with reinforced concrete floors,
which were laid at the rate of one a week. If I say that the
floors are of the ‘Diespeker’ type then some of you will recognise
that I am not referring to a modern building. So much for fast
track construction being a modern idea as the building was,
in fact, erected in 1933 for the London Midland and Scottish
Railway. We have the dated construction photograph to prove
it.
Not
only do we have the progress photographs, we also have a full
set of structural drawings as, Bertram Hurst, our founding partner,
was the Engineer for the project.
 So,
when we were asked by William Verry Ltd to provide structural
engineering advice for a major refurbishment, we were able to
compliment our expertise in the refurbishment of old buildings
with a saving in excess of £10,000 as exploratory work to determine
beam, column and foundation sizes was unnecessary.
We
have archive records of nearly all the ten thousand or so buildings
upon which we have worked plus many other buildings where we
have advised on party walls or checked alterations by others.
So the next time you are thinking of altering or developing
a building a five minute call to us to check to see if we have
any records could pay dividends (see following article and Euston
House and HPM Archive).
Andrew
Dutton
Back
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HPM
Database
Over the last 3 years we have assembled
a database of all our jobs, which data back to 1910. All
our staff are able to search for buildings at the touch of a
button, given a street name or other reference. The project
data sheet records details of the project including whether
any archive material is held and where to find it. For
projects since 1997 we operate a fully computerised contact,
time, cost and document management system with a place for every
file and every file in its place.
This allows rapid information and document
retrieval and automatic fax or e-mail issues to the project
team.
Andrew Dutton has put a great deal of time
and effort into this development of the system, which all our
staff now agree they would be bereft without.
See HPM Archive
Back
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CDM And All That
 Regular
readers will recall the picture taken by Lawrance Hurst showing
an existing party wall foundation with an unusual inclusion.
We invited readers to submit captions for what Lawrance's Instructing
Surveyor might have said upon encountering this unusual 'reinforcement'
in the wall footing. We were pleased to receive a number
of entries including:
"Lawrance, could 'Thisbe' reinforcement?
'Pyramus' know, I'll ask him."
Richard Thelwell
For those of you who are unfamiliar with
party wall legislation and party wall surveyors, their association
goes under the title Pyramus and Thisbe Club, which comes from
the affair conducted by Pyrmus and Thisbe through the Wall in
Shakespeare's 'A Midsummer Night's Dream'.
Peter Offord sent us the following:
"The 'Instructing' Surveyor would
ask himself and say:
Q. When is a Special Foundation not a Special Foundation?
A. When it's got a shovel in it.
Q. When is a Special Foundation a Special Foundation?
A. When it's got a shovel and an iron mattress in it.
Because that assemblage should comfortably distribute the load."
Those of you who are familiar with the Party
Wall etc. Act 1996 will know Section 20 of The Act which defines
Special Foundations as foundations in which an assemblage of
beams or rods is employed for the purpose of distributing any
load.
Surveyors appointed by building owners will
normally advise strongly against the incorporation of 'Special
Foundations' in their projects because of the potentially onerous
obligations in The Act with building owners and their successors
in perpetuity.
Finally, Johnny Johnson erstwhile of Hillier
Parker sent us his suggestion from New Zealand:
"The system may well be referred
to in one of your collection of late 19th Century brochures
but my friend its still a bloody shovel."
The judges deliberated for some time before
agreeing that Richard Thelwell's entry was the most appropriate.
A bottle of champagne is on its way to him and our thanks are
extended to the other entrants for the time and trouble they
took in submitting their entries.
We would like you to put your mind to the
next caption competition. Lawrance Hurst took this view
recently, in Central London.
We are all aware that recent changes to
health and safety legislation including the CDM Regulations
have increased awareness of safety issues. Even so, the
wording on the sign is somewhat unusual. Perhaps readers
would like to submit captions speculating on the nature of the
hazard bearing in mind the environment and neighbours.
A bottle of champagne will be awarded to
the winning entry.
Back
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 PJ2
For HPM the beginning of Y2K saw the start
of the renovation of Peter Jones in Sloane Square, London.
The store, for which HPM were involved in the 1030s rebuild
of a large part of it, is the flagship of the John Lewis Partnership.
Essential works were carried out in the
previous year whilst Planning and English Heritage Approvals
were obtained. The project, programmed over five years
at a cost of £80M plus, required trading space to be provided
elsewhere whilst the centre of the store is being gutted and
renovated.
A fast conversion of part of one of the
stores two warehouses in nearby Draycott Avenue was needed before
departments could be re-arranged in the main store under Phase
1. Starting in January, Bovis Lend Lease transformed over
30,000sq ft. into a department store complete with a new window
frontage, customer staircase and well, passenger lift, associated
M & E services and an interior design in keeping with the
warehouse features. It opened on the 2nd of May with the
provision of two courtesy buses circulating back and forth to
the main store, and is now known as PJ2.
The enabling works carried out during this
year in the main store, including the movement of over 350 departments
and the temporary alterations to the M & E services, has
allowed the store to be split into three. Trading continues
at both the East and West ends with an external steel framed
link along the Kings Road, whilst the renovation of Phase 2
has now begun.
A team of four from HPM integrated into
a multi-disciplined project office of over fifty personnel at
the beginning of the year, and set up on the seventh floor of
the building to produce the working information. It has
been a very worthwhile exercise from our point of view, having
not only the existing structural information on our doorstep
but also the other consultants looking over your shoulders...
Hard work and dedication from both the Partnership's
project team and Bovis Lend Lease's management team, of which
HPM are pleased to be a part, has enabled Phase 2 projects to
be commenced four months ahead of schedule.
Back
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Partnership News
We extend a warm welcome to Alan Merison,
who joins us from Bylander Waddell, Colin Bowden and John Cook
who join us from Owen Williams (R. T. James & Partners),
Nadeem Masued, John Parkhouse who takes over as Accounts Manager,
Stan Ritter who has taken over our work checking license applications
for a number of the major estates in London, and Tom Newby,
who has been working on our computer system and internet site.
All members of staff can now be reached
via personal e-mail addresses. The address comprises of
the first letter of their Christian name followed by their full
surname and then @hurstpm.co.uk, all in lowercase. For
example, Andrew Dutton's e-mail address is adutton@hurstpm.co.uk.
Our receptionist will be pleased to help if you have any queries.
Of course you can also contact anyone via the general e-mail
address: enquiries@hurstpm.co.uk
Back
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And Finally...
A further entry in our series from the 19th
Century building practices and hazards to health, here is one
that some of our engineers can relate to; particularly
the reference to 'slack baked bricks'. There is at least
one street in London where our engineers would resist proposals
to remove the plaster in order not to destabilise the wall.
In one particular instance the clay from the bricks can be removed
with a teaspoon! Slack baked indeed! The article
is taken from 'The Complete Builder' by J. F. Sullivan, published
in 1880. Things are better now, aren't they? Answers
on a postcard to the editor please.
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