Mineral Point tribune. (Mineral Point, Wis.) 1869-1938, 1907-02-21

ted tunnel ring, and the shle.d ls tneTe-
by forced ahead. the p1terial lying in
advance of it beirg pulled toward the
center by the sand hogs, (as the com
mon tunnel laDorers are termed and
shove,ed ba.k through the opening into
cars, in which it is hauled by electric
power back through the tunnel and
hoisted up the shaft. When full
shove is accomplished the hydraulic
jacks are drawn home, giving space
for the building of another 2le #. ring
in the tail Of the shield The tail Of
the shield surrounds the tunnel lining
and laps back beyond the advance face
of the iron rings about 7la feet As
soon as the last erected ring is tightly
bolted and it is certain that the cutting
| edge is free from rock, we are ready
| for another shove and the process is
repeated.
'In the sub-aqueous construction
compressed air has to be employed
TO keep the tunnels dry. In ordinary
sub-aqueous work it requires about one
pound of air above normal for each two
! feet of head of water. The pressure
used in 81 tunnel since / have been
connected with the job has varied from
Is TO 80 pounds per square inches above
normal 1t is the aim in our tunnel to
use air enough to counterbalance an
hydrostatic head reaching to ah5ut the
center of the shield The a.nount var
les from day to day according to the
nature Of the material passed through,
and during the day with the ebb and
| flow Of the tide.
The air is furnished to the four
tubes Oh our tManhattan) side from a
plant Of eleven large compressors. con
Stunning on AN average about one billion
cubic feet of free air in twenty-four
hours. Admission is gained to the tun-
nels through set or air locks set in
concrete 5ulk-head. These are fitted
with valves by means Of which enc is
enabled to permit compression or de-
compression to take place at any rate
| he may desire 1t is common TO take
on 80 to IS pounds of compression in
from l , to 3 minutes. In coming out
of the compressed air it is well to allow
at least fifteen minutes for decompres-
sion, to permit the surplus air to get
out of your system.
The tube tunnels under East River
are being put in by s. Pearson & Sons,
! Gnc. contractors of London England
Their expenditures for materials and
labor for month range from $780, goo
to $500, 900, from which you can get
some idea of the magnitude of the
work. This being perhaps less than
one-fourth of the whole project.
"The operations are continuous for
twenty-four hours Of the day, with the
exception of every second Sunday. The
Pennsylvania r. K. has a representative
in charge Of its interests in the tunnel
every hour of the time, and it is sui a
position that | hold with the title'of
"Engineer-lnspector" The engineer
Inspector has an assistant called a
lgrout Inspector who looks after the
grouting of the outside Of tunnel lining
with cement and sand mixtures. For
us the day is divided into three shifts,
two men being assigned charge of each
tunnel, for each eight hours, alternate
ly two hours at time in the tunnel,
making four hours of service in the air
per day, with two hour interval on
the surface or in the Office.
"The engineering staff contains many
western men, several of them from the
University of Wisconsin. The chief en-
gineer, Mr.. Alfred Noble, draws year
~ salary of s25 900 for his direction of
the work, while his principal assistant
gets 81, 600 per month. My chief, Mr..
James II. Brace, is a graduate Of "Old
Wisconsin, - in the early nineties, and
the product of farm out near Lone
Rock, is still a young man. whose en-
gineering ability and judgment yield
him $3.50 per month.
eve like the East irstrate. If re-
main in tunnel work there is quite
future here in New York for twenty
years to come. 1t will be at least two
years before this job is complete. So
you can see it is quite predetermined
whether | will be located in the West
again and how soon. -
AND now it is said someone has blum
| I,,,l g.. a.