Disproportionation reaction (2Cu⁺-Cu⁰+Cu²⁺) of acidic cuprous sulfate solution was studied to obtain fine copper powder suitable for conductive paste. Cuprous sulfate solution was made by mutual reaction (Cuo⁺Cu²⁺-2Cu⁺) in a high temperature autoclave, e.g. 220°C, with copper wire and acidic cupric sulfate solution. In order to obtain fine copper powder, the solution was transferred into another vessel and cooled.
Cooling rate of cuprous solution had a large effect on the diameter and shape of the powder obtained. In batch operation, submicron particles with rough surface were obtained when cuprous solution was rapidly quenched, while some larger particles were obtained with relatively slow cooling rate. In continuous operation, copper particles of 2-3μm in diameter were obtained which were surrounded with well-developed crystal planes and showed an excellent oxidation resistance.

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To make and maintain deep underground openings, it is important to predict the mechanical phenomena accompanying their excavations in terms of the rockmass properties and the geological structures. In this paper, a large-scaled two dimensional strata model testing method has been developed to approach these problems. In the adopted system, it is possible to excavate cavities in the model under loading condition.
At first, some preliminary tests were performed to ensure the stress state created in the model by the loading system as well as the sensitivities of the built-in type sensors employed. Then, the test for a closely located two parallel excavations was performed. Two types of fractures were developed from the openings, which are interpreted, based on the corresponding finite element calculations, to be shear and tensile failures. The stress sensors recorded the local changes (increase and relief) in the model, with accompanying progress of excavation. P-wave velocity and the amplitude of its first motion increased with stress, and decreased on failure.
It is concluded that this testing method can almost simulate various circumstances for the underground openings.

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To predict the long-term strength of granite, fatigue and creep tests were conducted under uniaxial compression. Fatigue and creep properties of granite were investigated and compared. The results showed that thestrength properties are different for fatigue and creep. For lower applied stresses, the time to failure in the fatigue becomes shorter than that in the creep. This indicates that it is important to evaluate both the fatigue and creep strengths for the prediction of long-term strength of granite. The behaviour of dilatant strain in fatigue is similar to that in creep. The volume of dilatant strain, giving an indication of the degree of damage in rock, is larger in the fatigue than in the creep at lower stress levels. This implies that the damage in rock is influenced strongly under cyclic loading than under constant stress.
Effect of stress amplitude on fatigue failure time was investigated and the mechanism of fatigue failure was discussed based on the Costin's model. It is concluded that fatigue failure can be explained by the two mechanism. One is stress corrosion cracking ruled by the mean stress level and the other is fatigue cracking influenced by the stress amplitude. The relative contribution of the latter becomes more when maximum stress is small and/or stress amplitude is large.

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The extraction of nickel, cobalt and copper from cobalt crusts was carried out by using ammoniacal alkaline solution. The cobalt crusts which were collected from the seamountain of the Pacific Ocean were used grinding below 74μm. The leaching test was done by using ammonium hydroxide, ammonium chloride, ammonium sulfate, ammonium sulfite and ammonium carbonate as leaching reagent.
In the leaching using only ammonium salt solution except for ammonium sulfite, the extraction of metallic components was low. On the other hand, the addition of ammonium sulfite as the reducing agent to ammonium salt solution increased the extraction of cobalt, nickel and copper considerably. For instance, the extraction rates of the metallic components on leaching of ADO1 at 80°C for 60 minutes in the mixed solution of 100 g/l (NH₄) ₂CO₃ and 50 g/l (NH₄) ₂SO₃ were 97.7% for Co, 95.9% for Ni, 94.1% for Cu, 0.55% for Mn and 0.19% for Fe, respectively, and the leaching residue was identified as manganese carbonate, MnCO₃.
Concequently, cobalt, nickel and copper were selectively extracted from the cobalt crusts with the mixed solution of ammonium carbonate and ammonium sulfite.

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Equations to represent the relationship between numerically predicted maximum stress and actual roadway deformation is newly presented here. These equations are deduced based on the result of a physical model experiment. Six cases in three coal mines in Hokkaido, Japan, were analyzed by using the equation. In the case studies, expansion of coal sidewall, roof to floor and sidewall's convergence, which were induced due to mining activities, were measured at roadways in coal seam or rock mass. Stress state varies mainly due to the longwall face advance. Existence of oldworkings adjacent to and above the panel and faults crossing the roadway also effected the stress state. It is cleared that the equations can be applied for five cases out of the six.

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It is important to evaluate the damage of architectures and structures caused by blasting vibration. In this paper, 1) the characteristics of spectra was presented, 2) blasting vibration were observed in underground and on a ground surface, and 3) a simple numerical model was proposed to explain the spectra of the vibration. The used model, which is based on frequency domain using Fourier transform, estimates the blasting vibration spectra in tunnel advance. The spectra of the observed vibration is represented by the product of the blasting source spectra, the wave path effect and the local properties of the ground around sensors. The spectra were characterized by elastic wave velocity, rock density, rupture radius, tensile strength of rock, distance from blasting point to observation site and attenuation coefficient. The proposed method has found with sufficient accuracy to account for the evaluation of the blasting spectra.

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Stress relief method is widely used in coal mines in many countries to prevent the gas outburst and rock burst. It is one of the effective methods to relieve the stress by boring in coal seams.
The author made a model experiment to investigate the effect of the boring bored near fractured zone at the heading face on the stress relief. A three-dimensional model experimental apparatus of about 1: 80 geometrical scale was used. As the model rock mass, the gypsum plate was used and as the model coal seam, an artificial seam made from the mixture of water, gypsum and diatomite was used. The scale factor of the stress and strength was 1: 40.
The effect of the stress relief was measured by varying the location of fractured zone, the thickness of fractured zone and the strength of model coal seam. The effect of the stress relief was evaluated by the degree of stress relief defined by the author. The characteristics of the stress distribution near the fractured zone and the relationship between the degree of the stress relief and the above experimental parameters were reported.

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The purpose of this paper is to clarify the effect of the axial pressure of a tunnel with a circular section on the behavior of the surrounding rock, and to classify the types of stress distribution and yielding modes. The rock mass is assumed to be elastic-perfectly plastic and to obey the linear Mohr-Coulomb yield criterion as well as the associated flow rule of the theory of plasticity; hence dilation is included. It is also assumed that a rock behaves in accordance with the condition of plane strain, and that the internal radial pressure decreases as the excavation of a tunnel proceeds. As the internal pressure is decreasing, yielding occurs. There are three different modes and two other composite modes on this primary yielding stage. As the internal pressure is further decreasing, the primary yielding stage gets into the secondary yielding stage, where the yielding mode is different to that in the primary stage. The variations of yielding pressures, plastic boundary radii and tunnel closures are given as a function of far-field rock pressure ratio. It is concluded that the axial pressure exerts a greater influence on the yielding behavior of the surrounding rock mass, and that hence the axial pressure is an essential factor in the elasto-plastic analyses of a tunnel.

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Effect of mixed grinding of a kaolinite-gibbsite mixture on formation of mullite has been investigated by the X-ray diffraction method, DTA, SEM and surface area determination of powders. The both structures of individual specimen and their mixture are transformed easily into an amorphous state within about 60 minutes grinding by a planetary ball mill under dry condition. The amount of amorphous phase in the ground specimen increases with increasing grinding time. Accordingly, there has been a rapid decrease in the density of the mixture in the beginning of grinding and a leveling off with the progress of grinding. The specific surface area of the mixture increases sharply at the initial stage of grinding, then decreases gradually with an increase in grinding time, because of the coagulation. The mixed grinding has resulted in the formation of mullite directly from spinel phase without formation of corundum and cristobalite phases during sintering at more than 1223K. The ratio of formation of mullite has increased with an increase of grinding time and sintering temperature.

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In order to prove the practical effect of a water spray zone on suppression of the spread of underground fire, a full-scale experiment was performed in a 400 m long test gallery with a cross section of 5.4 m².
Firstly, it is clarified that a water spray method is effective when water droplets are uniformly sprayed in the gallery and the mean diameter is less than 0.4 mm. Secondly, the cooling effect of water spray is quantitatively discussed from many aspects such as heat transfer and ventilation. Finally, it is shown that the quantity of water required to suppress the spread of fire is proportional to the air velocity and the cross section of gallery and that for a strongest fire can be estimated by equation (5) in the paper.

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