Richmond dispatch. [volume] (Richmond, Va.) 1884-1903, 1899-09-05
MARVELLOUS ENGINEERING FEAT.
TunneiIing Machines of Wonderful
Ingenuity Used for the First Time
working Amid N Wilderness of
Pipes, Drains, and wires.
CFor the Dlspatch.)

way lUdt IS 10 De called the BANK Sid
ton, suggests very little that Is difficult
10 the American mind. but when 81 Is
known that this railroad station Is being
constructed in the very midst Of one OK
the most intricate network OF pipes and
drains 70 be found in any street In tho
world; that the operations are carried on
in a tangle Of gas-pipes watcr-pipes.
pneumatic tubes, acknowledgement pipes
electric cables. drains, sewers and cham
nels Of all kinds, lead, iron. pottery brick,
stone, wood, crossing and interlacing, al
ways Unexpectedly like a tangled skein,
when IL is stated that this work is being
done In the very busiest spot In ths whole
city OF London. where the Mansion House,
Bank Of England, Royal Exchange. and
other bis public buildings face each other,
and the scene Is unrivallcd Tor the cease
| less whirl Of It's traffic, some idea can
be had OF the enormous difficulties In the
way OF the engineers who are directing
the operations. Overhead the busy swirl
of London's lie goes on, while Tar down
the worlNnen toll, TIE engines pounding
away night and day to keep up the sup
ply Of compressed air. the stoppage Of
which for a single minute would mean
death to all hands. and the steam exca-
yators digging further and further intO
the earth as the operation proceeds.
THE FIRST STEPS
When the work was first begun "a tenn
porary shaft was sunk and az the mass
OF pipes were net the various companies
were called upon 10 come and identity
their property. When they had done SO
they were left 60 make arrangements for
tho protection Of that particular pipe du-
ring tho further progress OF the work.
Tho further down the workmen went tho
greater became the wilderness OF en-
barrassments for underground London
at this point is fearfully and wonderfully
utilized.
Having disposed Of the pipes and drains,
work was begun on the central space.
| Cross-headings were driven north and
| south from ono side 90 the other, cut
| ting the area up into sections. aud IN
these headings temporary wills were
| built. which were actually three feet in
| thickness. Temporary work 50 substan-
| tal as this is remarkable. but was
| deemed inevitable, as II was vital TO tho
success of the enterprise that there should
| be no accident to the traffic overhead.
! AS the site was ready for II, section by
section, the framework OF the station
| was built in position. in its greatest
diameter IL IS lij feet one way and 10
feet the other. From floor 10 roof Il a.
u feet inches high. the roof Consisting
| OF grders on which rests the steel
| troughing which carries the concrete on
which is laid the asphalt paving OF what
the casual observer would suppose Is an
ordinary road with solid ground beneath.
THE RAILWAY.
This IL the station, which, in other re-
| spects, is like any Other station on tho
| street level. But where T. the railway?
| That is lower still In fact IT IS at
| a depth Of nearly nifty feet from tho
station floor. the platforms being ap-
preached by five elevator shafts OF %
feet in diameter. and one stairway SHAFT
OF is feet in diameter, 50 that should
! a break through occur overhead there
Is plenty Of room for an omnibus with
It's horses 10 take a fan OF 20 feet 80 meet
it's competitors In the tunnels below.
And beyond these tunnels there Is stu
a lower depth In this much-porforated
area. for underneath the Central London
there runs the tunnels OF the City and
South London railway.
In sinking the shafts. the London clay
was met with at ~ - feet below the sur
face. and here that most ingenious en-
| cheering device, the greathead shield
had 20 be used by this shield the art or
tunnelling has been almost reyolutionized.
The shields are Of the size OF the tun-
nels they have TO make. the smaller. for
instance Y feet inches IN diameter, and
it Is feet deep. At first sight IL looks
like q big drum standing on It's side,
waiting 20 be pushed along, head first,
as Inc way for it is cleared. A space at
the foot OF the shaft IS excavated, and
In this IL is put together. The front or
cutting head of the drum Is a strong,
cast-iron ring divided In pieces. bearing
a row OF steel knives in short segments.
forming a perfectly true cutting edge. and
so arranged that they can cut a slightly
larger circle than the shield, II necessary.
| At the back Is another ring. made in
xix segments, bolted together through
/ their Ranges, and on each OF these seq
ments is a hydraulic ram, each ram with
"a crosshead designed 10 bed on the iange
Of tho tunnel rings, which are put In as
the shield moves forward. the method be-
ing as follows: In the shield IS bulk
! head, with a heading-out hole through
which the clay is passed, as # IL dug out
IN 'front.' for a space OK about ~ Inches
deep an round. except for a small ring
about inches thick. which IS left for the
cutting edge 10 remove Before the move
ment takes place a number Of pointed
pieces Of wood are inserted INTO the clay
horizontally. with their ends resting
against the shields and as the shield
moves forward under hydraulic pressure
Il drives those stakes In 'front.' OF II as
well as cuts the ring true, the object or
the stakes beins 20 break up the clay so
borers an this way the work goes on,
the earth being dug out In 'front.' OF the
| shield, passed through h, and sent aloft
to be carted away the shield pushed for
ward into the vacant space, and the 'rn-
mel built up 40 tho shields toll.
To deal with material with which the rc-
tary principle Is useless Mr. Thos Thomp-
son designed his electric excavator,
which was here first used. This consists
essentially Of a dredger-ladder, which car
be moved vertically. horizontally, ana
| i0ngitudinallY. and rigidly held down In
position on the face OF tho rock IL opc-
rates on. This ladder IS II feet long and
carries 81 skeleton buckets. each having
a bottom and back only. II Is run out
through the front OF tho shield and
works from below upwards. the truck
which carries Il being az the back Of the
shield I'm the completed tunnel alto
gether a wonderfully powerful arrange
ment OF beyels and worms. and wire
ropes. driven by Q iOO-ampere motor al
30 volts. by lts AID three 20-lnch rings
could be put In every shift OF ten hours,
There has been a noticeable absence o.
fuss about the work OF driving these
great machines into the soil OF thu
r busiest spot IN the world but tho British
engineers have a right 20 feel very proud
/ Of the work thus approaching completion
in the depths Of Iondon's throbbin1
] | heart.
fg They Had Wings.