Evening star. [volume] (Washington, D.C.) 1854-1972, 1930-05-18
HUGE DETROIT RIVER TUBE
CHANGES TUNNEL-BUILDINC
Is First Subway to Be Constructed ON
Dry Land, Floated to Suite
and Submerged.

sible to the required grade Of the tube, ~
Mai. Vale said This necessitated q
trench with an approximate bottom Of
20 feet and q depth of water varying
from IS to 80 feet. The clay bed OF
the river is very stiff and stands better
than 1-to-1 slope. Just previous to
sinking q tube . bed of sand and gravel
was placed in the bottom of the trench
and brought to the exact grade by use
Of a specially designed leveling device.
This consists of a raft constructed of
steel pOntoOns feet in diameter.
The two outside pontoonS are 10
feet in length, and at either end four
shorter pontoons are placed parallel
with the longer ones thus making a
rectangular float bound by steel pom
toons. Steel rails are mounted on the
two long pontoons, on which runs a
travelling crane. Suspended by four
cables from this carriage is a steel grill
age constructed of I-beamS The float
Is anchored directly over the trench,
and at each corner are suspended con-
crete blocks Weighing about 1915 tons
In water.
Blocks Lowered Into Trench.
"These blocks are lowered into the
trench and the suspending cables are
pulled out. Submerging the float about
6 inches deeper than It's normal draft.
This prevents the action of the waves
from moving the float and holds the
track on the pontoon at the correct
position. AS clam shells filled the
trench with sand and gravel. this de-
vice moves backward and forward and
the grillage dragS the material to the
correct grade.
Some 800 feet from the Detroit Har-
Dor line five clusters Of piles were
driven down. To these were moored
each tube while 1t was being prepared
for the sinking operation. When ready
for the submerging, two buoyance scowS
were placed over the partly submerged
tube. Heavy cables were attached to
water was admitted to the tube. very
little in excess Of so tons weight was
handled, although each segment weighed
from $500 to 1000 tons.
THE metho1 of connecting the tubes
when they were submerged into the
trench may be of special interest An
unusually simple and effective detail
was devised to join the several SUBJ
aqueous sections. Cast-steel Tugs were
riveted TO the sections. On one end OF
the lug was placed, Immediately below
extended about 10 inches beyond the
upper half On the other end of the
lug was placed similar plate.
Steel Pin Joins Luxs.
THE first section sunk had this lug
on its outer end below the horizontal
diameter, so that the next was lowered
into position quite easily. The Tugs
were connected by 5-inch steel pin,
held In position by a ring This as
sisted the divers in putting the sections
securely together, before the wooden
bulkheads were knocked out"
In excavating the approaches to the
tunnel, the largest shield machine ever
used in America was employed. It was
necessary to bore distance of 466 feet
on the Detroit side of the river and 986
feet on the Ontario side. The Detroit
terminal Is but one block distant from
the woodward avenue business district
and opens into four streets, which will
materially assist in handling the heavy
traf11c without congestion. The tunnel
extends under Randolph street to the
river, to the Canadian harbor line and
thence under private property to the
Windsor terminal.
The total length from terminal to
terminal Ia 5,135 feet and its length
from street grade to street grade SEAS
feet. The maximum grade on the De-
troit side Is per cent, as compared
With 3.05 per cent on the Windsor side.
The location of the terminals and the
government requirements of 80 feet of
water at the harbor lines and IS feet In
the channel. were the governing factors
in establishing the grades.
Shield Machine Bores to River.
The giant shield machine which
bored" the tunnel from the terminal
to the under-river location of the steel
and concrete Segments, Is 35 feet wide
and is feet long. More than 100 muck
ers" toll In three 6-hour shifts digging
away the earth from the front of the
machine by use Of small power shovels.
Hydraulic jacks, exerting a pressure of
$50 tons. drive the monster machine
forward 80 inches at jump.
THE outstanding feature of the
shield-driven tunnel is Its steel lining"
said Maj Vale. Heretofore, on shield
driven tunnels, cast iron or wooden lin
ing has been used. In this tunnel the lin
ing consists of stamped and electrically
welded steel plates. This kind of lining
was adopted over the cast iron on the
basis Of economy. The weight of the
steel lining is about as tons a lineal
foot OF tunnel while q comparable one
of cast iron would weigh about tons
a lineal foot.
THE liner plates are in the shape of
pans az feet vide, feet long and 10
inches Deep made Of three-eighths steel
plate. The top chsners are stiffened by
means Of structural angles and stiffen-