t
197
30 ML. DVOR A
I
the shaft has been widened.
8. I am sending under separate cover a drawing C.R.E.
No 517 showing the section I was trying to work to in this
tunnel for flying arch. A great length was left approximately
to this section without liningpending Mr A.J.Barry's in-
spection. On his inspection it was shown him that it was
very difficult to form a good skew back to spring this flying
arch from owing to the massive nature of the rock and the
consequent difficulty in dressing the sides even approximately
to the desired section. He saw that it was not necessary to
put in the same thickness of lining through-out and asked me
to send home a drawing of what I considered could be most
economically worked to.
9. I have gone into the question of putting a concrete
face wall up to the springing of the arch shown in red
sufficient to bring the rock surface up to a smooth face and
I consider this too costly as the amount of timbering is very
large compared with the quantity of concrete. The cost of
cleaning the rock face and arranging good keys where the sides
are very smooth also would be a heavy item. I therefore am
proposing only to put a concrete face and three ring arch
on the length that is now excavated to that section and for
the rest to adhere to the same internal sectional dimensions
as for the lengths in soft ground, only making the thickness
of side walls and arch three rings of brick instead of five
rings or a thickness of about thirteen inches of brickwork.
The backing would as a rule be only drystone but if necessary
concrete could be put in where ever extra strength was re-
quired. I am at present working on these lines and would
ask you to cable me your approval on receipt of this letter.
The progress under the various minor heads is as
10.
follows:-
-16-
Headings.
Wa
No comments yet.
Private notes are available after approval.