Delaware tribune. [volume] (Wilmington, Del.) 1867-1877, 1870-01-27
Tho GREAT bridge ut Omaha.

THE PROCESS or BUILDING IT-A TRIUMPH OF
ENGINEERING SKILL.
Mr. T, E. Sickels, the efficient Engineer in
Charge of the great work of building the Pacific
Rail- oaa bridge across the Missouri, at Omaha,
has progressed during the fall, very satisfactory,
in his gigantic work. Al our suggestion, he nus
furnished the COMMERCIAL with the following
interesting description of the successive steps
taken in the process of erecting the structure. IL
should be added that these data have been In our
hands some weeks, but will be OF us much inter-
est, now, as ever .
Quaintance of many of our readers His home is
at Keppett Square, Chester county, and he wss
Chief Engineer in the construction of the Phila-
delphia and Baltimore Central Railroad
THE BRIDGE AT OMAHA
will consist of eleven spans OF superstructure of
| twenty-five feet each, supported by one masonry
| abutmept, and eleven piers formed of iron col
| umns sunk by the poncumatc process Three
| columns will be sunk Tor each pier, Win lneir
centres on line at right angle to the line OF the
bridge. The up stream column will be five feet
| In diameter, aud the two other columns of the
pier will be eight and half feet in diameter, WIN
spaces intermediate OF twenty ieet and ten icct
| respectively, making the length OF the pier nifty
| two feet On the line of the bridge the soundings
| indicate that rock undelies the river to depths
varying from twenty-tour feet on the west side 10
seyeuty-fve feet on the east side helow low water
mark, the greatest depth of water at this time
being about fifteen feet. II Is intended that the
iron columns shall be sunk not only 10 the ck
but shall also be securely fastened thereto, VIII. re-
by stability of foundation will be insured. The
column five feet in diameter will extend from Inc
rock to the level of low water only, and VIII
serve for the support of the end of the iron ice
breaker the upper end of which will rest again
the side of the adjoining maia column, and i's
fastened thereto. The main columns Will extend
from the rock to the bridge seat which is to be
fifty feet above high water and will vary in length
/, from eighty-ive feet to one hundred and iorty-
five feet the distance between high and low
, water being twenty feet The columns VIII DC
formed OF sections ten feet long, cast with q
nauge at each end, bolted together with one-inch
) bolts four inches apart. The thickness of iron
I will be one and three quarter inches IN the ~
stream column, and one aud n half inches in the
: lower column. The weight of tue sections average
. eight and q half tons each When the columns
are sunk to the rock and fastened they Will ht
a filled with cement rnbble masonry. Betwe en- loN
and high water, the spaces between the column
Ia will also be filled with cement masonry, restlni
l. on iron floors supported by brackets b0lted to th
!, columns, and cnveloping the masonry thus laid
will be large wroughtiron plates rivelted togethe
!. and to the columns. Above high water, and ex
5. tending up to the bridge seat, frame oil cas-
h iron braces and wrought iron rods will be pace
between the columns
% PROCESS OF SINKING THE COLUMN.
Il When q column is to be sunk, several Of th
~ sections are bolted together to form such lcngt
A. that when the bottom OF the column rests on th
T. he'd of the river the top will extend ten or htee
: feet above the surface of the water. These SET
Ut tons are lowered by derrick until the boltoi
Is rests on the bed of the river, care being take
re that the column shall stand perpendicular, On
shall be precisely in the required position. a
airtight iron cap is next bolted to the top OF u
-st sectops, and air is forced into the column by
Is pumps driven by n steam engine. The condel
ed sation Of air within forces out the water eitn
under the lower edge of the column or through
ng pipe provided for the purpose. When the wat
&c. Is excluded workmen descend to the bottom, az
los shovel up the sand to the lower end OF d
as charge pipe, when the material Is caught oy Y
40 escaping air current, and carried up through q
are discharge pipe and delivered on the outside.
&c. the material is thus excavated, the column
re, scends by its weight, analogous to the operate
ted moved, another section bolted on, the cap repac
md and the process OF excavation continued until !
ety bottom OF the column rests ON the solid roc
.r This process of airexcavation is the discovery
~ Charles Pontez, Esq, OF New YORK, an engine
'ho of distinguished ability.
Be- When any material is encountered, In the pr
the cess of excavating, that cannot be discharged
the air-current such as clay or bouders, 1t
rRe hoisted up into an air chamber, bolted on top
the cap, by small steam engine attached there
as | aud thence discharged through an ar-tght TIT
-, The euperstructure will consist of eleven spf
iiai OF Posts Pruss. This truss will be composed
ties iron throughout, the top chord only,to be oi
nee iron.
=, This plan of euperstructure is in extensive
'as aud is highly approved by engineers.
M. The entire length OF the bridge and approach
lien will be two miles, and the cost is estimated
ma two millions of dollars. At the present time fl
of the columcs have been sunk TO depth vary
oou from forty to seventy.ave feet The mater
through which the columns pass in their desce
cite CONSIST of fine sand for about twenty feet,
rar proaching to quicksand in character, and the
No' TO the rock, coarse sand with thin stratt
and clay. At the depth of thirty feet below the
best Of the river limbs OF trees have been encounter
ora and water worn Jumps Of coal have been foun,
a.o kind known as g lguite," which is believe,
the have been washed down by the Missouri from
er Of Rocky Mountains,-a distance of 2500 miles.
The work proves to be of more favorable cl
acter than was anticipated. No difficulty, is
date perieuced in sinking the columns, nor have
have of the laborers inside the columns been luuri
ain q undar pressure Of forty poundr per square
Abovs atmospheric pressure =