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

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front portion of the wall. For convenience in construction, both retain-
ing walls were made as chords instead of arcs or circles, the angles
being at the pilasters, which also serve as expansion joints. The outer
portals are recessed 9 ft. into the embankment, and are joined to the
main wall by curved wing-walls.




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6'" 16'




Less than 6 '








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Constr. Joint

R. 12


J^'q tw. dj'o long. 12"o.c.
H'd tw. if eVc

C Rods !
Al, Bl, B2 Rods6"o.c.


Fig. 7.


Thirty tunnels through the embankment are provided as entrances
to the amphitheater for spectators. These are all 7 ft. wide and 8 ft.
high. They start from the level of the ground outside the Bowl and



terminate at the twenty-fifth row of seats from the bottom, where they
are spaced uniformly along the cross-aisle. As the level of the groimd
opposite the main gate-house is 11 ft. lower than that on the opposite
side, these tunnels are all on a slope, those on the westerly side being
down toward the field on a maximum grade of 2.37%, and those on the
easterly side up on a maximum grade of 4.18 per cent. The end tunnels
have grades of 0.24 and 0.26%, respectively, just sufficient to afi'ord good





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in the thinnest part, under the junction of the tread with the riser. In
addition to the regular reinforcement, a strip of wire lath, 6 in. wide,
was built into each of the aisle steps, ^ in. below the surface, in order
to prevent the spalling of the corners of the steps.

To prevent the glare from such a large surface of concrete, if left
in its natural color, and to afiord variety of coloring, the facing was
made a dark slate by the addition of 1 lb. of lampblack to each barrel
of cement used in the granolithic surfacing. The inner retaining wall
was left in the natural color of the concrete.

Wood Facing.

The wood facing, on the slope of the embankment, consists of 2
by 6-in. sills, laid radially not more than 4 ft. apart. To these were
spiked triangular-shaped blocks, 3 in. thick and 18 in. long on the
upper edge, for supporting the tread of the steps, which are 18 in.
wide, the remainder of the 30-in. space allowed for each row of seats
being left uncovered. Although this left the earth slope exposed to
the elements, the material in the embankment is so porous and absorbs
water so readily that little trouble has been experienced from washing
of the embankment.


The permanent seats built on the concrete facing consist of 2 by
10-in. planks, with the upper side planed to a curved surface, sup-
ported on galvanized-steel standards anchored to the concrete. These
standards were made in four different sizes, in order to fit the varying
height of the risers and make the height of the seat within the limits
of 17| and 18^ in. The back rest is a 1^ by 5-in. board, with the front
face curved and the corners roimded, supported by 2i by 2J-in. wooden
standards bolted to the backs of the steel ones. The wood for the
permanent benches is rift-sawed Douglas fir from Oregon. U-shaped
Tobin bronze bolts were specified for anchoring the steel standards to
the concrete, but a lower price being offered by the contractor for
Sherardized-steel anchor-bolts, the first benches erected were anchored
with them, but, as these proved to be not well adapted for the purpose,
their use was abandoned, and about two-thirds of the seats are fastened
with the bronze bolts as originally planned.

The temporary benches on the wood facing consist of 1^ by 10-in.
spruce boards supported by 2 by 12-in. wood standards spiked to the



sills. These benches are provided with back rests of the same kind as
the permanent seats.

A minimum spacing of 17| in., with an average of a little more
than 18 in. was allowed for each sitting. With this spacing there are
60 C17 seats for spectators.


Fig. 12.

A stand for the representatives of the Press was erected on the
westerly side of the Bowl, just below the top of the embankment.



This is provided with two rows of seats, and shelves for convenience
in writing or telegraphing. With a spacing of 21 in., this stand will
accommodate 249 persons, sitting. In addition to this, there is pro-

Blocks 3 thick:
Spaced equidistant between
aisles, and not over


Pig. 13.

vision for three rows of persons, standing, giving accommodations for
about 400 additional, or a total of about 650 in the press-stand. Back
of the press-stand, and raised a little above it, a stand for pho-
tographers will accommodate about 50 operators.


Peculiarity of Seating Arrangements.

The seating arrangements in the Bowl are noticeably different from
those in other large stands, such as the Harvard, Princeton, and Syra-
cuse Stadia. The plan of having a low riser for the bottom step and
then increasing uniformly to a high one at the top is peculiar to this
structure, and has the advantage that, while it gives the spectators
occupying the upper rows of seats the same facility for seeing over the
heads of those sitting in front of them which the occupants of the
lower rows enjoy, it permits of a lower and, consequently, a much
cheaper and more stable structure. For example, in the Harvard
Stadium the 31 rows of seats occupy a height of about 41 ft.; in the
Syracuse Stadium the 18 rows of seats have a height of 27 ft.; in the
Princeton Stadium the 48 rows have a height of about 62 ft.; but, in
the Bowl, the 60 rows of seats have a height of only 49 J ft. In these
other stands, the height of the riser is the height of the seat, the
spectator sitting directly on the concrete step or on a board laid
directly on it. Seats thus constructed are not very inviting on a cold
day, particularly during a rain storm, when the water is dammed back
on the seats by the spectators sitting on them. In the Bowl, the
benches are raised a sufficient height above the concrete to permit the
water to run freely over the steps without coming into contact with
the spectators. The Bowl seats, also, are provided with back rests, but
those of these other structures have none.


Ground for the Bowl was broken on June 23d, 1913, by President
Hadley, of the University, turning the first sod. The construction
was begun during the following month by first removing the loam
from the site and from the adjoining area which required grading.
The black and yellow loam was stored in separate piles and saved for
resurfacing the grounds after the completion of the structure. The
average depth of this preparatory stripping was about 22 in. For
removing the loam, on short hauls up to about 100 ft., drag-scrapers
were used; on hauls from about 100 to 250 ft., wheel scrapers; and for
long hauls, bottom-dump wagons.

Several plans for placing the material in the embankment were con-
sidered by the contractor, but the one finally adopted for handling the
greater part of it was the use of two drag-line scrapers running on


adjustable cables and operated from two towers, 85 ft. high, by two
12 by 16-in. double-drum engines, supplied with steam from two
125-h.p. locomotive boilers. The towers ran on a four-rail elliptical
track laid aroimd the outside of the Bowl. One end of the carrying
cable was fastened to a "deadman" on the opposite side of the field
from the tower; the other end ran over a pulley at the top of the
tower and was fastened to one of the drums of the engine, by which
means it could be regulated for filling or emptying the bucket, the
cable being slackened for filling the scraper and then tightened for
dumping it. The second drum was used for hauling the scraper up
the slope; it ran back to the filling point by gravity.

As the two scrapers, working night and day, did not remove the
material rapidly enough to indicate the probable completion of the con-
tract within the time specified, two f-yd. rotary steam shovels were
started, in order to expedite the work, and these filled bottom-dump
wagons. The teams with their loads were then drawn to the top of
the embankment by a portable hoisting engine working there, and the
material was distributed as desired.

As it was impracticable to roll the embankment below the level of
the tops of the tunnels, dependence for packing the material in this
portion of the work was placed on such consolidation as could be ob-
tained by the liberal use of water, and such tamping as was done by
the teams being driven over it. Streams of water were always kept
playing on the embankment where material was being deposited, and
the portions next to the tunnels and the retaining walls were generally
sluiced into place from piles deposited by the teams or scrapers.

Above the tops of the tunnels, the material deposited by the scrapers
was left in ridges extending across the embankment; that from the
wagons was left in scattered piles; in each case sufficient material was
placed to make layers 6 in. deep when leveled down. The leveling was
done with horse-drawn scrapers. The material was thoroughly watered
and then rolled, first with a grooved and then a smooth roller, one fol-
lowing in the track of the other. The rollers weighed 800 lb. per ft.
of length, and, by using them alternately, the effective weight was
practically doubled. Each roller was drawn by four horses, and each
passed four times over the entire area being rolled. The embankment
was kept about 1 ft. wider than the theoretical lines in order to insure
the compacting of the material out to the edges of the finished fill.


To ascertain the settlement in the embankment, after its comple-
tion thirty-one benches were established around the top. Each bench
consisted of a mass of concrete in which was inserted a ^-in. square
steel rod, placed about 4 ft. below the surface, the end of the rod
terminating a few inches below the surface. Levels taken on these
benches have shown that, after a lapse of 2 years, the average settle-
ment has been only about J in., and the maximum settlement at any
bench about i in. About one-half of this settlement occurred within
the first month after the establishment of the benches.

A comparison of the volume of the embankment with that of the
excavation shows that the material in the former is nearly 7% more
dense than that of the natural bank. It is probable, therefore, that the
slight settlement which occurred was caused by the compression of the
underlying material, due to the added weight of the fill, rather than by
any subsequent consolidation of the embankment itself.

The favorable results obtained in securing a solid embankment
were probably due to the character of the material of which it is com-
posed and the method of placing it. The material was sand and gravel,
almost entirely free from clay, loam, or other substance which would
retain water. By the alternate use of the two kinds of roller, not only
was a downward pressure exerted, but, at the same time, a lateral
motion was given to the particles of sand, thereby tending to bring
them into close contact with one another.

Water for sprinkling the embankment and mixing concrete was
obtained from a group of driven wells at the foot of the bluff, at the
edge of the marsh, and was distributed by a 4-in. pipe, laid around the

Online LibraryAmerican Society of Civil EngineersTransactions of the American Society of Civil Engineers (Volume 81) → online text (page 22 of 167)