Charles George Warnford Lock.

Economic mining: a practical handbook for the miner, the metallurgist and ... online

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the surface on the side of the hiU
or from a hoisting shaft in the

They are usually on the flint
wall, wnether it be the foot or the
hanging, because the flint is a
better guide in following the vein.
These levels are driven along the
vein to such a distance from the
Pio. 41.— WoRKiNO ON Soft Obb- hoisting-shaft as may be required
BODIES. to reach all the ore which it is

intended to raise through that
shaft — in some instances over half a mile. While the main levels are
being driven, thejpillar between two levels is usually left untouched,
except by up-raises connecting the two levels every 400-600 ft. for
ventilation. When the levels are completed, the portions of two levels
farthest from the hoisting-shafts are connected with up-raises d, 60-75
ft. apart, two or three up-raises are joined by air-drifts «, and the
ground is ready for stoping. The timber in the air-drifts is re-
covered ifi stoping. Tne stopes are 12-15 ft. high, each pillar
between two main levels making 4-6 stopes. As soon as a stope is
worked out for 40-60 ft. along the vein, a floor is laid, consisting of
sills covered with refuse timber or slabs, and the props are shot dowiu
The waste material / from above packs solidly upon this floor, and in
a short time the next lower stope can be worKed, using the floor pre-
viously laid as a roof to hold the waste material from the ore. A
stope 40-60 ft. long, measured along the vein, is begun in the drifts,
by first mining the ore g above the drift-timbers till the floor of the
next stope above is reached, and setting props. The face of the ore
for the length of the stope is then mined back to the opposite wall,
as shown at ^. The ore is dumped into the shutes c2, drawn from
them into cars on the main levels c, and hauled by mules to the sur-
face or to the hoisting-shaft*

When the vein is 12 ft. or less in thickness, so that a single
prop will reach from wall to wall, the method is somewhat modified.
A stope-drift is driven a short distance above the main level, parallel
with it, and connected with it by shutes at intervals of about 60 ft.
The ore is then stoped from this drift to the next upper main level,
props being placed from wall to wall. These props are eventually
shot down, and the waste material is caught by a horizontal floor,

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whioh will serve as a roof for the next lower stope, as before. In
this way the timber for a number of floors is saved, but the modification
is (mly of advantage when the vein is narrow enough to permit a
single prop to reach from wall to wall, and where, moreover, the hang-
ing waJl is fairly good. In this way all the ore is mined, no filling is
required, and the work is comparatively safe. In some instances, means
must be taken to exclude snrfaoe water from the breaks which run up
to daylight when the country rock sinks to fill cavities.

The term " stripping " is applied to what is really simple quarry-
ing adapted to the exploitation of a vein. It has been rendered possible
by modem improvements in mining machinery and appliances, which
allow of much more complete preliminary determination of the quality
and extent of underground deposits, and much less costly blasting
operations. The advantages of stripping are that the work is con-
ducted in the open day, and that there is less risk of unremunerative
dead work on tbe one hand and of overlooking ore on the other.

At the Peters mine, Ringwood, New Jersey, where the limit of
profitable mining by the old method has been reached, it is intended
to remove the ore floors and pillars by stripping. While the vein
stands nearly vertical, the ore shoots overlie each other at an angle of
35^ and some 10-30 ft. apart. It is proposed to take advantage of this,
and pile up the waste on the end wall of the lowest shoot as rapidly
as the wall is uncovered by removal of ore. This back filling will
make the mine safer, and will obviate much excavation by allowing
the slopes to be considerably steeper than if the pit were to be left
open permanently.

At the Bertha zinc mines, in Virginia, zinc carbonates are found
to the extent of about 8000 tons per acre, underlying some 80 ft. of
earth, so that 30 cub. yd. of earth have to be removed for every ton of
ore mined, and this is done profitably.

In the case of the Dannemora mine, Sweden, stripping has been
ro c o o a sfu Uy carried to a depth of about 500 ft., and at uie Fahlun
copper mines to even greater depths.

When mining was first begun at the mines of the Longdale Iron
Company, Virginia, the outcrop was 500 ft. above the creek level, and
the deposit was for manv years worked entirely by open cuts. As
time went on, however, the excavation was carried so deep (130 ft.)
that the cover grew too heavy, and it became necessary to obtain the
ore by underground workings. It was finally decided to stope the
9re from the top down. This plan was adopted in 1881, and has been
bllowed ever since with complete success.

The method of attack is to sink a test-shaft upon the ore to the
depth at which it is desired to drive an adit.

The line of least distance from the surface to the ore at the level
chosen (tbe length of which line is obviously largely governed by the
heightof the "lift" tobe secured) is then determined, and the adit
is driven straight in, through the overlying shale, to the ore, a
distance varying from 300 to 1200 ft, according to the height above
the creek at which the adit is driven. The highest adit was driven
directly upon the ore from the bottom of a I'avine which cut across the

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On reaching the ore^ the adit is continued by galleries in both
directions, following the bends of the vein. These, it may be
remarked, are both many and sharp. Parallel with the main entry
or car-level, an air- way is driven at a height of 20 fb. from the bottom
of the main entry at the bottom of the air- way. As the main entries
are 6 ft. high, this leaves a pillar of ore 14 ft. thick between the two
levels. At intervals of about 120 ft. on the car- level, shutes or raises
are driven up through this pillar to the air-way. These shutes are
supplied with spouts and gates for loading the mine cars ; 20 ft
beyond each shute, in the direction of the heculing, a second passa^,
called the man-way, is driven up, to afford means of ascent for the
men who are working above.

As the air-way is always connected with the test-shaft above
mentioned, this system affords very perfect means of ventilation.
Of course, it is necessary to keep most of the bhutes and man-ways
nearest the mouth of the adit closed in order to force the incoming
air to the headings. From the air-way the shutes and man- ways are
driven up until they reach the surface in the bottom of the old open-
cut workings. This, however, is not all done at once, but only as
needed for the working of the mine.

At every 10 ft. of vertical height above the air-way a lateral
level 5 ft. high is driven off along the ore, thus leaving a 5 ft. pillar
under each drift.

When the open-cut workings, mentioned above, were about to be
finally abandoned, a grillage of small poles was laid down ; this formed
a floor resting upon the ore in the bottom of the cut.

Outside working was then discontinued, and the sides were suffered
to fall in upon the grillage, after which the mines were ready for
underground working. The system is as follows: —

The pillar of ore over the highest level, or, in other words, the
ore left in the bottom of the old cut, is first attacked and tak^i
out, the roof being supported during this operation by heavy propq
set up a short distance behind the working-face, under the grUlage
mentioned above, and standing upon a similar grillage plaoed upon
the ore under foot. Where the vein is horizontal, or nearly so, the
lower grillage may be omitted, the roof being allowed to fall directly
upon the floor, which, in such cases, is the fuot-walL This row of poets
supports the roof until the ore has been taken out for a short distance
ahead of them, when a second series is set up in similar manner.

It is customary not to leave the roof standing, even if the prop^
are strong enough to support it for some time, but to cause it to fal^
by either " shooting out ' the props (i. e. breaking them down b>
means of dynamite) or by drawing them out if they can b|

The ore that comes from the face is wheeled to the nearest shu
into which it is dumped. After the top pillar has been robbed fois
few feet, generally 10 to 20 ft., the next one below is attacked in t
same way. Every level in the mine can thus be worked simultaneous]
the workings resembling a series of 10 ft. steps.

The construction of a cheap floor or grillage of poles is repeati
on every level to prevent the sliding of the waste from old oavl

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slopes above. This floor is of oourse removed after serving its tem-
poranr but important purpose.

The ore dumped into the shute descends by gravity to the
car-level, unless it is stopped by meeting a flat place or " bench "
in the vein and consequently in the shute. When this occurs,
rehandling becomes necessary, which is carried out in the manner
best suited to the circumstances. As the ore finally ai-rives at the
car-level it is drawn into mine cars, hauled to daylight, and dumped
upon a horizontal screen of round iron bars, which is set in the top
of the ore-bin beside the railroad. The fine ore falls through the
screen into a pocket, while the lumps remaining upon the bars are
farther broken and sorted by hand and thrown into an adjoining
pocket. From these pockets the ore is drawn into cars on the
railroad leading to the famaces, the lump ore being taken directly
to the furnace bins, while the fine is conveyed to the washer.

In the case of flat beds, such as coal and ironstone, a totally
different method is adopted, the main object being to a£ford support
to the roof.

The •• longwall " method, which closely resembles the overhead
system already described, is applicable to nearly horizontal thin


Figs. 42, 4.3. — Lonowall Wobkiko.

beds which furnish sufficient waste for filling. The main tunnel a.
Figs. 42, 43, is built high enough to accommodate the trucks for
transporting the mineral to the hoisting shaft &, and is run at the
lowest part of the bed, so as to form a natural drainage for the mine
water. From it drifts are run into the mineral, either diagonally
as at c, or transversely as at d, and connected by parallel levels e.
The direction of the drifts is governed by the rate of dip of the
bed, the object being to secure a suitable incline for the trucks
which carry out the mineral. The workings are connected all round
by cross-cuts as at/, to complete the circulation of air for ventilation.

The system known as '* pillar and st^iU " is adopted where the beds
are thicker, and do not afford sufficient waste for filling, so that pillars
of mineral have to be left standing as a support for the roof. The
main tunnel a, Figs. 44, 45, is run as before from the shaft &, and
from it are run drifts c at intervals, and crossing these again, levels d
parallel with a, and occasionally diagonal drifts e. The bed is thus
divided into regular blocks, portions of which, varying in size, are
left to form the pillars that support the roof, these being finally with-
drawn as far as safety will allow.

In seams having a rate of dip of 40-60"^ it is the custom to drive
the stalls square off from the gangway, up the '' rise " of the seam, and

H 2

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. lOO


have tbe coal to run down the shute into the tram at the bottom of
it : with this rate of dip the shute does not require planking at the
side or bottom to make the ooal mn, and by keeping the shute fall,
except 3-4 ft. working room at the breast, there is very little coal
lost by pulverising in its descent down the shute, as by that method
it descends by slow settling in proportion as it is allowed to run into
the trams at the bottom.











Figs. 44, 45.— Pillar and Stall Wobking.

In seams of 30-40° rate of dip the .miners are compelled to plank
the sides of the shute to some extent, in order to enable the coal to
slide down without assistance. In seams of 25-30° the coal will not
descend in the shute unless the sides are partly planked, and the bottom
covered with sheet iron. In working seams having a dip of 10** or
under, the stalls are driven diagonally to the direction of the gangway,
unless the rate of dip is less than 4°.

The trams or mine cars used in Europe are, in nearly every
case, smaller than the American ; the reason for making them so, in
most cases, is to reduce the enormous first cost of the deep shafts.


^ \






vV\^ ^











e i









Fig. 47.

Steep Coal Vein

: Bad Roof.

Steep Coal Vein: Good Koop.

b>' having a small shaft area, thus leaving but a email space for the
mine cars or cages and pump way ; the small mine cars also suit the
large number of boys employed in European mines.

For more detailed illustration of the manners of working coal and
similar beds, the reader is refen-ed to the following figures and
descriptions : —

In Fig. 46 is shown a very steep coal vein. The coal

a IS over

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4 ft. thick ; the roof h is full of joints and very treacherous, necessi-
tating the use of many timbers d\ the floor c is hard and sound.
The waste e from floor and
roof is allowed to fall and
aocamulate under the feet of
the miners, and by it the
timbers are gradually and
saccessively buried.

Fig. 47 delineates a simi-
larly steep bed, but in this
case the roof is very good,
and consequently no timber-
ing is necessary. Both roof
6 and fl«K>r c, however, are
lined with a friable rock some
inches in thickness, which
£&lls with the coal a, and is
allowed to collect as at e,
fonoing a platform for the
miners. The seam is worked
in sections, which are sepa-
rated by stout timbering d.

Fig. 48 illustrates the
mode of timbering a road-
way. The coal seam a is sur-
mounted by a considerable
thickness of weak shale e,

which does not long survive « .« m « ^

the wmoval of the subjacent ^'''- *8-T«bebing Boai-wat in Coal.

coal, and is quite distinct from the firm and reliable sandstone roof 6.
The practice is, therefore, to let this shale break down and accumulate,
as at /, on the floor
proper c, and to lay
the tramway g upon
it Falls from the
upper part of the
66am into the road-
way are prevented
by a lining of posts
and slabs d, well
secured in roof and
floor, and further
strengthened by

Fig. 49 repre-
sents a seam carry-
ing three separate

quaUties or kinds of yv^, 49.-Seam with tbbbe kinds op Coal.

coal, called respec-
tively «* tops " o, " middles" 6, and " bottoms " c. The roof d and floor
e are both very sound and firm. Owing to the top coal being very

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strong, it is possible to work the middles and bottoms separately,
leaving the tops tor a distinot operation. The tramway / is laid on
waste, and at ^ is shown a staging of slab-posts, on which the coal
is collected, and from which the loading is done in safety.

A few examples of the props used m flat veins are given below.
In Fig. 50, a is the prop, h the roof, c rock overlying the coal, d, ooaL

Fios. 50, 51, 52. — Examples or Pbops ik Flat Ykins.

In Fig. 51, the coal e is cut away in advance, a prop a supporting
the bed of oil-shale d, and a further prop h sustaining the sandstone
roof c, the props resting in the hard floor/. In Fig. 52, a prop with a
lid c holds up the top coal e, while a " knee joint " or " cockermeg " <f
temporarily prevents the fall of coal a, while it is being worked on
from below. The floor h is Arm and resisting.

Preserving Mine Timbers, — Experiments made at the Altenwald
Colliery, Saarbrlicken, in coating mine timber with lime, coal tar,
wood tar, and carbolineum, proved that lime was the worst and carbo-
linenm the best preventive against dry rot. The cost of a doable
coating of carbolineum to a prop 8^ ft. long and 10 in. diam. was 6(2.
for the carbolineum and Ifd. for labour. At various mines in Saxony
not only are the supports wetted occasionally to prevent dry rot, but
the wood is first impregnated with a solution of ferrous sulphate
before being put into use. This method of treatment has been
adopted for some time, and has been found to give very good results.


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When the mineral, of whatever kind, has been broken down in the
mine ready for removal, the next stop is to load it into receptacles in
which it can be hauled along the levels and hoisted up the shafts at
the least possible expenditure of time, labour, and wear and tear of

Wagan$, — The ordinary mineral wagon or hutch is simply a
miniature railway truck running on a miniature line of rails. I'hese
latter are generally of iron, but often also of squared timber covered
with strap iron, and sometimes are simply small round poles laid end
to end. The wagons are of numberless kinds : some entirely of wood,
some entirely of iron, some of wood and iron combined ; some have no
tipping arrangement, some tip sideways, some tip endways, some tip
in any desired direction. For details of construction and illustrations
of many forms, the reader is referred to the author's work on * Mining

Figs. 53, 54. — Automatic Independent Tippleb.

and Ore-dressing Machinery.' It will suffice here to describe an in-
genious arrangement for tipping wagons which has the twofold
advantage of being quite automatic, and of providing a tipping con-
trivance independent of the wagon, by which means the 'common
ordinary wagon is rendered available, avoiding the complicated struc-
ture, increased cost, and serious wear and tear incidental to the
specially built " tippler." The arrangement is shown in Figs. 53, 64.
The wagon a, running upon 4 wheels 6, is made to ascend a slight
incline just before tipping, being drawn by the bow / attached to the
ropey. The bow is also rigidly united to the axles of the hind wheels,
and in front it carries the door t of the wagon ; k is the railway at
the top of the incline, and |> is an additional outer line of rails laid on
a steeper grade. When the wagon in its upward course reaches the
point ty the rails p pick up the small outer wheels c on the hind axle,

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BO that the hind wheels travel up the steeper grade while the front
wheels follow the rails i. Consequently the wagon is tilted forward,
and as the door or front end i is attach^ to and rises with the bow /,
the contents of the wagon are shot out. A stud g prevents the wagon
being drawn too far. On slackening the rope /the wagon rights
itself and descends properlv, the door t automatically dosing.

Underground Hauling. — ^The loaded wagons have to be hamed either
to the mouth of the adit or to the bottom of the shaft. The power to
perform this hauling may either be attached to and move with the
wagon, e.g. men, horses, engines; or it may be derived from a
distance, as in rope and chain haulage. Whenever possible, the road-
ways are made with a slight and regular gradient, so that the wagon
shall exert its own gravity in traveling loaded to its destination, and
it is sometimes p>ssible to make the loaded wagons running downhill
pull the empties up again, which is manifestly an economy of power.

In such a self-acting incline the road must be more or less uniform
in gradient, for if steeper in some parts than in others the train must
be run over the steep portion with great velocity in order that it ma}'
acquire sufficient momentum to carry it through the flatter poiiJon ;
wlule in a great many cases it is impossible to work an incline by
trains at all if the flat portion of the road happens to be at the
top and the steep portion at the bottom, as a start cannot be

In working with a self-acting endless chain, if the average inclina-
tion of the road is not less than will give an excess of power in the
pull side sufficient to overcome all the frictional resititances and the
weight of the empty side, the incline will work no matter how un-
dulating it is, provided the average inclination is calculated from the
total length of the road, and not from the horizontal distance on the
section. The surplus power on a steep mine may be utilibed for tho
purpose of drawing from a dook or level, not necessarily in the same
straight line, by fitting the top wheel with a long shaft and putting
on it a second driving wheel, or clip-pulley, or rope-drum provided
with a clutch. In the same way water may be pumped, or almost any
description of work done, if the power be sufficient.

The advantages which a self-acting endless chain poBsesses ovetan
ordinary incline may be summed up shortly as follow : —

(1) Small cost of upkeep of rolling stock, owing to slow speed
causing few breakages. When a wagon goes ofif the road the chain

(2) Begularity of delivery. The wagons arrive at their destina-
tion in sucn a regular manner that only very short lyes are required,
and consequently the travel of the bottomers or landers is diminished,
and their labour is rendered so much the more effidctive.

(3) When the output exceeds 100 tons a day, and probably before
that, it can be worked much more cheaply than an ordinajy self-
acting incline.

(4) Length makes no difference in the output or cost farther than
the increased upkeep of the road.

(5) Much less expenditure is required in making benches, as no
long trains require to be collected on the incline. *

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(6) The coet for chains is less than for ropes, as a good chain will
last 12-18 jears.

The question of the relative economies of man power, horse power,
endless ropes or chains, electric engines, compressed air, &c., for
eSbcting hanlage, is very largely governed by local conditions. The
enbject is dealt with at length in the author's ' Miners' Pocket Book,'
where many instances of actual costs under various circumstances
are given.

EoUHng. — ^Hoisting, during the early stages of a mine's history, is
done in buckets or kibbles of various forms by means of a common
windlass. This is feasible, up to a depth not much exceeding 150 ft.,
bevond which a horse whim is useful up to about 300 ft. As the
depth increases, hydraulic, electric, or steam power is called into re-
quisition, usually the last named.

Fig. 55.— Gravity Hoist.

Where the contour of the country at the pit mouth is suitable, the
arrangement shown in Fig. 65 is very economical, gravity being the
force employed. The drums or windlasses of the apparatus are carried
by two shafts geared together at their inner ends, each shaft carrying
two drums, one of which is larger than the other. On the smaller
drums are wound the hoisting ropes, which pass over pulleys on a
shaft on a suitably construct^ frame, and are connected vidth the
buckets travelling in the shaft, the arrangement being such that when
one bucket descends the other rises, and vice versd, On^ the larger
drams are wound cables connected with cars travelling in opposite
directions on inclined tracks, the cables and the hoisting ropes being
so arranged relatively to each other that when an empty car ig at the
upper end of the incline a filled bucket will also be at the top of the
shaft, in position to be conveniently emptied into the car, the down-

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ward travel of eaob filled oar along tbe inelined road exerting a pull
on one of the ropes on the large cbnms to cause a filled bucket to be
raised, while at the same time an empty car is drawn up and an empty
bucket is let down. A brake-band is provided for each shaft, operated
by a lever conveniently arranged, and that the two shafts may be
readily disconnected, for lengthening or shortening the cables or
other purposes, their inner bearings are fitted to slide, and are each
connected by a link with a lever pivoted on the frame, by means of

Online LibraryCharles George Warnford LockEconomic mining: a practical handbook for the miner, the metallurgist and ... → online text (page 12 of 76)