coal trade bulletin - Clpdigital.org

50 THE COAL TRADE BULLETIN.
CONCRETE IN MINE CONSTRUCTION*
By A F. Allard. Chief Engineer Bunsen Coal Company, Adams Building, Danville, Ills.
Within the last few years a great many import
advances have been made at the modern coal
plant in the use of concrete for buildings, shaft
lining walls and constructions inside of the mine.
The appearance of the up-to-date plant is wonderfully
improved with its concrete mine building,
consisting of the Power Plant, Hoist House, Repair
Shop, Miners' Bath House, Fan House, Supply
House, Powder House and Outside Stable.
These fire-proof structures with reinforced concrete
walls, concrete floors and cement tile roof
covering, are permanent and involve little or no
expense for up-keep during the life of the plant.
The boiler house, with its reinforced concrete
chimney towering to a great height, is substantial
and attractive in appearance as compared with
an installation of steel stacks which are subject
to deterioration from rust and require frequent
painting and attention; while no expense for maintenance
after first cost is necessary on a concrete
stack. The coal storage bins and water supply
tanks erected of reinforced concrete, mark the
advance made in the use of concrete for these
structures. This material now replaces the
wooden walls and platforms of the steel tipple
and the members themselves are protected from
rust and mine gases with a covering of the same
material. Swimming tanks built of concrete prove
a source of amusement and recreation for the
employees at a coal mining plant. The house site
of the miners' home is made bright and clean
looking with concrete sidewalks, street curbing
and gutters. House foundations and outbuilding
vaults of this material are watertight and sanitary.
Those who have had to deal with the growing
scarcity and steadily increasing cost of large size
timbers for inside mine construction, will welcome
concrete as a substitute for this material,
not only at new plants, but for the renewal of
wooden structures at mines in operation. By its
selection, the mine owner will be amply compensated
for the increased first cost of the installation
as compared with wood, when the stability, permanency
and fireproof qualities of the concrete
are taken into consideration.
As a fire-proof and permanent material for the
lining of shaft walls, concrete is without a rival,
and its adaptability for this class of work is
well recognized, judging by the large number of
concrete shafts now being constructed. In fact,
we have hoisting and ventilating shafts completed
"Paper read at Mining Conference in connection with the
dedication of the Mining Laboratory, University of Illinois
1913.
from top to bottom without a piece of timber, the
lining walls, cross-buntons, and division wall of
the air compartment are of concrete, with the
guides and stairways of steel. The method of
sinking mine shafts by means of the concrete
caisson with a steel cutting edge or shoe, through
soft and water bearing strata has come into prominent
use, for by its weight, penetration to great
depth is possible, rapid sinking progress is made,
the flow of water met with is reduced and a great
saving in cost of labor and material is obtained
by the omission of timber curbing.
From comparative cost data, I find that price
per vertical foot of a completed concrete lined
shaft to be about one-third more than that of
the wooden structure; this amount is in the first
cost only, for after a few years' time, renewal of
timbers would be necessary in the latter.
There are numerous designs for concrete shafts
including rectangular, circular, elliptical and the
straight sides with circular end walls; the latter
is a very economical section, utilizing the end
spaces for pipeways or stairways and reducing
to a minimum, excavation and concrete yardage.
The circular end walls have great strength to
resist the strata and water pressures, forming a
continuous concrete arch from top to bottom; the
side wall pressures are taken care of by the
thickness of concrete lining, depending upon the
nature and depth of strata penetrated. Generally
a self-sustaining strata, such as rock, slate
or good shale requires a wall of from six to nine
inches in thickness, which is sufficient for the
anchorage of the bunions, while a heavy fire clay
or wet sand seam would require a much thicker
wall.
In the Western iron and coal districts, a number
of reinforced concrete shafts have been sunk
through quick-sand in water-bearing ground by
means of the pneumatic caisson or compressed
air system. This process has proven effective in
wet strata for obtaining dry shaft walls; also for
making a watertight joint when the concrete
caisson reaches the bed rock. Air pressure is
provided in the working chamber to displace the
water encountered, and the pressure maintained
until the concrete has set.
The construction of shaft bottom landings of
plain and reinforced concrete includes the single
or double track entry, providing storage room
for loaded cars, space for empty car lift back of
the shaft and room for empty car storage track,
together with the necessary chutes. For this
work, I have used three different designs in concrete
construction for supporting side walls and