964

THE COLLIERY GUARDIAN.

May 7, 1915.

Report on the Explosion at the Hojo Colliery, Japan.

By S. MEGURO.

(Concluded from page 910.)

Site of the Explosion.

The direction of the explosion wave, as indicated by
arrow marks in the underground map (fig. 2, see Colliery
Guardian, April 30, p. 908), originated in the working-
face of the 4th oroshi, Right 16th kata, 74 oroshi, and
traversed every level of the Right 12| kata, 13th, 14th,
15th, 16th, 17th kata, from right to left. The wave
left 15th kata to the left, passing through Second
New Oyama oroshi and Second New Kuroki oroshi
from the upper portion to the lower portion. In
this quarter of the mine the number of roof falls and
amount of cohering coke dust were very great. Now,
the reason of ascertaining 7-J- oroshi as the originating
point of the explosion was as follows :—This 74 oroshi
stretches only 12 yds. from the level of the 16th kata; its
breadth is 3 yds., height 8 ft., and inclination 18 degs.
At present, in the bottom of the working face, there
accumulate small quantities of water. The roof coal
of this working face was much carbonised, the surface
of the coal being changed to a coke; the bituminous
matter was melted by the heat of ignition, and hung
down like a thread from the roof, reaching a length of
1 in. On the working face and both walls an abundance
of coke and soot adhered. As in the face there are no
props, it was not possible to find adhering coke scale,
but in the neighbouring gallery coke scale was found,
which had been deposited upon the surface of the
timbered road. This coke scale faced to the face of 74
oroshi. The brattice in 7-J oroshi, which was con-
structed with planks, props, and straw mat, was broken
into small pieces, and blown against the right side wall-
of 74 oroshi and the point of 16th kata facing towards
7| oroshi. Besides, as there was a doubt as to whether
the end working face of the 16th kata was an originating
point of the explosion, I examined this face very care-
fully. The roof coal was found to be much carbonised,
and the surface of coal changed to coke, and abundant
coke dust was attached to both walls. But from the
fact that two coal tubs which had been laid upon the
rails of the 16th kata, and brattice which had been con-,
structed in the 16th kata before the end face, were all
broken into small pieces and blown against the end
face, also clay which lay at this point of the surface being-
blown against the face, it is evident that the explosion
wave was blown against the end face. From the funda-
mental principles of the coke adhering theory, it is
evident that at the origin or its vicinity, the attached
thick coke scale faces to the origin, and on the reverse
side only a few grains of coke are scattered, indicating
an abundance of coke dust, intense heat, but not much
movement. On the front surface facing away from the
end of three props which stand on the left side of the
working face at the 16th kata, a thick coke scale adhered,
while on the back surface (facing towards the end) of
the props were attached only a few scattered grains of
coke. This kind of coke is of perfectly round form.
From the above facts it is clearly evident that the end
of the 16th kata was not an origin, and that the true
originating point must lie in the neighbourhood of
74 oroshi.

The explosion wave in the 4th oroshi traversed clearly
from below upwards. As New Kuroki oroshi had been
used as the main inlet which hauls the coal produced
from the quarter of Second New Kuroki oroshi and
Second New Oyama oroshi, the accumulated fine coal
dust was abundant; hence the explosion wave exhibited
extreme violence. At the 4th kata an air bridge, which
had been constructed with brick, was thoroughly broken
up, and the wave, after having demolished a 100-horse
power electrical hauling engine and its room, passed out
of Oyama oroshi and Kuroki oroshi. On the other hand,
in New Oyama Oroshi, which is parallel to New Kuroki
oroshi, being only used for laying drain pipes and cable
lines, there was no accumulated coal dust; hence the
wave force was very weak, and could not sweep away
the props which had been set in that incline, there being
only roof falls at 11th kata and Right 3rd kata. More-
over, the amount of adhering coke was so scanty that it
could scarcely be recognised.

In the left quarter of New Kuroki oroshi, left 11th,
10th, 9| kata, the wave went from New Kuroki oroshi
towards the left. In every incline it passed from below
upwards, through the broken air bridge at 4th kata. As
the above passage before the explosion corresponded to
the return airway of Second New Kuroki oroshi quarter,
if the gas which was emitted from Second New Kuroki
oroshi, Left 21st kata, 4| kata, caused the explosion,
the return airway, which had a direct relation to the ..gas,
must have at first been subjected to extreme violence
by the sweeping force of the explosion wave. But, on
the contrary, this airway.was not destroyed, and there
was no adhering coke scale, the props remaining in the
greater portion of the airway. The above facts
evidently show that the gas which issued from the 4j
oroshi did not originate the explosion.

In the interior portion of New Kuroki oroshi, Left
10th kata, a few years ago, spontaneous combustion had
occurred, and at that time all passage ways communi-
cating with the gob fire were packed by means of sand
flushing; and at Left 94 kata, 2nd oroshi, Left 11th kata,
the left diagonal incline which also communicated with
the above sand-flushed area, was constructed of pack
walls or dams with shale, and plastered over with clay
and lime. Now, in examining these dams, it was found
that no change had occurred in the walls; hence it may
be clearly recognised that the ignition of the explosion
did not originate from the fire. In the four inclines of
Togo, Kuroki, Oyama, and first incline, the wave

* The Chief Engineer of Fukuoka Komusho (Mine Inspec-
tion Office of the Japanese Department of Agriculture and
Commerce').

generally passed from below. Heavy roof falls, com-
plete destruction of props, abundance of adhering coke,
etc., all indicated the extreme violence of the explosion;
in particular the office, which was situated between the
3rd kata and 4th kata of Kuroki oroshi, was totally
broken down into small pieces; six tables, 35 chairs, and
five boxes were all converted into simple fragments of
wood, and blown away, leaving behind but slight traces.
The surface of books w’ere burned black, but the
dynamite remained unexploded.

The wave, which went up the 4th oroshi, was split
into two parts at the Sth kata; one passed up New
Oyama oroshi, after passing through the self-acting
plane of the 8th kata; the other went out into the 7th
kata of Right Mata oroshi, possing through the com-
munication road. This road is a gob road, where abun-
dant accumulations of coal dust and gas were present.
When the flame of the explosion arrived here it
generated a secondary explosion ; and in one direction the
wave blew out of the 7th kata of Right Mata oroshi; on
the other side, the wave traversed the road in a reverse
direction, that is, from right to left, and finally went
out of the 1st oroshi, after passing through 5th kata,
4th oroshi, 4th kata, 4th nobori, 3rd nobori, 3rd kata.
As in this gob road a stench of spontaneous combustion
was detected, this passage was always watched. Though
it was necessary to examine this road, the roof falls were
not only too great, but at the top of the fallen rock gas
accumulated, and rendered it inaccessible. This road,
when opened thoroughly, will be examined again.

In the quarter of Right Mata oroshi the explosion
wave originated in the standpoint of the 7th kata (com-
munication road), and split into three portions, in 8th
oroshi of 7th kata :—(a) The wave went straight to the
interior of 7th kata; (b) ascended 8th oroshi from 7th
kata; (c) descended 8th oroshi from 7th kata.

(a)	This wave indicated most violence, and in pro-
ceeding to 84 oroshi split itself into three portions. In
this quarter the explosion -wave had blown away com-
pletely all the props, and caused-.heavy falls and thick
coke scales.

(b)	It was urged that the wave in the 8th oroshi, 4th
kata, had gone in a downward direction, by the fact
that the handle of the 15-horse power electrical hauling
engine (situated at the 4th kata of Sth oroshi) was bent
in a downward direction, the transformers were blown’
against the corner of the ribs at the rear of the hauling
engine, and the pulley for the rope, which was in front
of the engine, was blown downwards. On the other
hand, I have clearly ascertained that the wave, on the
contrary, passed from below upwards, by the fact that
the position and form of the adhering coke dust neces-
sarily indicated there had been swept by an ascending
current. Again, by careful investigation, it became
evident that the bending of the handle was caused by
falling roof which was provoked by the explosion, and
not directly by the wave. The blown-off transformer
and blown-down pulley were the results of falling down-
wards after they had been raised from their positions,
and broken and detached by the explosion force.

(c)	A portion of the wave which swept the quarter of
Right Mata oroshi reached the intersecting point of
Second Right Mata oroshi, 5th kata, and 28th oroshi,
after passing through the various passages of gob of
Right Mata oroshi, 18th nobori, Right 2| kata, and level
way. At the 5th kata, as this corresponded to the
haulage road of the Second Right Mata oroshi, there was
an abundant accumulation of coal dust. In this por-
tion of 5th kata of Second Right Mata oroshi, the wave
generally passed from below upwards, and swept away
all props in that incline, as well as leaving an abund-
ance of coke dust. In the level gallery, as it was a
rock cutting near a fault, the quantity of cohering coke
was very small. In the lower portion of the 5th kata of
28th, 29th, and 30th oroshi, the wave blew downwards,
and in the 5th kata the wave blew towards the interior.
In the Four-feet seam, which is connected to Right
2| kata, the explosion wave only blew in; hence the
miners and overmen of the seam were killed by
suffocation.

In the self-acting plane and Second Right Mata oroshi,
Left 1st kata, the wave blew from right to left. The
telephone, which was set at the end of the self-acting
plane, was blown to the left, 18 ft. being broken up. The
roof falls were great, and all props were swept away.
The drum was broken down. In this vicinity many
bodies were considerably mutilated. These facts indi-
cate the violent force of the wave. Against the drum of
the 15-horse power electrical hauling engine, which was
situated at Right 1st kata of Second Right Mata oroshi,
the coal tub, which was filled and attached to the rope,
was blown from below upwards, and greatly damaged.
In this quarter the quantity of attached coke was very
great.

In the upper portion of Nogi kata of Third Right Mata
oroshi, the wave blew from below” upwards; but in the
lower portion of Nogi kata the direction of the wave
was not clear. It seemed to have had no motion, and
the stalactitic carbon hung down from the roof to the
length of 14 to 2 in. But by careful examination of the
coke dust it was clear that the wave blew in to some
extent towards the interior. In the 4th kata of 38th
oroshi and 39th oroshi a coal cutter had been employed
before the explosion, and the cutter itself was not broken,
but the roof coal was greatly burned and coked. When
the flame of the wave lingered in this part of the mine,
the glowing particles of coke became attached fo the
roof coal, and ignited the coal; hence this part of the
mine is not believed to have been an originating point
of the explosion.

The wave in 38th oroshi, 39th oroshi, blew from below
upwards, and combined with the wave which came from
the interior of Nogi kata, whence it went to Rise 1st
kata and Rise 2nd kata, again combining with the wave
which ascended Third Right Mata oroshi and 29th oroshi,
passed through 2nd kata, rose to Second Right Mata
oroshi, and went to Rise 6th kata. Here the roof falls
were considerable. The toothed wheel of a hand winch
which was set in 21st oroshi of Rise 6th kata was torn
into two parts by the force of the explosion, and one
part was blown a distance of 28 yds. The weight of
one part was 80 lb. The explosion wave went towards
the left up to the 7th oroshi, and passed out through the
upcast shaft. But at the bottom of the shaft, as the
force of the wave which came from the lower portion of
the mine was strong until Rise 1st kata was reached,
coke dust deposited by the explosion wave which came
from the dip side was clearly seen.

The explosion wave which entered the Left Mata
oroshi on reaching the quarter of Second New Mata
oroshi, ignited the coal dust clouds, and showed still
further violence. The air bridge which was constructed
at the pipe oroshi was thoroughly broken up by the
wave.

The wave descended both inclines of the Second New
Mata oroshi and pipe oroshi from New 7th kata, and
reaching 11th kata, split into two parts :—(1) The wave
descending Right diagonal oroshi; (2) the wave descend-
ing straight down the incline.

The wave which descended Right diagonal oroshi was
violent, the falls of roof and quantity of adhering coke
dust being very great. But in the centre of this
quarter a man died from suffocation, whilst the bodies
which were found in the other part of the mine were all
burned.

The wave which descended the incline caused heavy
falls in every gallery, so great that the height reached
13 ft., and it was very rarely that the coal seam could
be seen. Accordingly the quantity of cohering coke
dust was very abundant. The bodies were generally
burned, but those found in 5th oroshi, 14th kata, and
15th kata died from suffocation.

The wave which proceeded along New 7th kata,
reached the 9th kata of Third New Mata oroshi, and
raised here new coal dust clouds, causing a secondary
explosion, the flame of which descended the incline of
Third New Mata oroshi to the end, and ascended
gradually the 17th, 16th, and 15th katas. The one
current of wave went to the 17th kata of the 15th oroshi,
after passing through the 17th kata fault cutting gallery.
In •the 17th oroshi and 18th oroshi an electrical pump
was situated, but no adhering coke dust could be seen,
and the condition of the wave was rather still. I have
considered that neither incline was the originating point
of the explosion.

The wave which ascended the 17th oroshi from 17th
kata, reached the 15th oroshi. In this quarter roof falls
and adhering coke and coal dust were most abundant.
Again the wave passed the mouth of Second New Mata
oroshi, Left Mata oroshi, and ascended Togo oroshi. The
greater part of the wave passed up the downcast shaft,
but one part of it passed the bottom of the shaft, and
entered Togo nobori, causing a fire there. Another part
proceeded as far as 3rd oroshi of Left Nogi kata, causing
a great fall.

The explosion wave which was generated in the
quarter of the Third New Mata oroshi passed upwards.
In this quarter generally the falls were very great, the
height reaching 20 ft. or more. The sweeping away of
props was extremely violent, the quantity of cohering
coke dust being very great. But as in the vicinity of the
16th kata of this incline the direction of wave pointed
to every side, I considered that the originating point of
the explosion must lie there. With this view I examined
this place very carefully, but, on the contrary, I found
that the miners’ clothes which were hanging on the
props of the 16th kata were not burned at all. Also the
adhering coke dust was very scanty. The wave passed
from this Mata oroshi to the 7th kata and 18th nobori,
and entered the 1st kata of New Nogi kata, blowing out
of the upcast shaft after passing the 12th oroshi, Rise
5th and 6th kata. In the quarter of New Nogi kata
there was no indication of flame; accordingly, the adher-
ing coke dust was very small.

The explosion wave entered the New Togo oroshi from
Right 3rd kata of Togo oroshi. In one direction the
wave blew straight down New Togo oroshi, ascended 1st
nobori, and ceased in the 2nd kata after blowing the
working places of 1st nobori. On the other side, the
wave which came from the 9th oroshi of New 7th kata,
proceeded along the 5th kata towards the right,
ascended the 4th nobori, and combined with the above
wave. Again it descended the 4th nobori from the 5th
kata, entered the 6th kata, proceeded to the right, and
combined with the wave which came from New Togo
oroshi. In the 1st nobori, 2nd kata, 4th nobori, 9th
oroshi, 5th kata, the wave generally was very weak. The
quantity of adhering coke dust was also scanty. The
props of the gallery almost all remained in a perfect con-
dition, but in the 6th kata, between Second New Mata
oroshi and pipe oroshi, the props were all burned,
causing fire. This was a result of flame lingering,
which came from both the Second New Mata oroshi and
pipe oroshi, attaching to the props glowing particles of
coke.

Investigation of the Cause.

(1) Spontaneous Combustion. — In this mine, as
already stated, a few years ago spontaneous combustion
had occurred at the interior part of New Kuroki oroshi,
Left 10th kata, in which coal was converted into
dust at a fault. The temperature at that point was
being raised gradually, and began to emit smoke and
fire. At that time, as a method of extinction, in
the neighbourhood of the fire a gallery was opened which
totally surrounded the place. This gallery was packed
with sand flushing, all the passage ways which com-
municated with the flushed gallery were also packed
with shale and stone, and plastered over with clay and