For storage of industrial disposal and carbon dioxide, underground caverns are increasingly necessary due to the shielding effect of rock masses. Effective shielding properties of underground caverns are highly demanded for protecting surface environment. Thus, developing quantitative evaluation and long-term monitor methods for the properties of rock masses are indispensible. Additionally, shilding effects of rock masses are closely related to ground water flow through rock discontinuities, studies on the mechanism of discontinuity behaviour in rock mass based on three dimentional monitoring will be extremely useful for the safty control of underground caverns.

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Deformation rate analysis (DRA), although it has a poor theoretical basis, is a useful method for estimating rock stress in the laboratory using core samples. DRA is thought to be closely related to changes in the inner microstructure of rock samples undergoing a de formation process. Ultrasonic measurement is a useful technique for investigating structural changes in rocks. In this study, both methods were applied simultaneously to rock samples to confirm the applicability of ultrasonic measurement for the estimation of rock stress using a system of ultrasonic propagation time with accuracy in 10^-2 nsec.
In the experiments, core samples of sandstone were loaded up to a certain stress in order to artificially input memory of the stress into the samples, and the propagation time in the horizontal direction to the loading axis and the deformation rate were measured simultaneously. Consequently, the propagation time through the specimen was measured with high accuracy during deformation. Variations in the propagation time and lateral strain almost coincided during the loading-up process. Furthermore, the propagation time was drastically changed at the memorized stress corresponding to the deflection point of the deformation rate curve. These experimental results show that highly accurate measurement of the ultrasonic propagation time is useful, as is the DRA method using core samples, for examining changes in the microstructure inside rock samples under stress and applicable for estimating underground rock stress.

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The purpose of this study is to prove the effect of internal pore pressure on unsteady-state gas flow in coal. Practically, the gas permeation model of coal which consists of the gas permeable and non-permeable crack network was proposed. Then the numerical simulations of gas permeation by this model were carried out by changing the parameters such as inlet pressure in the crack network, confining pressure against coal, closing probability of cracks, etc.
The results of these simulations on fluctuations of unsteady-state gas flow were in agreements with the experiments of gas permeation of coal. From these considerations it was found that the above gas permeation model was accurate enough for practically. Moreover, the results of the simulations on unsteady-state gas flow in coal gave an explanation to the deviation from the Darcy's law in the relationsbetween gas flow and difference pressure.

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The purpose of the present study is the effect of crack orientation on the gas permeability and gradient of gas pressure in coal. Practically, the model of anisotropic crack network was applied to the computer simulations under the state of an uniaxial compressive stress. Additionally, the simulations of gas permeation and gas pressure were investigated by setting the normal distribution as the frequency distribution of crack orientation. The results of these simulations were as follows.
1) The anisotropy of crack orientation in coal is very effective on gas permeability, and the gas permeability in the orientation of maximum principal stress is higher than that of minimum principal stress.
2) In the anisotropy crack network, the gas permeable cracks of the direction of minimum principal stress close at their neck. Consequently, gas flow is intercepted by the difference stress between an external stress and gas pressure in the cracks of the direction of minimum principal stress become high.
3) The occurrence mechanism of a gas outburst is explained by applying the bending theory of circular plates to the anisotropic crack network saturated with high pressures gas.

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A drilling model was previously proposed by Okubo and Nishimatsu (1991), and a computer program which had capability to simulate continuous drilling-process was also developed bythem. The model which consists of a drill-body, a piston, a rod and a bit was analyzed based on the one-dimensional stress-wave theory. A force-penetration curve with hysteresis was assumed for bit/rock interface.
In this study, comprehensive simulation for a heavy drifter of 150 kg-class was carried out. Special care was taken to clarify the effect of thrust on rock-drilling performance such as penetration rate, piston stroke, piston velocity, elastic wave in rod. Calculation was performed under more than two-thousand conditions changing thrust, bit/rock interface parameters and attenuation rate on drill/rod interface.
An appropriate thrust, Fth_apl, was proposed as follows; F_th-apl≅A_back·P_back-A_front·P_front, Where ‘A’ denotes effective cross-sectional area, and ‘P’ pressure. Subscripts ‘back’ and ‘front’ indicate back and front cylinders, respectively.

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In production of super-clean coal by any physical coal-cleaning process, the feedcoal must be micronized to liberate finely disseminated mineral matter. One of the most efficient devices for micronizing coal is a stirred ball mill. Using the laboratory mill with a relatively high media loading (80 % filling), small grinding media (less than 1 mm diameter), and three coals, effects of some parameters such as media size, stirring speed, and pulp density on the grinding of coals have been studied. The product with a mediansize of 2μm was obtained at a suitable operating conditions with a mean residence time of 6 min. The wear loss of the grinding media and vessel depended strongly on the amount of the hard minerals disseminated in coal, such as quartz, pyrite and iron oxide.

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It is usual to notice the size distribution of particles in simulations studies ofpowder processes. On the other hand, specific surface (Blaine value) has been applied as a standard for describing product quality particularly in cement industry. Therefore, in order to transfer experimental resultsobtained in a laboratory to the data for an industrial use, it is necessary to estimatethe specific surface from the size distribution data. For this purpose, the authors have successfully applied an inferential method with an artificial neural network (ANN) to the size distribution based calculation of the specific surface.

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Leaching of chalcopyrite concentrate having specific surface area of about 3 m²/g in 0.5 mol/dm³ HCl solution was conducted at 333 K using hematite (Fe₂O₃) and ferric chloride (FeCl₃) powders, respectively. The leaching of the concentrate with Fe₂O₃ powder permits to achieve about 75 % copperextraction within 24 hours, while about 65 % copper is extracted by the leaching with FeCl₃ powder. Theyield of copper in the leaching with Fe₂O₃ powder is twice or more higher than that without the promoters. High copper extraction can be achieved when much of the elemental sulfur is formed on thesolid residue after the leaching. Especially, the presence of Fe₂O₃ powder gives us the elemental sulfurprecipitates more than that of FeCl₃ powder. Therefore, Fe₂O₃ can be an effective promoter inthe leaching of chalcopyrite concentrate using HCl solution.

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In order to clarify the behavior of the metallurgical phases in the oxidation zone of the QSL lead smelting process, the phase equilibrium between the metallic lead and the PbO-FeO_x-CaO-SiO₂or PbO-FeO_x-CaO-SiO₂-ZnO slag was investigated at 1, 423 K. The EMF method using a solid electrolyte with calcia-stabilized zirconia was applied to measure the oxygen partial pressure in the system. The oxygen pressure increases with increasing PbO content in the slag. The PbO activity and activity coefficient estimated from the oxygen pressure increase with the addition of CaO into the slag. However, the PbO activity is slightly affected by the FeO_xcontent at constant PbO concentration in the experimental region. Itwas clarified that ZnO gives a small effect to the activity coefficient of PbO in the PbO-FeO_x-CaO-SiO₂-ZnO slag. The partial pressure of the PbO component in the gas phasecalculated by using the PbO activity coefficient in the slag isconsiderably small compared with that of metallic lead.

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The ZnGa₂O₄phosphors were prepared using the solid state reaction method to investigate their photoluminescence characteristics and luminescence mechanism. Under 254 nm excitation, the ZnGa₂O₄phosphor exhibited abroad-band blue luminescence with an emission spectral peak at 450 nm. The reduction treatment of ZnGa2O4 phosphors in partial hydrogen atmosphere showed a tremendous increase of emission intensity of all mphosphors. On the other hand, Mn²⁺-doped ZnGa₂O₄phosphor exhibited a strong narrow-band green luminescence with an emission spectral peak at 504 nm, and showed a maximum emission intensity at the Mn²⁺concentration of 0.006 mol %.

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