The Salt Lake herald. [volume] (Salt Lake City [Utah]) 1870-1909, 1897-06-06
BY FRANK W. SKINNER, NJ. AM.
soc. C. E.
Copyright, 1897 by S. s. Mcclure COP

Copyright, 1897, by S. S. Mcclure Coz
The building of the Offender building
on the northwest corner of Wall and
Nassau streets. New York, adds an
other conspicuous landmark TO the mar
vicious construction that within half a
dozen years has sprung up upon the
lower end of Manhattan island. AL
though it is not the tallest of the mod
ern office buildings. its design, con-
Struction and equipment is Of the same
class, its extremely narrow width made
it much more slender in proportion than
the tallest of them, increased the diff
ficulties Of design and the boldness of
construction, and makes it notable
example of its class, affording a fair
illustration Of some Of the most diff
cult and successful work that has been
executed.
First. some small steel pipes were
sunk 40 or 80 feet through the cellar
floor into the ground. The difficulties
of driving down such long and I'M
wieldy tubes in such restricted quarters
without disturbing the low ceiling were
overcome By driving successive short
sections Of pipe and screwing them to-
gether TO form a single continuous YER
tical pipe, whose penetration was aided
and samples of the soil brought up
from different levels by the operation
of high-pressure water jet inside the
pipe. The result indicated that the soil
was composed of cuic1sand, earth and
bOulders, about 50 feet deep, saturated
with water about 20 feet deep, above
a stratum of rocky hard pan.
This subterranean exploration had
been made to investigate the site upon
which Calender building, steel struc-
ture of practically 20 stories in height,
was TO be built and for which il was
necessary to design, estimate and con-
tract foundations adapted TO its i'm
Irense Weight and the character of the
soil. Il was calculated that the finished
building might develop foundation
pressure of about 10000 pounds per
square foot over the entire 1852 feet of
area of the building lot, and as this
was far more than the soil could safely
support, the foundations had to be car
RED down to the solid hard pan, which
was finally loaded to only 24.000 pounds
per square foot although it had sus-
tanned pressures of 10000 pounds per
square inch without perceptible signs of
yielding. Large and deep excavations
were. therefore, required, and they
could not be made in the wet and
treacherous ground. even by the most
careful and costly methods, without
danger of disturbing the yielding soil.
so as TO cause it to settle or flow from
under the walls of the tall and heavy
building adjacent so as to undermine /
their foundations and jeopardize their |
stability and the safety Of their occu- /
pants.
The responsibility rested upon the |
contractors, who determined TO avoid /
all risk by building under the old foun- |
dations columns extending down to the /
hard pan, and carrying the weight of /
the whole wall 10 that safe support (
Narrow vertical slots were cut close /
together partly through the foot of the +
wall in its outside face, thin and short 4
sections of very heavy steel pipe set up /
right in them, and forced down into the /
ground by powerful jacks on top, and 1
hydraulic jets inside. that cut away the
core like chisel; as fast as one section
of pipe was forced down another was
on to its upper end until at
depth of 40 or so feet the hard pan was
encountered and could not be pene-
trated even by pressure of 100 tons
under which the steel pipe itself was
compressed one-cuarter inch only to
expand again to its original length
when the strain was removed
The interior Of the pipe was then
cleaned out and filled with concrete.
and brickwork built on it TO the top of
the slot. where pairs of steel wedges
were driven in against steel cross ii
beams embedded in the old masonry
until they carried the full weight OF the
wall above
This novel method of UNDERMINING
had never before been attempted except
IN the recent case of the Commercials, Il
Cable building, where the columns were
made large enough for men to enter