818

THE COLLIERY GUARDIAN

OCTOBKK 16 1914

method to be used for its distribution underground.
For this purpose two methods are employed, namely :
(1) by transport under pressure in pipes; and (2) by
transport in launders. Transport under pressure in
pipes is necessary in all mines when the filling material
has to be conveyed along roads that are either horizontal
or that only slightly dip or rise, the pressure being
obtained by the head of pull on the vertical pipes in
the shaft.

On the Rand only three kinds of pipes have been
used, the ordinary cast iron pipe, wood lined pipes, and
to a very small extent porcelain lined pipes. The pipe
line is laid either along the foot of the drives and stopes,
or when this is not practicable, the pipes are hung from
the “ hanging ” by means of chains attached to eye-
bolts, or e se they are supported on timber trestles.
The pipes may have loose or fixed flanges, rubber
(insertion) washers being placed between them- After
a few months’ use the pipes are given a turn, in order
that the bottom segment of the pipe, where the greatest
wear takes place, may be replaced by a portion of the
pipe which has suffered comparatively little damage
through the abras:on of the sand particles. By this
means the pipes can be used for a considerable length
of time. The life of the pipes used on the Rand appears
to be very variable, and it is therefore difficult to give
any exact figures on this point.

Transport in launders is preferable to that in pipes
wherever the gradient is suitable. The gradient
required is dependent not merely upon the size of the
sand particles and the ratio of sand to water, but also
upon the volume of pulp and the roughness and internal
shape of the launder. In a wooden launder, sand pulp
containing 30 per cent, of moisture will flow slowly on
a grade of 30 per cent, approximately 17 degs.; with
40 per cent, moisture on a 20 per cent, grade, approxi-
mately 11 degs.; and with 60 per cent, moisture on a
10 per cent, grade, approximately 6 degs. Launders
are made up of planks, the bottoms being provided
with a liner of hard wood and with angle pieces of hard
wood in the corners, as shown in fig. 2. V-shaped
launders (fig. 3) are easy of construction, cheap, and
being light, are useful when frequent replacement is
necessary. At the Robinson Mine launders having
concrete liners (fig. 4) were used. These were made in
3 ft. lengt1 s and placed inside the wooden launders.

Drainage launders are used for carrying off the water
from the surface of the filling. These launders are in
box form, and must be of fairly strong construction in
order, to withstand the pressure of the filling material
down through which they pass. Fresh lengths are
added as the filling rises, each length provided with
some means of escape for the water as it rises along its
entire length. Either holes are drilled or the top
plank is left off and short lengths nailed on as the
water rises, cocoa nut matting or wire netting being
placed over the openings for the purpose of clearing
the water.

Barriers.

Before filling can take place underground, the place
which it is desired to fill must be prepared for the
purpose. Wherever possible, faults, dykes, or portions
of unprofitable bodies of ore are used as natural
barriers; but as in many mines these natural barriers
do not exist, or as is more often the case, do not occur
in that portion of the mine where they could be made
use of, it is necessary to build artificial barriers.

Barriers should be built with two purposes in view—
first to hold the sand in the position required, and
secondly, to allow of the drainage of the water. The
first barriers built underground on the Rand were
constructed as watertight as possible, all the water
being carried off from the surface of the filling by
means of special drainage launders, which passed down
through the sand and barriers, and were gradually
lengthened as the sand was filled in. It is now found
to be preferable to drain as much water as possible

Cost of Sand-filling

ON THE W1TWATERSRAND.

Mine.	Period.	Tons of sand lowered.		Average surface cost.		Average underground cost.		Average total cost.	
		Total.	Average per month.	Per month.	Per ton of sand lowered.	Per month.	Per ton of sand lowered	Per month.	Per ton I of sand ; 1-wered.
				<£ s. d.	d.	£ s. d.	d.	£ s. d.	d.
Simmer and Jack 		9 months		172,535	19,171	269 0 1	3*368	523 10 3	6’554	792 10 4	i 9-92
East Rand Proprietary	Average mth.	—	19,490	189 0 0	2’320	374 0 0	4’610	563 0 0	6’93
W it watersrand Deep...	12 months ...	328,645	27,387	440 1 6	3’820	426 12 7	3’740	866 14 1	■	7-56
Robinson Deep		4 months		103,261*	25,815	191 14 2	1’780	821 14 2	7’600	1,013 8 4	9’42

* It is interesting to note that the 103,261 tons of sand lowered at the Robinson Deep represents 95’1 per cent, of the
total production of sand residue at this mine.

through the barriers, which must therefore be con-
stru3ted to act as a form of filter bed. Draining the
water off direct through the barriers naturally reduces
the pressure upon them to a very considerable extent,
with the result that they need not be of such heavy
construction as previously.

A barrier which has given good results, and does away
entirely with the use of timber, is one built up of waste
rock in the form of a pack. The outer wall is first built
of large stones, and on the inside of this smaller stones
are used, gradually decreasing in size until sufficient
thickness of barrier has been constructed, ash being last
of all thrown on. Such a barrier is shown in fig 5, and,
if well constructed, will retain all the sand and only
allow practically clear water to pass through it,

Sexeral types of timber barriers have been used, all
more or less similar in construction, only differing
slightly as to their method of drainage. Fig. 6 shows a
barrier suitable for supporting the sides of the sand-
pack, and consists of props set from 4 to 6 ft. apart, and
hitched at the bottom and the top. On the inside of the

props either pitchpine or blue gum planks are nailed.
The top and bottom planks are scribed to the roof and
floor, and hay is often used to fill up any remaining
openings. Cocoanut matting may be nailed to the
planks, so as to act as a filter for the escaping water.
Fig. 7 shows a barrier which is intended for use in a
narrow opening, such as a box hole, and should only be
used at the lowest point in the portion of ground that
is to be fill°d. As will be seen, its object is to act as a
filter bed; ash is used as the filtering medium, and the
filtered water is conveyed through the stone pack by
means of a 3in. pipe.

Hydraulic Stowing in Deep Mines.

When sand filling was first introduced on the Rand,
it was only employed at the outcrop mines, in order to
permit of the extraction of valuable pillars of rich ore
which had been left as supports (fig. 8). As time went
on, sand filling was carried on at greater depths, and in
the very deep mines it is especially necessary on account
of the great roof pressure.

When filling takes place at a depth of from 3,000 to
4,000 ft., a heavy charge is incurred for pumping all the
extra water introduced into the mine with the stowing
material from this depth, as well as the extra cost for
pipes due to their rapid destruction, caused by the high
pressure and velocity of the pulp. In order to avoid
these extra costs, a system was introduced on the
Cinderella Deep mine, by which the sand was sent into
the mine in a dry condition. In order to effect this, a
wooden box-launder was constructed measuring 12 by
11 inches in inside cross-section. This launder was
carried down the vertical shaft to the level at which the
filling material was required, which was at a depth of
3,900 ft. The sand, which should not contain more
than 7 per cent, of moisture, is stored in a surface bin,
from which it is taken on a conveyor belt to the top of
the shaft and there discharged into the launder. On
reaching the bottom of the launder, it falls on to a
steeply-inclined iron plate, at which point jets of water
are turned into the sand, which is then carried away as
a pulp either by means of pipes or by launders to
wherever it may be required.

The great objection to this system is the difficulty of
securing a constant supply of dry i-and. As soon as the
sand c< ntains more than 7 per cent, of moisture, it is
inclined to gradually adhere to the sides of the launder,
which in time becomes choked. The launder was con-
nected upto a Roots blower and jets of compressed air
introduced, the idea being to assist the drying of the
sand and to increase the velocity of the falling stream,
but this device was found to result in only a very slight
improvement, The system has much in its favour,
but unless some method can be devised to enable sand
containing more than 7 per cent, of moisture to be used
successfully, it is certain to be a failure.

Drainage.

The clarifying of the overflow water before pumping
is a matter of some importance, as, of course, water
containing only a small percentage of sand and slime is
injurious to the pumps. At those mines where old
dumps are being used for filling, trouble is experienced
with the large quantities of slime present with the
sand. Great difficulty is found in getting the slime to
settle, and on this account the use of current sand-
residues is much to be preferred. Slime has also the
additional objection that it prevents, to a considerable
extent, the rapid filtration of the water, on account of
its forming a more or less impervious covering on the
filter bed at the barriers.

All the water overflowing from the sand filling is
made to pass through the catch pits and filter beds
constructed in old drives or stopes. The catch pits and
filter beds should always be constructed in duplicate, so
that, in the event of one becoming filled up with sludge,
the water may be turned into the other while the first is
being cleaned out, thus preventing any stoppage.

It is often found necessary to add lime to the water

before pumping, on account of its having become acid,
due to the decomposition of the pyrites in the sand.
The lime can be conveniently added at the catch pits.

Costs.

The cost of sand filling varies considerably at different
mines, but will, no doubt, be reduced as further
economies are introduced. The above costs are
those incurred by four mines on the Rand, which
correspond very favourably with the costs incurred by
the coal mines of Upper Silesia.

Immingham Coal Exports.—The official returns for the
week ending October 9 show that a total of 32,257 tons of
coal were exported to foreign ports. Exports were as
follow:—To Aalborg, 2,012; Archangel, 2,616; Bruges,
2,393; Gefle, 2,366; Gothenburg, 6,807; Oxelosund, 3,553;
Bonne, 1,054; Santos, 4,933; Skutskar, 3,082; and Stock-
holm, 3,441. No coal was sent coastwise. The coal
exported during the corresponding period last year totalled
56,905 tons to foreign destinations.

MINING INSTITUTE OF SCOTLAND.

Meeting at Edinburgh.

A general meeting of the Mining Institute of Scot-
land was held in the Heriot-Watt College, Edinburgh,
on Saturday last, Mr. James Hamilton (president),
Glasgow, in the chair. At the outset the following
gentlemen were admitted to membership :—Messrs.
Claude Hinshelwood, colliery manager, Dunsyston Col-
liery, Ayrshire; and D. H. McNicol, mining agent,
Derwas, Denbigh; and as an associate, Mr. Michael
John Wemyss, colliery owner, Wemyss Castle, Fife-
shire.

The Rosehall Signal Indicator.

The discussion was resumed on the paper read at
the last meeting of the institute by Mr. James Black
on “ The Rosehall Signal Indicator.”

Mr. Robert McLaren, H.M. inspector of mines, said
that for work in a shaft—getting a slide in or some
other thing—where it was essential that they should be
able to raise the cage 6 in. or lower it to exactly a
similar distance, they required a hanging bell. Now
there was nothing in any of the instruments he had
seen yet which provided a substitute for this useful,
and indeed necessary, hanging bell. Therefore, would
it not be better for, say, operations in the shaft, if the
work were done by some other method than by means
of signalling? He was not saying anything against the
particular instrument which Mr. Black had described,
and he merely raised the point as one that would appeal
to them as practical men.

Mr. Black said he quite appreciated Mr. McLaren's
remarks, and, personally speaking, he preferred to work
in the shaft by the method of hanging the bell.

Mr. McLaren observed that he had raised the point
simply to get the views of the members upon it. He
had put this instrument to a very severe test, and so far
as he knew it complied with every provision of the Act.

Mr. John Masterton, H.M. inspector of mines, said
he would point out to his colleague, Mr. McLaren, that
there was nothing in the Act about hanging the hammer.

Mr. McLaren said that while there was nothing in the
Act about hanging the bell, it was an old custom which
had worked well. If a custom had worked well in the
past, why, he asked, should they interfere with it? As
practical men, he would say to them that he did not see
how any instrument in the world would ever compensate
them for the advantages of the system they had at
present in doing shaft work of a somewhat particular
nature.

Mr. Masterton said he had distinctly objected to
hanging bells since an occasion when he nearly got one
of his arms pulled out of its socket.

Mr. Roberts gave it as his opinion that Mr. McLaren
was not so old-fashioned as to make it impossible for
him to become new-fashioned in some things. Person-
ally, he thought the instrument they had before them
was going to do away with the hanging of the bell,
which was not essential.

Mr. James Black observed that the indicator was
quite capable of doing anything that was required by the
Code and by the Mines Act.

Mr. David Beveridge, Kelty, remarked that he was
disposed to agree with Mr. McLaren’s idea, old-
fashioned although it might be. Possibly he had done
as much work in deep shafts and with heavy cages as
any member present, and he was bound to admit that
the custom of hanging the hammer at critical points in
their operations was an important item in shaft work.

Mr. G. L. Kerr (secretary) thought it had been
amply demonstrated that this indicator could give the
signals required by the Mines Act. Secondly, it was
non-cumulative, and that was a good point in its favour.
The third advantage it possessed was that it could
record only the fixed position of the wind, or it could
register only at the end of the wind if that was desired.
It seemed to him it would have been much more advan-
tageous for all concerned had this, and similar, discus-
sions taken place before these regulations were intro-
duced, instead of now, when they had come into force.
The whole fault rested with the Home Office in making
certain provisions before they knew definitely that there
was any instrument on the market which would comply
with them. Had a reasonable time been allowed for
apparatus to be devised and worked out, then many
managers would not be in the fix they were now in
respect that they had fixed up instruments which the
inspectors of mines declared did not comply with the
Mines Act. That was most unfortunate for managers
and coal owners who had already laid out their money
on the purchase of apparatus. The fault did not lie
with managers, who had tried to comply with the Act.
He did say, however, that the blame rested with the
Home Office in making regulations without first con-
sulting those practical men who were in charge of col-
lieries every day in life.

Further discussion on the paper was adjourned till
next meeting.