Four-point bending tests were carried out in a pressure vessel in order to know the effect of both confining pressure and pore pressure on fracture toughness of Ogino tuff, Tohoku marble and Inada granite. In the first experiment dried specimens were sealed with vinyl film and copper foil to know the effect of confining pressure and in the second experiment water saturated specimens were supplied in pressurized water without sealing to know the effect of pore pressure which is equal to confining pressure. A fatigue crack of 2-3 mm in length was created from the tip of a notch prior to testing and the fracture toughness K_Q was evaluated by 5% offset method.
Main results obtained in this work are summarized as follows:
(1) The effect of confining pressure on fracture toughness is different between Ogino tuff and the crystalline rocks of Inada granite and Tohoku marble. The fracture toughness of the crystalline rocks significantly increases with confining pressure while that of Ogino tuff increases slightly.
(2) Fracture grows more straightly with confining pressure for all the rocks.
(3) The closure of pre-existing cracks in the directions parallel to the notch plane due to the components of confining pressure in those directions enhances the resistance against the fracture growth and also forces the crack to grow more straightly.
(4) Fracture toughness of water saturated specimen under atmospheric pressure decreases to about 90% of dried specimen for the crystalline rocks and to about 50% for Ogino tuff.
(5) Fracture toughness of the crystalline rocks can be described with the effective confining pressure where as that of Ogino tuff remarkably increases with pore pressure which is equal to confining pressure. This phenomenon in Ogino tuff seems to be due to the change of microstructure with pore and confining pressures since the main component of the rock is the weak minerals such as zeolite and montmorillonite.

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In order to investigate the characteristics of underground open fire, a series of experiments have been carried out by using a 400m long test gallery with a cross section of 5.4 m² and timber sets arranged as in practical roadways. Also the scale effect on the spread behavior of fire was studied on the basis of the experimental results by the small and the full scale galleries.
The results obtained are summarized as follows;
(1) When the timber is exposed to the ignition source emitting heat more than 780 kW/m³, the fire develops into the fuel-rich condition, expanding the fire zone to the maximum length where most oxygen is consumed.
(2) The fire spread rates and the fire zone lengths in the full scale gallery are both proportional to the air velocity.
(3) Types of timbering also influence the behavior of fire. The fire temperatures in arch lined timbering are lower than those in three piece timber sets. Fires of arch lined timbering tend to become the oxygen-rich condition in which large quantity of oxygen remains in the fume.
(4) Scale effects are observed between the model and full scale experiments. Supposing fuel and ventilation conditions are the same, the fire spread rate of timber zone is proportional to the ratio of gallery dimension to timber dimension, and the fire zone length is proportional to the gallery dimension.
(5) A calculating method for estimating the fire spread rate and the fire zone length of underground open fires is proposed, the scale effect on fire spread characteristics and the change in ventilation being taken into account.

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An about one-tenth scale model experimental apparatus was used to investigate the cooling effectiveness of local ventilation and the heat transfer at the heading face.
The following two major results were obtained through this experimental study. 1) For the purpose of effective cooling at the heading face, there is an optimal setting place for the local ventilation duct. 2) The following heat transfer relationship was obtained. Nu=C·Re^0.9·Pr^0.5 where, Nu: Nusselt Number defined by the authors. Re: Reynolds Number defined by the authors. Pr: Prandtl Number of air. C: Coefficient dependent on the position of the air duct and the support dimensions.

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Underground coal gasification was examined to be a new system for hydrogen production. For this purpose, a packed bed of coal in a quartz glass tube was used to simulate experimentally an underground coal gasification system. Carbonization of coal and char gasification reactions were investigated for discussion of the process of hydrogen production with H₂O as a gasifier.
Results are summarized as follows.(1) Combustion reaction rate of the packed bed of coal was obtained from the propagation speed of flame front. Apparent activation energy for combustion reaction of coal in oxygen was 33 kJ/mol, which implies that mass transfer process may affect the combustion reaction. This means that the reaction rate and combustion temperature can be controlled by the flow rate of oxygen.(2) Production of hydrogen increased with combustion temperature and partial pressure of steam in the range of experiment. In the present study, 60 percent increment of hydrogen was attained in comparison with experiment of 02 as a gasifier.(3) Reaction, CO+H₂O H₂+CO₂ was the most important for the increase of hydrogen production in a case of 600°C of combustion temperature, and both reactions, C+H₂O H₂+CO and CO +H₂O-H₂+CO₂ contributed to the hydrogen production in the case of combustion temperatures higher than 750°C.

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Usually segments are set up by a segment erector which is controlled manually. Recently a few segment erectors which can be controlled automatically have been developed to minimize the set up time. In the automated erectors, segment displacement is controlled, that is, a segment is hauled and fitted to the existing segments controlling the displacement. By this method, it is well known that the very accurate control is necessary.
This results in a comparatively expensive control system and also very careful maintenance schedule.
In this paper, the authors discussed on an applicability of control method where a linear combination of force and displacement is chosen as the control variable. By this method, segment is controlled as the conventional displacement control method as far as the segment is not contacted to the existing segments. However, after the contact, force is taken into consideration as the control variable and excessive force is minimized.
The computer simulation revealed that by this control method, a segment is hauled and fitted to existing segment smoothly. Also small scale model experiment is carried out successfully and the results support the calculated one.

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As a fundamental study with regards to the recovery of fine mineral particles by liquid-liquid extraction, the effect of the number of carbon atoms in n-alkylamine has been investigated with respect to amine concentration, pH, and zeta potential.
Good recoveries were obtained using n-alkylamine with eight and more carbon atoms in the pH range where xenotime particles were charged negatively. At pH 8, increased concentration of amine up to the zpc yielded higher recoveries. However an increase in the amine concentration over the zpc led to a decrease in the recoveries.
In order to make it clearer, the stability of fine xenotime particles in amine solutions were also investigated using decylamine at pH 8 and 10. This was done by means of flocculation tests with a spectrophotometer. The maximum transmittance of the suspension was consistent with the zpc in the amine solution. From the results obtained above, it was considered that the electrostatic repulsion between xenotime particles prevented them from concentrating near the O/W interfaces.
As to the effect of pH, an increase in the pH above 8 resulted in a decrease in the recoveries. Based on the distribution of the neutral n-alkylamine molecules between oil and water phases, the concentrations of amine species in the water phase were calculated as a function of pH. Compared with the recovery curves, the concentrations of amine species in the water phase were considerably related to the recoveries. It was considered that the repulsion between xenotime particles increased with decreasing amine concentration in alkaline solutions and prevented the particles from concentrating near the O/W interfaces, which led to a decrease in the recoveries.

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Chromium-Carbide layers were deposited on diamond particles by disproportionation reaction in molten salt. In order to clarify the effect of the chromium-carbide layers on diamond particles for thermal property of the coated diamond particles, the specimens were tested by thermogravimetry at high temperature (700°-800°), scanning electron microscopy of the surface and X-ray diffractometry. In addition, the change of the specimens surface at high temperature in air atmosphere and reducing atmosphere was observed by high temperature microscope. The results obtained were as follows.
1) Under air atmosphere, weight loss of chromium-carbide coated diamonds were within 0.1% at 700° and 750°, and 18.6% at 800° for 40min. On the other hand, weight loss for non coated diamonds was 24.7% under the last conditions.
2) Under air atmosphere, appearance of each chromium-carbide layer did not nearly change, but heat treatment at 800° worsened the surface of internal diamond particles.
3) Chromium-carbide layers on the surface of specimen were Cr₃C₂ and Cr₇C₃ in initial condition, but thin Cr₂O₃ phase was formed by heat treatment under air atmosphere.
4) The change of appearance of chromium-carbide layers did not occur through the observation under high temperature microscope.

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A novel preparation method of ultrafine particles of precious metals using an emulsion-type liquid membrane technique has been developed by the present authors. In this method, water-in-oil emulsion, consisting of an organic phase of MIBK-Span 80-kerosene solution and an internal aqueous phase containing a suitable reductant, is contacted with an external aqueous solution containing precious metal salts. Various factors, which affect the particle size of gold, including the concentrations of MIBK, Span 80 and Au (III), identity of reductant and its concentration, etc, were examined. An increase in the concentration of Au (III) and a decrease in the concentrations of Span 80 and reductant result in an increase in particle size of gold powders. The value of pH of internal solution is another important factor to control the particle size. Gold particles can also be prepared by contacting external aqueous solution containing reductant with emulsion where Au (III) is contained in the internal aqueous phase.

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For the purpose of obtaining basic information on the reduction-diffusion process, diffusion experiments were carried out for the Sm-Co binary system at 1000, 1050, 1100, 1150, and 1200°C. Sm was made diffuse into Co by contacting a vapor from a molten Sm-Ca alloy with a polished surface of a Co block. The use of the Sm-containing vapor was effective to suppress the formation of a Co-containing melt on the surface of the Co block. The formation of the Co-containing melt hindered the uniform growth of diffusion layers and blurred the time of initiation of the diffusion. Though several intermetallic compounds are present in the Sm-Co binary system. only SmCo₅ and Sm₂Co₁₇ phases were found to grow systematically. Diffusion coefficients of Sm for the reactive diffusion in these phases at the respective temperatures were calculated from the relationships between the diffusion layer thickness and the diffusion time by utilizing Sm concentrations at the boundaries of the phases which were read from Sm-Co binary phase diagrams. The diffusion coefficient of Sm in SmCo₅ has been found at least three times larger than that in Sm₂Co₁₇ at each temperature of this study, and the reason for their difference was qualitatively discussed by considering the difference in their crystal structures. Also a reasonable explanation could be given for contradictory results reported by other investigators about the preferential growth of the Sm₂Co₁₇ phase.

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