The purpose of this report is to discuss the application of the suggested methods for stress determination and pressurizing cycle on hydraulic fracturing to in-situ stress measurement (presented in 4th report). In-situ hydraulic fracturing tests were conducted for four vertical and inclined boreholes. The test site is located at about 600 meters deep level from the surface in Toyoha mine and a rock is green massive dacite.
The stress conditions were determined at the site by selected re-opening and shut-in pressures with high reproducibility. The difference of stress conditions shows that the pressure data used to stress evaluation must be selected by means of repressurizing tests. The comparison of primary and secondary pressure histories show that the tensile strength of dacite at the test site is about 38kgf/cm² and the energy to extend hydro-fracture is smaller than 60J/m². The comparison of hydro-fracture impression and fracture form which is imagined on the basis of stress distribution and weakness plane on the borehole wall suggests that the direction of fracture may be influenced by not only the direction of borehole axis and stress condition but also rock anisotropy (Fig. 20).
The suggested method to determine in-situ stress in anisotropic rocks is proved to be apropriate by the experimental study in this report.

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To discuss the validity of theoretical expressions, shown in eq.(1), for rock deformability obtained in the 1st report, a series of experimental studies on the elastic moduli of rock is performed.
To evaluate the theoretical expressions requires the knowledge of the crack density Φ, the intrinsic elastic moduli E and ν, the frictional coefficient μ on the crack surface, and the state coefficient q. q proposed in the 1st report is the ratio of the crack density of open cracks to that of total cracks.
Four kinds of granite specimens with different crack concentration were employed in experiments. Modal analysis, hydrostatic compression test, and observation of cracks on the polished surface of specimens were carried out. By analyzing these results, the crack density and the intrinsic elastic moduli of the specimen were evaluated and the theoretical values of effective elastic moduli were calculated in two cases, that q=1.0 and q=0.0, by using eq.(1). q=1.0 corresponds to the case that all pre-existing cracks are open and q=0.0 corresponds to the case of closed cracks. The former condition gives the minimum values of the elastic moduli and the latter one gives the maximum values.
The tangential elastic moduli of the specimen were measured as a function of the applied stress by uniaxial compression test. The maximum. and minimum values of elastic moduli obtained experimentaly were comnared with the thenretiral vallieq Reasonable agreement was obtained (shown in Table 3 and Table 4).
It is concluded that the theory proposed has a promise to estimate rock deformability quantitatively.

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This paper describes a scale model study of strata mechanics related to the development of fracture zone above a goaf as a longwall face is advanced. The laminated roof strata were made of tens of sand-plaster sheets with 1cm of thickness whose strength was lowered down to 1kg/cm² by adding some detergent. The experimental results showed the bottom stratum of immediate roof collapsed as its span became long enough to crack at the ends. The progressive failure of the laminated roof followed the initial fracture until the goaf was filled with caved fragments, and resulted in a trapezoidal fracture zone. After the transient caving, the fracture behind the face support turned in a steady fashion that was either continuous or periodic depending upon whether the caving was within the immediate roof or not.
The experimental results can be well explained by a structural model in which a beam is assumed to be continuous along the full span before failure, but to be torn in two jointed on its upper surface at the mid-span after cracking at the ends. The largest span of any roof stratum, at which it can be competent to its own weight, seems to be determined from the fracture criterion of a beam lying on elastic foundation in cooperation with the caving angle. Finally the caving angle is formulated in terms of the geometrical and mechanical properties of the roof beam on the basis of the limit equilibrium of the beam segment. The structural model described in this paper appears to be relevant to not only interpreting the development of roof caving behind a longwall face, but also predicting the load applied on the face supports.

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Theoretical method has been developed for analysing the critical speed of a rod rotating in a flexible casing in case of an off-shore boring. Then, the critical numbers of revolution of the rod in practical cases have been calculated. and the results have indicated the useful guides for the design and operation of the off-shoreboring.
The main guides obtained are as follows:(1) There are two kinds of the critical numbers of revolution of the rod, one of which is caused by the in-phase mode of the coupled lateral vibration of the rod and casing, and the other by the out-of-phase mode of the vibration.
(2) The critical number of revolution of the rod pertaining to the in-phase mode becomes higher in case of a larger value of the diameter-ratio which is defined as the ratio of the outer radius of the casing to that of the rod. Furthermore, the rate of rise of this critical number is greater in case of a higher mode of the critical speed. On the other hand, as the diameter-ratio increases, the critical number of revolution of the rod pertaining to the out-of-phase mode first rises and then approaches to a constant value.
(3) An increase of the span-length of the rod, which is equal to the depth of the water, causes the critical numberof revolution of the rod to be lowered, but it does not affect the above-mentioned phenomena.
(4) The critical number of revolution of the rod rises as the tensile load axially applied at the top of the rod increases. However, the rate of rise of the critical number is greater within the range of a smaller diameter-ratio in case of the in-phase mode of vibration. In case of the out-of-phase mode, however, the rate is greater in the range of a larger diameter-ratio.
(5) The increasing tensile load axially applied at the top of the casing leads to a little rise of the critical number of revolution of the rod pertaining to the in-phase mode of vibration and it causes a slight rise of the critical number pertaining to the out-of-phase mode only in the range of a smaller diameter-ratio.
(6) As the ratio of the Young's modulus of the casing to that of the rod increases, the critical number of revolution of the rod pertaining to the in-phase mode rises, especially in the ratio larger than 1.0 but the critical number pertaining to the out-of-phase mode tends to approach a constant value.

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The effect of starch xanthate on the separation of chalcopyrite and galena was studied in the flotation using potassium ethyl xanthate (KEX) as a collector. Starch xanthate synthesized was found to contain a xanthate radical at the rate of one part per 82 glucose units of starch.
Galena was depressed preferentially by starch xanthate and recovered as a sink. The best result obtained in the flotation carried out on an artificial mixture (1:1 by weight) revealed as follows: chalcopyrite as a float, recovery=97% and grade=83%; galena as a sink, recovery=83% and grade=97%, respectively.
KEX was adsorbed on galena forming a multilayer lead xanthate by metathesis reaction with oxidized products on galena surfaces, while KEX was adsorbed on chalcopyrite surfaces as a monolayer that ensures the hydrophobicity of chalcopyrite.
Starch xanthate produced a hydrophilic multilayer film on galena surfaces whereby galena is depressed effectively. Muchl ess adsorption of starch xanthate was obtained on chalcopyrite surfaces than that on galena surfaces. This provides major reason for selective depression of galena.
Starch was also adsorbed on both chalcopyrite and galena surfaces with almost the same adsorption density which is much less than that of starch xanthate. No successful separation of chalcopyrite and galena was achieved with starch.

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High gradient magnetic separation (HGMS) tests were performed after selective magnetic coating of magnetite to galena.
The results are as follows:
1) The capture rate in HGMS of quartz mixed with magnetite colloid decreased at slurry pH 9 to 11, where high potential energy barrieres calculated from DLVO theory were present. On the other hand the large capture rate of galena mixed with magnetite colloid was shown at pH 3 to 11. Therefore, the HGMS test of artificial mixture (galena 45.5%, quartz 45.5% and magnetite colloid 9%) was performed at slurry pH10. Approximately 80% grade of quartz as non-magnetics and 80% of galena as magnetics excluding magnetite were achieved at a recovery of 50% in two stages of HGMS. Subsequently, galena as a magnetics was separated effectively from magnetite by HGMS after slurry was adjusted at pH 10 and at the concentration of 1×10^-3kmol/m³ of sodium hexametaphosphate.
2) 0.5T of applied magnetic field intensity was enough to capture minerals selectively coated with magnetite by HGMS. The employment of permanent magnet is possible and the energy cost for the selective magnetic coating separation will decrease. The amount of magnetite to use in selective coating to galena was more than 50 times of that which was calculated by force balance model because of the coagulation of magnetite particles themselves.
3) The capture rate of galena mixed with magnetite did not depend on the particle size of magnetite at slurry pH 10. Especially the magnetite particles which were prepared by oxidation of ferrous hydroxide were effective to capture galena and showed strong magnetic flocculation in water because of single domain size.

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Pelletizing and reduction tests for direct reduction process using laterite nickel leached residue were carried out. Green pellet showed sufficient compressive strength and drop resistance for handling without addition of bentonite. The compressive strength of fired pellet was greatly increased when a small amount of limestone was added and the maximum strength was achieved at the CaO/SiO₂ratio of 0.2. Pellet with a compressive strength of 240kg/pellet and a porosity of 30% was obtained by means of a pot-grate furnace at a firing temperature of1220°C. When reduction tests were carried out by using noncoking coal as reductant, the highest degree of reduction of 85.8% was achieved at a reduction temperature of 1100°C.
It is clarified that the melting point of gangue minerals such as forsterite and silicate are lowered by addition of CaO, and at the same time MgO component moves into iron oxide to compose a solid solution of magnesioferrite and magnetite (MgO-Fe₂O₃-FeOTe₂O₃).

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Reductive roasting is an important pre-treatment stage of the extractive metallurgical processes of laterite ore. A coalcontaining pellet method, in which ore pellets containing coals are roasted in a combustion gas atmosphere, seems to have economical and technical advantages over the conventional methods. This paper is concerned with various fundamental factors in the selective roasting of limonitic ores.
A high reduction rate of nickel and a selective metallization of nickel were achieved in the coal-containing pellet method. Lignite and bituminous coal were suitable as effective reagents for reduction.
The influences of temperature and addition rate of coal on the reduction of nickel and iron were discussed, and the mechanism of reduction in the coal-containing pellet method was considered based on the temperature dependency of the amount of reductive gas evolved from coal as well as the chemical reactions.

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