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Interborough Rapid Transit: the New York subway; its construction and equipment online

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with the excavation. This was accomplished by temporary bridges for each track, each bridge consisting of




PAGE 4.6INTERBOROUGH RAPID TRANSIT



THE SUBWAY



U C T I



P M E N T




MOVING BRICK AND CONCRETE RETAINING WALL Tu MAKE ROOM FUR THIRD TRACK BROADWAY AND Ij4TH STREET



a pair of timber trusses about 55 feet long, braced together overhead high enough to let a car pass
below the bracing. These trusses were set up on crib-work supports at each end, and the track hung from
the lower chords. (See photograph on page 42.) The excavation then proceeded until the trench was
finished and posts could be put into place between its bottom and the track. When the track was securely
supported in this way, the trusses were lifted on flat cars and moved ahead 50 feet.

At 66th Street station the subway roof was about 2 feet from the electric railway yokes and
structures of the street surface line. In order to build at this point it was necessary to remove two large gas
mains, one 30 inches and the other 36 inches in diameter, and substitute for them, in troughs built between
the roof beams of the subway, five smaller gas mains, each 24 inches in diameter. This was done without
interrupting the use of the mains.

At the station on 42d Street, between Park and Madison Avenues, where there are five subway
tracks, and along 4id Street to Broadway, a special method of construction was employed which was
not followed elsewhere. The excavation here was about 35 feet deep and extended 10 to 15 feet into
rock. A trench 30 feet wide was first sunk on the south side of the street and the subway built in it tor a
width of two tracks. Then, at intervals of 50 feet, tunnels were driven toward the north side ot the street.
Their tops were about 4 feet above the roof of the subway and their bottoms were on the roof. When they



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THE SUBWAY



had been driven just beyond the line of the fourth track,
their ends were connected by a tunnel parallel with
the axis of the subway. The rock in the bot-
tom of all these tunnels was then excavated
to its final depth. In the small tunnel
parallel with the subway axis, a bed of
concrete was placed and the third row
of steel columns was erected ready
to carry the steel and concrete
roof. When this work was com-
pleted, the earth between the trav-
erse tunnels was excavated, the
material above being supported
on poling boards and struts. The
roof ot the subway was then ex-



MOVING WEST SIDE WALL TO WIDEN SUBWAY FOR
THIRD




r.H NEW "TIMES" BUILDING, SHOWING INDEPENDENT CONSTRUCTION THE WORKMEN STAND ON FLOOR GIRDERS OF SUBWAY



PAGE 4 8 INTERBOROUGH RAPID TRANSIT



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tended sidewise over the rock below from the second to the third row of columns, and it was not until the
roof was finished that the rock beneath was excavated. In this way the subway was finished for a width ot
four tracks. For the fifth track the earth was removed by tunneling to the limits of the subway, and then
the rock below was blasted out.

In a number of places it was necessary to underpin the columns of the elevated railways, and a variety
of methods were adopted for the work. A typical example of the difficulties involved was afforded at the
Manhattan Railway Elevated Station at Sixth Avenue and 4id Street. The stairways of this station were
directly over the open excavation for the subway in the latter thoroughfare and were used by a large number
of people. The work was done in the same manner at each of the four corners. Two narrow pits about 40
feet apart, were first sunk and their bottoms covered with concrete at the elevation of the floor of the subway.
A trestle was built in each pit, and on these were placed a pair of j-foot plate girders, one on each side ot
the elevated column, which was midway between the trestles. The column was then riveted to the girders
and was thus held independent of its original foundations. Other pits were then sunk under the stairway
and trestles built in them to support it. When this work was completed it was possible to carry out the
remaining excavation without interfering with the elevated railway traffic.

At 64th Street and Broadway, also, the whole elevated railway had to be supported during construction.
A temporary wooden bent was used to carry the elevated structure. The elevated columns were removed
until the subway structure was completed at that point. (See photograph on page 45.)



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THE S U B W A V



FACE AND SUBWAY ROOF, SUBSTITUTED FOR t
LARGE MAIN I^TH STREET AND LENOX AVE.




A feature of the construc-
tion which attracted consider-
able public attention while it
was in progress, was the un-
derpinning of a part of the
Columbus Monument near
the southwest entrance to Cen-
tral Park. This handsome
memorial column has a stone
shaft rising about 75 feet
above the street levd and
\v r eighs about 700 tons. The
rubble masonry foundation is
45 feet square and rests on a
2-foot course ot concrete.
The subway passes under its
east side within 3 feet of its



SPECIAL CONSTRUCTION OF 6 U -FOOT SEWER, I'NDER CHATHAM SQUARE



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center, thus cutting; out about three-tenths of the original support. At this place the footing was on dry
sand of considerable depth, but on the other side of the monument rock rose within 3 reet of the surface.
The steep slope of the rock surface toward the subway necessitated particular care in underpinning the
footings. The work was done by first driving a tunnel 6 feet wide and 7 feet high under the monument
just outside the wall line of the subway. The tunnel was given a 2-foot bottom of concrete as a support
for a row of wood posts a foot square, which were put in every 5 feet to carry the footing above. When
these posts were securely wedged in place the tunnel was filled with rubble masonry. This wall was strong
enough to carry the weight of the portion of the monument over the subway, but the monument had to be
supported to prevent its breaking off when undermined. To support it thus a small tunnel was driven
through the rubble masonry foundation just below the street level and a pair of plate girders run through it.
A trestle bent was then built under each end of the girders in the finished excavation tor the subway. The
girders were wedged up against the top of the tunnel in the masonry and the excavation was carried out
under the monument without any injury to that structure.

At I34th Street and Broadway a two-track structure of the steel beam type about 200 feet long was
completed. Approaching it from the south, leading from Manhattan Valley Viaduct, was an open cut with



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retaining walls 300 feet long and
from 3 to 13 feet in height. After
all this work was finished (and it
happened to be the first finished
on the subway), it was decided to
widen the road to three tracks, and a
unique piece of work was success-
fully accomplished. The retaining
walls were moved bodily on slides,
by means of jacks, to a line 6'^. feet
on each side, widening the road-
bed I2 1 , teet, without a break in
either wall. The method of widen-
ing the steel-beam typical subway







ONCRETR SEWER BACK UF ELECTRIC DUCT MANHOLE BROADWAY AND cIJTH STREET



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THE S U B W A Y



T K U C T I



E N T



portion was equally novel. The
west wall was moved bodily by
jacks the necessary distance to
bring it in line with the new-
position of the west retaining
wall. The remainder ot the
structure was then moved bodily,
also by jacks, 6 I 4 feet to the east.
The new roof of the usual type
was then added over 12 1 2 feet
of additional opening. (See pho-
tographs on pages 46 and 47.

Provision had to be made,
not only for buildings along the
route that towered far above the




LARGE GAS AND WATER PIPES, RELA1D BEHIND EACH bIDE WALL ON ELM STREET



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53




DIFFICULT PIPE WORK BROADWAY AND 7OTH STREfcl



street surface, but also for some which burrowed far below the subway. Photograph on page 47 shows
an interesting example at 420! Street and Broadway, where the pressroom of the new building of the "New
York Times" is beneath the subway, the first floor is above it, and the first basement is alongside ot it.
Incidentally it should be noted that the steel structure of the building and the subway are independent, the
columns of the building passing through the subway station.

At 42d Street and Park Avenue the road passes under the Hotel Belmont, which necessitated the use
of extra heavy steel girders and foundations for the support of the hotel and reinforced subway station. (See
photograph on page 48.)

Along the east side of Park Row the ascending line of the "loop" was built through the pressroom ot
the "New York Times" (the older downtown building), and as the excavation was considerably below the
bottom ot the foundation of the building, great care was necessary to avoid any settlement. Instead of
wood sheathing, steel channels were driven and thoroughly braced, and construction proceeded without
disturbance of the building, which is very tall.

At i 25th Street and Lenox Avenue one of the most complicated network of subsurface structures was
encountered. Street surface electric lines with their conduits intersect. On the south side of 1251)1 Street



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THE S U B W A Y




ED RECTANGULAR WATER PIPE,



UBVVAY AT I a6TH STREET AND LENOX AVENUE



were a 48-inch water main and a 6-inch water main, a I 2-inch and two lo-inch gas pipes and a hank ot
electric light and power ducts. On the north side were a 2O-mch water mam, one 6-inch, one lo-inch, and
one i 2-inch gas pipe and two banks of electric ducts. The headroom between the subway root and the
surface of the street was 4.75 feet. It was necessary to relocate the yokes of the street railway tracks on
Lenox Avenue so as to bring them directly over the tunnel roof-beams. Between the lower flanges ot the
roof-beams, for four bents, were laid heavy steel plates well stiffened, and in these troughs were laid four
2o-inch pipes, which carried the water of the 48-inch main. (See photograph on page 49.) Special cast-
ings were necessary to make the connections at each end. The smaller pipes and ducts were rearranged and
carried over the roof or laid in troughs composed of j-inch I-beams laid on the lower flanges of the root-
beams. In addition to all the transverse pipes, there were numerous pipes and duct lines to be relaid and
rebuilt parallel to the subway and around the station. The change was accomplished without stopping or
delaying the street cars. The water mains were shut off for only a few hours.

As has been said, the typical subway near the surface was used for about one-halt nt the road. Since
the sewers were at such a depth as to interfere with the construction of the subway, it meant that the sewers
along that half had to be reconstructed. This indicates but very partially the magnitude of the sewer work,
however, because nearly as many main sewers had to be reconstructed off the route ot the subway as on the



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THE S U B \V A Y




route; 7.21 miles of main sewers along the route were reconstructed and 5.13 miles oi mam sewers oft the
route. The reason why so many main sewers on streets away from the subway had to be rebuilt, was that,
from 42d Street, south, there is a natural ridge, and before the construction of the subway sewers drained to
the Kast River and to the North River from the ridge. The route of the subway was so near to the
dividing line that the only way to care for the sewers was, in many instances, to build entirely new outfall
sewers.

A notable example of sewer diversion was at Canal Street, where the flow ot the sewer was carried into
the Kast River instead of into the Hudson River, permitting the sewer to be bulkheaded on the west side
and continued in use. On the east side a new main sewer was constructed to empty into the Kast River.
The new east-side sewer was built off the route of the subway for over a mile. An interesting feature in
the construction was the work at Chatham Square, where a 6 T 2 -foot circular brick conduit was built. I he
conjunction at this point of numerous electric surface car lines, elevated railroad pillars, and enormous
vehicular street traffic, made it imperative that the surface of the street should not be disturbed, and the
sewer was built by tunneling. This tunneling was through very fine running sand and the section to be
excavated was small. To meet these conditions a novel method of construction was used. Interlocked



PAGE 56



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THE S U B W A Y




poling boards were employed to support the roof and were driven by lever jacks, somewhat as a shield is
driven in the shield system of tunneling. The forward ends of the poling boards were supported by a
cantilever beam. The sides and front of the excavation were supported by lagging boards laid flat against
and over strips of canvas, which were rolled down as the excavation progressed. The sewer was completed
and lined in lengths of from i foot to 4^ feet, and at the maximum rate of work about 12 reet of sewer
were finished per week.

At i loth Street and Lenox Avenue a 6 '..-foot circular brick sewer intersected the line ot the subway
at a level which necessitated its removal or subdivision. The latter expedient was adopted, and three
42-inch cast-iron pipes were passed under the subway. (See photograph on page 50.) At i49th Street and
Railroad Avenue a sewer had to be lowered below tide level in order to cross under the subway. 1 o do this
t\\ i) permanent inverted siphons were built of 48-inch cast-iron pipe. Two were built in order that one might
be used, while the other could be shut off for cleaning, and they have proved very satisfactory. This was
the only instance where siphons were used. In this connection it is worthy of note that the general changes
referred to gave to the city much better sewers as substitutes for the old ones.

A number of interesting methods of providing for subsurface structures are shown in photographs



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THE S U B \Y A Y



pages <;t to 54. From the General Post-office at Park
Rowto 28th Street, just belowthe surface, there is a
system of pneumatic mail tubes tor postal de-
livery. Of course, absolutely no change
in alignment could be permitted while
these tubes were in use carrying mail.
It was necessary, therefore, to sup-
port them very carefully. 'I he
slightest deviation in alignment
would have stopped the service.

Between jjd Street and 4
Street under Park Avenue, be-
tween 1 1 6th Street and I 2Oth
Street under Broadway, between
1 57th Street and Fort George




Concrete-lined
Tunnel



PAGE 5 8 INTERBOROUGH RAPID TRANSIT



THE SUBWAY



under Broadway and Eleventh Avenue (the second longest
double-track rock tunnel in the United States, the Hoo-
sac tunnel being the only one of greater length),
and between io_|.th Street and Broadway
under Central Park to Lenox Avenue, the
road is in rock tunnel lined with concrete.
From i 1 6th Street to 1 2Oth Street
the tunnel is 37 ', feet wide, one of
the widest concrete arches in the
world. On the section from Broad-
way and io,d Street to Lenox
Avenue and I loth Street under
Central Park, a two-track subway
was driven through micaceous rock
BE by taking out top headings and then
two full-width benches. The work




INTERBOROUGH RAPID TRANSIT PA GE 59



THE SUB \V A Y







ERECTION OF ARCH, MANHATTAN VALLEY VIADUCT

was done from two shafts and one portal. All drilling for the headings was done by an eight-hour night
shift, using percussion drills. The blasting was done early in the morning and the day gang removed the
spoil, which was hauled to the shafts and the portal in cars drawn by mules. A large part of the rock was
crushed for concrete. The concrete floor was the first part of the lining to be put in place. Rails were
laid on it for a traveler having moulds attached to its sides, against which the walls were built. A similar
traveler followed with the centering for the arch roof, a length of about 50 feet being completed at one
operation.

On the Park. Avenue section from 34th Street to 4ist Street two separate double-track tunnels were
driven below a double-track electric railway tunnel, one on each side. The work was done from four shafts,
one at each end of each tunnel. At first, top headings were employed at the north ends of both tunnels
and at the south end of the west tunnel; at the south end of the east tunnel a bottom heading was used.
Later, a bottom heading was also used at the south end of the west tunnel. The rock was very irregular
and treacherous in character, and the strata inclined so as to make the danger of slips a serious one. 1 he
two headings of the west tunnel met in February and those of the east tunnel in March, 1902, and the
widening of the tunnels to the full section was immediately begun. Despite the adoption of every



PAGE 60



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Steel Viaduct



THE SUBWAY




precaution suggested by experience in such work, some disturbance of the surface above the east tunnel
resulted, and several house fronts were damaged. The portion of the tunnel affected was bulkheaded at
each end, packed with rubble and grouted with Portland cement mortar injected under pressure through
pipes sunk from the street surface above. When the interior was firm, the tunnel was redriven, using much
the same methods that are employed for tunnels through earth when the arch lining is built before the
central core, or dumpling of earth, is removed. The work had to be done very slowly to prevent any
further settlement ot the ground, and the completion of the widening of the other parts of the tunnels also
proceeded very slowly, because as soon as the slip occurred a large amount of timbering was introduced, which
interfered seriously with the operations. After the lining was completed, Portland cement grout was again
injected under pressure, through holes left in the roof, until further movement of the fill overhead was
absolutely prevented.

As has been said, the tunnel between I57th Street and Fort George is the second longest two-track
tunnel in the United States. It was built in a remarkably short time, considering the fact that the work was
prosecuted from two portal headings and from two shafts. One shaft was at i68th Street and the other at
1 8 ist Street, the work proceeding both north and south from each shaft. The method employed for the
work (Photograph on page 56) was similar to that used under Central Park. The shafts at i68th Street and at
i 8 ist Street were located at those points so that they might be used for the permanent elevator equipment
for the stations at these streets. These stations each have an arch span of about 50 feet, lined \\ith brick.

The elevated viaduct construction extends from I25th Street to ijjd Street and from Dyckman Street
to Bailey Avenue on the western branch, and from Brook and Westchester Avenues to Bronx Park on the
eastern, a total distance ot about 5 miles. The three-track viaducts are carried on two column bents where



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PAGE 6l



THE SUBWAY




NOTES.

Rock lino shown is niijiroximate only.
Elevations shown are referred to city datum.



PROFILE OF

HARLEM RIVKR TUNNEL
AND APPROACHES

the rail is not more than 29 feet above the ground level, and on four-column towers for higher structures.
In the latter case, the posts of a tower are 29 feet apart transversely and 20 or 25 feet longitudinally, as a
rule, and the towers are from 70 to 90 feet apart on centers. The tops of the towers have X-bracing and
the connecting spans have two panels of intermediate vertical sway bracing between the three pairs of longi-
tudinal girders. In the low viaducts, where there are no towers, every fourth panel has zigzag lateral bracing
in the two panels between the pairs of longitudinal girders.





HAKLK.M KlvtK TUNNtL DL'KING L I >.N-> I K I ' . r I u N



PAGE 62INTERBOROUGH RAPID TRANSIT



THE SUBWAY




The towers have columns consisting as a rule of a 16 x Vio-inch web plate and four 6 X4X 5,,-inch bulb
angles. The horizontal struts in their cross-bracing are made of four 4Xj-inch angles, latticed to form an
I-shaped cross-section. The X-bracing consists of single 5X3 : ..-inch angles. The tops of the columns
have horizontal cap angles on which are riveted the lower flanges of the tranverse girders; the end angles of
the girder and the top of the column are also connected by a riveted splice plate. The six longitudinal
girders are web-riveted to the transverse girders. The outside longitudinal girder on each side of the viaduct
has the same depth across the tower as in the connecting span, but the tour intermediate lines are not so deep
across the towers. In the single trestle bents the columns are the same as those just described, but the
diagonal bracing is replaced by plate knee-braces.

The Manhattan Valley Viaduct on the West Side line, has a total length of 2,174 feet. Its most
important feature is a two-hinged arch of I68 1 ,' feet span, which carries platforms shaded by canopies, but
no station buildings. The station is on the ground between the surface railway tracks. Access to the plat-
forms is obtained by means of escalators. It has three lattice-girder two-hinge ribs 24 1 2 feet apart on
centers, the center line of each rib being a parabola. Each half rib supports six spandrel posts carrying the



INTERBOROUGH RAPID TRANSIT PAGE 6 3



THE SUBWAY




ONCRETE OVER IRON



.VORK HARLtM HIVt-H TUNNEL



roadway, the posts being seated directly over vertical web members of the rib. The chords of the ribs are
6 feet apart and of an H-section, having four 6 x 6-inch angles and six I 5-inch flange and web plates for the
center rib and lighter sections for the outside ribs. The arch was erected without false work.

The viaduct spans of either approach to the arch are 46 to 71 feet long. All transverse girders are 31
feet 4 inches long, and have a 70 x 3,, -inch web plate and four 6 x 4-inch angles. The two outside longitu-
dinal girders of deck spans are 72 inches deep and the other 36 inches. All are 3,, -inch thick and their four
flange angles vary in size from 5x3', to 6 x 6 inches, and on the longest spans there are flange plates. At
each end of the viaduct there is a through span with 9<D-inch web longitudinal girders.

Each track was proportioned for a dead load of 330 pounds per lineal toot and a live load of 25,000
pounds per axle. The axle spacing in the truck was 5 feet and the pairs of axles were alternately 27 and y
feet apart. The traction load was taken at 20 per cent, of the live load, and a wind pressure of 500 pounds
per lineal foot was assumed over the whole structure.

One of the most interesting sections of the work is that which approaches and passes under the Harlem 7//^<?J" under
River, carrying the two tracks of the East Side line. The War Department required a minimum depth ot Ha?'lc!H River
20 feet in the river at low tide, which fixed the elevation of the roof of the submerged part of the tunnel.
This part of the line, 641 feet long, consists of twin single-track cast-iron cylinders 1 6 feet in diameter



PAGE 64INTERBOROUGH RAPID TRANSIT



THE S U B W A Y



enveloped in a large mass of concrete and lined with the same material. The approach on either side is a
double-track concrete arched structure. The total length of the section is 1,500 feet.

The methods of construction employed were novel in subaqueous tunneling and are partly shown on
photographs on pages 62 and 63. The bed ot the Harlem River at the point ot tunneling consists of mud,
silt, and sand, much of which was so nearly in a fluid condition that it was removed by means of a jet. The
maximum depth of excavation was about 50 feet. Instead of employing the usual method of a shield and
compressed air at high pressure, a much speedier device was contrived.

The river crossing has been built in two sections. The west section was first built, the War Depart-
ment having forbidden the closing of more than half the river at one time. A trench was dredged over the
line of the tunnel about 50 feet wide and 39 feet below low water. This depth was about 10 feet


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Online LibraryInterborough Rapid Transit CompanyInterborough Rapid Transit: the New York subway; its construction and equipment → online text (page 4 of 13)