Hrs. _Hours._
Min. _Minutes._
----------------+----------+---------------+----------------
Date. | Place. | Total | Number of feet
| | working time. | drilled.
----------------+----------+---------------+----------------
| | Hrs. Min. |
Jan. 14th, 1907 | Whk. N. | 8 0 | 15
" 15th, 1907 | " N. | 7 32 | 12
| " N. | 7 22 | 14
" 12th, 1907 | " S. | 8 0 | 20
| " S. | 8 0 | 11
| " S. | 8 0 | 10
" 11th, 1907 | Hack. N. | 8 0 | 13
" 17th, 1907 | " N. | 7 10 | 10
| " N. | 7 5 | 11
| " N. | 7 10 | 10
" 16th, 1907 | " S. | 4 20 | 10
| " S. | 6 9 | 10
| " S. | 7 ... | 8
----------------+----------+---------------+---------------
Totals. | | 93 48 | 154
----------------+----------+---------------+---------------
Average: 36.6 min. per ft. drilled, or 1.64 ft. drilled per hour.
As a check on the average figures obtained from various sources, the
following estimate of the cost of drilling per cubic yard was made up
from these average figures, for comparison with the actual average cost
on the whole work. The cost records show this to be about $2.25 per yd.,
exclusive of power for running the drills, almost exactly what the
following estimates give for theoretical average conditions, although no
effort was made to have this latter compare so closely.
_Estimated Cost per Drill per Day._
Drill Runner 1 at $3.50 per day, $3.50
Helper 1 " 2.00 " " 2.00
Nipper 1/5 " 1.75 " " 0.35
Heading foreman 1/12 " 5.00 " " 0.42
Walking boss 1/50 " 7.50 " " 0.15
Blacksmith 1/12 " 4.00 " " 0.34
Blacksmith helper 1/12 " 2.00 " " 0.16
Machinist 1/12 " 3.00 " " 0.25
Machinist helper 1/24 " 1.75 " " 0.07
Pipe fitter and helper 1/50 " 5.00 " " 0.10
Oil, waste, blacksmith coal, etc. 0.24
Drill steel, 6 in. per shift 0.20
-----
$7.78
Average number of feet drilled per cubic yard 3 to 3.5
Number of feet drilled per drill, per shift 10.5 to 12
Number of yards per drill, per shift 3.5±
Cost of drilling, per yard, $7.78/3.5 $2.22±
In all the foregoing tables and computations, the quantities used have
been those paid for. The quantity taken out, however, has been 10% more
than that paid for, and 28% more than the contractor was actually
required to take out.
The specifications required that the excavation should be taken entirely
outside of the neat line, as shown on Plate VIII of the paper by Mr.
Jacobs, but not necessarily beyond this line, but that the contractor
would be paid for rock out to the standard section line, which is 1 ft.
larger on the sides and top and 6 in. deeper in the bottom than the neat
line.
A great deal of the extra quantity was due to rock falling from the
core-wall side whenever one working face was behind the other. Blasting
at the face behind generally loosened more or less rock on the core-wall
side of the tunnel which was ahead, in one or two instances breaking
entirely through, as shown in Fig. 2, Plate XXVI, the hole in the
core-wall in this case being utilized by building a storage chamber in
it.
Table 3 gives some of the statistics of drilling in the Simplon Tunnel,
as compared with the drilling on this work, the figures for the Simplon
being taken from papers read before the Institution of Civil Engineers
of Great Britain.
TABLE 3.
-------------------------------------------+--------------+----------
| |
| Bergen Hill. | Simplon.
-------------------------------------------+--------------+----------
Drills set up in heading, percentage of | |
total elapsed time | 50% | 60%
Actually drilling the rock, percentage of | |
total elapsed time | 25% | 50%
Average advance per round (attack) | 8.5 ft. | 3.8 ft.
Average time for each attack | 36 hours. | 5 hours.
Average advance per day of 24 hours | 5 ft. | 18 ft.**
Depth of holes | 10 ft. | 4.6 ft.
Diameter of holes | 2¾ in. | 2¾ in.
Linear feet drilled per hour, per drill | 2.7 | 7.0
Linear feet drilled per cubic yard | 5.0 | 6.0
Pounds of dynamite per cubic yard | 3.4 to 5.7 | 8½
Average depth drilled with one sharpening | 12 in. | 6½ in.
Total number of men per day of 24 hours* | 450 | 3,300
-------------------------------------------+--------------+----------
[* On Bergen Hill Tunnels, for two full working faces at the
Hackensack end, about 3,000 ft. in from portal (March, 1908). At
Simplon, two full faces and two headings, at a distance of about
5,000 ft. in from the portal (January, 1900). These both include
lining as well as excavation. The lining of the Bergen Hill Tunnels
progressed about twice as fast as the excavation; it is inferred
that on the Simplon it progressed at about the same rate as the
excavation.]
[** At the Italian end, in Antigoric gneiss, which is stated to be
very hard rock.]
The figures in Table 3 are for "heading only" in both cases, except for
the last item (number of men), the heading in the Simplon Tunnels being
about 60 sq. ft., as compared with the heading of Method No 4 (which has
been used for comparison), of 210 sq. ft.
_Mucking and Disposal._--The conditions affecting the disposal of the
muck, after blasting, were quite different at the two ends, the grade
descending in the direction of the loads at Weehawken and ascending at
the Hackensack end. At the Weehawken end the mouth of the tunnels was at
the bottom of a shaft some 80 ft. deep, Fig. 2, Plate XXII, the muck in
the tunnel cars being hoisted by elevators to a platform at the top from
which it was dumped into standard-gauge cars supplied by the Erie
Railroad, as shown by Fig. 7; or later hauled to the crusher or storage
pile, some 500 ft. distant, on the north side of Baldwin Avenue. At the
western end, the cars were hauled directly to the surface through the
approach cut, and the material, except that required for concrete and
rock packing, was deposited in the embankment across the Hackensack
Meadows, a haul of from 1,000 to 3,000 ft. beyond the portal.
All disposal tracks were of 3-ft. gauge, the main running tracks being
generally laid with 60-lb. second-hand rails, although some of lighter
weight were used.
Except for about 1,000 ft. in each tunnel at the Weehawken end, where
the muck was loaded by hand, four steam shovels, operated by compressed
air, were used, one at each working face. One of these was a "Marion,
Model No. 20," weighing 38 tons, the others were "Vulcan Little Giant,"
of about 30 tons each. All these shovels were on standard-gauge track,
and were moved back from 300 to 500 ft. from the working face during
blasting.
[Illustration: Fig. 7.
METHOD OF EMPTYING DUMP CARS AT WEEHAWKEN SHAFT:
FRONT VIEW, SIDE VIEW]
At Weehawken, previous to the time the shovels were installed, the muck
was shoveled by hand into the cars from the bottom of the bench, and the
heading muck was dumped into them from the movable platform (Jumbo)
shown by Fig. 1, Plate XXII. There were three loading tracks at the
face. The cars used at that time were similar to that shown by Fig. 5,
but were about two-thirds the size and had no end door; stop-planks were
supposed to be placed in the ends but seldom were. The loads averaged
about ½ cu. yd. (measured in place). After the shovel was installed the
cars shown by Fig. 5 were used, and the loads averaged nearly 1 cu. yd.
The empty cars were pushed up to the shovel by hand from the storage
track. When loaded, they were given a start with the bucket of the
shovel, and were then allowed to coast by gravity out to the storage
track near the shaft, where they were stopped by placing rolls of cement
bags or burlap on the rails. After the lining was started, the loaded
cars were stopped on the inside of the lining and only sent out over the
single track through this latter at stated intervals, when several cars
followed in close succession, with a long interval which permitted the
concrete to be brought in. The empty cars were hauled back to the
storage track near the working face by mules, one mule usually hauling
two cars at a time.
Up to the time the trap rock was reached, about 1,100 ft. from the
shaft, the excavated material was disposed of by loading it on flat
cars. All the trap, however, was stored to be used later for concrete
and ballast.
When the tunnels were in full working order, sixty muck cars of the type
shown by Fig. 5, were in use, about evenly divided between the two
tunnels. For some time the work was greatly hampered by lack of cars,
and even with the sixty finally obtained, there were many times when
extra cars could have been used to advantage to keep the shovel working.
When mucking by hand, the mucking gangs consisted of from 15 to 20 men.
The maximum output was 50 cu. yd., and averaged about 35 cu. yd. per
shift; there was a great deal of trouble in keeping the gangs full, as
labor at that time was very scarce, and the tunnels were quite wet. The
maximum output of either of the shovels was 159 cu. yd. in one shift,
and the best average in any month--which was between July and December,
1907, during which time only the enlargement and bench of the Central
Shaft headings was being taken out from the western end--was 60 cu. yd.
per shift. As the shovels were generally idle for one shift out of
three, the quantity actually handled averaged 90 cu. yd. per shift
during the shifts the shovel worked. All these quantities were "measured
in place," and, as previously noted, would be about equal to twice as
much measured loose in the cars.
The shovels at both ends were usually worked with three crews for the
two tunnels; two day crews, one at each shovel, and a night crew which
was used in either tunnel as occasion required. The day crews generally
averaged from 45 to 60 hours overtime during the month, one of them
working during the early part of the evenings in the opposite tunnel to
the night crew. For a short time, when the ventilation at the western
end was very bad, four crews were worked, day and night crews in each
tunnel; but, as a general rule, the method of working three crews was
preferred by the men, and was less expensive for the contractor.
At the Hackensack end, 4-yd., Allison, one-way, dump cars were used,
being handled by "dinky" locomotives, of which there were three in use
up to October, 1907, and four after that. One 15-ton Porter engine, with
10 by 16-in. cylinders, was used outside the tunnels for handling the
trains (from 6 to 8 cars) on the dumps and to the crusher; the other
three, 12-ton Vulcans, 9 by 14-in., were used in the tunnels. About 30
dump cars were in use, and of these there were generally from 3 to 6
under repair.
Generally, 4 cars were hauled out together, although 5 and occasionally
6 were handled. The work was generally arranged so that the heavy
mucking shift alternated in the two tunnels, the two engines being
worked there and a single engine in the other tunnel.
The tunnel engines left the cars on a track just outside the portal,
from which they were made up into trains of from 6 to 8 cars and taken
to the dump or crusher by the large "dinky."
The muck from the Central Shaft headings was loaded by hand into cars
similar to that shown by Fig. 5, but smaller and having no door at the
forward end. A double elevator took the cars to a platform about 20 ft.
above the surface, where they were dumped by revolving platforms,
similar to those at Weehawken, into storage bins or directly into
wagons. The muck was all hauled away in wagons; part of it was used to
fill some vacant lots, and part was hauled to the crusher at the Western
Portal.
The method under which the best results were obtained was that in which
a full round was blasted every 36 hours, securing an advance of
practically 9 ft. of full section. During the first shift of the three,
as soon as the blasting had been completed and lights strung, the shovel
was moved forward, and cleaned up the floor to the main pile of muck,
the material from the blast being scattered from 150 to 300 ft. back
from the face; during this shift, also, the drillers mucked the heading
and set up their drills, the muckers helping to carry in the columns and
drills. During the second shift the main pile of muck was disposed of,
leaving not more than 2 or 3 hours' work for the shovel on the third
shift. This left nearly the whole of the third shift for drilling the
lift holes.
_Ventilation._--At Weehawken considerable difficulty was caused by fog
and smoke accumulating in the tunnels after blasting. This was generally
worse on days when the barometric pressure was low outside, and worse in
the North than in the South Tunnel. A 6-ft. fan, driven by an electric
motor, was installed in the cross-passage at Station 274, 900 ft. from
the shaft, the headings at that time being about 300 ft. in advance of
this point, to force the air from the South into the North Tunnel,
drawing it in at the mouth of the South Tunnel and discharging it at the
mouth of the North Tunnel, thus insuring a circulation in both tunnels,
as shown in plan by Fig. 8.
[Illustration: Fig. 8.]
This necessitated, of course, that the cross-passages between that in
which the fan was placed and the mouths of the tunnels should be blocked
tight. There was some difficulty in keeping this blocking tight, owing
to the force of the blasting blowing out the bulkheads. The fan,
however, did good service when it and the bulkheads were in good order.
The compressed air discharged from the drills kept the headings fairly
clear, as well as that part of the tunnel between the headings and the
fan. The fan was moved ahead to the next cross-passage at Station 277
when the work had progressed far enough, and was used there for some
time; it was found, however, that by the time the excavation had reached
Station 280, about 1,500 ft. from the shaft, there was practically no
further difficulty from fog and smoke. No satisfactory explanation was
found for this, as it would rather be expected that the ventilation and
trouble with smoke and fumes from blasting would be worse as the
distance increased between the mouth of the tunnel and the working face.
One explanation was offered: That the blasting of the softer sandstone
tended to create more and lighter dust than the heavier trap rock;
whether or not this was so, it is a fact that there was far less trouble
with fog and smoke after the sandstone was passed.
At Hackensack, the principal cause of trouble was the smoke from the
"dinky" locomotives. As the tunnels progressed, this gradually became
worse, until a connection was made with the Central Shaft headings.
A fan was installed in the cross-passage at Station 316 (700 ft. in from
the portal), but was never worked properly. Apparently, the men, at
least the walking bosses and foremen, had little faith in the fan as a
means of ventilation; no real attempt was made to keep it in order or
operate it properly, and a great deal of time and money was lost groping
around in the smoke and fog, the density of which increased, not only
with the state of the atmosphere, but also with the direction of the
wind. On some days the tunnels easily cleared themselves, and on others
the smoke was so thick that a candle held at arm's length could not be
seen. At this end, the South Tunnel was generally worse than the North.
After the headings were holed through between the portal and the Central
Shaft there was very little trouble, there being usually a strong
up-draft through the shaft. This was so pronounced when the wind was
blowing toward the portal, that the moisture-laden air, as it ascended
from the mouth of the shaft, presented the appearance of a heavy
rainstorm with the rain ascending instead of descending. When the wind
was blowing away from the portal, that is, from the southeast, the
effect of the shaft as a chimney was neutralized, and, consequently, the
smoke accumulated in the tunnels. To overcome this, a large blower, with
a fan 9 ft. in diameter, and with blades 4 ft. wide and 2 ft. 3 in.
long, operated by a vertical 12-h.p. engine, was installed at the top of
the shaft, and this kept the tunnels reasonably clear of smoke at all
times. After the bench and enlargement had passed the bottom of the
shaft, the use of the fan was abandoned, as it was found that the
tunnels cleared themselves fairly well, probably owing to the larger
cross-section reaching all the way to the Shaft. What little fog and
smoke there might be did not cause enough trouble to warrant the cost of
running the fan, which, owing to its location, required the whole time
of a mechanic in attendance day and night.
_Lighting._--During the earlier stages of the work, gasoline lamps and
Kitson lights were used. The former, of the familiar banjo type, and a
modification of this, with a section of wrought-iron pipe for the
reservoir, were very unsatisfactory, and were out of repair and leaking
a large proportion of the time. The Kitson lights were given only a
short trial, but were found unsatisfactory, owing to the necessity of
moving them frequently and having to set them up in insecure positions.
Electric lights were installed by Mr. Bradley, on his assumption of the
contract.
The number of lamps maintained in each of the tunnels for the excavation
was approximately as follows:
At the main working face From 8 to 10
On and around the shovel " 9 to 12
Between the portal and the working face " 60 to 80
The cost of lighting for the whole work averaged about 15 cents per
cu. yd., which is quite large. This was mainly due to the fact that
current was bought from outside sources during a large part of the time
(one-third of the yardage). Part of this current cost 5 cents per
kw-hr., and there were fairly heavy charges for connecting the tunnel
wiring system with the source of supply. Current bought from the Public
Service Corporation cost from 10 to 12 cents per kw-hr. delivered at the
mouth of the tunnel.
_Pumping._--The quantity of water encountered during the excavation of
the tunnels, measured somewhat roughly, was approximately as follows:
At Weehawken 74 gal. per min.
At Central Shaft 1 " " "
At Hackensack 18 " " "
The water at the Weehawken end had to be pumped from the bottom of the
shaft, a lift of about 90 ft., while at the Hackensack end it had to be
pumped back from the face up grade to the portal.
The cost of pumping was about $100 to $125 per month for labor for the
whole work, besides the cost of the plant (about $1,200) and the power
for running it.