New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1903-12-06
SINKING SCREW PILES.
4 Machine To Be Used an Construct
inc the North RiUer Tunnel.

The great novelty about the twin tubes which
the Pennsylvania Railroad Company Will construct
under the Hudson will consist in the foundation to
be provided for them. This as The Tribune has
already pointed out will consist Of a series of
hollow cylindrical cast iron piles fifteen feet
apart and about two feet In diameter. These piles
differ from those in common use In several inn
portant particulars One OF them is the material
of which they are composed. Another is the way
in which they to be forced downward into the
silt clay which forms the river bed.
A wooden pile be driven with hammer. the
latter. being mounted on a scow. That system In
wolves temporary obstruction of navigation and
IN the present must be avoided Hence these
piles are to be sunk by screwing. and for that
purpose each will have point OF special design. to
enable it to be driven down when rotated. AS this
operation will he conducted at considerable dis
lance below the surface of the water-in the yet
Incomplete tunnel for which II is needed-the piles
Will be made in short sections, seven eight feet
long, and will be boIted to another as Oc-
casion requires 1t is possible that piles may
thus be built up to a length Of hundred and
fifty feet
test has recently been made OF the apparatus
for sinking the piles. The experiment was con-
Quoted at the outer end of wharf In weehawken
only a short distance from the site of the proposed
tunnels.
Rotation impaired to the pile by water IN
two horizontal cylinders in which the plungers
have an 1S-inch stroke. The cylinders themselves
were 111A inches in diameter. pressure of 100
and the power exerted at a single stroke may
reach $4,000 foot-pounds or more Ten strokes were
needed to secure complete rotation of the
screw A stout ratchet was so attached TO the top
OF the pile that the latter could not backward
after 1t had been turned in direction.
Lest the combination OF this tremendous force
and the weight Of pile might not be sufficient
to overcome the resistance OF the clay to the down
ward progress OF the pile. especially after 1t had
been driven considerable distance, the possibility
OF exerting direct vertical pressure its upper
end was considered. Means for that purpose
were finally devised A hydraulic jack ar
ranged directly over the pile. and in of the
experiments it was made to impart thrust equva-
lent TO a load of SS3, $50 pounds.
According to The Iron Age" which describes
the work, pile driven downward 81 feet
10 inches in the course of 3S& turns. about II
inches to a revolution. The time expended was
nine hours and five minutes, fourteen minutes TO
a turn. No doubt more rapid work Will be done
when the tunnel itself is taken in hand
An entirely different set OF experiments. de-
signed TO show how much screw piles likely to
settle when In service has also been in progress.
or these THE Iron Age gives the following ac-
count:
The dead. load tests occupied period of hye
and one-haf months. The load, including the pile
itself was gradually increased from 100000 TO 500 00C
pounds by increments of 20 900 pounds. During the
first five days the pile subsidized about one-quarter
of an nch and for every 10000 pounds added there
after the pile apparently subsidized about OBS inch