Transactions of the American Society of Civil Engineers, vol. LXVIII, Sept. 1910 | Page 8

to another by lifting them
bodily by jacks, and putting in filler pieces before releasing the jacks,
not trusting to wedging to transfer the loads. In fact, apart from the
boxing-in of the surface railway concrete, no wedges whatever were
used. This appears to have been a decided advantage, for, with the
constant pounding of trains on the elevated railway and the jarring due
to heavy trucks on the pavement blocks, it is very likely that wedging
would have become loosened and displaced, whereas, with blocking,
there was little or no tendency toward displacement due to vibration.
Although the vibration of the structure, when a long length was
supported on girders "C" resting on the permanent viaduct girders on
the sides of the avenue, appeared to be considerable, not only vertically
but transversely, very careful observation showed that the sag in the
girder "C" due a live load of three elevated railway trains, one surface
railway car, and one heavy truck, amounted to 1/8 in. The sideway
vibration did not amount to more than 1/32 in. on either side of the
normal position. More vibration was caused by heavy trucks and
wagons going over the stone pavement than by the elevated railway
trains or surface cars.
No blasting was done near the supports of the elevated railway
structure while trains were passing over it, and occasionally trains were
stopped during a heavy or uncertain blast. A watchman on the surface,
day and night, and at first one and later two flagmen on the elevated
railway structure, were on duty at all times, reporting to the
Interborough Rapid Transit Company, by whom they were employed.
Log mats and timber protection for the girders and the columns of the
permanent viaduct were used, as shown by Figs. 1 and 4, Plate XLIX,
during the excavation of the rock core, and timber was also used to
protect the face of the completed portions of the concrete abutments.
In excavating the sides of the avenue, the rock broke better on the east
than on the west side, where large seams developed and some slides
occurred.
_Abutments._--As shown on Fig. 7, the face of the north abutment has

a batter of 2 in. to the foot, and the face of the south abutment has a
variable batter, the base being on a grade and the bridge seat being
level, and both maintaining a uniform distance from the center of the
Terminal Yard. The back walls of the abutments were not built until the
steel had been put in place.
No attempt was made to water-proof these abutments, but, in the rear of
the wall, open spaces were left, about 6 ft. from center to center, which
were connected with drain pipes at the base of and extending through
the wall, for the purpose of carrying off any water that might develop in
the rock. These drains were formed by building wooden boxes with the
side toward the rock open and the joints in the boxes and against the
rock plastered with mortar in advance of the wall. A hose was used to
run water through these drains during the placing of the concrete, for
the purpose of washing out any grout which might run into them. Each
box was washed out at frequent intervals, and there was no clogging of
the drains whatever. This method of keeping the drains open was
adopted and used successfully for the entire work. The abutments were
built of concrete, and the mixture was 1 part of cement, 3 parts of sand,
and 6 parts of broken stone.
The concrete was mixed in a No. 3 Ransome mixer, and was placed
very wet. No facing mixture or facing diaphragms were used, but the
stone was spaded away from the face of the wall as the concrete was
laid. Chutes were used inside the form, if the concrete had to drop some
distance. Work was continued day and night, without any intermission,
from the time of commencement to the time of completion of each
section.
The face of the concrete wall was rubbed and finished in a manner
similar to that used on the walls between Ninth and Tenth Avenues, as
described later.
Fig. 2, Plate LII, shows the east and central portions of the south
abutment, completed and carrying the permanent viaduct, and the
excavation completed for the west portion.
WORK BETWEEN NINTH AND TENTH AVENUES.

_General Description._--The work involved the excavation of about 5.4
acres, between the west house line of Ninth Avenue and the east house
line of Tenth Avenue, to an average depth of about 50 ft., the
construction of a stone masonry portal at Tenth Avenue leading to the
River Tunnels, and the construction around the site of the concrete
retaining and face walls.
The following estimated quantities