Evening star. [volume] (Washington, D.C.) 1854-1972, 1904-09-03
TO HANDLE FREIGHT
WORK PROGRESSING ON VIR-
GINA AVENUE TUNNEL.
Character of Soil Through Which Ex-
cavations Are Made-Com-
pressed Air Power.

Work on the Virginia avenue tunnel.
which is being built to handle the freight
of the Philadelphia. Baltimore and WASH
ington railroad in connection with the new
terminal improvements and abolition OF
grade crossings in the city, is progressing
rapidly. the big steam shovel having push
ed the excavation beyond 9th street south
east
The tunnel is to be a double-track struc-
ture about 2S0 feet long, and already
over 1900 feet of earth has been removed.
For over 500 feet the arch has been con-
structed and the mason work has been
completed for twice that distance. All the
men that can be accommodated on the work
are employed in order that it may be push
ed to a conclusion without any delay. There
are about 800 men on the job.
Just when the tunnel will be completed
cannot be predicted at this time, but 1t
is thought it will be before many weeks
have passed. If rock or water is encoun-
tered in any quantities new difficulties Will
be presented and will have to be overcome.
Red and Yellow Clay.
So far. the excavation is through stiff,
dry red and yellow clay, and it is not ex-
pected that rock or much water will be
encountered. The tunnel occupies the middle
of the street, which is SO wide that there
Is sufficient space on both sides to allow
plenty of room for the sides of the cut
without ordinary settlement or slopes en-
dangering the adjacent buildings. So far,
the excavation has been made by single
steam shovel with a 2ls-yard bucket that
has record of 2T5 cars in ten-hour day
shift and 80 cars in ten-hour night shift
These cars are nomnally of yards capac
ity, but actually hold 10 yards measured
In place before excavation.
The shovel moves on center longitudinal
track and has so far been able to make
the excavation to the width and depth of
the trench at one cut. y short time ago
the shovel was eXcavating on a face about
twenty eight feet high. and as the bucket
has vertical limit of about twenty-five
feet, the work was being accomplished by
underwriting the stiff yellow clay bank to a
depth OF four feet or more and then break
ing off the undermined portion and load
Ing II by the shovel into the spoil BY
the exercise of considerable care in the I'M
dermining. this method has proved success
full and is considered more rapid and eco
nomical than it would be to make the eX
cavation in two cuts. The shovel bucket
discharges directly into the side dump spoil
cars which are brought alongside on
three-foot gauge industrial track which is
extended by the addition of five-foot sec
tons, so as to bring the cars always with
in reach of the shovel as the latter adj
vanceS.
Arch Built in Sections.
The brick arch is built In sections thirty
feet long, which are laid on movable CEN
tiers, having seven heavily trussed trans
verse ribs connected by four-inch tagging.
The ribs are seated on vertical longitudinal
trusseS about eight feet deep over all. They
are made with 12x12-inch timbers and are
blocked up on pairs of longitudinal Sills
carefully leveled on the bottom of the
trench. The centering is adjusted by pairs
of wedges under the lower chords of the
trusses and between the trusses and faces
of the side walls. The patchwork is built
by two gangs Of five men. each working on
opposite sides of the arch.
The brickwork has been commenced in
three places. to allow it to be pushed
rapidly and to build finished sections of
the arch in the lines of cross streets and
provide for the permanent support of the
latter. Before the travellers were installed,
the derrcks used for the eXcavating and
side wall work were mounted trestle
falsework, but the work progressed, the
travelling towers were substituted for the
falseWork.
The power used in the construction all
comes from a compressed air plant, located
near the work.