January 17, 1913.

THE COLLIERY GUARDIAN.

127

MANCHESTER GEOLOGICAL AND MINING
SOCIETY.

An ordinary meeting of this society was held on
Tuesday afternoon in the society’s rooms, 5, John
Dalton-street, Manchester, under the chairmanship of
Sir Thomas Holland, president of the society.

The first business was the election of new members,
as follow:—Members (Federated): Mr. Harry La Trobe
Campbell, mining engineer, 11, Old Hall-street, Liver-
pool ; Mr. George Elce, jun., colliery manager, Mountain
Mine Colliery, Pimbo-lane, Upholland; Mr. Arthur
William Kay-Menzies, slate quarry director, Carnarvon ;
Mr. Albert Street, 1, Clifton-road, Burnley. Associate
member (Federated): Mr. Tyaga Rajan, 39, Ceylon-lane,
Penang, Straits Settlements. Associate (Federated):
Mr. William Caulton Wright, under-manager, 19,
Alexandra-terrace, Pinxton, Alfreton, Derby. Students
(Federated): Mr. Thomas Hodson, mining student,
Grosvenor Hotel, Widnes; Mr. Amos Ogden, draughts-
man, 67a, Mesnes-street, Wigan.

Misfires and Accidents in Blasting Operations.

Mr. J. S. King read a paper on “ The Prevention
of Misfires and of Accidents in Blasting Operations.”
He described a new safety shot-firing appliance, and the
inventors, Messrs. Price and Pryse, gave a demonstra-
tion of its simplicity and effectiveness.

(The apparatus has already been described'in the
Colliery Guardian, July 12, 1912.)

On the motion of Mr. John Gerbard, H.M. inspector
of mines, seconded by Mr. Stanley Atherton, the
thanks of the society were accorded to Mr. King and
Messrs. Price and Pryse.

Hydraulic Stowing of Goaves.

Mr. George Knox, of the Wigan Mining School,
contributed a supplementary paper on “ The Hydraulic
Stowing of Goaves.” At the December meeting he
read a paper descriptive of the relation between sub-
sidence and packing, and of the hydraulic stowing of
goaves.

Although experiments in hydraulic stowing had been
carried out in Germany and America 20 years ago, Upper
Silesia, he said, may be considered the birthplace of the
system. Eleven years ago, faced with the increasing
dangers from gob- fires and the damage from subsidence
through working seams up to 40 ft. in thickness, the mine-
owners of Upper Silesia adopted the process on a large scale,
and, with*perseverance and the application of a considerable
amount of engineering skill, they have evolved a system
capable of being applied in everyday mining practice. At
the present day, 28 out of a total of 58 collieries in the
coalfield are working the mines by hydraulic stowing.
Some of them possess two (others as many as four or five)
separate installations, bringing the total number up to
48 independent stowing plants. In Lower Silesia, six out
of the 20 collieries in the coalfield have adopted the system,
with 12 independent installations. In Rhenish Westphalia
27 collieries have introduced the system, with about
40 separate installations. At one colliery—the Deutscher
Kaiser, Hamborn—they have installations in seven pits, and
several additions are contemplated shortly. In the Saar
district 11 mines have 20 independent installations at work ;
and in other parts of Germany the system has been
successfully applied to iron ore and potassium mines as
well as to coal mines. In Belgium, 10 collieries have
installed stowing plants ; and in France the system has been
successfully applied for many years. Plants have also
recently been installed in Spain and Russian Poland, and
large installations have been ordered recently for the latter
country as a result of the successes achieved by the initial
experiments.

As it is essential that the flow of the flushed debris—from
the surface to the pack—should be downhill, the best place
for the erection of the installation is at the rise end of the
royalty, where a special stowing shaft is sunk, if suitable
packing material can be found at (or cheaply transported
to) this point. The power to drive the plant would be
transmitted from the power station at the collliery. In
other cases, where the coal measures are overlaid with
thick deposits of very loose strata, rendering the sinking of
small shafts very costly, or where it would be difficult to
get a cheap supply of suitable packing material, tunnels
are driven from the rise side of the winding shafts to
connect the rise sections of the various seams. In any case,
the method adopted for packing will not interfere with the
general arrangement of laying out the workings, whereby
advantage is taken of gravity to assist in haulage. Even
collieries in which the workings are well advanced before
the hydraulic system of packing is applied can be adapted
to either of the systems mentioned, by driving headings
forward in the coalseam to connect with the tunnel from
winding shaft on the small shaft near the outcrop, through
which the pipes are carried to convey the packing material
to the working face.

The design of the installation required at the surface will
be largely determined by the nature of the materials
available for packing. Where sand, dirt washings from the

coal washery, or other small debris is used, only a mixing
plant is required.

The size and cost of . plant will be determined by the
quantity of debris required for packing and the amount of
crushing necessary. A pipe 6 in. internal diameter will
carry 100 to 150 tons per hour if the material is crushed to
under 1*18 in. (30 mm.) size. The average cost of a stowing
plant where the material has to be crushed from 15 5 by
23*5 in. (400 by 600 mm.) down to f in. size, for ah output
of 40 to 80 cubic yards of packing per hour, will be about
.£1,500 to £2,250, depending on the hardness of the material
used. Where only a mixing plant is required the cost will
be considerably less. In Upper Silesia the quantity of
debris flushed varies from 40 to 300 cubic yards per hour.
Generally an eight to 10 hours flushing shift is in vogue
with a maximum of about 3,150 cubic yards of packing per
shift, but in the Giesche mine 5,000 cubic yards of packing
is put in every 24 hours. It has been found from experience
that the best size for crushed material is from 0*788 to
1-18 in. (20 to 30 mm.). This prevents clogging, and
produces better packing than coarser materials would give.
Fine stowing material will also prevent the tendency for
air to get into the pipes at the top (causing sudden
stoppages), as the fine stowing and water keeps the connec-
tion between the pipes and mixing hopper completely filled.
This also prevents an irregular discharge at the packing
end.

The most difficult and important point regarding the
stowing problem was the solution of the pipe question
which can now be considered as settled. Cast iron and cast
steel (unlined) pipes have been discarded because they
were too heavy and difficult to handle. In addition to this,
they offered considerable resistance to the flushing current,
causing excessive wear and requiring the use of large
volumes of water. In the unlined systems only mild
ungalvanised steel pipes are used, but these are being
replaced by some form or other of lined pipes. The first
form of lining used was of hard wood blocks about 8 in.
long, forced inside the pipes by means of an hydraulic ram.
These cost about 2s. per metre length (39*5 in.), and acted
very well where sand was used, conveying in some cases
450,000 tons of flushed debris before being worn out.
The Monnertz system of porcelain - lined pipes used
at the Deutscher Kaiser Collieries appeared to be best
for ground slag, but they are more costly than the
oval - lined pipes of the Busch or Stephan systems,
as described in the previous paper on ° Subsidence in
Relation to Packing.” The oval-lined pipes have con-
veyed 1,100,000 cubic yards of flushing debris per inch wear
of lining. The distance horizontally to which the flushing
material may be carried, depends upon the smoothness of
the inside of the pipes, the size and nature of flushed debris,
and the amount of water used, but lengths up to 4,400
yards are working (in the Koenigin Luise Mine, Upper
Silesia), and if sufficient water is used the distance hori-
zontally to which the packing may be carried is five times
the vertical working head. The pipes are usually 16j ft.
(5 m.) long, and where circular steel linings are used there
are five lengths of 39’5 in. (Im.) lining to each pipe. In
shafts and on inclines the linings are kept in position—
when pipes are being changed for repairs—by means of a
loose flange placed between the fixed flanges, and having an
internal diameter equal to that of the lining. When a
pipe has to be taken out, short bolts are put in between the
upper fixed flange and the loose one, as each of the long
bolts are removed. The pipes placed in the levels
do not require this arrangement as there is no danger of
the lining coming out when a joint has to be broken. In
the shaft the pipes are supported by collarings on the
buntons on the inclines by collarings on pairs of stout props
every second or third pipe length, while on the level small
brick supports, 12 to 15 inches high, are put in, two to each
pipe, and placed about 20 in. from each flange. Where
quick curves have to be negotiated a great deal of wear
takes place, and many methods have been tried to reduce
the grinding action or to admit of easy renewal of the worn
parts when required. The unlined pipes were made thicker
on the outside curve, and brackets were often cast on the
inner surface of the thick side, so that part of the debris
which collected behind them formed a cushion, thus
preventing excessive grinding on the part of the flushing
current. With porcelain-lined pipes a 90 degs. curve is
usually constructed of seven separate parts (five of 134 degs.
sectors and one of 9 degs.).

In the earlier stages of flushing packing considerable
trouble was caused through air getting into the pipes at the
delivery end. This difficulty was overcome by having the
delivery pipe slightly tapered to a smaller diameter at
the outlet. This provides a full supply at the delivery end,
and prevents air getting in. It is necessary to have some
rapid and accurate method of signalling between the packing
end and the mixer on the surface to communicate the
requirements of the particular district to be packed, and to
regulate the supply of packing material. Portable tele-
phones, which can be transferred from one district to
another, are used for this purpose.

The Method of Working.

In laying out the workings of a mine fo hydraulic
stowing, the method commonly adopted is to cut up the
royalty area into pillars (or panels), varying in size

according to the thickness of the seam. In seams over 5 ft.
in thickness—where ripping for main haulage and ventila-
tion roadways is not required—levels and headings are set
out about 4 to 5 yards wide to form pillars from 30 to 400
yards square, depending on the thickness of the seam. In
thick seams which have to be extracted in two or more
layers, smaller pillars are formed than in seams about 8 to

10	feet in thickness, where the whole of the coal may be
extracted in one operation. The drivages to the rise side
are carried forward as quickly as possible to form a connec-
tion with the rise stowing tunnel (or special stowing shaft),
after which the extraction of the pillarsis commenced in the
form of “widework” faces. As these widework faces
advance to the rise, the worked coal passes to the level
below and the packing is conveyed down from the level
above. In very thick seams like that of Upper Silesia
(which is 36 to 40 feet thick), where the coal is extracted in
two operations, the pillars are small—in the older workings

11	yards (10 m.) and in the newer mines 33 yards (30 m.)
square. In extracting the pillars the lower half (19 ft.) of
the seam is worked until the rise of the adjoining pillar is
reached, the goaf being completely packed by hydraulic
stowing. This face is continued in the second pillar, while
a new face is opened out in the upper half of the seam in
the first pillar, thus keeping an oblique line of face running
across the pillars in both layers. Each roadway as it
becomes disused is filled up by allowing the water drained
from the packs to pass through it, rough dams being erected
in the lower roadways, thus preventing the water passing
along the main haulage roadway. This also serves as a
settling pond for the clarification of the water. The direc-
tion of the flow of water from the packs towards the sump.
Before hydraulic stowing was used in this seam the pillars
were formed about 11 yards square, but much of the coal
was lost through heavy roof weights and gob fires. In
moderately thick (4*5 to 10 feet) seams, where the coal in
the pillars can be extracted in one operation, the pillars are
made much larger (and usually rectangular in shape), thus
saving the extra cost of driving so many headings and
levels. The pillars usually vary in size from 50 by 10Q yards
to 100 by 200 yards, and the roadways are set out as in the
last case, so that gravity may be taken advantage of in
hauling the coal from the face and conveying the packing
to it.

In seams under 4*5 ft. in thickness the pillars are usually
made as large as possible, to reduce the cost of ripping and
haulage of ripped debris before “ pillaring ” and hydraulic
packing can be started—that is to say, until the first pillar
has been formed and connection made to the stowing tunnel.
In extracting the pillars in this case two methods may be
adopted, according to the rate of dip of the seam and the
amount of ripping required to form the main roadways.
Where the dip is sufficiently high, advantage is taken of
gravity to “ shoot” the coal down narrow openings left in
the pack, which prevents the ripping of gate-roads for
haulage, from the face to the levels. The general plan of
this arrangement is similar to ordinary advancing longwall
with gate-roads about every 14 yards apart, except that in
this case narrow unripped openings (shoots) take the place
of the ordinary gate-roads. In flatter seams the coal may
be mechanically conveyed along the face to gate-roads 100
to 200 yards apart, constructed as the longwall face
advances, so that the debris from the ripping can be put into
the pack and form draining walls for the flushed material.
The stowing pipes are brought down the headings
originally driven to form the pillars, branching to right and
left along the face to pack the 50 to 100 yards on either
side. The water drains away from the pack through the
now disused heading, which acts as a filter pond, leaving
only the gate-roads unpacked. Where seams are very
thin (2 to 3 feet thick) longwall faces up to 100 yards long
may take the place of the ordinary headings and levels in
forming the large pillars or panels, whereby all the
ripping in making the main roadways can be disposed of in
the packs. With mechanical coal-cutting and conveying on
these faces a larger output can be obtained much earlier in
the development of the colliery. In thin seams producing
more debris than could be conveniently used as draining
packs, this material can be used up by erecting a crushing
and mixing plant underground—preferably in a lower seam
—and the excess debris from the thin seam is conveyed to
this point, ground up, and flushed into the lower workings.
This method has been successfully applied in several
collieries both in Westphalia and France.

Drainage of Water.

The partitions erected to hold the packing while draining
and setting are very variable in construction. The most
commonly used type is formed by setting a row of
props up to an 8 in. by 4 in. plank running along the
roof, the lower ends of props being firmly fixed in the
floor. Behind the props thin deals 9 in. broad are nailed
about 2 in. apart, and hanging behind these is a long
strip of brattice cloth attached to the 8 in. by 4 in. plank.
When the packs are being made the water drains off
through the brattice cloth between the deals, care being
taken not to let the cloth get clogged up and prevent the
water from draining off. Where the floor is soft, the waters
from the packs should, if possible, be passed through old
disused roadways, as already mentioned, but when this
cannot be done, the water as it comes from the pack should