March 16, 1917.

THE COLLIERY GUARDIAN

529

The American authorities for some of the information
contained herein include Mr. Augustus Smith, who has
been responsible for the construction of several of the
United States naval coaling stations; Lieut. Robinson,
who was concerned with the modern collier referred to;
and Mr. Spencer Miller, who has been prominent in
advocating coaling at sea by cableway and in perfecting
details of such equipment.

MIDLAND INSTITUTE OF MINING, CIVIL
AND MECHANICAL ENGINEERS.

The cementation process as applied to mining was the
subject of an interesting discussion >at a meeting of mem-
bers of the Midland Institute of Mining, Civil, and
Mechanical Engineers, held at the Danum Hotel,
Doncaster, on Thursday, March 8. There was a large
attendance. Mr. E. W. Thirkell (vice-president)
occupied the chair during the early part of the meeting,
and afterwards, when he had to leave for another
appointment, his place was taken by Mr. W. H.
Chambers, a past-president.

The Secretary (Mr. G. Blake Walker) announced
that the president (Mr. C. C. Ellison) had had a severe
attack of influenza, and, although he was better, his
doctor advised him not to travel from Scarborough, in
view of the cold weather. Several members of the
council, including Messrs. Lloyd, Smithson, and Har-
greaves, were unable to attend owing to the fact that the
West Yorkshire coal owners were holding an important
meeting. Mr. Blandford, who. had contributed a paper
on “ The Cementation Process as Applied to Mining
(Francois System),” wias detained in South Wales on a
ticklish job that he could not very well leave. The
secretary also reported that at present 34 colliery com-
panies were subscribing members of the institute, which
was a very satisfactory recognition of the work that that
body had been doing.

New Members.

The following elections were agreed to :—Member,
Mr. Sydney Gill; associate members, Mr. Joseph
Norman Roberts and Mr. Aly Yousef; student, Air.
Gerald Thomas Newbould.

The Cementation Process as Applied to Mining
(Francois System).

The Secretary then read Air. Blandford’s paper.*

DISCUSSION.

Air. Thirkell said they had had a very interesting
paper. One important part of it, to his mind, was the
number of examples which had been given in order to
show that the process of cementation could be carried
out successfully in a practical manner under almost
every conceivable condition.

Air. H. N. Berry (Hatfield Alain) said the paper con-
tained a very interesting general account of the various
applications to which the cementation process had been
put in this country, each of which, he thought, would
form the subject for a complete paper in itself if only
the details could be given, as no doubt they would be
on some future occasion. The author had omitted one
instance in which cementation had recently been use-
fully employed in Yorkshire. This was a case where
ground under winding engines had been giving way, and
the winding engine pillars had been shattered. Those
pillars had been cemented together, and the ground made
perfectly secure. With regard to Hatfield Alain, the
author had made one mistake, where he stated that the
cement was washed out of the ground by the pressure of
the water. If there was one thing more certain than
another with regard to cementation, it was that once
they got cement into the ground, they could not wash
it out. The trouble at Hatfield Alain, at that time, was
that they could not get the cement into the ground. It
was never washed out : they could not get it in. He
mentioned this because the statement in the paper might
give members a wrong impression with regard to the
process of cementation. There was another mistake in
the paper, which he thought must be a printer’s error.
Speaking of shaft lining with concrete blocks, it was
stated : “ In dry ground where it is necessary to close
off any water by means of such lining, this method is
quite satisfactory.” He thought Air. Blandford meant
“ where it is 'unnecessary to close off any water,” which
was quite a different thing. Any gentleman who was
seeking trouble with regard to wet shafts could get it by
using concrete blocks, and could avoid it by using mass
concrete. He was sure Mr. Blandford’s intention was
not to recommend concrete blocks, even where it was
necessary to close off any small quantity of water. Air.
Blandford mentioned two methods of cementation—one
where the holes were put down outside the circumference
of the shaft as in freezing, and the other where they
were put inside the perimeter of the shaft. In the
speaker’s opinion, the latter was the only practical
method of going to any depth. They all knew how diffi-
cult it was to keep boreholes straight when they were
boring from the surface. If they had a fair depth of
water-bearing ground, and they put their holes in from
the surface to go down to a depth of 200 or 300 yds.—
which they might have to do in such ground as the new
red sandstone, going further east—it would be almost
impossible to guarantee that those holes would not come
into the shaft. There were many other reasons why the
boreholes should not b-e put outside the shaft. He would
not like to have men in the pit bottom, sinking, when
the pressures involved in the cementation process were
on the unlined portion of the shaft. He should not
mind them being on the lined portion, because he knew
from experience that ferro-concrete would stand pres-
sures that really were surprising. He now had a static

* See Colliery Guardian, March 9, 1917, p. 479.

pressure of 250 lb. per sq. in. on the ferro-concrete lining
at Hatfield Main, but that shaft lining had stood
2,0001b. pressure per sq. in. in injecting, and the shaft,
too, was dry at that particular place. The whole of the
backing of the wall was solid. In the previous week’s
Colliery Guardian* was a report of a paper by Mr.
Sidebottom on the cementation of shaft linings at Llay
Hall, Wales, in which it was stated, in general terms,
that marls could not be cemented. He thought Air.
Sidebottom was wrong in that particular. Marls had
been cemented abroad, and were also being cemented
in this country. They had just recently been cemented
in Warwickshire. Mr. Sidebottom also stated that gravel
could not be cemented. That depended somewhat on
the gravel. If it was in juxtaposition with running
sand, the statement was probably right; but gravel beds
in certaiin cases could be cemented, and successfully.
With regard to the origin of the cementation process, he
found that in 1904 the Society of Lens, in France,
carried out some work by cementation. He believed
there was a paper, describing this particular work, in
vol. 31 of the Transactions of the institute. Another
claim which Air. Blandford might justly have made for
cementation, as carried out by the particular process he
referred to, was its great comparative safety. He
thought, from his experience of cementing ground, that
the work of the pit sinker was made more secure, and
there was less liability to shaft accident due to falls of
ground on the shaft sides in bad ground. He had sunk
through ground which, without the cementation process,
it would have been very difficult to make really secure
by temporary timbering; but that ground, which was
naturally bad, was made artificially secure before sink-
ing through it, and no special precautions were required
when temporary timbering was put in.

Mr., Thirkell asked if the chemical mixture did not
prevent the cement from being washed out.

Experience at Hatfield Main.

Air. Berry said he did not want to discuss Hatfield
Alain very much, because he hoped, when he had time,
to give a paper upon it, but he would be very pleased to
answer any questions that might arise out of the present
‘paper. The process which was adopted at Hatfield
Main, in the first instance, was one that had been
employed very successfully, on other kinds of ground, in
the North of France and in Belgium. It had been found
that 2501b. per sq. in. was quite ample for all pressures
that were necessary to cement ground of the character
that had been tried up to that date, these grounds being
in chalk, marl, white marl, and limestone. At Hatfield
Alain they had to deal with the new red sandstone, which
gave off enormous quantities of water, but unfortunately
had very few fissures; and such fissures as were there
were not clean, but full of sand. They found that they
could not drive the cement into these fissures with the
pumps which they had at that particular time, and which
were built for a working pressure of 250 lb. The pumps
were on the surface. They tried higher pressure pumps,
and at 8001b. pressure per sq. in. their results were
better, but not perfect. They only got perfect results
when they combined with the ordinary cementation
process the two chemicals, which had many effects, one
of which was lubrication of the fissures. It was found
that they got at least some quantity of cement in with
one-sixth of the pressure when they injected the two
chemicals first. Where they could not get any cement
in a hole at all by forcing the thinnest possible mixtures
of cement and water at any pressure the pump would go
up to, they found that, if they uncoupled the cement
pump and put on the pump which was kept for these two
mixtures, and forced the mixtures in first, then the
cement would go in, and at a very low pressure. The
chemicals had also, in his opinion, a further action in
preventing the sand in the fissures from packing up. If
they exposed a fissure, with some loose sand in it, giving
off plenty of water, a little sand would sometimes run
out, but the water would not clear the fissure, and then,
when they came to pump a thin grouting of cement, they
found that it would not go into the fissure at all. What
he thought happened in that particular case was that the
loose sand went in front of the water, and reached a point
where it became a lump : it packed up, and prevented
the cement from going any further. The injection of the
two chemicals prevented that packing up. It was diffi-
cult to explain in a short description,, and he hoped to
explain it more fully later on. The third principal
action of the two chemicals was the precipitation, in the
porosity of the ground, by the two separately mixed
chemicals being injected separately, and choking the
porosity of the ground and preventing bleeding through
the porous rock after the main fissures were cemented.

Mr. P. Sidebottom (Llay Hall, Wrexham) said he
would like to have details as to the treatment of the
wood-lined shaft in Lanarkshire which Air. Blandford
mentioned. His own experience was that they must
have something that would hold the cement more or
less—a brick wall, or tubbing, or an iron plate, or some-
thing of that sort. He could not see how Mr. Bland-
ford managed to keep the cement behind timbering, and
would like to know how he tackled the job.

Air. Blake Walker asked if it would not be very
much like a retaining wall with planks in front. These
shafts were lined with planks, and if there was a bottom
for the filling to rest upon, they would close up the space
between the boards and get a concrete wall.

Cementation and Gob-Fires.

Mr. Sidebottom said that was so, but the cement must
be injected under considerable pressure, and unless the
plank was like match-boarding the cement would come
out into the shaft rather than face the fissure. He
should like a little information about that. Then, again,
Mr. Blandford mentioned treating gob-fires. Well, if
they got a gob-fire more or less effectively stanked off,
so that they had plenty of time, he could quite see what
a very useful thing cementation would be in that case.

* Colliery Guardian, March 2, 1917, p. 429.

But he should like some information as to the real
utility of injecting in the case of a gob-fire. He had
had to deal with one igob-fire within the last two years,
and his experience was that the ground was so broken
that, in spite of building substantial brick dams with
good foundation, and cutting well into the side, the gas
got through the fissures and breaks quicker than they
could build dirt stoppings. They emptied the dirt of
the whole distance of the pit against these stoppings,
but the gas seemed to beat them. Eventually, they did
stop it. His point was that where they had a gob-fire,
it had to be tackled pretty quickly. Therefore, they
would want to have their cement on the job. It looked
to him as though, to deal effectively with a gob-fire,
they would want to have a cement injecting plant some-
where in the pit, always available. A thing like that
would be excellent, but he was afraid it was not very
practicable. With regard to the paper on Llay Hall,
which Mr. Berry had mentioned, he (the speaker) was
probably unfortunate in the use of the term “ marls.”
What he meant was the sort of marls that they had in
North Wales, which were of glacial formation. One
would hardly call them stratified measures. They
underlay the gravels, which were no doubt glacial
deposits, found extensively in North Wales. He
thought it would be very difficult to cement those marls.
He supposed Mir. Berry referred more to the marls
which were mentioned in Mr. Blandford’s paper, and
were a sort of red sandstone found in Staffordshire. He
supposed this material was more or less a stratified rock,
but he had no experience of it. One point which pleased
him was the fact that the present paper had been pre-
sented at all. It would bring the question of cementa-
tion before mining engineers. After nearly 20 years’
experience in Yorkshire, he went into North Wales,
where he found the state of the shafts deplorable. The
quantity of water in them rather alarmed him. Those
concerned were used to it, and took it as a necessary
evil, he supposed. It did not seem to give them any
concern. He saw the evil, but he did not see the neces-
sity for its existence. He set to work to cure it, and it
occurred to him that, if cementation were any good at
all, this was a case for adopting it. He fortunately
rubbed shoulders with Air. Brydon, and the result was
that they got the work done in a highly satisfactory
manner. There was no doubt that the benefits that
accrued were out of all proportion to the money that was
spent. If more colliery managers knew what could be
done by cementation, he had no doubt they would make
efforts to get their pits dried. The benefits were really
very great, and took a great load off a manager’s
shoulders. In writing a paper like the present, and
bringing the matter before the mining world, a great
deal of good was done.

Interior v. Exterior Boreholes.

M. Schmidt (Paris, chairman of the French section
of the Liege Institution of Alining Engineers) said that
on the Continent the process of cementation had been
used 20 or 25 years. It was called the Portier process,
after the name of the inventor. It had also been
adopted in Saxony; he did not know how many years
ago. Air. Blandford’s statement as to there being two
distinct methods of applying the process was not entirely
exact. Boreholes could be put down either outside or
inside the shaft. At the mines of Maries, one, or
perhaps two shafts, were sunk with inside boreholes,
and at other mines in the east of France the same
method was adopted. The question of the deviation of
the boreholes into the interior of the shaft, therefore,
was not important. They were perfectly able to sink
shafts with inner boreholes from the surface. It was a
question of the kind of rock which they had to cement.
In France, near Vimy,. where the British troops were
fighting at the present moment, he had sunk two shafts
in chalk. The ground was very wet, but they cemented
it to the depth of 130 yds., and they had not had a
single bucketful of water. He was not sure, however,
that they would have the same excellent result in sand-
stone. The application of cementation with the internal
method of boning, at Alarles in 1908, was not the first,
for the method was used several years before. The
Alarles instance, however, was certainly the most
interesting of all, because when the shaft collapsed the
best part of the mine could no longer be worked. Thus
a very rich part of that big coal field wTas saved by the
process. The rock drills used were supplied by M.
Franqois, and all the drilling was done under his per-
sonal supervision. He believed that M. Franqois was
the first to use chemical solutions, injected for cement-
ing, and, he thought, with good results. M. Francois
had also used very high pressures, as was stated in the
paper. These high pressures, however, could only be
used with this process of internal injection, and not in
the neighbourhood of the surface. If they were inject-
ing cement in the neighbourhood of the surface by
internal injections, or by holes put down from the sur-
face, they must have a strong stratum of clay, or, in
its absence, they must make an artificial watertight
platform. With high pressures, however, this stratum
of clay would be quickly broken; in fact, he had seen
cases in which all the foundations in the neighbourhood
were broken by a pressure of not more than 1001b. per
sq. in. It was only with the internal process that it was
possible to use high pressures, and at great depth.
With regard to defective boreholes, he said there was
one method which was carried out entirely with cement-
ing, neither casings nor linings being used for the bore-
holes. He thought it was possible to cement wooden
linings perfectly, at least when the shaft was round or
elliptical. The first example of that was at the Cour-
rieres Colliery, where, at the time, M. Portier was chief
engineer. There, two shafts lined with wood were made
entirely watertight, so much -so that not one drop came
into the shaft. Many engineers thought that the terrible
catastrophe at those mines was partly due to the cement-
ing, because the coal dust in the shaft was more than