Chikubetu coal mine situated in Hokkaido, their area are about 3, 000 hectares, estimated available reserves about 43, 000, 000t, in which about 2, 900, 000t mined out.
The largest difficulty we met on the rationalization process was how to deal with the mudstone, which we found under side of coal seam. This mudstone containes a lot of bentonite and very brittle.
At the same time, it absorbs water very easily and increases itself.
Therefore, it was very difficult to maintain the gallery, which was excarvated in this rock seam. As the first adequate measure for that, we excarvated the transportation gallery in the other harder floor rock, and we adopted the so called“Pocket mining system”.
As above mentioned, our suitable measure for the brittle and absorbable mudstone rock seam led us to The mechanization in face and rationalization of the transportation system, and we could get the large output of coal in face.
Well, we will describe this rationalization process in more detail as follows ; after we succeeded the“Kappe mining system”, we excarvated the great transportation cross cut as the first step to rationalization of Transportation system.(“Kappe mining system”is a mining system, in which we use the Kappe-iron beam, iron prop and armed conveyer)
Then, as the second step, we tried to concentrate the coal face, rationalize the incline belt shaft and armed conveyer gate road. After that, we adopted the so called“slicing mining system”as we see it today.
The great effects of rationalization were increase of output per man shift, and decrease of mining cost.The output per man shift became 7 times larger than before, total coal output 10 times, mining cost became 13 times.
Without adaptation of any new machine and special mining method, we got these good effects by only effective using of our machines and installations.
Now we think, our rationalization process till now was the only first step. And we must try to develop the new mining technic as the second step of our rationalization.
We believe that, on the base of our above mentioned rationalization, we can develop the new mining Technic in our coal mine, for instance, adaptation of hydraulic prop, hyaraulic transportation of coal, new Technic of shaft sinking etc.
Well, we got also good results of safety in coal mine, and this owed to the improvement of our technic and rationalization, we think.
We mentioned above only the rationalization of technic, but we must stress here finally the adequateness of our labour management was the important element to the good reconstraction of our coal mine, which was ever facining a terrible crisis.

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At Oshima coal mine, the advancing method of the long wall system is adopted to mine three close successive coal seams. The amount of transudatory methane gas from surrounding coal measures to the working face of coal seam mined first was several times of other two working faces mined after about 10 and 20 months respectively. So that we were obliged to mine only one shift a day at the first mining, because the gas in gate airway became over 2.0%, even though we ventilated 1, 000m3/min of air.
In order to reduce the volume of methane gas transudated to the face mined first, the method of gas drainage from the goaf has been examined since 1953. This experiment unexpectedly has shown that thereis little hope to draw out enough mine gases by this method.
Therefore, I have been performing some fundamental investigations of the amount of mine gases and their pressures in virgin coal measures, and have found that about 40% of the total methane gas in coal measures is contained in these three coal seams and it can easily escape from the seams through many small cracks, which are formed by adding slight rock pressure and connect pores containing methane gas each other.
This investigations have shown that the method of gas drainage from the virgin area of coal measures may not be impossible, and, moreover, that experiment has shown that this method must be established to mine the first coal seam safely.
Accordingly, we have been studying on the method of gas drainage from the virgine coal measures by means of gas drainage drift opend into the rocks under the virgin coal seams, in which drift many bore holes have been drilled towards the upper virgin coal measures.
It has been proofed that more than half of the total amount of methane gas in coal measures has been brought out by this method and that two or three shifts mining a day even at the first mined coal seam becomes possible as the results.
The Utilization of this gas drainage method has made the concentration and reduction of the working faces and the the ventliaiton system possible, consequently the increase of mining efficiency has been attained by means of the mechanization of mine.

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The considerable rationalization of the beneficiation at Ôtani Mill has been accomplished by the Awamura Mining Co. Ltd, since it's reopening 1952. Principal improvements are given as follows:
1) The crushing capacity has been increased to 150% by the adoption of wet crushing.
2) It makes possible to be more effective for the heavy media separation process, by means of changing feed size range to-20+4mm from-25+6mm, and choosing optimum viscosity of heavy media. In order to get optimum viscosity, magnetite has mixed with ferro-silicon for heavy fluid.
3) To avoid over-grinding the closed-circuit operation (Ball mill and Dorr-F classifier) was changed to the open-circuit operation (Rod mill and Elliptex vibrating screen), so the mill capacity has increased to 230% with reduction of cost.
4) By the application of electro-static separation and differential-flotation methods, chief minerals such as scheelite, cassiterite, chalcopyrite and pyrites has been effectively separated, and mill recovery has increased.
5) The average grade and recovery of scheelite concentration has advanced by the adoption of fore table.
6) By the use of wet cyclone for classification of flotation tailing, the cost of tailing disposal has been a little or not.
By these improvements the saving of more than 57% in the total costs has been attained in 1959 as compared with in 1952.

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With the purpose of rehabilitation and modernization of zinc smelting, the vertical retort- plant was constructed at Miike smelter, and it was put into operation in January 1954. This plant is characterized from the regular process with the following features;
(1) The application of compression spring for the retort binding.
(2) The separate support of the retort upper extension.
(3) The application of AMCO-Recuperator separately installed from the distillation furnace.
The operation result has shown that an average output of 1100 tons of metallic zinc per month from 8 retorts with 97% elimination and 94% recovery has been maintained by firing at 1250°C. The grade of zinc from vertical retort is 99.7-99.9%.
The three zinc smelting processes of horizontal retort, electrolytic zinc and vertical retort are now in operation in parallel at Miike. The smelting cost of the vertical retort process is the cheapest among them.

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In resistivity method, the Wenner's electrode configuration is generally emploied and many investigations are given of the above configuration by many authors. The resistivity curves obtained by this configuration are generally complicated. When we interpretate the above resistivity curves, we need the master curves which are- obtained mathematically under simplified assumptions. On the other hand, the resistivity curves obtained by the two-electrode resistivity method are simple but this curves cannot represent the true resistivity of the earth.
The authors discuss the problem: Which of apparent resistivity curves obtained by various kinds of electrode configuration can represent the true resistivity more accurately? The authors propose a new interpretation method-namely input resistance method.

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