Examination of Witnesses (Questions 3200
- 3219)
3200. Along with, I dare say, an awful lot of
the Petitioners and Agents, we are not wholly conversant with
the conventions. We had passed the copies of all the evidence
that we thought you did need to see to your Clerks yesterday,
which has provided these bundles, but I was not aware that it
was to include the content of our text—our oral presentation.
3201. CHAIRMAN: Is this part of your
presentation?
3202. MR WHEELER: Yes, it is.
3203. CHAIRMAN: Right. It is, obviously,
substantially technical.
3204. MR WHEELER: It is.
3205. CHAIRMAN: We have to understand
it. We have, after all, to do our job, which is to report to Parliament.
3206. MR WHEELER: Yes. I think, obviously,
all parties—us as Petitioners and your Lordships as our
representatives—need to rely on the technical evidence because
neither of us fully understand a great many of these engineering
issues. So I sympathise with your point. We struggle to understand
an awful lot of what is proposed to happen in the Spitalfields
area, but that is why we are asking these technical questions,
because we need the answers in a form that can be understood by
the man in the street—if I can put it like that.
3207. The first point here is that there is
no information on what analytical model they have used, nor the
data and assumptions that have been made in their input to that
model As it stands, all we have to go on is a table of results,
giving predicted settlements, strains and the likely severity
of damage, which is usually defined in terms of "negligible"
and "slight" and so on.
3208. CHAIRMAN: Where are those?
3209. MR WHEELER: Those appear at the
bottom of every page of the Mott MacDonald report.
3210. CHAIRMAN: No, they do not. There
is nothing about "strains".
3211. MR WHEELER: I was referring to
the predicted settlements, yes. Is there nothing about strains?
3212. CHAIRMAN: I have not seen anything.
3213. MR WHEELER: If we may leave the
issue of strains aside ----
3214. CHAIRMAN: We have now found one
in relation to 25 Wilkes Street.
3215. MR WHEELER: The next item, two:
even if the predicted degree of settlement is accepted it is not
clear how they have used this to predict a likely crack width
in a particular property. Three: they have given a prediction
of maximum strain in the buildings of 0.024%, but have not stated
where this occurs in the building. This is the strain that is
likely to occur at the foundation and subsoil interface, and will
in fact be magnified up through the building, as a result of the
hogging component of the settlement wave, for example. That is
what I was referring to, your Lordships, when I was talking about
the Wilkes Street properties and the importance of at least gauging
exactly how high the buildings are, because the higher you get
the greater the settlement will be apparent.
3216. CHAIRMAN: Mr Wheeler, there are
two separate sorts of strains; there are tensile strains and there
are compressive strains. It depends where, on the curve of the
settlement trough, the building stands which of these will occur.
I do not think we have got any information about this at all.
3217. MR WHEELER: That is correct. It
is partly because, I believe, the buildings have been treated
individually and not as a whole—not as a terrace. They look
at them as a series of individual buildings, not as a terrace.
3218. CHAIRMAN: If you have a terrace
of ancient houses going across at right angles, say, to a settlement
trough, the ones on the edge will get tensile strains, the ones
on the slope may get none, the ones at the bottom might get compressive
strains, and then so on up the other side. Therefore, there will
be a different sort of strain for each of the houses in the terrace.
3219. MR WHEELER: You get my point entirely.
That is exactly what we find rather alarming. We have right at
the beginning of this piece, many years ago, attended a seminar
or a meeting with Professor Mair, who I believe is talking tomorrow,
who explained these consequences of tunnelling to us, and so we
do understand that. My house, for example, sits in the bottom
of the trough, so I am actually quite relaxed about the compressive
strain, because I think the building will deal with that. It is
the tensile ones that really cause the problems, and as you go
up the buildings, of course, it does that (indicating), does it
not? That is why we are so alarmed that they miscalculate the
height of the buildings and do not refer to these sorts of procedures
as they make these reports.
| 
