Happenings at Tesco
Tunnel
Gerrards Cross
2006
A part of Guy
Gorton's website
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After
trains began to run again on August 20, 2005, the
construction site was virtually shut down. It was
presumably inspected from time to time because various
minor works appeared, such as improved drainage at the
gap in the tunnel. Some survey marks were attached
here and there, probably to allow movement to be
detected.
Click
on a thumbnail to see a larger image. You can go
the TescoTunnel home page here.
A forlorn sight
on the station side of Packhorse Road Bridge, early
February 2006. In the picture are to be seen the
conveyor belt, including the bridge over Station Approach
in the distance and the tube taking it through the north
arch of Packhorse Road Bridge.
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The Tesco shed
itself, held up by rusting girders, is unchanged for six
months, and the machine in the centre-rear has not moved
over the same period.
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The main entrance, where the light
structure is to the left of the main shed,
should have been busy with customers last
October.
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A drain has been put in on each side of the tracks to
channel water to where it should be. Otherwise,
everything is as it was left..
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Hardhats and high vis jackets began to
appear again in late March 2006 when Costain took over
the site from Jackson. The first works seemed to
be safety related - perhaps Costain operate different
rules. Here is a new fence right across the site
and there were other new fences further from the
camera.
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Meanwhile, Gerrards Cross put Tesco's shop
out of its mind and celebrated the centenary of the
opening of the railway on April 2, 1906 in great
style. Notables from Chiltern Railways were
there and it was particularly pleasing to meet the
grandson of the first Station Master of Gerrards
Cross. It was the coming of the railway that
created modern Gerrards Cross so there was a big
exhibition later in April covering many aspects of the
first hundred years.
Chiltern Railways entered ito the spirit of things with
steam specials between Marylebone and High Wycombe,
48151 on the London end, Leander on the country end.
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The thought entered some people's head
that this was really a test to see how the tunnel
and its measuring instruments stood up to a good
exhaust blast! Here is 48151 accelerating
through the tunnel gap.
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Part way through April, a few
things started happening on site.
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Back in January 2005 the huge crawler crane used the
line of tunnel segment bases and a set of concrete slabs
as its track. Segments were delivered through the
tunnel. This is clearly not an option in the
present situation.
In early June
2005 the multi-wheeled crane was standing on raised
ground and required a great width for its stabilising
feet. The segments were delivered on semi-trailers
reversed down the slope behind them. After the
last segments were positioned and 2 of the 4 tunnel
portal pieces were in place, the crane left by the same
route. I do not know what was intended for the
placement of the final tunnel portal pieces,
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Small
drilling rigs started making test bores all along
the filled area, close to the tunnel segments but
probably just clear of the foundations.
Presumably Costain need to check that the
layers of fill material are where they should be.
These are the
two remaining parts of the eastern tunnel portal.
The top image was taken as part of a wider scene
on 14 April, illustrating no change since August
The lower image was taken on 16 May showing how
the ground has been shored up with sandbags, probably
as a precaution against slippage of the cutting side
which has been quite sharply cut away at this point..
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Surveying
levels has been going on all over the site for some
weeks now. Here the surveying has entered the east
end of the west tunnel where there is a tower and what
looks like a permanent survey point - invisible to the
naked eye from Marsham Lane bridge but a digital camera
can just about bring it out.
I do not know when it was taken away,
but the last stage of the conveyor belt system is
no longer there! It was there on 14 April,
it was not on 23 May, but I did not see it go.
The drive system at the destination end has
gone too. Probably an economy measure to
save hire costs.
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The segment foundations in the collapse area are
undergoing detailed inspection, a task that seems to
need a lot of people. From this distance, the
groove in which the tunnel segments sit seems in good
order.
The southern side comes under close
scrutiny and some measurement it seems.
The glimpse at the top of a tripod is of
another surveying team.
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If the
project goes ahead, how will the tunnel segments be
placed?
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Back in January 2005 the huge crawler crane used the
line of tunnel segment bases and a set of concrete slabs
as its track. Segments were delivered through the
tunnel. This is clearly not an option in the
present situation.
In early June
2005 the multi-wheeled crane was standing on raised
ground and required a great width for its stabilising
feet. The segments were delivered on semi-trailers
reversed down the slope behind them. After the
last segments were positioned and 2 of the 4 tunnel
portal pieces were in place, the crane left by the same
route. I do not know what was intended for the
placement of the final tunnel portal pieces,
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May 2006.
The present situation near the tunnel gap is that the
ground is built up, retained by a wooden wall as seen
here. This is much higher than the level used by
the wheeled crane last year. The slope in the
distance is also very steep. An interesting factor
is that surely the retaining wall will have to be
removed, otherwise the necessary side pressure from fill
material will not be present. How will it be done?
Answers on a postcard to Costain.
You can go the TescoTunnel home page
here.
Pictures
and text © Guy Gorton 2006
Page constrained to 1024 pix, no other changes, October
2014
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