Wessington Springs herald. (Wessington Springs, Aurora County, Dakota [S.D.]) 1883-1891, 1891-03-27

rises one foot in fifty feet for 3,192 feet.
Inc American great cutting is fifty-two
feet deep. about 200 feet wide at its
broadcast part, and rises one foot in fifty
feet for 2.533 feet. An inclined track
was laid for fiat cars to haul out the tun-
mel SOIL In September, 1890, two steam
ShoVels began work on each side of the
river Each shovel was attended by a
locomotive and train of fiat cars Hun
ofeds OF men are employed day and
night When the tunnel proper was
commenced scarcely more than two lay
erS OF the soil had been removed. The
tunnel company grew impatient, and on
Monday, Feb. 0, 1891, took the Canadian
work from the contractors. Over 500
men are employed. AS the tunnel will
not be opened for traffic until after the
approaches are completed the work on
1le cutting is being rushed.
Ar. Alfred T.. Beach, an American
engineer. designed and used shield in
!he broadway tunnel, New York City,
~ 1868. Since then similar shields have
p nee used in Chicago, Buffalo, Hudson
hVer, London, and other tunnels. This
eAG:aVatlng shield may be compared to
s!iihder with no head. 1t is circle of
s.eeI plates. Inside these plates are
p'ates doors, and aids for the workmen
~ 'ie 'front.' end are knife-edges to pene-
t '[i the SOIL In the rear portion Of the
S A around the main walls, are n.y.
ulaui'c Jacks, each supplied with valve,
~ that Its action may be independent of
o'l '' The material of the tunnel
nuns masonry, or cast iron, is built in
.'ie rear OF the shield. Pressure is APP
p ~: TO the hydraulic rams, and thus the
iaield IS pushed ahead the length of the
t t1 plstons. The soil is pushed into
u'Ae 'front.' OF the shield, and the men re-
moNe 1T by loading it upon cars, which
vi" ",; pushed out to the tramways, on
n %nlth they are drawn by mules, or
, nu' Ses 10 the entrance of the tunnel,
"ncfe they are hoisted to the regular
" ns' cars and taken to the dumping
.,i'uiia. While the men are removing
s'le soil in front the men in the rear are
IIuss erecting the walls of the tunnel.
IN case of iron plates, a revolving crane
ny i'iIs thc plate by means of counter
" I'd, weight to the desired position,
WI wiIefe 1T is bolted to the other plates.
' mneli the section of the tunnel is COM
1 plesed' and the pistons of the rams have
nseh Drawn back, the air is applied again,
a an" the Jacks pushed forward for an
o'n ~ section of the tunnel to be put in.
,,,.N thls arrangement the workmen are
WAYS anS protected from danger above,
I'o"lid or below. The air pressure
r nneps the water back in front, and the
T S'pleted tunnel protects the rear.
"o shlelds were used in the st. Clair
,r T,'lei, Each weighed eighty tons.
no ni We're brought in sections to the
wnra bank of the cutting. where they
n,n ,. erected. Then came the problem OF
ni rao1ls the shields in position. Wooden
ar %Shs We're laid, huge ropes were placed
va Gal' I, each shield, and they were grad
nta .S lowered by men. In eighty min
mo,,t they were in place at the proposed
IL so OF the tunnel. Each shield was
Of t Ne, long, and had an outside diameter
nci - Z, z feet. The steel plates were
l,Na muck. Each shield had twenty-four
E :"i"lilc rams at equal distances apart.
"Sl ram had a stroke of 3 feet and
Him. u'ameter of inches. Each
''' She plstons were shoY.d ahead the