During last 12 years the annual output of coal mines has decreased from 38.3 millions tons to 17.5 millions tons and the number of coal mines from 74 to 28 in Japan. Most of the output was transported to the surface with belt conveyors through inclines. The loading operation in drift and roadway driving is highly mechanized and side dump loaders predominate in loaders. As driving machines 7 Road Headers and 16 Continuous Miners are used in March 1982. About 69% of the output of longwall faces was got in flat seams, 13% in semi-steep seams and 18% in steep seams. And 96.5% of the flat seam output was got in completely mechanised working faces. There are 30 shearers with ranging drums and 6 planers in use and most of the powered roof supports are shield type. The productivity of workers in such working faces is 33.1 tons/shift on the average. The remote controls of many kinds of machines, such as coal getting machines, battery locomotives and electric winders are brought into operation.
The rate of underground accidents decreased gradually in recent years and it was 118 men/million shift in 1982. But deep coal mines are attended with many dangers. Especially gas outbursts occur. Every pit has a control room with a watching board on the surface to inspect underground conditions. The government promotes the study of the safety problems in deep coal mines. It also promotes the study of gasification and liquefaction of coal in order to use more coal.

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Present coal policy is carried out based on the seventh report of advisary committee for coal industry in 1982 under the basic concept which aims the self-support of Japan's coal mining industry maintaining the harmony between stability and economy of coal supply.
After World War II, there was a big change in circumstances surrounding the coal industry and the coal policy has been changed.
Even in the latest decade, we are meeting the turning point in energy situation influenced by two times oil shocks, and new coal policy has been requested again.
In this paper, we will make clear the development of coal policies after World War II and the hinterland of its ages, and would like to image what the coal policy is in future.

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In spite of increasing of working depth in coal mines, the number of accidents and victims have remarkably decreased so far.
However, 1 the accident rate is still high, compared with other industrial sectors, 2 there is no denying that a large scale accident peculiar to deep coal mines, might occur.
On the other hand, in the future, as the working depth will continue to become deeper.
Therefore, proper safety countermeasures for accidents (especially for serious ones such as gas outbursts, rock outbursts and so on) should be established as soon as possible.

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Undersea coal mine, Ikeshima operated by Matsushima Coal Mining Co., Ltd. is located in the western part of Nagasaki Prefecture.
It was a necessary condition to develop a new low sulfurous coal field for the regulation of SOx.
Development started in 1971 on the basis of the geological survey and the removal of the faces to Hikishima was performed within 1974.
It is now producing 1.35 million tons clean coal a year successfully.
New field is the area of the isle of Hikishima, 0.22km²and its circumference.
This paper describes on the following points.
(1) Geological survey
a) geophysical prospecting
b) deep boring on the sea
(2) Progress of the development
a) tunneling and shaft sinking (inlet, outlet and service wind)
b) mining method (long wall system combined with shield support and drum shearer)
c) ventilation, cooling and drainage system
(3) Plans in the future
a) development of the southern part of Hikishima area
b) rationalization of the transport system

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Ashibetsu Colliery has been working steeply inclined seams for 40 years. The expanded and complicated structure calmed by tne rapid increase of mining depth urged the fundamental reformation of the colliery. “Ashibetsu Long-term Stabilization Plan” has been denved trom such situation and the decision was made to develop Ashibetsu Slope. The construction work of Ashibetsu Slope, started in Oct. 1981, encountered many difficulties and was completed at -790m level in Apr. 1982. Ashibetsu Colliery presents here the report of the construction work of the slope which has contributed the colliery much more than expected.

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It is serious problem for undersea steaming coal mine to increase output and efficiency. We have solved this problem by means of mechanization.
SD longwall system is a typical highly-mechanized mining system which we achieved. Output and efficiency of the mine has been reached high level by this system. In the process of the development of this system, high-speed in-seam roadway driving system has been also developed to meet high advancing-rate of the retreat longwall face. Today, the total distance of the in-seam roadway drivage per year is approximately 40, 000m, and most of them are driven by continuous miner system. Many changes of equipment, roof support, and panel layout have taken place in these 25 years since the first introduction of the continuous miner in 1958.
Now, we are planning to develope further advanced in-seam roadway driving system.

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The rock heading in Miike Colliery is a matter of great importance recognizing the fact of increased heading meters per thousand tons of coal produced, 9.54m in 1972 and 12.7m in 1981, and that the innovative progresses in this field have been required. The conventional heading techniques are based on the short hole firing system where the V-Cut using portable leg drills is prevalent for the pattern of centre cut. Miike Colliery, therefore, has made practical collaboration with the Coal Mining Research Centre in Mikawa Mine on the subject applying the long hole firing system. This report presents the improvements in drilling, blasting and loading techniques realized so far.

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The development of the large diameter boring by ring cutter was required for the alternative safety construction method of large diameter holes to compensate the lack of skilled labours for raise and drift construction, and other various relevant aspects.Conventional large diameter borings require to break all rocks within the hole, whic means high cost requirements and less effective operations consequently.
Sumitomo Akabira Colliery introduced the large diameter boring by ring cutter to avoid the demerits of conventional methods.In July 1978, the first test of 550mm diameter was carried, then 770mm diameter test was tried progressively. Through the test, the disking phenomenon which has no direct relations with joints or cracks of strata was confirmed. This disking phenomenon occurred expectedly in the practical operations, which made possible for the smooth improvement of further larger diameter boring. However, no disking phenomenon was recognized in some area exceptionally, where wedgeshaped breaker was fitted additionally to the cutter to obtain sufficient results. Now, large diameter borings of 1, 500mm diameter are possible and the flexible selection of diameters is applied according to the purpose, that is, ventilation holes for decreasing the underground high temperature caused by mine deepening, effective countermeasures for gas outburst, etc.
Recently, horizontal large diameter borings upto 30m has been possible using this method, and further horizontal long boring operation is possible if high power machine is introduced.
Regarding the cutting width of the ring part, it is fixed to 40mm width and single cone rotary bits are applied in stead of hard metal bits to decrease the cutting losses.The method is also applied for the advanced boring in the drift sinking operation. Thus the wide range of usages of this method is hopefully expanded to various ways.

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The Takashima coal mine of the Mitsubishi Coal Mining Co. Ltd. is located at the Takashima Island about 15km to the southwest of the Nagasaki-Harbour.
The mine has been put into operation over 280 years before and has yielded the highest class of metallurgical coal. The mining field was moved into the offshore area in 1917 and extended to the northwest from the Takashima Island.
Although many kinds of geological data have been obtained actively in this area, the data obtained is not sufficient enough for the long term mining plan as the coal bearing palaeogene is overlaid by the thick Quaternary sediments.
Recently in the field of petroleum exploration, the reflection seismic survey has intensively developed both the data aquisition and processing.
Takashima Coal Mine decided to apply this method with some modification to delineate the geological structure and to directly interprete the coal related reflections. However bore core sampling is necessary to get a precise information on coal layering, seam thickness and coal qualities such as ash contents and coking properties etc.
The seismic survey was carried out in 1981, which resulted in detecting coal related reflections in the non-faulted and gently inclined new field next to present mining area.
In 1982, drilling was carried out at the center of the new field by a semi-submersible drilling rig.
The drilling encountered the thick coal seams at the depth of 500m below the sea bottom, that coincided with the coal related reflections on the seismic sections and the estimated depth.
These exploration works resulted in discovering a huge amount of coal reserves in a structurally stable area.It is also confirmed that the reflection seismic survey was a useful and economically efficient method for the offshore coal field.

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The main mining system at Kushiro Colliery is the longwall mining system with shield supports and drum shearer. On the occasion of this mining, generally main gate road, tail gate road and face road must be driven by means of continuous miner before mining. However, with the increase of mining depth, successive maintenance of gate roads has been confronted with difficulties.
Accordingly, for the purpose of solving this problem, liner road system was investigated and adopted to the longwall mining system. In the liner road system, at the beginning main gate road and face road are driven, and tail gate road is constructed in goaf with advance of face.
From September 1979 to February 1983 this liner road system has been adopted to 17 mining panels. Total distance of liner road was 7, 644 m and total coal productions amounted 2, 168, 010 tons (clean coal).
In the future longwall mining plan, the proportion of liner road system will increase. Furthermore, in order to increase the recovery and reduce the cost, the new technical and economical improvement of liner road system is examined and the first step has put into practice

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The history of the hobel mining at Takashima Colliery is very long. It began with introducing the LObbe hobel in Decem ber 1957, and has been followed by the Umbau hobel and Reisshaken hobel which are working as the main mining machines now.
Firstly the Lobbe hobel was introduced in order to increase the productivity in a thin coal seam (=Banto seam).
It proved fairly successful.
Secondly in January 1961 the Umbau hobel which hobel and conveyor drive are done by different motors were introduced.
And in 1962 the productivity was led to 7.6t/M. S. in the Banto face.
Then, the heavy duty mechanization which combined the powered supports are the double drum shearer were proceeded.
But it had to be given up and it was taken the place by the single prop supports mining.
Because the barriers for the face mechanization are as follows.
1 the short working field 2 inclination 3 Matsuiwa (silicified hard rock in coal seam) 4 faults 5 the poor roof condition.
To deal with these problems Takashima colliery looked for the new coal mining machine.
As a result the S-3 Reisshaken hobel was chosen because of its adaptability to the matsuiwa, the faults, the inclination, the single prop supports and the working height.
The production by it started in July 1979 and all faces are equipped with the hobel at present.
But there.still remain a lot of problems concerning the face mechanization, especially such as the stable elimination and the combination with the powered supports.
The hobel mining has a long history, and today, the hobel occupies an important part in the coal winning machines in the the world, but the hobel mining is apt to be looked down, for the shearer mining occupies the speriority in number domestically.
This paper is nothing but discribing the hobel mining at a colliery, and yet it summarizes the introduction in the genesis' of the hobel mining and its changes, present and future, so, it would be grateful, if it is useful to you.

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We invested heavily in the medium seams to raise the productivity by a high degree of mechanization.
As the next step, to realize an economic coal-production in thin seams became our important and pressing problem. There fore, we have been studying and advancing the mechanization of coal-production in thin seams since the Fiscal Year 1981.
We selected Drum Shearer EDW-170-LN as we judged it could cut our hard coal having FD15-24 in hardness without any anxiety. It has the favourable interchangeability with other machines in us in respect of spare parts. And, also, we chose strong Face Conveyor having bottom plates of 22mm thickness and the strongest connection in order to guide the Drum Shearer smoothly, to keep the supports' positions right and to get long life.
Now, we are studying about a support most suitable for our conditions. Therefore, we have a big expection for the trial Shield Support, which CMRC will test at Horonai before long, The concept of principal design adopted into it is as follows:
1) To fit for seams having 0.8-1.5m in thickness.
2) To employ Crawl-pan System to obtain a good path.
3) To employ Batch-control System as the control system.
4) To employ multi-tube hose between two supports.
We think that it is necessary for us to advance the elimination of labour by further automating.
We intend to make an effort to raise the productivity and to attain the fully safety for coal-getting in this seams.

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Minami Oyubari Coal Mine has three minable coal seams. They are lying in an extremely complicated geologic structure; therefore, manual operations with hydraulic props have been mainly adopted together with an Air Blaster system unless good mining conditions had been foreseen beforehand. The annual production is approximately one million tons with 4 longwall sections. At present two of these are mechanized. and the others are manually onerated.
Eleven longwall panels were equipped with several types of powered supports, and drum shearers were tried in 13 longwall panels up to now. Most of the panels, however, could not be considered to be successful owing to various types of difficulties. The biggest problem would be the widend unsupported roof ahead of the canopy of powered supports created by a wide lift of the drum shearers.
The coal ploughs were introduced first in December, 1980, and are achieving a satisfactory productivity. This year the production from the mechanized longwall faces will exceed 60% of the total production for the first time in this mine's history. This is nothing but a result of the ploughs, and consequently all longwall faces will be tried being mined by the ploughs in the future. One of the main mechanization plans is a trial on the combination of powered suPnorts and a coal plough.
The mining environments of this mine will be getting severer in terms of mine safety and operatina costs. so any efforts will be given to tne mechamzation focused on the coal ploughs in order to achieve a safe, inexpensive, and steady production system.

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Investigations for improving the environmental conditions of the longwall faces in Yotsuyama Mine, Miike Colliery, were conducted using new ventilation systems. The E-shaped ventilation system is the one and the W-Shaped ventilation system is the other.
The results obtained are
(1) Both systems are effective for controlling the environmental conditions of the face worked in highly heated surrounding rocks.
(2) Ventilating by Wr-System, labour intesive areas are placed in fresh air and the total capacity of heat exchangers required for a face including face entries are only 60 to 70% of that required in the Ur-System.
(3) In the Wr-System, two patterns of ventilation air flow is observed due to the different flow rates in the two intake airways.
(4) In gassy areas, the Wr-System could be inadequate because of the tendency of fire-damp accumulation in the goaf. In such cases, the E-System should be applied.

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Sunagawa Colliery has managed to solve many difficult problems since 1914 and the technical innovation took place in 1964 when the colliery employed hydraulic mining. Subsequently, the hydraulic mining has been steadily improved widening the range of its application. The colliery is now working steeply inclined seams at the depth of 900 to 1000 meters below surface. The author intends to introduce parts of the results successfully practiced in the deep mining at Sunagawa Colliery.

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Mayachi colliery is producing 2, 000-2, 100 tons of coking coal per day. Working coal seams are in the Yubari coal-bearing formation. The seams steeply inclined, i. e. 40°-80°. Mechanization of the coal mining has been hindered because of the steepness of the coal seams. Therefore, manpower has to play an important role especially in the coal producing faces. Latterly the number of young people joining the company has decreased. In addition to this, fairly long training periods are necessary forthe new workers in order to obtain enough knowledge of the mining operation under such special conditions. As a result, the average age of the workers is becoming higher and higher. It is forecasted that the constant coal production will become difficult in the near future. To solve this problem, a few counter measures have been conducted. One of the approaches to solve this problem is the application of light iron props made of aluminum alloy to reduce the fatigue of the workers. Another measure is the test of special boom type coal cutting machine which is a modified form of the road-header used for driving work. This report contains the abstracts of the above mentioned progresses and tests.

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Sorachi colliery was established by open coal mining system in 1977 and its production was 65, 000 t/year. Presently, two methods, bench cut and inclined stoping, are operated and the production is increased about 500, 000 t/year for the progress of mechanization.
This paper is described the development of open coal mine at the colliery, under the following items.
1) Outline of the colliery
2) Present situation on the development.
3) Geological survey for outcrop area
4) Establishment of working face and regulation by forestry conservation
5) Mining method
6) Calculation of mining cost
7) Reclamation

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Thirteen years have passed since Minami Oyubari Coal Mine began its production. The conspicuous character of the mine is unfavorable geological condition which causes gas and geopressure problems. Gas and geopressure problems are the both sides of a coin. Advancing underground road excavation is inevitable and effective to solve gas problem, but used to encounter geopressure problem.
Actually, advancing road excavation and retreaving longwall system have been adopted as the means to settle the gas problem in this mine. Recent tendency of activating area into deeper places forces us to turn our certain energy to maintainance work for underground road. Maintainance of underground road is the one of the most important subjects. We examined and studied all possible ways to keep underground road as it was. As the result, underground road condition is drastically improved and man power engaged in maintainance work steadily reduced.

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We developed 4 type of small dinting machines, which has some feauture to get high efficiency and reduction of labor Then, we put to use them at some pit in fact and investigated about following points
(1) Ability of dinting
(2) Suitability of machines
(3) Durability of machines
(4) Application to subsidiary work
In findings, every machine made higher efficiency by a large marginlv than human efforts. And they can raise it morenver by improvement of way.
About suitability of machines, they have no difficulty on space where we planned.
Also they can answer to operations to make the most of each feauture.
About durability of machines, each was dammeged partly, but there were no defect in structural. We can find COMP of subsidiary work with them.
We expect that they could raise the overall effeciency on maintenance of roadway.

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In the Coal Mining Reserch Centre, Japan, we developed five “Bolt Setters” for the purpose of preventing emergency and improving efficiency at Bolting works.
First one has tracks and two hydraulic rotation moters for drilling and Bolting, which is operated by electric moter.
Second one has a percussion drill which is installed on the simple wheel. It is operated by human power. Third one hastracks and hydraulic rotary percussion drill, which is operated by air motor (4kg/cm² pressure).
Fourth one has tracks and hydraulic rotary percussion drill, which is operated by electric moter.
Last one has tracks, hydraulic rotary percussion or rotary drill and special mechanism which is able to choice rotary or rotary percussion drilling methods. It is operated by air moter (4kg/cm² pressure).

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Ashibetsu Colliery reestablished the underground main structure by developing Ashibetsu Slope where an automatic winding machine was installed in Sept. 1981. The machine started regular running in Apr. 1982. The author introduces the first automatic winding machine in Japanese collieries.

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The main transportation system at Kushiro Colliery is constituted of large winding machine at the trunk drift, and trolley wire locomotive or battery locomotive at level.
However, free haul with battery locomotive is restricted by the undulation due to the folds and faults. Therefore transportation of mine car has depended on main and tail haulage system using two small winding machines. However, this system has many difficult problems, e. g. number of workers, operations and maintenance. In order to solve this problem endless rope haulage system was developed in January 1981.
This endless rope haulage system has been driven with one winding machine, and adopted remote control technique by radio equipment. Although this system was used only for material transport at the beginning, possibility for transport of workers was examined in 1982 from which we aquired good result of this system. Then, several improvement and development of new apparatus have been done and safety of man car haulage by endless rope haulage system has been ensured.

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In this paper the outline of recent progress in researches of the cause, mechanism and prediction and prevention methods of gas outbursts is described.
It is presumed that the rock pressure caused by excavations play an important roll in the cause of gas outbursts. And a number of hypotheses for the cause and mechanism of gas outbursts are put in order simply.
For the prediction of gas outbursts, AE and rock tremors have been measured by accelerometers or seismometers earnestly. But the pattern for a sympton which can predict gas outbursts has been still in groping. It is expected that the relation between AE and the pattern of fracture of rock or coal will be studied in the future.
Moreover, gas concentration in the air near the face is being measured continuously by the automatic recorders at present.
For the prevention methods of gas outbursts, a method by removal of stress in roof strata is offered and tested in situ. If the above method is proved to be effective, the development of the more economical methods based on this method will be expected.

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Yotsuyama Mine is one of the three mines in Miike Colliery. Retreating longwall mining system is exclusively employed and the mechanized faces are equipped with sheeld supports and a double ranging drum shearer. The working faces are developed in the Upper, Main and in the selected area of the Lower Split of the Upper Seam. In 1977, the mine experienced an extraordinary phenomenon in a face worked in the Upper Seam West 35th District where the cover of depth was 550 meters, the deepest cover of the colliery at that time. The phenomenon was very similar to outburst. Since then, mine has experienced such severe phenomena very often in the area especially where the seam is immediately covered with hard sandstone and/or the face is very close to the rib of or beneath the residuall pillars. The mine, therefore, has established its own preventives tackling on the problem. This report presents the mine's overall preventives taken to keep the safety and the production.

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The observations with the seismometer at Sunagawa Coal Mine started as the study entrusted from Coal TechnologyResearch Institute in 1971. Then processing and analyzing system owned by Coal Technology Research Institute were removed to Horonai Coal Mine in June 1980. So that, at this coal mine, we had recorded on only pen-recorders.
But meanwhile the credibility of systems was lost extremely because it became difficult to record on a pen-oscilograph owing to inferiority of signal transmission lines and increase of noises. In this time the hydraulic mining blocks were shifting to 860L, we had to enrich the measuring instruments of seismic events for the purpose of strengthing safety. The recording on penoscilograph became more correct as a result of carring out immediately strengthing and renewing the signal transmission lines and decreasing noises.
We tried the automatic of signal processor after the improvement of signal transmission system. The system owned by Coal Technology Research Institute was so excellent as corresponding to academic study, but in this coal mine, we planed to simplify the obtained data by means of the minimum processing i.e. a seismic source location and magnitude calculation. So that we made for the system to operate easily as one of centralized supervision.
In regard to the processing system, two microcomputers display their abilities which are equivalent to a minicomputer by connecting them in series. The former is in use for sampling the data and the latter for operation and controling peripheral equipments. We order the measuring instruments from electric works, and they are controled in our own program. It is easy for us to operate it in our place of work.

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In proportion to underground operational depth, observation of underground changes such as geopressure change became quite important to predict and avoid possible bursts.
Minami Oyubari Coal Mine has introduced a sophisticated computer system in 1982 which collects various data such as AE, Geopressure and Displacement, which also presents us useful results of analysis. The system consists of sensor, transmission, calculation and analysis sections. Maximum quantities of sensors are twenty each for AE and Geopressure and sixteen for Displacement. Each are buried mainly in gateroad near production area. Sensors send signals for twenty-four hours continuously through transmission to calculation and analysis sections.
Collected all data are analysed automatically by computer. It is also possible to calculate in various ways under an operator's instruction.
At present, calculation and analysis sections at surface are receiving relatively almost constant signals from underground which show abnormal pressure phenomenon would not occur for a time being.
Accumulation of data must be continued as it is indispensable for an accurate prediction and effective measurements against possible disaster.

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At Akabira Colliery, the instance of fire fightings for mine fire tells one side of the history of the colliery since the mine was opend. Six mine fires which have occured in the colliery in the past seven years resulted from spontaneous combustion of the residual unmined coal around operating areas. In every case such as the fire could not be detected in early stage and was not extinguished by direct water spraying, the firing zone was immediately sealed off from the other area. The accumulated experiences in our mine have suggested that the early detection of spontaneous combustions of coal is important countermeasures and is able to minimize the trouble.
This paper gives an account of early detection methods of spontaneous combustions and typical countermeasures applied at Akabira Colliery. It reports, in addition, the most up-to-date methods for early detection in spontaneous combustion and the prospect for the development of underground integrated monitoring system.

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If a mine fire takes place somewhere underground and unfortunately does the mine fail to suppress in its early stage, there is a great possibility to cause heavy casualities.
In many coal producing countries, therefore, they put great efforts into development work on new fire detection and control methods.
Herein, the author presents situation and results so far in research field on mine fire characteristics such as propagation speed, temperature distribution, gas composition, explosibility of aftergas mixture, smoke emission and ventilation disturbance, and also describes current state and trend of underground mine fire detection and suppression technologies.

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Recently LSI technology has made a remarkable progress, in particular microprossesor has caused a technical inovation in every industry.
Ikeshima Colliery adopted a centralized underground mine monitering system based on microprossesors in 1978, for the purpose of modernizing safety installation, environmental and production control.
This report describes on the detail of system which is specialy arranged to meet the requirements of the underground coal mine.
The system consists of following consitituents by colour CRT display, analogue indicator and switch units; CH₄ gas density, air temperature, compressed air pressure, spray water pressure, cooled water volume, electric current and etc.; centralized monitoring, detection and remote operation of plans and safbty control devices.

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