Wauwatosa news. [volume] (Wauwatosa, Wis.) 1900-1948, 1903-12-26
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 10 be
provided for them. This, as The Trib-
une has already pointed out, will consist
OF a series OF hollow, cylindrical castiron
piles, hfteen feet apart and about two
feet III diameter. These piles differ from
those in common use in several inn
portant particulars. One of them is tine
material of which they are composed.
Another is the way i'll which they are to
be forced downward into the silt or clay
which forms the river bed.
wooden pile can be driven with a
hammer, the latter being mounted on il
scow. That system involves tempo
rary obstruction of navigation, and in
the present case must be avoided. Hence
these piles are to be sunk by screwing,
ana for that purpose each will have i
point of special design, TO enable it TO
be driven down when rotated. AS this
operation will be conducted at a consid-
cradle distance below the surface of the
Water-in the yet incomplete tunnel for
which it is needed-the piles will be
made in short sections, seven or eight
feet long, and one will be bolted TO an.
other as occasion requires. 1t is pos
slbie that some piles may be thus built
up TO length of $50 feet.
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 shor.
distance from the site of the proposed
tunnels.
Rotation was impaired to the pile by
water in two horizontal cylinders, in
which the plungers have an 1S-inch
stroke. The cylinders themselves were
1lH2 inches in diameter. A pressure Of
100 or 1900 pounds to the square inch
can be developed, and the power exerted
at single stroke may reach 10000 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 il had been
turned in one direction.
Lest the combination of this tremen-
dous 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
mad been driven considerable distance,
the possibility Of exerting direct vertical
pressure on its upper end was consid-
cred. Means for that purpose were
hnaily devised. y hydraulic jack was
arranged directly over the pile, and in
some of the experiments il was made to
lmpart thrust equivalent to a load OF
1880 pounds.
According to The Iron Age. which de-
scribes the work, one pile was driven
downward 81 feet 10 inches in the course
Of 3SA turns, or about IL inches to
revolution. The time expended was nine
hours and five minutes, or fourteen min
utes to a 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 IN
service, has also been in progress. OF
these The Iron Age gives the following
account
The dead load tests occupied period
Of five 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
sided about one-quarter of an inch, and
Tor every 10000 pounds added thereafter
the pile apparently subsidized about .02J
inch. but this was compression in tho
Pile itself. which now measured t4S feet
between the screw point and micrometer
attachment. The J0O00U pounds was
kept on for about one and one-half
months. when the load was increased to
100000 pounds for another month and
half without subsiding. The pile was
then removed.
Before this was done a series 81 drop
tests was made. A hammer of $3.50
pounds tnearly two tons, with fall Of
one foot, was applied in 1872 series Of go
drops each. while the dead load m The
same time was increased from POO, 900 TO
10000 pounds. Altogether $4,000
blows were applied at a rate averaging
thirty blows a minute without producing
any appreciate effect. New York
Tribune.