Vermont phÅ“nix. [volume] (Brattleboro, Vt.) 1834-1955, 1905-02-10
AN AMAZING TUNNEL.

A Method Of Boring That Not only
crawIs Into a Hole and Pulls the Hole
In After It, but Pushes the Hole on
Ahead.
The rapid progress made i'm the con-
struction of the trolley tunnel under
the Hudson river at New York is excit-
ing the wonder and admiration of en-
gineers. The records of fast tunnel
driving have not only been broken, but
left out of sight And yet the chief
feature Of the work is it's extreme sim
plicity-the ease with which the task
formerly abandoned as all but impossible
is being pushed ahead at so great speed
Says Engineering News in an Editorial:
Everyone has heard of the person
who, for the purpose of escaping from
the observation of his felowmen, crawled
into a hole and pulled the hole in after
him. That mythical feat is now equalled
by the achievement of a well-known
New York engineer who is driving a
tunnel under the Hudson river and act
ualy pushing the hole ahead of him.
The work on the south tube for the Hud-
son river tunnel, represents method
of tunnel-drving which, we risk little
in saying, has never been carried on or
attempted before In the world. That 1t is
successful Is attested by the rate at which
the tunnel is being driven, which far ex-
ceeds all records of fast tunnel-driving
ever made.
What is being done is to push the
hydraulic shield right into the soft mud,
which is forced to either side and up
ward into the bed of the river. The
tunnel is thus not being eXcavated at all,
but 1t Is actually bored in the same
manner that an awl bores a hole in
wood or leather. OF course, in driving
tunnel in this manner, nearly all the
u 10
upon submarine tunnelling are elimin-
ated The workmen are protected by the
iron walled tunnel around them and the
shield in front. So long as the shield
can shove its way ahead without en-
countering boulders or other obstacle,
necesstating the opening of the bulk
head doors and work in front of the
shield, the workmen are as safe as IL
they were in the open air. Moreover
when the shield is pushed forward in
this manner, there is actually no tun-
melting work to be done. All the work
men have TO do is to place ring after
ring of the cast-iron lining as the shield
moves ahead Hydraulic power makes
the hole that is ordinarily dug by pick
and shovel and dynamite.
1T will be evident. of course, that this
method of working is only made possible
by the exceeding softness OF the semi
fluid silt underlying the Hudson river and
This semi-fiuid silt has defeated every
engineer who has hitherto attempted to
penetrate it by ordinary tunneling
methods. De Witt Haskins spent years
of time and a large slice of Trenor w.
Parks fortune in driving 1000 feet of
the north tunnel, and the enterprise was
then abandoned by both engineers and
capitalists. After lying idle for half a
dozen years, an English corporation un-
dertook to complete it with the famous
| firm of S. Pierson & Son as the con-
tractor and the distinguished Sir Ben
jamin Baker as consulting engineer.
But the million and a half OF money
which was raised proved insufficient to
complete even the one river tunnel. and
again the work was abandoned and lay
untouched for thirteen years.
1T was in November, 1874, that work
on the Hudson river tunnel was begun
so that thirty years have now elapsed
since Mr.. Haskns first undertook the
work. 1t had come to be universally re-
garded by engineers and contractors as
the most difficult work ever attempted
And now comes forward Mr. Charles NJ
Jacobs, and, by simply putting on force
enough to push his shield right through
the soft silt, discovers that, instead OF
being the most difficult tunnelling prom
osition ever undertaken, II is really the
easiest and he drives his south tunnel
along at the astounding rate of nearly
fifty feet per day!
1T is doubtless true that the condi-
tons under the Hudson river are ex-
tremely unusual Probably in no other
submarine tunnel ever attempted has
the material penetrated been soft enough
to do with it what is being done now under
| the Hudson. There is however, another
piece of tunnel work in connection with
the same enterprise which represents
conditions only too common. The en-
glneer Is often asked to drive a tunnel
beneath street surface through soft
material loaded overhead by buildings
OFTEN OF great value. II he Judges by
the records of the past experience. he
Will probably advise that the probabili-
ties are exceedingly strong that settle
ment OF the building foundations will
occur. In driving the Howard street tun-
mel In Baltimore, for example, building
after building along the line Of the tun-
mel was injured or ruined. In BROOKLYN.
numerous cases of settlement have oc-
CURED along the streets where sewer
tunnels have been driven: and other
instances might easily be cited.
But the approach to the north tube
OF the Hudson river tunnel is being built
through course, easily moved sand,
loaded above by high brick buildings,
ana the work is being done with such
care as to contine the excavated mater
lal TO the exact section cut out by the
shield and so far the buildings above
are intact. more noteworthy achieve
ment in soft-ground tunnel-driving n