The Worthington advance. [volume] (Worthington, Minn.) 1874-1908, 1898-12-15
.cHIcAGo's NEW POST OFFICE.
Laying OF the Foundations Was q
Vast and Difficult UNDER "
n taking.

If all the materials in the recently
completed foundation for Chicago's
magnificent government building were
to be loaded on wagons, ton to each
load, and Is feet allowed for each
wagon and team, the procession of
teams and wagons would reach 731
miles, or as far as from Chicago to
Rochester. Gen. William Sooy Smith,
engineer in charge of the foundation,
recently read a paper on the sub
structure at meeting of the Western
Society of Engineers, in which he gave
many interesting data regarding the
work that has been done The past year.
These are some of the facts:
The soil On which Chicago rests is
loose and sandy, in general, for about
IL feet. Then comes stratum of hard,
brittle clay about three feet thick. Be-
low this, for so to 60 feet, there is very
soft, blue plastic clay, with spots of
sitter clay here and there and traces
of gravel, but nowhere is the clay firm
enough to sustain any considerable
weight. At a depth of from 69% to 71%
feet below the surface hardpan is
struck, and this is almost impossible to
penetrate. On account of this peculiar
nature of the soil it was decided that
the most feasible, safest and also least
expensive foundation would be one of
piles, resting upon the hardpan lime
stone.
Piles of Norway pine, 5,os7 in num-
Der, and none less than 16 inches in di-
ameter at the butt and more than ten
inches in diameter at the end, were
driven by the powerful drivers, and
each pile driven until it required from
six to eight blows of the hammer to
drive the pile one inch. The piles were
driven with lower ends squared, not
sharpened, and were cut off 261a feet
below street level and 1914 feet lower
than low water level of the lake. It
was nice job to cut off these tops of
piles at the required depth below, for
the trenches kept filling up with water
that oozed all too freely through the
clay. The work, in fact had to be
done under water. The piles and oak
platforms bolted to their tops are thus
perpetually immersed, insuring ever
lasting durability. Fifty-nine of the
piles are driven under the place where
the snbtreasury is to be.
AS the building is to weigh not less
than 100000 tons, each pile will have
it's share to perform in sustaining this
great weight. But the building will be
safe, for each pile is required to uphold
but 30 tons, whereas the extreme load
it will sustain is 1875 tons. There are
piles under London bridges over the
Thames, and also in bridges over the
Seine, which sustain weights of from 60
to 100 tons each. When the new Chi
cago public library was being built SO
tons of pigiron were loaded upon the
top of one of the piles, and the weight
stood for weeks without settlement.
Upon the tops of the groups of piles
white oak timber platforms are secure
~ bolted, and upon these platforms are
beds of fint-ike concrete three feet
thick which have undergone thorough
searching tests. The masonry for re-
tanning walls is of Joliet and Lemont
limestone. This was laid by eight der.
ricks, laying from 1000 to $500 cubic
feet of stone per day. In the excava
tions for the basement in the center OF
the lot 22,267 cubic yards of earth were
taken out, and in the digging of the
outer trenches 54,294 cubic yards more
were removed. Concrete to the extent
of 5,122 cubic yards, FOG, 1852 board meas
ure of timber Gaping, 2S4,144 cubic
yards of stone and 1897 cubic yards
of rubble masonry have been used.
The whole constitutes n typical pile
foundation, one in which engineers and
architects everywhere are interested
and one which builders CT edifces in
Chicago would do well to copy. There
is no danger that the new government
building will settle and crack. Anoth.
er significant fact, and one which re.
fleets great credit upon the architects
and contractors, is that not one of the
surrounding big uildings-Monad.
mock, Great Northern, Marquette OF
Grand Paciic-has been moved one
inch from it's place, Notwithstanding
the heavy pile driving that has been
going on for many months. The de-
preston of a part of Jackson boule
ward, on account of the pile driving
was because the temporary plank wall
that had been driven in the outer side
of the trench was not strong enough tc
prevent the spongy, watery clay from
coming in to fill up the depression
caused within the fence by the pile
driving. Chicago Times-Herald.