The study of dielectric properties of rocks are usefull for improvement and development of the existing electric prospecting method and interpretation of field data. In order to attend these objectivies, it is necessary to accumulate data on the dielectric properties of rocks.
22 core samples of basalt, andesite, dacite, liparite, sandstone, tuff and mudstone taken from drill holes in Kosaka mine area were used in this study. Dielectric constant and loss tangent (tan δ) were measured in the frequency range from 30 Hz to 1 M Hz at 28°C.
The following results were obtained.
(1) Dielectric constant of rocks was decreased in proportion to the increase of frequency and were tended to approach the characteristic constant of rocks.
(2) Dielectric constant of rocks was increased on account of increasing water content in this frequency range.
(3) When the water content in rocks exceeds 0.3%, dielectric constant becomes large, e. g. up to the order of 10² at 30 Hz, compared to the value for pure water, which is about 80.
(4) Dried rocks or pure water alone did not exhibit the dielectric dispersion effect in this frequency range and these dielectric constants were constant.
(5) The dielectric constant theory of heterogeneous mixture applies to dried rocks, but not to water bearing rocks.
(6) Dielectric constant of rock, which was dried and then moisturized with pure water (wt. 0.47%) showed the different value from the natural state rock (wt. 0.41%) and the dielectric characteristics of the moisturized rock was different from that of the natural state rock.
(7) Water bearing rocks had the maximum tan 5 at certain frequency, basalt had at about 1 KHz, andesite at about 5 KHz, mudstone, tuff and sandstone at about 100 KHz. The frequencies obtained seemed to be the characteristic properties of rocks, but dried rocks had not the maximum.
For water bearing rocks, phenomena showing large dielectric constant in low frequency would be the effect of dielectric dispersion due to interfacial polarization. The effect of such rocks could be of important in relation to ground noise as experienced in the induced polarization method.

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In order to solve water pollution problems in abandoned mines, the mine sealing has been investigated. In particular, it is an important subject to predict the variation of mine water flowing out before and after sealing.
Authors have tried to analyze the behavior of ground water flowing through the rock formation under the mine area, based on the Darcy's flow in the homogeneous medium. The theoretical analysis has been carried out on a model in which the stope exists under the hill-side with a gentle slope and the shape of stoped zone is a horizontal disk, by using the finite element method.
As the result, a method of analysis on the filtration could be developed and the correlation between the recharged water and the behavior of filtration could be made clear. The tendency of variation in the drained water is following:(1) The amount of drained water increases gradually like a saturation curve with increasing the amount of recharged water
(2) If the mine water can be impounded in the stoped zone by sealing water flowingout of the lowest level and it can be made flow out of the upper level, the amount of drained water may decrease about 13-35% on the condition describing in this paper.
(3) The amount of drained water increases gradually like a saturation curve with increasing the volume of stoped zone.
(4) The amount of drained water is proportional to the permeability of the ground.

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A series of model experiments on the mechanism of floor lift in coal mines were carried out in our laboratory, and some effects of several factors (depth of roadway etc.) to the floor lift were examined. Refering to the experimental results and todays Japanese coal mines conditions, we applied the floor bolting as one of the useful method of combating floor lift and the effect was demonstrated experimentally. As the material of floor bolting, wood dowels or vinyl pipes are suitable. The relations between length of bolt and effect of bolting were shown and discussed.

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The model experiments were carried out in order to study the damping effects of surrounding water and air on the lateral vibrations of rods, and these experimental results enabled to estimate the damping effect of water in case of the lateral vibration of a full-scale boring rod.
The results obtained by these experiments were as follows:(1) The damping coefficient due to water was three to fifteen times greater than that due to air in the range covered by these experiments.
(2) The damping coefficient was greater in case of the rod with larger outer-diameter and with shorter span-length.
(3) The relationship between the damping coefficient, n (1/sec), and the Reynolds number, Re, derived from the average vibration-velocity of a rod, which was defined in this paper, was represented by the following equation.
n=0.54 log₁₀ Re-0.39
Furthermore, the above equation proved to be available for the estimation of the damping coefficient pertaining to a full-scale rod.
(4) The damping effect of surrounding water was not considered as viscous damping (linear damping) in the rigorous sense. However, the viscous damping could be assumed for the calculation of the lateral vibration of an off=shore boring rod without loss of precision in the practical sense if the size and property of the rod were constant.

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As a hydrodynamic approach to the flotation process, the turbulent energy propagation in flotation cells was considered on the basis of the fluctuation velocity and the velocity correlation to yield the following results:(1) The power number in a Agitair type flotation cell or a Warman type flotation cell was constant in the region of Reynolds number>10⁴.
(2) The power consumption without gas phase could be expressed by eq.(4).
(3) The power consumption containing gas phase was decreased with the larger air flow number and this tendency was enhanced by the addition of frother because of the recirculation of dispersed bubbles to the impeller zone.
(4) The energy spectrum function was expressed by eq.(10) or eq.(11) under assumption of isotropic turbulence.
(5) The velocity correlation function in the upper zone of the cell was in accord with the function derived by neglecting the transfer spectrum function, 'whereas it was recognized that such mixing process was a diffusional mixing process.
(6) Nearly 90% of the input energy was reckoned to be dissipated in the impeller zone and about 1% of it was consumed for generation of bubbles.

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Kinetic study of the oxidative leaching of synthetic ferrous sulfides in an aqueous ferric chloride solution was made.The principal results obtained are as follows:(1) A rate equation appliciable to the leaching reaction, in which both the surface area of powdered materials and the concentration of leachant change significantly, was derived.
(2) The main leaching reaction of ferrous sulfide is the oxidative reaction forming elemental sulfur, but this reaction is depressed by competitive reaction of acid leaching below pH 1.
(3) The oxidative leaching of stoichiometric ferrous sulfide proceedes faster than non-stoichiometric ore.
(4) Rate equation for the oxidative leaching of ferrous sulfide with ferric chloride is found to be R=K·A·(Fe³⁺) and E_a=12.0 kcal/mol (49.98 at % Fe) and 14.5 kcal/mol (46.93 at % Fe)
From this, a chemically controlled direct oxidation mechanism is proposed.

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