The effectiveness of rock bolting to regulate mine roadway deformation and failure condition is studied using finite element analyses and scale model tests. The results obtained in this study are as follows.
(1) The roof-side-floor bolting is the most effective support system of other bolting patterns in any strata conditions and ground pressures.
(2) The optimum bolt length is about 60% of roadway height or width. Further increases in bolt length beyond this value do not produce a proportional benefit in improving roadway conditions.
(3) The smaller the bolt spacing is, the better the roadway conditions are. It may be suggested to exsist a certain bolt spacing over which a sudden drop of the effectiveness of rock bolting occurs.
(4) The bolting in weaker rock shows higher effectiveness than in stronger one.

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Methane in a coal seam flows into a gas drainage bore hole through a two-step process; firstly diffusion through solid coal and secondly flow along interconnected fissures.
The purpose of this paper is to estimate the gas permeability of solid coal which contains few or no fissures in it. This permeability is thought to be useful for understanding gas flow characteristics of gas drainage bore holes in a virgin solid coal seam. The apparatus used in this experiment is shown in Fig. 1. As the smaller the coal particle, the fewer the fissures in it, powdered coal samples ranging from 20mesh to 100mesh were used for this experiment. Basing upon Darcy's law, the equations describing gas emission from powdered coal and change of gas pressure in the flask were derived. Comparing the calculated gas pressure change with the measured ones, gas permeabilities of two coal seams were estimated as approximately 10^-10 darcy. Owing to the low gas permeability of solid coal, gas drainage from coal seam is thought to be difficult if the coal seam does not contain any fissures. In addition to this, experimental values of gas permeability agree well with the easinesses of gas drainage from in-situ coal seams.

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In-situ measurement has been carried out at Sunagawa Coal Mine to study the seismicity in two mining panels; in the first panel the extraction ratio amounted to 77%, on the contrary in the second panel coal pillars were so extensively left that the extraction ratio was 48%. Magnitude distributions of seismic events were followed by the Gutenberg-Richter's formula, log N=a-bM, in which the b-value was the same for two mining panels but the a-value was lower in the panel whose extraction ratio was lower. Spatial rates of seismic energy were 87.4 and 38.4J/m² in the first and second panels respectively.
On the other hand energy release rates associated with mining were determined from the Face Element Method as 1.20 and 0.57MJ/m² in the two mining panels respectively. It was, therefore, concluded that spatial rate of seismic energy was in proportion to energy release rate presumed from an elastic model. Furthermore it was suggested that a slight decrease in extraction ratio might be effective to reduce the hazards of rockburst as well as stowing with wastes and packing with artificial materials.

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Apparent terminal velocity, U, of a cloud of spheres with narrow size distribution was measured in fluidized bed and the effect of pipe wall on the velocity was evaluated by including d/D term in the following equations,
_??_
where U_o=terminal settling velocity of a single sphere in an infinite fluid, C=volume fraction of particles, Φ=CiRe/24, C_i=inertial drag coefficient for a single sphere, Re=Reynolds number for a single sphere, d, D=particle and pipe diameter respectively.
According to the equation above, the effect of d/D on terminal velocities varied with particle Reynolds number and Concentration.
However, considering a size ratio of particle to pipe diameter and particle Reynolds number in a practical hydraulic transportation, the effect of d/D was reduced to a simple term as 1-d/D.
Based on this result and the simplification of the other terms, the equation for a rough estimation was derived as follows.

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The authors, in 1975, developed the Chain System Sedimentation Balance for the analysis of particle size distribution of powder. They later developed the Electromagnetic Sedimentation Balance (ESB) which is an improved version of the above apparatus. The present paper describes the outline and reproducibility of measurement by the ESB.
(1) The ESB has a maximum weighing load of about 5g and weight detection sensitivity of 0.1mg, and equiped with a small, light weighing pan for the particle size distribution analysis.
(2) Since the weighing pan is small, the buoyancy acting on it in suspension is correspondingly small.
(3) In order to prevent the effect of the room temperature variation, heat transfer from the room to the balance box was cut off by covering the apparatus with a styrene resin plate containing air bubbles. The zero point of the balance was maintained constant for a long period during the measurement.
(4) Particle size distribution analysis of quartz powder was repeated 10times. The particle size distribution curves obtained by the ESB and the Chain System Sedimentation Balance agreed with each other very well.
(5) For high reproducibility of the measurement, a reduction of the variation of the measurement in the large particle size region is advisable. This purpose could be attained by making the falling distance of the particles long enough in order to enable the obtention of a straight line at the begining of the sedimentation curve.
(6) The ratio of the weight of the suspended solids which actually settled on the weighing pan to that of the ideal weight was calculated. This ratio, n%, was 77.0±3.3 and 66.0±3.0% for short (8cm) and long (24cm) falling distances of the particles respectively. It would therefore mean that about 11% of the particles missed settling on the weighing pan in the case of the long falling distance.

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Properties of the raw material and the leach residue of Nonoc laterite treating plant together with morphology, some physical and chemical properties, and mineral dressing behavior of the iron resources contained in the leach residue were investigated. The results obtained are summarized as follows:
(1) Properties of the leach residue.
a) Iron content in the leach residue varies from about 42 to 56% with changes of the operating time. On the other hand, the iron content greatly varies dependent on particle size of the residue. That is, the minus 20μm portion shows the maximum iron content, while 74 to 105μm of that shows the minimum one.
b) The leach residue contains a large quantity of fine particles. Weight percent of the minus 37μm reaches approximately 70%.
(2) Morphology, some physical and chemical properties of the iron resources.
a) The iron resources are mainly composed of magnetite-like iron oxides, which are accompanied by a small quantity of wustite.
b) Most of the magnetite-like iron oxides are not pure and they contain Mg²⁺, Cr³⁺, and Al³⁺ with a wide variation. The lattice constant values observed on two samples are 8.342 and 8.316Å, and their saturation magnetic moments are 44.4 and 35.1emu/g, respectively. These values are smaller than the respective values of normal magnetite.
(3) Mineral dressing behavior of the iron resources. Effective upgrading of the iron resources may be realized by magnetic separation on oversize of 20 to 37μm of the residue. Since undersize of 20 to 37μm is relatively high grade and refractory to magnetic separation, it can be used as a part of iron concentrate without separation. The above-mentioned idea seems to be favorable from the view points of cost saving and environmental quality control.

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The known effect of increasing electrolyte temperature in preventing anode passivation in copper refining was extensively reviewed.
It has been found that a layer of anode slimes formed at a higher electrolyte temperature tends to become more porous with the simultaneous decrease in slime fall. While this increased permeability allows the diffusing ability of Cu² ions away from the surface of a corroding anode to increase, a gravitational flow of the electrolyte also becomes more pronounced within the slime layer. That is, a more concentrated copper electrolyte at the anode surface streams downwards through the micro pores and cracks, and this type of mass transport removes excessive Cu²⁺ ions far more efficiently.
A thorough investigation of electrolyte properties such as diffusion coefficient of Cu²⁺ ions, viscosity, solubility of copper sulfate and vapor pressure etc. measured using copper electrolyte of a nominal composition over the temperature range 45-65°C, proves the fact that the gravitational flow is a predominant factor contributing to the decreased tendency to passivate at a higher temperature.
That anode passivation occurs more readily at a lower level of anode height is also explainable by this claim.

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In the previous paper (J. MMIJ) a method for the thermoelectric power measurement of pulverized samples of metal sulphide ores is described in detail. This paper presents the results for the thermoelectric power α of chalcopyrite, white metal, BF copper matte, and 4 kinds of copper concentrates.
Chalcopyrite (Size: 1.4-1000μm)
The coarse samples (about 50-1000μm) have a nearly constant α of about-300μV/deg, hence they provide the semiconducting character of an n-type. From the temperature-dependences of α and the resistance R, the ionization energies E_α and E_σ for α and the conductivity σ, respectively, are calculated according to empiricale quations,
α=const±B/T, E_α=2eB R=const exp (C/T), E_σ=2kC
where B and C are constants, T, e, and k are the absolute temperature, the charge of an electron, and the Boltzmann constant, respectively. The values obtained fall in the range from 0.1 to 0.3eV, which are comparable with that in the literatures.
As for the fine samples less than 10μm, |α|, E_α, E_σ decrease with a decrease in size, and finally α approaches to zero at a size of about 2μm. The decrease of |α| is tentatively illustrated by a shell model of a spherical particle, where it is assumed that the particle consists of an outer shell (α=0) of a constant thickness and an inner core (α=-295μv/deg). The calculated thickness of the shell amounts to about 0.75μm.
Copper concentrate (Size: 3.5-10.8μ)
The values of α, E_α, and E_σ of these samples are comparable with those of the chalcopyrite sample of the corresponding size; two fine concentrates are α=0, while coarse two are apparently an n-type. After re-grinding with a vibrating mill one of the concentrates has converted into a p-type.
White metal and BF copper matte (Size: 4.6/6.7-190μm)
The coarse samples of white metal (larger than 100μm) and copper matte (larger than 10μm) are a p-type (α=700μV/deg) and an n-type (α=-200μV/deg), respectively. The |α| of both samples also decreases with a decrease in size. The decrease of α for the white metal is, similar to the chalcopyrite, illustrated by the shell model. The thickness amounts to about 5μm.

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