This paper describes a new method for the determination of fracture toughness of rock by the use of core boring data. In order to examine the validity of this method, the fracture toughness values of the core specimens at the Eastern Hachimantai field, the model field of the F-project at Tohoku University, were compared with those evaluated by this method. Then, both results agreed satisfactorily. This method could be also useful to in situ measure the fracture toughness value of rock.

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A non-linear theological model has been applied to simulate the time-dependent behaviour of underground roadway in mine. In the calculation, FEM technique is used with parameters assumed on the basis of test results of sample rock. The calculated results are compared with those of field measurement conducted at Fukazawa and Matsumine mines. The roadways considered in this study are U-shaped, and supported by rock bolts in case of Fukazawa mine. The calculated results of convergence and extension in the rock wall indicate a fairly good coincidence, at least in qualitative means, with measured ones. It can be said that the model showed a good potential for application purpose. However, for quantitative discussion, more accurate estimation of rock pressure and strength of rock mass may be inevitable.

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Avelage mining depth of Japanese coal mines has attained 700m from the surface.
Some countermeasures to prevent coal and gas outbursts are necessary. Especially, pre-gas drainage and large diameter relief boring have carried out popularly at some Coal Mines.
Results of those have been successful, but the drilling of such large diameter boreholes (more than 250mm) requires a igh powered large drilling machine.
This is significant problem, because roadways where it is used are generally narrow and it needs much labor to set up the drilling machine. Therefore, we attempted to drill large diameter boreholes by a small drilling machine assisted with a water jet at Akabira and Taiheiyo Coal Mines.
In this report, the results of fundamental tests on cement mortar and coal samples are described.
From the results of these tests, we found follow conditions to enlarge boreholes in coal seams.
The pressure of water jets; 300kg/cm²-600kg/cm². The diameter of a nozzle; 1mm-2mm. The flow rate; about 40l/min.

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Long-lasting high stability is of primary importance to successful COM combustion. Much has been done in the way of research on stability of COM in the still storage, and the mechanism of COM still stability is almost completely known. On the other hand, the knowledge about the dynamic stability of COM, such as COM stability while being transported aboard the COM carrier at sea, is still limited at the moment.
The motion of COM aboard the COM carrier and how COM would settle under dynamic ship motions were tested by simulation using different sized model cargo holds. In the tests the mechanism of COM dynamic stability was analysed with the effect of the size of each model cargo hold in mind. The tests showed that the ship rolling motion would have undesirable effect of promoting the settling of coal content of COM in the cargo hold.

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Kaolin-clay deposit in Iriki-machi, Kagoshima prefecture, has been made clear to consist of kaolin, montmorillonite and weakly altered zones and so on. Clay in the kaolin zone is called “Iriki kaolin-clay” and has not yet been used as a blending material for “white porcelain” because of high iron and titanium content.
The kaolin zone is largely classified into “pyrites zone” and “oxidized zone” depending upon whether the kaolin-clay includes pyrite or not. The measurement of mineralogical properties and the purification by a high gradient magnetic separator (HGMS) of the kaolin-clay belonging to “pyrites zone” were carried out in order to utilize it as a blending material for “white porcelain”. In the latter, the influence of dispersive state of the clay in slurries and the operating variables of HGMS on the yield and quality of the concentrate was studied.
The results obtained are summarized as follows. It was found that Iriki kaolin-clay mainly consists of kaolinite and quartz and also contains a little amount of dickite, pyrite and anatase and so on. The particle size of the clay was comparatively small and the cumulative weight percent of less than 2 μm was about 55.
2. When the clay was treated with HGMS, the effect of addition of dispersants on the yield and quality of the concentrate was clearly recognized but the influence of kind of dispersants was hardly found.
3. The pyrite mainly existing in coarser particle size range seemed to be easily removed in HGMS treatment while the titanium oxide being mostly contained in finer particle size region was rather difficult to be removed. It was also recognized in HGMS experiments that the iron and titanium content were decreased with decreasing the matrix loading and with increasing the intensity of magnetic field.
4. The whiteness of the clay treated with HGMS under the dispersive condition was made clear to be superior to that of the clay treated under the non-dispersive condition irrespective of heating up to 1300°C.

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Two adjustable parameters, namely the oxygen efficiency and the “imperfect combustion ratio” of the furnace charge, were introduced into an equilibrium calculation program developed by Goto. In order to calculate the weights of matte and slag more accurately, all the other elements which are not incorporated in Goto's program were treated as one component. The overall pyrometallurgical reaction in a copper flash smelting furnace was analyzed by the modified program.

The results obtained are summarized as follows:
(1) The important elemental compositions calculated for matte, slag and gas phases were in good agreement with the values of chemical analyses by setting the oxygen efficiency so that the experimental and calculated matte grades are equal.
(2) In the case of the magnetite content of the slag, however, the analyzed values were much larger than the calculated ones. The re-evaluation of the activity coefficient of magnetite in slag brought a relatively good agreement although the analyzed values were still larger by about 3% than the calulated ones.
(3) The measured oxygen pressures were 2 times as high as the calculated ones, and this result shows the same trend as the magnetite content of the slag. These results may imply that the magnetite and hematite which are contained in the furnace charge and/or formed in the upper zone of the reaction shaft are absorbed by the slag to a greater extent than the equilibrium content.
(4) If the performance of the concentrate-burner is not adequate, the calculated temperature will be higher than the measured one. This temperature difference was explained to some extent by evaluating the “imperfect combustion ratio” of the furnace charge.

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For the purpose of obtaining fundamental thermodynamic data for the carbothermic reduction of alumina, two types of experiments were carried out. In the first type of experiments, alumina was reduced with graphite powder at 2173K in a graphite crucible in an atmosphere of argon in the presence of iron at 2173K. In the second, a liquid Al-Fe-C ternary alloy was equilibrated with both graphite and Al₄C₃ in a graphic crucible in an atmosphere of argon at temperatures between 2073 and 2373K.
Alumina was reduced fairly fast and the aluminum content in the resultant Al-Fe-C alloy increased with time for at least the first 90min, but the evaporation of aluminum from the alloy and the formation of Al₄C₃ through the reaction between Al in the alloy and C from the crucible caused the aluminum content to decrease gradually. From the equilibration experiments it has been found that the activity coefficient of Al in the Al-Fe-C alloy and the equilibrium alloy composition can be adequately obtained by applying the regular solution model to the liquid alloy and by using the data of a functions available from literature along with the standard Gibbs energies of formation of the existing chemical species in the system.

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