Watertown republican. [volume] (Watertown, Wis.) 1860-1906, 1903-12-23
SINKING SCREW PILES.
A Machine to Be Used in Constructing
the North River Tunnel


The great novelty about the twin
tubes which the Pennsylvania Railroad
company will construct under the Hud-
son will consist in the foundation to be
provided for them. This, as The Trib
une has already pointed out, will consist
of series of hollow, cylindrical castiron
piles, fifteen feet apart and about two
feet IN diameter. These piles differ from
those III common use III several inn
portant particulars. One of them is the
material of which they are composed.
Another is the way in which they are to
be forced downward into the silt or clay
Which forms the river bed
A wooden pile can be driven with
hammer, the latter being mounted on a
ScoW. That system involves a tempo
rary obstruction of navigation, and i'll
the present case must be avoided. Hence
these piles are to be sunk by screwing,
and for that purpose each will have Il
point of special design, to enable it to
be driven down when rotated. AS this
operation will be conducted al a conSid
cradle distance below the surface Of the
water-in the yet incomplete tunnel for
Which 1T is needed-the piles will be
made III short sections, seven or eight
feet long, and one will be bolted to an
other as occasion requires. 1t is pos
Slble that some piles may be thus built
UP to length of 80 feet.
A test has recently been made of the
apparatus for sinking the piles. The ex-
pertinent was conducted at the outer end
of wharf in Weehawken, only short
distance from the site Of the proposed
tunnels.
Rotation was impaired to the pile By
water in two horizontal cylinders, III
which the plungers have an 1S-inch
stroke. The cylinders themselves were
1111a inches in diameter. A pressure OF
Zoo or 1900 pounds to the square inch
can be developed, and the power eXerted
at a single stroke may reach $4,000 foot
pounds or more. Ten strokes were need
ed to secure one complete rotation of the
screw. a stout ratchet was SO attached
to the top of the pile that the latter could
not move backward after it had been
turned III one direction.
Lest the combination of this tremen-
Gous force and the weight Of a pile
might not be sufficient to overcome the
resistance Of the clay to the downward
progress of the pile especially after 1t
NAG been driven a considerable distance,
the possibility of eXerting direct vertical
pressure .on its upper end was consid-
cred, Means for that purpose were
nnaily devised. hydraulic jack was
arranged directly over the pile, and IN
some OF the experiments it was made to
mpart a thrust equivalent to d load of
3S3,333O pounds.
According to The Iron Age, which de-
Scrlbes the work, one pile was driven
w WI " tIu OF JSeI III 1ncn0S IN the COURSE
OF 5SA turns, or about IL inches to a
revolution. The time expended was nine
hours and five minutes, or fourteen min
ntes to turn. No doubt more rapid
work will be done when the tunnel itself
Is taken in hand
An entirely different set of expert
ments, designed to show how much
screw piles are likely to settle when III
service, has also been in progress. OF
these The Iron Age gives the following
account:
The dead load tests occupied a period
OF i've and one-half months. The load,
including the pile itself. was gradually
increased from 100000 to 100000
pounds by increments Of 10000 pounds.
During the first five days the pile sub
slued about one-quarter of an inch, and
TOR every 10000 pounds added thereafter
the pile apparently subsidized about .02o
inch, but this was compression in the
plle Itself, which now measured 14S feet
between the screw point and micrometer
attachment. The 100000 pounds was
Kept on for about one and one-haif
months, when the load was increased TO
6UOOOO pounds for another month and a
half without subsiding. The pile was
then removed
Before this was done a series of drop
tests was made. A hammer of 1850
pounds nearly two tons), with fall OF
one foot, was applied in 1872 series Of 250
drops each, while the dead load at the
same time was increased from 100000 to
$4,000 pounds. Altogether 1000
blows were applied at a rate averaging
thirty blows a minute without producing
any appreciate effect" New York
Tribune