Mineral Point tribune. (Mineral Point, Wis.) 1869-1938, 1900-12-27

moving the material /. a rather COM
plicated one 1t is met by placing two
pairs of massive I-bears. two feet in
depth and about 80 feet in length,
parallel with the tracks and spanning
the section to be excavated. and sup
porting beneath them a series of
transverse IL by Il timbers, the tim
bers being secured TO the longitudinal
steel I-beams by bolts, each timber
bearing against the base of the track
| yokes. With the track thus securely
supported, it was possible TO eXcavate
| beneath the structure without inter-
fering with the traffic After the ex-
cayation has been carried out down
to subgrade, the footings for the steel
/ columns are laid, the columns erected
and the I-beams which form the
! framework OF the walls and roof of
the subway are laid in place, The
temporary timber false work is then
| removed, and the concrete arches are
turned between the steel framing.
| Following this, four layers of felt and
tar waterpreofing are laid completely
around the concrete, and an outer pro
| jecting sheath of concrete and brick
is placed over the whole subway. The
| loose material is then filled in and the
street restored to its original surface.
| This framing, by the way, is spaced
about five feet apart, and answers in
some sense to the framing or ribs of
| modern steamship. During the ex
! cavation provision has to be made for
supporting the water and gas mains
and cable condults. and this is done by
singing them by chains from II by
IL timbers, which are temporarily
supported on timber struts.
The particular piece of work to
which we have just referred is, in
respect of the difficulties of excava-
ton one of the easiest on the whole
route of the subway, the material be-
ing loose, sandy soil, easily removable
| by pick and shovel Over a great por-
ton of the line, however, the excava-
ton will be through solid rock, and
blasting will be necessary. Drilling
will be carried out almost exclusively
by pneumatic drills, and to provide the
power for operating these, two out Of
| several power stations have already
/ been erected, one in Union square,
and the other at One Hundred and
| Sixty-fifth street and the Hudson river,
/ The compressed air is led from the
station by and 10-inch mains of steel
pipe, the mains being laid parallel to
the route of the tunnel throughout the
sections which they are intended to
serve. The air is led from the mains
/ to the drills by flexible piping.
/ Although not much of the RAPID tran.
sit road will lie in tunnel proper,
where it does pass beneath the sur.
/ face it will, in places lie at very
considerable depth, particularly be-
meath Washington Heights. In the
stretch of about "a miles, from One
Hundred and Fiftieth street to One
/ Hundred and Ninety-fifth street, the
road will be at an average depth of
about 120 feet below the surface of
| Broadway and in that distance there
will be two subterranean stations, one
at One Hundred and SiXty-ninth street,
/ 100 feet below the street, and another
at One Hundred and Eighty-first
street, at a depth of 100 feet The YER
/ teal excavation for the shaft will con
/ tain two large elevators and stair
way, the stairway being provided in
case of a breakdown at any time in
the elevator service The station Will
consist of a large chamber exeavated
! in the solid rock, the roof being in
the form of an elliptical arch There
will be two elevator landings at the
bottom Of the shaft, the upper one of
which viii discharge its passengers at
| the level Of a bridge which viii eX-
| tend across the tracks and enable the
| passengers to reach the downtown
, tracks During the morning hours the
elevators will stop at this level for
the reason that almost all of the
travel at that time viii be in the
downtown direction During the even
ing hours, when business men are re-
turning from the city the elevators
will run to the lower level, so as to
save passengers the necessity for
climbing any stairways The elcva-
tor cars will be unusually large, with
sufficient capacity to remove all the
passengers unloaded from one train
before the next train enters the sta
ton The excavation for the One Hun
dred and Sixty ninth-street station is
so far advanced that the vertical
shaft and the transverse tunnel lead
ing from the shaft to beneath Broad
way are completed. and about % feet
Of drifting has already been completed
north and south beneath Broadway on
the line of the tunnel itself