Looking at the penultimate picture in
http://freespace.virgin.net/guy.gorton/makesafe.html
it occurs to me that if the girders spanning the tunnel crown were to
be lowered (which they can be now the fill has been removed), similar
ones inserted at the eastern end and a floor put in spanning the
excavated area (with suitable foundations), the store could be built
without loading the tunnel top again. Change the levels for the car
park to minimise fill requirement and the job is done.
Just an idea.
Why should I want to give Tesco my brilliant ideas?

Guy Gorton

In message , at 09:23:43 on 
Mon, 22 Aug 2005, Guy Gorton  
remarked:

>Looking at the penultimate picture in
>http://freespace.virgin.net/guy.gorton/makesafe.html
>it occurs to me that if the girders spanning the tunnel crown were to
>be lowered (which they can be now the fill has been removed), similar
>ones inserted at the eastern end and a floor put in spanning the
>excavated area (with suitable foundations), the store could be built
>without loading the tunnel top again. Change the levels for the car
>park to minimise fill requirement and the job is done.
>Just an idea.
>Why should I want to give Tesco my brilliant ideas?


I should think that there are two reasons why this isn't a goer.

Firstly, the calculations on the tunnel segments will take account of 
the pressure of the fill on the sides and the top balancing. When it's 
all in place! (We know what happens when building...) So I might expect 
the tunnel to be improperly balanced if there isn't the full design load 
on the top when it's finished.

Secondly, the weight of the "shed" bit of the Tesco store isn't all that 
high, so removing it won't help very much (other than to make another 
unbalancing contribution as above). There will be a weight involved in 
whatever form of reinforced concrete floor they pour over the whole 
thing later. But that's not going to be significantly more than a 
similar depth of fill.
-- 
Roland Perry

Guy Gorton  wrote:


>Looking at the penultimate picture in
>http://freespace.virgin.net/guy.gorton/makesafe.html
>it occurs to me that if the girders spanning the tunnel crown were to
>be lowered (which they can be now the fill has been removed), similar
>ones inserted at the eastern end and a floor put in spanning the
>excavated area (with suitable foundations), the store could be built
>without loading the tunnel top again. Change the levels for the car
>park to minimise fill requirement and the job is done.
>Just an idea.


It's a good idea.  But the superimposed loading required by the design
codes would mean heavy beams and the need for different, very much
stronger foundations for the supporting columns.  Still, it could be
made to work and it is certainly a workable way of avoiding loading
the tunnel segments with loads from the intermediate columns.  


>Why should I want to give Tesco my brilliant ideas?


If it had been established that there was a need to avoid loading the
tunnel segments, this idea would have been the automatic choice of
Tesco's structural designers.  

Sorry.  ;-)

On Mon, 22 Aug 2005 11:04:55 +0100, Tony   Polson 
wrote:


>If it had been established that there was a need to avoid loading the
>tunnel segments, this idea would have been the automatic choice of
>Tesco's structural designers.  
>
>Sorry.  ;-)
>

Don't be!  There was no need to avoid loading the tunnel segments in
the original design and there is probably no need to avoid it now in a
strict structural sense.  The snag for Tesco will be that if the work
goes back on stream exactly as it was before, the public will not
trust the end result.  I think Tesco will need to be seen to be doing
something different.
Pushing a project through against local opposition is one thing, but
trying to persuade potential shoppers from a much wider area that it
is safe is quite another.
Although, having watched commuters this morning crowd on to their
trains at Gerrards Cross without a glance at the tunnel structure may
suggest that the public can be convinced, but the need to commute is
much more imperative than choosing this store out of the many within a
short distance.
BTW a new page entitled 'finale' should be up and running tomorrow
morning on my website.

Guy Gorton

Guy Gorton wrote:

> >If it had been established that there was a need to avoid loading the
> >tunnel segments, this idea would have been the automatic choice of
> >Tesco's structural designers.
> >
> >Sorry.  ;-)
> >
> Don't be!  There was no need to avoid loading the tunnel segments in
> the original design and there is probably no need to avoid it now in a
> strict structural sense.  The snag for Tesco will be that if the work
> goes back on stream exactly as it was before, the public will not
> trust the end result.  I think Tesco will need to be seen to be doing
> something different.


It might well have been in the NG before (and if so I've missed it),
but why didn't they opt for a more conventional covered way structure
in the first place?

Something along the lines of a column and girder steel framework, or
concrete cast in-situ would surely have been less risky - like on the
approaches to Liverpool Street, or the DLR south of Bow Church, or on
numerous sections of the London Underground sub-surface lines where
cuttings have been converted to covered way.

Would it have been cost, construction/possesion time, or that they were
seduced by the arch-and-fill method?

As a PS, huge thanks to Guy for the excellent photographic work over
the last two months and for the time taken to post in the NG and on the
web.

"Guy Gorton"  wrote in message
news:c92jg1lkeabasuiokur6o7kg7p0ljfhpha@4ax.com...

> Looking at the penultimate picture in
> http://freespace.virgin.net/guy.gorton/makesafe.html
> it occurs to me that if the girders spanning the tunnel crown were to
> be lowered (which they can be now the fill has been removed), similar
> ones inserted at the eastern end and a floor put in spanning the
> excavated area (with suitable foundations), the store could be built
> without loading the tunnel top again. Change the levels for the car
> park to minimise fill requirement and the job is done.
> Just an idea.
> Why should I want to give Tesco my brilliant ideas?
>
> Guy Gorton


As a matter of interest, how long did it take to get the trains running
through again?

I don't know who said 3 days, but even my other half thought it would be
weeks when watching the news pictures after the collapse, and she knows b.
all about civil engineering and other muddy professions!

I thought that that was a dumb statement aswell. You only have to a
freight train derailment and moving a few wagons takes a week.

Kevin

In message <xbQX4NQG3YCDFAx$@donald.internetpolicynews.co.uk> on Mon, 22 Aug
2005 09:33:10 +0100 in uk.railway, Roland Perry  tapped out
on the keyboard:


> 
> Secondly, the weight of the "shed" bit of the Tesco store isn't all that 
> high, so removing it won't help very much (other than to make another 
> unbalancing contribution as above). There will be a weight involved in 
> whatever form of reinforced concrete floor they pour over the whole 
> thing later. But that's not going to be significantly more than a 
> similar depth of fill.


But don't forget the weight of the merchandise - Tesco's motto is "pile it high
and sell it cheap" <G>.

--
John Youles   Norwich   England   UK

Max Turner wrote:


> As a matter of interest, how long did it take to get the trains running
> through again?
>
> I don't know who said 3 days, but even my other half thought it would be
> weeks when watching the news pictures after the collapse, and she knows b.
> all about civil engineering and other muddy professions!


The accident happened on the 30th June; the line was due to re-open on
the 20th August, but it was reported that a few trains ran the previous
day, due to signalling problems on the Aylesbury route.  Just a day
over seven weeks; a very commendable effort by all involved I think.
The amount of material removed was reported to be either 25 or 27
thousand tonnes, five thousand of which was over the collapsed section.
 Track and signalling cables had to be replaced, and the structure had
to be inspected, both to determine the cause of the failure, and to
establish that it was safe to run the trains through the remaining
sections.

Something which I mentioned before in another thread was that I read a
report which said something to the effect that the structure had to be
inspected to determine what had happened, and what had to be done to
put it right, which was expected to take about two days.  I think this
may have been mis-interpreted my somebody in the media as meaning that
the re-opening itself would only take this long.  Clearly, this was
never going to be the case.

As others have said, thank you to Guy for the photographs.

On Mon, 22 Aug 2005 09:33:10 +0100 someone who may be Roland Perry
 wrote this:-


>Firstly, the calculations on the tunnel segments will take account of 
>the pressure of the fill on the sides and the top balancing. When it's 
>all in place! (We know what happens when building...) So I might expect 
>the tunnel to be improperly balanced if there isn't the full design load 
>on the top when it's finished.


But presumably if it is safe to run trains through it now then the
fill is not necessary.


-- 
 David Hansen, Edinburgh | PGP email preferred-key number F566DA0E
 I will always explain revoked keys, unless the UK government
 prevents me by using the RIP Act 2000.

Guy Gorton  wrote:


>On Mon, 22 Aug 2005 11:04:55 +0100, Tony   Polson 
>wrote:
>
>>If it had been established that there was a need to avoid loading the
>>tunnel segments, this idea would have been the automatic choice of
>>Tesco's structural designers.  
>>
>>Sorry.  ;-)
>>
>Don't be!  There was no need to avoid loading the tunnel segments in
>the original design and there is probably no need to avoid it now in a
>strict structural sense.  The snag for Tesco will be that if the work
>goes back on stream exactly as it was before, the public will not
>trust the end result.  I think Tesco will need to be seen to be doing
>something different.
>Pushing a project through against local opposition is one thing, but
>trying to persuade potential shoppers from a much wider area that it
>is safe is quite another.
>Although, having watched commuters this morning crowd on to their
>trains at Gerrards Cross without a glance at the tunnel structure may
>suggest that the public can be convinced, but the need to commute is
>much more imperative than choosing this store out of the many within a
>short distance.



In my opinion, more than 90% of the potential customers for this
branch of Tesco will not give the tunnel collapse more than a moment's
thought before deciding to shop there.  On the basis that there is no
such thing as bad publicity, it might actually encourage even more
people to give it a try than would otherwise have been the case.  

I'm sorry that this isn't what you want to hear.

On 22 Aug 2005 08:05:28 -0700, "Stephen Furley"
 wrote:


>The accident happened on the 30th June; the line was due to re-open on
>the 20th August, but it was reported that a few trains ran the previous
>day, due to signalling problems on the Aylesbury route.  


Did any trains actually make it through the tunnel on the 19th?
Someone I know spoke to someone from Chiltern (Chinese whispers..?)
who apparently denied that any trains used it before Saturday.

-- 
Arthur Figgis                Surrey, UK

"Arthur Figgis"  wrote in message
news:5rgkg153o00ffjdn23qep4igagr4p8nlrh@4ax.com...

> On 22 Aug 2005 08:05:28 -0700, "Stephen Furley"
>  wrote:
>
> >The accident happened on the 30th June; the line was due to re-open on
> >the 20th August, but it was reported that a few trains ran the previous
> >day, due to signalling problems on the Aylesbury route.
>
> Did any trains actually make it through the tunnel on the 19th?
> Someone I know spoke to someone from Chiltern (Chinese whispers..?)
> who apparently denied that any trains used it before Saturday.
>

I noticed one train on Live Departure Boards (06xx from Kidderminster, IIRC)
which apparently arrived at Marylebone around 40 early - which I think must
mean it had run via Gerrards Cross.

Peter

On Mon, 22 Aug 2005 22:30:06 +0100, Arthur Figgis
 wrote:


>On 22 Aug 2005 08:05:28 -0700, "Stephen Furley"
> wrote:
>
>>The accident happened on the 30th June; the line was due to re-open on
>>the 20th August, but it was reported that a few trains ran the previous
>>day, due to signalling problems on the Aylesbury route.  
>
>Did any trains actually make it through the tunnel on the 19th?
>Someone I know spoke to someone from Chiltern (Chinese whispers..?)
>who apparently denied that any trains used it before Saturday.



Not many - but I don't know the total...............

G

On Mon, 22 Aug 2005 22:30:06 +0100, Arthur Figgis
 wrote:


>On 22 Aug 2005 08:05:28 -0700, "Stephen Furley"
> wrote:
>
>>The accident happened on the 30th June; the line was due to re-open on
>>the 20th August, but it was reported that a few trains ran the previous
>>day, due to signalling problems on the Aylesbury route.  
>
>Did any trains actually make it through the tunnel on the 19th?
>Someone I know spoke to someone from Chiltern (Chinese whispers..?)
>who apparently denied that any trains used it before Saturday.


Yes they did.  See my new web page announced elsewhere on this ng.

Guy Gorton