A hydraulic fracturing system for three dimensional stress determination has been developed. The calculation procedure of the system introduces new interpretation based on the facts obtained through laboratory hydraulic fracturing tests of intact rocks. Hydraulic fracturing data incorporated in the system include at least both the fluid pressures at steady flows in two longitudinalfractures produced around the boreholes of different orientationand the shut-in pressure in a transverse fracture which is apt to develop along a natural joint. Stress states in impermeable rock can then be evaluated by the system with neither assuming thedirection of principal stresses nor seismic measurements.
In this paper, the principles of the new method for three dimensional stress determination and the measuring system are described first, and then the results of in-situ measurements at several sites where the new system was applied for stress determination are reported.

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Estimating methods of the flow rate and concentrations of the components of a mine water from measured results for the past yearhave been investigated in order to develop a new treating process of the mine water applied a technique of foam fractionation.
The summary of the result was as follows:
(1) Concentrationof the mine water components did not change at random, but varied almost all together.
(2) A correlation line have been obtained by the analysis of eigenvectors about the correlation coefficient matrix of the mine water.
(3) The variation of the flowrate depended mainly on the amount of rain except a snowy season.
(4) A relation between the amount of rain and the flow rateof the mine water has been analyzed, using the physical model consisted of two vessels.

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The determination of yield functions is the first step for the derivation of the constitutive law of geo-materials. In thi: paper, a new yield function is proposed by incorporating a parameter k, which is related to the creation of new fracture surfaced uring failure of materials, into the modified Cam-Clay model based on the classical plasticity theory and the critical state concept in soil mechanics. The critical state is the stress state where materials plastically deform without plastic volumetric strain increments. The proposed model characteristically shows that plastic strain increment vectors are normal to the yiek surfaceswhich have more general shape on the Rendulic stress plane than an ellipse of the modified Cam-Clay model and that the yield surfaces intersect perpendicularly the hydrostatic axis aside from the origin of stress space.
The application of the proposed model to the experimental data of cement mortar (uniaxial compressive strength Dc=205kgf/cm₂) givesM=0.77 andk=0.66, where M is the ratio of octahedral shear stressτ_octto mean principal stressσ_mat the critical state. These values of M and k are considered to be appropriate in comparison with those of rocks in published papers. The assumption that M does not depend on Lode's parameter but is constant, in the proposed model, represents that the shape ofyield surfaces is a circle of Von Mises on the octahedral stressplanes. Furthermore, the initial yield stress, experimentally obtained, of am=250kgf/cm²on the hydrostatic axis causes the onset of dilatancy at about 80% stress level ofσ_cwhich may be a little higher. Since the experimental data used in this paper cover the region of contractancy only, it is necessary to confirm the validity of the proposed model for all stress states including that of dilatancy.

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In recent years many serious accidents have occured in Japanese coal mines. Because of these accidents, it is generally believedthat the working place in a coal mine, especially in Japanese coal mine, is very dangerous one. To clarify the safety performance in Japanese coal mine quantitatively, comparative analysis of coal mine safety statistics of Japan with that of other countries was carried out. This study gaye the following results.
1. The rate of fatal accidents in Japanese coal mine per year is about 0.5 per 1 million working hours. This value is higher than those of European countries and U.S.A.
2. The rate of accidents in Japanese coal mines is far less than that of West Germany.Moreover, a new method for statistical approach using equation (4) was proposed.

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The pressure loss of the flow with a moving bed is investigated theoretically and experimentally in this paper. Two kinds of experimental apparatus was used. One of them consists of three kinds of pipes of 30.8, 39.7, and 49.6mm i. d., and the other consists of two kinds of pipes of 80.2 and 105.1 mm i.d. And two kinds of glass beads and P.C.V.Pellet were used in measuring pressure loss.
The pressure loss increased as the mean velocity of mixture and the delivered concentration of solid increased, but the additional pressure loss due to the presence of solid is hardly affected by the mean velocity.
The data of pressure loss measured in this experiment were examined by Eq.(29), and then the relations shown in Fig. 10 and Eq.(30) were obtained.
Furthermore, the force balance model above the moving bed was made in order to examine the relation between the behavior of particles and the pressure loss of the flow with a moving bed. The components of this model consist of the shear stress at the pipe wall, the shear stress at the surface of the moving bed, the shear stress due to rolling and sliding particles and the thrust forceby fluid acting on particles. The calculated values of the pressure loss by this model were in good agreement with the experimental results.
It was ascertained from the result of analysis by this model that the thrust force was the dominant factor for the pressure loss, but this force decreased with an increase in the mean velocity, and it was found that this result was due to the increase of the velocity ratio of particles to fluid.

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Zone settling rates of limestone, coal and kaolin-water slurrieswere investigated using vertical settling cylinders or a centrifuge. Zone settling was divided in dilute and intermediate modes depending on whether or not the aggregates were in contact and formed a network structure, and concentrate mode of intimate contact settling due to compression was followed. Although the higher initial height of slurry brought on the higher settling rate in the intermediate, it was found that in the region of rather lower initial height the settling rate became solely a function ofconcentration.
Comparing experimental values with known analytical derivations, Richardson and Zaki's equation modified by Michaels and Roberts' equation were effective for the dilute and the concentrate, respectively. And also, Michaels method of capillary model was impressive for the intermediate in which the settling rate was depended on both of concentration and initial height. It was demonstrated that when the initial height was low enough to correlate the settling rate only with concentration, settling rate of the intermediate was well coincided with predicted rate appling Kynch's theory on the dilute. Zone settling rates of rather wide range of concentration and initial height were able to be summerized as expressed in a figure.
If the initial composition is uniform the slurry concentration in centrifuge is independent of radius, but decreases everywhere within the suspension at the same rate with respect to time. Centrifugal settling rate was calculated on the basis of that it was able to be calculated from the settling rate in a gravitational field, field acceleration and slurry concentration accounting for the changingconcentration. Equilibrium thickness of centrifugal sediment waspredicted in the manner which took into account the relationshipbetween compressive pressure and porosity in the sediment. Usingthese values led to good correlation of experimental and calculated sedimentation process in centrifuge over the range of this investigation.

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Selective reductive roasting have been conducted for garnieriticores by using a coal-containing pellet method. Influences of various fundamental factors were investigated on the reduction rateof nickel and the selective metallization of nickel againstiron, and the relation between these behaviors and the change of minerals contained in garnieritic ores during heating was discussed. Some results obtained are as follows.
Reduction rate for the nickel component in garnieritic ores was very low compared with that in limonitic ores. It was considered that the nickel oxide contained in garnieritic ores was a component of clay minerals such as serpentine, and the heating caused a change of these minerals to the silicate contained magnesia (forsterization), resulting in a decrease in the reduction rate of nickel above 800°C.
To improve the reduction rate of nickel in garnieritic ores, the addition of sulfur was effective for the coal-containing pellet method as well. It was considered that the addition of sulfur was effective for increasing the reductive power of atmosphere and decreasing the number of metallic nickel particles enclosed in the forsterite.

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The oxygen potential in the system of NaO_0.5-SiO₂-FeO slag and metallic copper saturated with solid iron was measured by using galvanic cell at 1250°C. Activity of FeO was calculated from the standard free energy of FeO formation and the oxygen potential, The copper solubility in slag was determined in this experiment. The results are as follows;
1) Theactivity of FeO exhibits the most positive deviation from ideal solution near the molar ratio of Na₂O/SiO₂=1.By representing oxide molecules with units of one metal atom, the similarity of the temperature-composition phase diagram between NaO_0.5-SiO₂system and CaO-SiO₂system becomes obvious. The iso-activity curves of FeO in thesystem of NaO_0.5-SiO₂-FeOn are comparable with those of CaO-SiO₂-FeO_nsystem.
2) Under such a low oxygen potential as the one saturated with metallic iron the dissolution form of copper in slag is mainly oxide.The copper solubility in the slags whose molar ratios of Na₂O/SiO₂are 1 to 0.5 is nearly 0.05% at po2=10^-14atm.

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