American Society of Civil Engineers.

Transactions of the American Society of Civil Engineers (Volume 81) online

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were made under ground. The hammer drills are convenient and
rapid, the delay and expense of their constant breakage perhaps balanc-
ing the advantage of speed under ordinary conditions. The drills
are mounted on a light horizontal bar, about 18 in. below the roof
line. Air and water are taken over the muck pile, or on hooks in the
side, by a single hose line for each, to a manifold from which short
individual hose lines supply the driUs.

Light cars (i cu. yd.) were used for muck, and the latter was
taken off the track, instead of building sidings for this purpose. Shov-
eling plates were used at the face and on the side away from the track
for some distance back of the face, in order to facilitate the handling
of empty muck cars. The ventilating pipe was a 12-in. wooden water
pipe connected to the Connersville blowers used for the exhaust.




Fig. 4. — Beginning Dellling from Upper Set-dp of Bar in the Pioneer Heading.




Fig. 5. — Main Heading, Showing Enx,akgement Drilling.



CONSTRUCTION METHODS FOR ROGERS PASS TUNNEL 461

This pipe was hung on the side away from the track, close up to the roof,
and was carried to within 20 ft. of the face. Little damage was done
to this pipe by blasting. The blowers were started exhausting when
the first shot was fired, or a little before, and were run for 20 min.
The men got back to work in from 5 to 10 min. No compressed air
was allowed to be blown out for ventilating purposes. After a round
was shot, the drillers followed the smoke back, barring down the roof,
bringing explosives to re-shoot, and wetting down the muck pile, sides,
roof, and face with water hose. The muckers cleared the track and
began loading the muck which was scattered back.

When no further blasting was required, the lights were himg,
the foreman sighted the line and grade point in the face, and the
drilling gang set up the horizontal bar, placed their drills and pro-
ceeded. There was rarely any muck to be handled before the drilling
could be started, as it was thrown back from the face by the heavy
loading in the bottom holes and the fact that they were shot last,
for this purpose. There were two helpers to three drills, and they
brought up and changed the steel and adjusted the drill machines.
When the drilling from the upper set-up was completed, the drillers
took down the machines and carried them back, with the hose con-
nections still attached, and oiled them up. After the mucking was
done, the bar was dropped to the lower set-up, near the floor, and the
drills were set to drill the bottom holes or lifters. The drills were
carried forward, put on the bar, and were drilling sometimes in less
than 2 min. after the bar was dropped. While the bottom holes were
being drilled, the muckers laid the trapk, adjusted and covered the
mucking sheets with muck, and brought up the explosives. The holea
were loaded by the machine men, helpers, and foremen.

For the small part of the tunnel where re-shooting was not neces-
sary, an 8-hour shift could do two rounds per shift, or a little better.
Two men pick down the muck, and three men load the car and push
it out, while three others stand by with an empty car, ready to put
it on the track and load it. The three men taking out the loaded
car return near the face with an empty car, take it off the track,
and rest until the load comes out. The men get a rest from the
monotony of steady continuous shoveling, and the empty car is avail-
able at once after the load goes back. The pipes for ventilating, and



463 CONSTRUCTIOX METHODS FOR EOGEES PASS TUNNEL

for air and water were laid by a pipe man and helper, who looked after
several headings.

Doing this work with muckers was unsatisfactory. Muck cars
were taken from the heading back to a siding by a single mule, and
from there to the dump by a two- or three-mule team driven tandem,
until this method became inadequate, and then compressed-air loco-
motive haulage was substituted for the long haul. The heading
muck cars, after the shovel and switching track had cleared a cross-
cut, were taken to the cross-cut, pulled up an inclined trestle by air
hoist and cable, and dumped into standard-gauge cars, as shown
by Fig. 2. The cross-cuts are from 1 500 to 2 000 ft. apart, as shown
by Fig. 6. Air pressure was maintained at about 90 lb. at the drills,
which required 125 lb. at the compressors toward the end of the
work.

The rounds were usually 6 ft. The cut holes were generally shot
once or twice, and the remainder of the cut was shot with the rest
of the round. All shooting in headings was done with fuse. The
explosives used were 40 and 60%, low-freezing gelatine, with ]^o. 8
caps. The rock was hard to break, and the quantity of explosives
was necessarily high. From 21 to 28 holes were drilled in the pioneer
face. Change of shifts was made at the heading, the shift coming
on taking the tools out of the hands of the shift finishing. Three
shifts a day were worked every day in the year, except for one day
at the east end, due to the burning of the fan house, and one day
due to the breaking of the air main by a snowslide. The pioneer
gang drove the cross-cuts between the pioneer and the main tmmel
heading. The pioneer tunnel was not driven for the last mile, con-
nection being made by the main heading only, which was all drilled
up for enlargement before the enlargement blasting reached this
section. The main heading work had to be completed before the
enlargement blasting and mucking reached the last cross-cut, as it
would have been impossible to maintain the air connections, or ven-
tilate the main heading, after that time, so as to allow continuous

work.

Main Heaping.

The main heading, generally known on the work as the "Center
Heading", was entirely through the rock section. It was 11 ft. wide
and 9 ft. high, the center line being the same as that of the com-



CONSTKUCTION METHODS FOR EOGERS PASS TUNNEL 463



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Online LibraryAmerican Society of Civil EngineersTransactions of the American Society of Civil Engineers (Volume 81) → online text (page 38 of 167)