As the results of microscopic observations on the failure planes produced in rock cutting, it was ascertained that there were two processes in i k failure. The first is the process of shear fractures caused directly along with the advance of blade. 2 second. is the process of an extension fracture due to the crack propagation which is brought about after the development of the yielding region under the high confining pressure.
In the present paper, yielding stresses of rock are analyzed with regard to the rake face and backing-off face of the blade in each process above mentioned. The analysis is done as a problem of a plane strain and an incipient plasticity of yielding region whose configuration is presumed on the basis of experimental evidence. The rock is assumed to yield when the Mohr stress circle becomes tangent to a parabolic failure envelope and the blade is represented by a two-dimensional idealized wedge. At the blade-rock interface the stress field no only satisfies the yield condition but also is such that the ratio of the shearing stress to the normd stress is qual to the coefficient of friction.
The analysis provides good agreement with the experimental results on the yielding stresses if the “size effectr” of compressive strength of rock is taken into consideration. Therefore, it may be possible to estimate the yielding stresses at blade-rock interface in rock cutting with considerable accuracy by applying theanalytical method in this paper.

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There are practical and financial difficulties to measure gas permeability of coal seams. So we tried to evaluate gas permeability of a coal seam using permeabilities of small lump coal samples.
From the results of measurement it was shown that; 1) Gas permeabilities of coal samples are distributed between very wide range, i.e. 10^-7-10⁰ darcy. 2) They fit to log-normal distribution. 3) In parallel or perpendicular direction of a seam, gas flow range has not significant difference.
From the results it was unsuitable to estimate coal seam gas permeability by using arithmetic mean of these permeabilities. So we used two and three-dimensional model of coal seam consisted of random elements whose permeabilities are distributed as in samples. We made simulating calculation about gas flow in the model.
Gas permeabilities of coal seams which were gained in this way are nearly same values with logarithmic means of sample permeabilities and showed good agreements with easiness of gas drainage in the colliery and values measured by other persons.

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Balling and pelletizing test were conducted for the sample of Algarrobo iron ore concentrate at the Pilot Plant and Research Laboratory of Kobe Steel, Ltd. The purpose of the test was to obtain technical data necessary for planning and engineering of the Grate Kiln system pelletizing plant for Acero del Pacifico SA. in Chile.
Prior to the pelletizing test, wet type magnetic separation of crude ore was performed and concentrate of 1540 cm²/g Elaine surface area with iron content of 69% was obtained.
Pelletizing test was performed to produce two type of pellets, that is, pellet with bentonite and with lime hydrate as additives.
In case of using bentonite as an additive, pellets preheated at high temperature were apt to produce concentric crack inside of them in the preheating and burning stage. As results product pellet had lower cold compressive strength and poor reducibility of JIS reduction test.
While, in case of using lime hydrate as an additive formation of crack in the preheated pellet was not obserbed at all even at the higher preheating temperature. However, pellet added two percent lime hydrate showed remarkable swelling in the reduction stage. Pellet added three percent lime hydrate were good and could satisfy all condition of the required qualities.
Out line of the pelletizing plant installed at Huasco district in Chile which started into operation from the beginning of 1977 is also introduced.

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The dynamic adsorption characteristics of heavy metal ions such as Cd²⁺, Pb²⁺, Cu²⁺ and Zn²⁺ on granular zeolite which is prepared from the preheated mixture of Shirasu volcanic ash and Na2O have been investigated by column method.
The column of granular zeolite used for adsorptionof heavy metal ions is 17.5 cm long and 0.5 cm in diameter. When feed solution containing 47.8 ppm of Cd²⁺was made to flow the columnof zeolite having faujasite contents of 62.9% to 91.0%, th e volume of effluent containing less than 0.01 ppm of Cd²⁺ (breakthrough capacity) was about 2600 times of bed volume.
The breakthrough capacity was not affected by changing the space velocity of feed solution in the range of 15 to 45.
The column saturated with Cd²⁺ was regenerated by washing with NaCl solution of 1.0 mol/l, but the ratio of regeneration was about 80% of adsorption capacity in virgin zeolite.
The zeolite column regenerated with NaCl solution found to be satisfactory used for adsorption of heavy metal ion again and again.

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When copper converter slag is used as a raw material for iron smelting, copper and zinc in the slag must be removed as much as possible.
In this experiment, the differences of chloridizing process of Cu₂S, Cu₂O, ZnS and ZnO have been investigated for the weight change by chloridizing roasting and X ray diffraction of roasted samples. Chlorine was obtained by decomposition of CaCl₂·2H₂0 or NaC1 mixed in the samples.
The obtained results are summarized as follows.
(1) When Cu₂S samples are roasted in the air, CaCl₂ is converted to CaSO₄ and Cu₂S is converted to CuCl by following equation.
Cu₂S+ CaCl₂+2O₂= 2CuCl+ CaSO₄ The volatilization temperature of CuCI formed by roasting is about 600°C.
(2) When the similar samples are roasted in the pure oxygen, Cu₂S is coilverted to CuO at 400-500°C by following reaction. Cu₂S+ CaCl₂+ 30₂= 2CuO+CaSO₄+Cl₂ CuO is converted to CuCl at 500°C.
(3) The formation rate and volatilization rate of CuCl will be balanced at about 600°C.
(4) ZnCl₂ is volatilized as soon as it is formed from ZnS or ZnO.
(5) Chloridization temperature of oxides is about 100-150°C higher than that of sulphides.

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In nonferrous metallurgy such as copper, nickel and lead smelting, occasionally speiss is formed because of arsenic or antimony contained in ore. Pb-Fe-As and Pb-Cu-As ternary systems are regarded as the most fundamental systems of speiss which occured in lead smelting. The miscibility gap and the distribution of silver between molten lead and speiss in these two systems have been determined by quenching method between 900°C and 1200°C.
In Pb-Fe-As system, the miscibility gap at 1000°C and 1200°C covers a wide composition range under 50 percent arsenic in speiss. Its temperature dependence could not be observed within the experimental error. The dissolution of lead in speiss remains at a constant value of about 3 percent up to 40 percent arsenic in speiss.
In Pb-Cu-As system the miscibility gap in Pb-Cu binary system is widened by addition of arsenic, and at 1000°C, lead dissolves into speiss nearly 11 percent at the composition of speiss about 19 percent arsenic which is equilibrated with metallic lead containing 2.5 percent of copper. When the arsenic content in speiss exceeds this composition, the miscibility gap drastically becomes narrower.
The distribution coefficient of silver between metallic lead and speiss K_Ag, defined by K_Ag= wt%Ag in speiss/ wt%Ag in metallic lead, increases from 0.02 to 0.4 when the arsenic content in speiss increases from 1 to 51 percent in Pb-Fe-As system. Specially, in the composition range over 40 percent arsenic in speiss, the increase of K_Ag is quite remarkable. On the contrary the value of K_Ag shows about unity in Pb-Cu-As system.

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