Evening star. [volume] (Washington, D.C.) 1854-1972, 1905-06-24

| though 1T be below the waters of the Hud-
son river.
Constructing the Tunnels,
When the tunnelers finally turn over the
system to the men who will euuip IL for
operation about sixteen miles of tube will
nave been bored or what amounts tn two
parallel lines Of eight miles each. At pres-
| ent what is known for purposes of ,dan+,e-
cation as the north tunnel Is bored. tho
SCUM tunnel Is within a thousand feet of
ene view YORK bulkhead. Active Eork will
soon De begun on the 9th avenue extension
OF the tubes. and the shaft il sunk for and
work Will shortly begin on the down town
river tunnels. All of the bores except the
north tunnel will be Of fifteen feet two
inches internal diameter; the north tunnel
| IS eighteen feet internal diameter
| Mr. Charles M. Jacobs is the engineer in
charge. He has employed the shield method
., construction from the start. In COM
pietfng the north tunnel he used the shield
iert IN 1t by the second company greatly
improving and strengthening the same
Ihat Mr. Jacobs has built one tunnel with
out 50 much as a serious or protracted de-
lay, and Is going ahead building Others
with as little fuss, is proof sufficient of the
ABILITY he has brought to the work in hand
In december. 1902. Mr.. Jacobs prepared
ployed in the building OF the tunnels: at
| the same time light is thrown on the char
| acter OF the earth through which the river
tunnels have been or are being driven:
| The work Is executed under pneumatic
pressure. The soil in which the tunnel is
| built is a stif, compact clay silt. forming
| the bed of the Hudson river. The shield
used at the face and for the purpose of con-
| struction Is a machine built up of boiler
| plates, strengthened with massive steel
| webs. both vertically and horizontally and
! divided up into number Of separate COM
| partments- This shield forms solid bulk
head across the face of the tunnel while
| construction Is proceeding. The soil is
| cavated in front of the shield. and is
| brought into the tunnel through doors left
| in the diaphragm by which name the bulk
| head Of the shield Is known. These doors
can be controlled from inside the tunnel
| according to the material to be moved. and
| the men are able to work through the doors
| in advance Of the shield whenever neces-
| sary The shield Is pushed forward by
| numbers of hydraulic jacks exerting enor-
nous pressure and in the shield at present
| Installed. as we'll as In the new shields now
! in process Of construction. the total power
| available for pushing the shield Is 1900
tons.
Working the Shield.
| "As the shield is pushed forward and the
material is excavated. cast-iron lining
plates are erected inside the tunnel and
| within the shelter Of the tail OF the shield.
! so that at no time is the material exposed.
| and there Is. therefore. at no time any
1
self during the process of construction. The
lining plates are erected by hydraulic
power acting on machine independent
of but attached to the shield, which ma
chine permits Of placing each plate exactly
| in the designated position in the finished
tunnel: and these plates securely bolt
! ed up and the joints calked and secured
| so to make absolutely water-tight
| lining of iron for the tunnel
In order to prevent any possible influx
OF water air pressure is carried inside the
tunnel and work is executed under this
pressure. Under ordinary conditions the
air pressure carried in tunnels being con-
structed by this company is very light,
and such as not to hurt in any way any
employee engaged in the work. At the
same time. however. in case any emer-
gency should arise it is Immediately pos
sible to increase this pressure in order to
keep the work absolutely safe. The way
! in which air pressure is carried is by the
| insertion. within the completed tunnel
and within considerable distance of the
rear Of the shield. of a solid bulkhead
wall in which airlocks are constructed
These afrlecks form chambers, with
doors at each end, both doors operating
| in the same direction-that is to say, in
ward to the tunnel-and by this means
| the pressure may be equalized at any
| time within the afrlock chamber. either
with the pressure carried inside the tun-
mel or the atmospheric pressure outside,
and this arrangement gives the means of
access to and from the outer atmosphere
and the face Of the tunnel work. In this
work the airlocks are arranged in dupli-
cate, forming two stages of air pressure,
and are located about 1900 feet apart,
which permits very easy movement into
and from the tunnel and makes the eff
feet of air pressure upon employees inap-
prectable.
Wonderful New Machinery.
"In the design of the machinery for car
rying out the remaining work, which ma
chinery is at present under contract, all
~ Ja1ry l.
mel building are being adopted. and it is
anticipated that double the quantity of
finished tunnel can be constructed each
day than has ever been done heretofore
New shields are being designed especially
suitable for the requirements of tunnel
building in the soil found under the Hud-
son river. The present shields and the
new shields will be operated by hydraulic
power under maximum pressure as high
as 5000 pounds to the square inch. while
pneumatic pressure is used for drilling
rock in the face and for driving the haul
age engines in the tunnel. and electric
power Is being used for lighting the
whole works.
TN the new portion Of the tunnel con-
structed by this company in the last two
months work has been carried on under
the most difficult condition known in tun-
mel building with absolute success and
! with great rapidity. This work has pro-
vided for the excavation OF the lower part
OF the tunnel In solid rock formation,
while the upper part OF the tunnel is in |
clay silt. The rock has been drilled and |
blasted In advance Of the shields prog |
ress with satisfactory results and COM |
plete success, and everything points to |
rapid construction and to an early COM |
pletton Of the entire undertaking."
& In the north tunnel. where Mr.. Jacobs |
worked with the shield that came with |
the purchase OF the old company's fran /
chlses and good will. eighteen feet advance |
day was the best that could DO done In |
sflt, and In rock from twenty inches-the 1
width Of the ring OF the cast-fron lining-to /
1--WE feet. Now. by means of the new ma |
chinery which was belng built when he /
made this statement, AZ high al thirty feet /
Of stlt has bssn displaced In . day and the