The Manitowoc tribune. [volume] (Manitowoc, Wis.) 1866-1878, 1869-04-29
THE BRIDGE AT OMAHA.
A Great Work in Engineering.

A Ufcdb VOfh III Engineering.
From'the Omaha Times.
TWAS not until spring of the present
year that work upon the structure COM
menced. The bridge which was designed
by Gen. G. NJ. Dodge, Chief Engineer of
the Union Pacific r. r. Co, will be ele-
waited on eleven piers, at distance apart
of $50 feet. These piers will be carried
to height of 10 feet above low water
mark. The superstructure will be Of iron
upon the plan of Posts patent infexible
truss. Its estimated cost is $1,000 900.
BY WHOM TO BE BUILT.
[. G. Sickles is in immediated charge
| of the work as chief engineer in behalf of
the company. E. B. Boomer & CO.. of
Chicago, the distinguished bridge build
ers, are contractors for the whole work.
and Gen. VIM. Sovy Smith, their chief
| engineer, is executing it. The following
| description of the manner of sinking the
enormous cylinders that compose the
PIERS and the way In which the latter
are constructed aud made firm, will be
read with interest at this time:
THE PENEUMAIIC PROCESS
for sinking cylinders for the piers of
bridges, foundations for docks, sea walls,
etc. was invented by Dr. Potts, of Eng
land, some twenty years ago, introduced
into this country by Charles Poutez. assist
ed by Z. E Sichies. now Chief Engineer
OF the Omaha bridge in behalf of the
Union Pacific Railroad Company. A
great many foundaions of this kind have
been sunk in Europe and in this country
Bridges over the Great Pedee, Santee,
and Cape Fear rivers, at the South, and
Harlem river, at the North. have been
built of piers consisting of pneumatic
cylinders
THE GREATEST WORK OF THE KIND,
In this country, however, is the enormous
iron Golfer dam, weig hing 90, 600 pounds.
sunk by Geo. w. Sovy Smith, at Waugo-
shance, In the Straits of Mackinac. The
General also sunk nine cylinders by this
same method in the Savannah river, for
the piers of a bridge to carry the Charles
ton and Savannah Railroad oyer thai
stream. This work was Interrupted By
the rebellion and destroyed during the
war.
The process and machinery employed
here are all the invention of Gen. Smith,
and so different from the original Dr.
Pott' S process, that they may be regard
ed as constituting new and much more
| rapid system.
LIE FLINDERS
| are 81 feet in diameter, ! inches thick,
and cast In sections 10 feet long. These
sections, except the bottom one of each
pile, are provided with interior fanges
at both ends, perforated with 81 holes,
to receive as many one-inch bolts for
uniting them. The bottom sections have
but one fange each, the lower end being
chamfered to reduce the resistance to
sinking.
PROCESS OF SINKING.
When pile is TO be sunk, one of these
lower sections is placed in position, an
alright cup is bolted upon it, the air ex-
hausted by air pumps driven by steam
engine, and the cylinder is driven down
by its own weight and the weight of the
atmosphere. The cap is then removed,
another section bottled on, the cap replac-
ed, and the air again exhausted.
The cylinder is thus driven to depth
depending upon the kind of material en-
countered. When the resistance to sink
ing becomes so great that the cylinder
can be driven no further In this way, the
process is reversed, and air Is forced into
the cylinder until the water is pressed
out under the bottom and through a
discharge pipe for that purpose. The
laborers then ascend to the bottom and
apply the flexible section, finishing the
discharge pipe, to the sand, when it is
caught up by the air current which is al
lowed to escape through the pipe and
| carried out with great rapIdity. This
method OF excavatlng by an air current,
invented and patented by General Smith,
is found so effective here that the first
| cylinder was sunk forty feet in ffty-four
| hours.
oBsTRUoTIoNs-uow OVERCOME.
| When material is encountered that
cannot be discharged by an air current,
such as clay or boulders, it is hoisted into
an air chamber bolted On top of the cylin-
| der, by a small hoisting engine attached
| to this air chamber, and discharged
through traps provided for the purpose,
and as the excavation from within pro-
] ceeds the cylinder Is forced down by