==================+=========+========+=============+========+==========
Grade. |Total No.|Rate per|Drilling and |Mucking:|Timbering:
| | day. |blasting: No.| No. | No.
------------------+---------+--------+-------------+--------+----------
Superintendent | 1 | $7.70 | ½ | 1/8 | 3/8
Assistant engineer| 1 | 5.80 | ½ | 1/8 | 3/8
Electrician | 1 | 3.50 | ½ | 1/8 | 3/8
Engineer | 1 | 3.50 | | 1 |
Signalman | 1 | 2.00 | | 1 |
Foreman | 3 | 4.00 | 1 | 1 | 1
Driller | 5 | 3.00 | 5 | |
Driller's helper | 5 | 2.00 | 5 | |
Laborers | 14 | 2.00 | | 14 |
Timbermen | 3 | 3.00 | | | 3
" helpers | 4 | 2.00 | | | 4
Machinist | 1 | 4.00 | 1 | |
Blacksmith | 2 | 3.50 | 2 | |
" helper | 2 | 2.00 | 2 | |
Nipper | 2 | 2.00 | 2 | |
Waterboy | 1 | 2.00 | 1 | |
------------------+---------+--------+-------------+--------+---------
Total | 47 | | 20½ | 17-3/8 | 9-1/8
==================+=========+========+=============+========+=========
The general scheme of excavation is shown by Plate XXXIII. The bench was
kept 50 or 60 ft. behind the face of the heading. The powder used was
60% Forcite. The general system of drilling was as shown in Fig. 7. The
average length of hole drilled per cubic yard of excavation was 2.9 ft.,
as against 7.70 ft. at Manhattan; and the amount of powder used was 1.96
lb. per cu. yd., as against 1.24 lb. at Manhattan. There was little
timbering. A length of about 30 or 40 ft. adjoining the Weehawken shaft
was timbered, and also a shattered seam of about 17 ft. in width between
Stations 262 + 10 and 262 + 27.
[Illustration: LAND TUNNELS TYPICAL METHOD OF DRILLING USED IN THE
WEEHAWKEN TUNNELS FIG. 7]
The two entirely separate tunnels gave a cross-section which was much
more easily timbered than the wide flat span at Manhattan, and the
segmental timbering was amply strong without posts or other
reinforcement.
Table 12 is a summary of the cost of excavating the Land Tunnels, based
on actual records carefully kept throughout the work.
TABLE 12.--COST OF EXCAVATION OF LAND TUNNELS, IN DOLLARS PER CUBIC
YARD.
======================================+=========+=========+=============
| | |Total yardage
| | | and
|Manhattan|Weehawken|average cost.
--------------------------------------+---------+---------+-------------
Cubic yards excavated |43,289 | 8,311 | 51,600
_Labor._ | | |
Surface transport | $0.49| $0.87| $0.55
Drilling and blasting | 2.37| 1.55| 2.24
Mucking | 2.49| 2.08| 2.42
Timbering | 0.87| 0.18| 0.76
--------------------------------------+---------+---------+-------------
Total labor | $6.22| $4.68| $5.97
--------------------------------------+---------+---------+-------------
_Material._ | | |
Drilling | $0.15| $0.15| $0.15
Blasting | 0.21| 0.21| 0.21
Timber | 0.39| 0.20| 0.36
--------------------------------------+---------+---------+-------------
Total material | $0.75| $0.56| $0.72
--------------------------------------+---------+---------+-------------
Plant running | $0.76| $0.65| $0.74
Surface labor, repairs and maintenance| 0.15| 0.08| 0.14
Field office administration | 1.05| 1.18| 1.07
--------------------------------------+---------+---------+-------------
Total field charges | $8.96| $7.15| $8.64
--------------------------------------+---------+---------+-------------
Chief office administration | $0.34| $0.38| $0.34
Plant depreciation | 0.66| 1.01| 0.72
Street and building repairs | 0.27| | 0.23
--------------------------------------+---------+---------+-------------
Total average cost per cubic yard | $10.23| $8.54| $9.93
======================================+=========+=========+=============
Masonry Lining of Land Tunnels.
Plates XXXII and XXXIV show in detail the tunnels as they were actually
built. It will be seen that in all work, except in the Gy-East contract,
there was a bench at each side of each tunnel in which the cable
conduits were embedded. In Gy-East the bank of ducts which came next to
the middle wall was carried below subgrade, and the inner benches were
omitted.
The side-walls and subgrade electric conduits were water-proofed with
felt and pitch. The water-proofing was placed on the outside of the
side-walls (that is, on the neat line), and the space between the rock
and the water-proofing was filled with concrete. This concrete was
called the "Sand-Wall."
The general sequence of building the masonry lining is shown in Fig. 8.
The operations were as follows:
1.--Laying concrete for the whole height of the
sand-walls, and for the floor and foundations for
walls and benches up to the level of the base of
the conduits;
2.--Water-proofing the side-walls, and, where there was
a middle trench containing subgrade conduits,
laying and water-proofing these conduits;
3.--Building concrete wall for conduits to be laid
against, and, where there was a middle trench,
filling up with concrete between the conduits;
4.--Laying conduits;
5.--Laying concrete for benches and middle-wall;
6.--Building haunches from top of bench to springing of
brick arch;
7.--Building brick arch and part of concrete
back-filling;
8.--Finishing back-filling.
The whole work will be generally described under the headings of
Concrete, Brickwork, Water-proofing, and Electric Conduits.
_Concrete._--The number of types and the obstructions caused by the
heavy posting of the timbering made it inadvisable to use built-up
traveling forms at the Manhattan side, though they were used in the
Weehawken Rock Tunnels.
The specifications required a facing mixture of mortar to be deposited
against the forms simultaneously with the placing of the concrete. This
facing mixture was dry, about 2 in. thick, and was kept separate from
the concrete during the placing by a steel diaphragm. The diaphragm was
removed when the concrete reached the top of each successive layer, and
the facing mixture and concrete were then tamped down together. This
method was at first followed and gave good results, which was indeed a
foregone conclusion, as the Weehawken shaft had been built in this way.
However, it was found that as good results, in the way of smooth finish,
were to be obtained without the facing mixture by spading the concrete
back from the forms, so that the stone was forced back and the finer
portion of the mixture came against the forms; this method was followed
for the rest of the work. All corners were rounded off on a 1-in. radius
by mouldings tacked to the forms. The side-bench forms were used about
four times, and were carefully scraped, planed, filled at open joints,
and oiled with soap grease each time they were set up. When too rough
for face work they were used for sand-wall and other rough work.
The mixing was done by a No. 4 Ransome mixer, driven by 30-h.p. electric
motors. The mixer at Manhattan was set on an elevated platform at the
north end of the intercepting arch; that at Weehawken was placed at the
entrance to the tunnels. The sand and stone were stored in bins above
the mixers, and were led to the hoppers of the mixers through chutes.
The hoppers were divided into two sections, which gave the correct
quantities of sand and stone, respectively, for one batch. The water was
measured in a small tank alongside. A "four-bag" batch was the amount
mixed at one time, that is, it consisted of 4 bags of cement, 8¾ cu.
ft. of sand, and 17½ cu. ft. of broken stone, and was called a 1 :
2½ : 5 mixture. It measured when mixed about ¾ cu. yd.
The cement was furnished to the contractor by the Railroad Company,
which undertook all the purchasing from the manufacturer, as well as the
sampling, testing, and storing until the contractor needed it. The
Railroad Company charged the contractor $2 a barrel for this material.
The sand was required by the specifications to be coarse, sharp, and
silicious, and to contain not more than 0.5% of mica, loam, dirt, or
clay. All sand was carefully tested before being used. The stone was to
be a sound trap or limestone, passing a 1½-in. mesh and being
retained on 3/8-in. mesh. The contractor was allowed to use a coarser
stone than this, namely, one that had passed a 2-in. and was retained on
a 1½-in. mesh.
The concrete was to be machine-mixed, except in cases of local
necessity. The quantity of water used in the mixture was to be such that
the concrete would quake on being deposited, but the engineer was to use
his discretion on this point. Concrete was to be deposited in such a
manner that the aggregates would not separate. It was to be laid in
layers, not exceeding 9 in. in thickness, and thoroughly rammed. When
placing was suspended, a joint was to be formed in a manner satisfactory
to the engineer. Before depositing fresh concrete, the entire surface on
which it was to be laid was to be cleaned, washed and brushed, and
slushed over with neat cement grout. Concrete which had begun to set was
not to be used, and retempering was not to be allowed.
[Illustration: MANHATTAN TYPES FIG. 8.]
The forms were to be substantial and hold their shape until the concrete
had set. The face forms were to be of matched and dressed planking,
finished to true lines and surfaces; adequate measures were to be taken
to prevent concrete from adhering to the forms. Warped or distorted
forms were to be replaced. Plastering the face was not allowed. Rock
surfaces were to be thoroughly washed and cleaned before the concrete
was deposited.
These specifications were followed quite closely.
A typical working gang, as divided among the various operations, is
shown below:
_Superintendence._
½ Superintendent @ $250 per month
½ Assistant engineer " 150 " "
1 Assistant superintendent " 150 " "
_Surface Transport._
1 Foreman @ $2.50 per day
1 Engineer " 3.00 " "
1 Signalman " 2.00 " "
16 Laborers " 1.75 " "
3 Teams " 7.50 " "
_Laying._
1 Foreman @ $4.00 per day
8 Laborers " 2.00 " "
_Forms._
1 Foreman @ $4.50 per day
4 Carpenters " 3.25 " "
5 Helpers " 2.25 " "
_Tunnel Transport._
¼ Foreman @ $3.25 per day
¼ Engineer " 3.00 " "
¼ Signalman " 2.00 " "
4 Laborers " 1.75 " "
_Mixers._
¼ Foreman @ $3.25 per day
2 Laborers " 1.75 " "
The superintendent and assistant engineer looked after the brickwork and
other work as well as the concrete. The surface transport gang handled
all the materials on the surface, including the fetching of the cement
from the cement warehouses.
The tunnel transport gang handled all materials in the tunnel, but, when
the haul became too long, the gang was reinforced with laborers from the
laying gang. Of the laying gang, two generally did the spading, two the
spreading and tamping, and the remaining force dumped the concrete. The
general cost of this part of the work is shown in Table 13.
The figures in Table 13 include the various items built into the
concrete and some that are certificate extras in connection with the
concrete, such as drains, ironwork and iron materials, rods and bars,
expanded metal, doors, frames and fittings, etc.
_Water-proofing._--According to the specifications, the water-proofing
was to consist of seven layers of pitch and six layers of felt on the
side-walls and a ½-in. layer of mastic, composed of coal-tar and
Portland cement, to be plastered over the outside of the arches.
By the time the work was in hand, some distrust had arisen as to the
efficiency of this mastic coating, and a great deal of study was devoted
to the problem of how to apply a felt and pitch water-proofing to the
arches. The difficulty was that there was no room between the rock and
the arch or between the timber and the arch (as the case might be) in
which to work. Several ingenious schemes of putting the felt on in
layers, or in small pieces like shingles, were proposed and discussed,
and a full-sized model of the tunnel arch was even built on which to try
experiments, but it was finally decided to overcome the difficulty by
leaving out the arch water-proofing altogether, and simply building in
pipes for grouting through under pressure, in case it was found that the
arch was wet.
As to the arch built through the length excavated by cut-and-cover on
the New York side, it was resolved to water-proof that with felt and
pitch exactly as the side-walls were done, the spandrel filling between
the arches being raised in a slight ridge along the concrete line
between tunnels in order to throw the water over to the sides. The
portions of arch not water-proofed were rather wet, and grouting with a
1:1 mixture was done, but only with the effect of stopping large local
leaks and distributing a general dampness over the whole surface of the
arch.