For the purpose of clarifying the mechanism of failure of jointed rock-mass, two series of uniaxial and triaxial compression tests were carried out on the specimens with an artificial cracked plane, which made various angles with the horizontal plane.
Two types of jointing conditions were used for cracked planes of the specimens; a) jointed with only surface friction, and b) adhered with polyester resin. The tests with these conditions were called “Friction test” and “Adhered test” respectively.
The following results are obtained;
1) The compressive strength of cracked specimen varied with the angle of cracked plane.
2) In both of the tests, there is a critical angle of cracked plane, which divides the failure state of the specimen into two states; breaking throughout the specimen or sliding on the cracked plane.
3) The compressive strength of the specimen, which has lower angle of cracked plane than the critical angle, is nearly equal to that of non-cracked specimen at the friction test, and s nearly equal to, or fairly lower than that of non-cracked specimen at the adhered test.
4) In both tests, Mohr envelope for the criterion of sliding, which is obtained by the stresses at sliding on the cracked plane with various angles, agrees with the envelope from simple plane of the weakness theory introduced by Jaeger.
5) But the Mohr envelope for the criterion of breaking at the adhered test does not agree with the envelope from Jaeger's theory.
These results will be checked again by further investigations.

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The compressive creep of Sanjome andesite was examined under the confining pressure from 0 to 400 kg/cm².
The results are as follows:
(1) The creep behavior of the specimen can be divided into two stages. During the first period starting immediately after loading, creep rate is continuously decreasing with time and the logarithmic creeplaw fits for most part of this period. In the successive stage, creep rate is increasing monotonously toward the failure.
(2) The characteristic time, tc, at which creep rate takes its minimum is found tobe related to the lifetime of the specimen, tf, by the following equation, tf=2tc. In other word, the period of the first stage is nearly equal to that of the second.
(3) Comparing at the same elapsed time, creep rate increases with creep stress level under a given confining pressure, and increases with confining pressure under a given stress level.

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The same technique as described in the last report (Part III) was used to obtain the equations showing the relation under explosion limit in the region of higher dust concentration than the apparent stoichiometric dust concentration, Cst, that is ca. 250g/m³. However the equation obtained did not fit the experimental data. Then the modified equation showing the relation between the mixed dust concentration, D, and the percentage of rock dust mixed, R, was obtained._??_, _??_
Comparisons of the equations to some experimental data are shown in figures.
Results so far obtained show that the most important characteristic functions are Rm, rm, and Cu. Then the correlation between these three values was obtained. Resultant equation is, _??_Cu may be estimated from a reported equation, Cu 60V +6.4/dc-1350where V: volatile content in pct, dc: coal particle diameter in cm. Values of Rm of most of coals produced in the world are known experimentally. Then rm can be estimated.

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In this research, the fracturing activity in coal seam due to advance boring was observed by applying the acoustic emission techniques in order to ascertain its preventive effect for coal and gas outburst
In the working faces of drifting, a transducer was installed near the drilling region. The detected signals associated with coal fractures were separated from drilling noises successfully, and were presented for the analyses on the waveforms, the frequency spectra and the parameters of fracturing activities. Consequently, itwas found that these analytical results offered the useful informations to estimate the hazard of coal and gas outburst in the coal seam ahead of driving faces. The main concluding remarks are as follows;
1) The acoustic emissions due to coal fractures during drilling occurred near the cutting points of the bottom of boreholes.
2) The acoustic emission activity accompanied with advance borings was extremely at a low degree in the relaxed region; and at a high degree in the region under a local stress concentration.
3) The location and the range of a local stress concentration were more clearly recognized from the histogram of acoustic emission counts per unit drilled length than that of volume of discharged cuttings.

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A theoretical investigation has been done for adsorption of ethylxanthate ion, hydroxyl ion, water, oxygen, and ethylxanthate pair on chalcopyrite by the extended Hückel method. An ethylxanthate ion can adsorb more preferentially on copper atoms than iron atoms on a chalcopyrite surface. Bonds formed between sulfur of ethylxanthate and copper or iron on chalcopyrite surface become stronger as the ethylxanthate ion is closer to the chalcopyrite surface. However, sulfur atoms without appearing on the chalcopyrite surface does not participate in binding the ethylxanthate ion. A hydroxyl ion can adsorb on chalcopyrite, which is energetically exchangeable by the ethylxanthate ion. Water can specifically adsorb on chalcopyrite. Oxygen on chalcopyrite is an acceptor of electrons which flow from chalcopyrite, and in consequence the energy level of the highest occupied molecular orbital of chalcopyrite tends to be a little lower. An ethylxanthate pair has a possibility to be theoretically formed on chalcopyrite.

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The size reduction of waste polymer and composite materials has become an important subject in the field of waste reclamation.
Therefore a fundamental investigation was carried out on the impact fracture energy of Glass Fibre Reinforced Plastic (GFRP) by using ten kinds of GFRP whose matrix and reinforcements are different.
(GFRP) by using ten kinds of GFRP whose matrix and reinforcements are different.
The fracture energy was determined by means of Charpy impact test. Both propagation energy and fracture initiation energy were determined by using the system illustrated Fig. 6.
The results obtained are as follows:
(1) The impact fracture energy for Roving cloth GFRP increased with increasing interlaminer shear strength, bur that for Chopped strand mat GFRP decreased with increasing interlaminer shear strength.
(2) The fracture initiation energy increased with increasing interlaminer shear strength and Glass fiber content.
(3) The crack propagation energy decreased with increasing interlaminer shear strength.
(4) The Interlaminer shear strength increased with fracture surface energy of matrix.

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Thermodynamic activities of Cu, Pb and S in the miscibility gap region of the ternary Cu-Pb-S System are calculated at 1473K. From a knowledge of the tie-line distribution in the region recently determined in the authors' lab, it is found that the method developed by Choudary and Chang is not applicable to the whole miscibility gap region and, therefore, the ternary suffix Margules equations are also employed in the calculation.
The activity values obtained by the method of Choudary and Chang are proved to be thermodynamically consistent, which confirms the applicability of the method and the correctness of the tie-line distribution adopted in this study. On the other hand, the values calculated from the Margules equations are partly, for the activity of Pb, contradictory to thermodynamics, which may be attributed to lack of information on limiting activity coefficients of Cu and Pb in sulfur at high temperatures, and also to the unsymmetrical nature of the ternary system, since the equations are considered useful for cases of relatively small unsymmetry.

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Reducibilities of the iron oxide contained in the leach residue with CO gas, and with coke in molten state were investigated. The latter is composed of two kinds of experiments; one uses an external-heating type small electric furnace, the other uses a resistance type smelting electric furnace. Finally, a possibility to make dechromiumed iron was examined. These are summarized as follows:
(1) Reducibility of the iron resources with CO gas.
a) The reduction rate in early stage of the iron oxide with CO gas is remarkably large. It is explained by the reason of that the material has an extremely large specific surface area.
b) Since the reducibility reached to 60-70%, the reduction rate of the iron oxide noticeably slows down for some reason or other.
(2) Reducibility of the iron resources in molten state by using an external-heating type furnace.
a) The iron oxide is reduced in molten state at 1400°C and is separated from slag layer with the optimum amount of flux.
b) The recovered metal contains 2% order of chromium and its chemical composition nearly corresponds to that of Japanese Industrial Standard of “Grinding balls and cylpebs (2nd category)”.
(3) Reducibility of the iron resources in molten state by using a resistance type smelting furnace.
a) This was performed as an applied experiment and the expected results were obtained.
b) Tension test, hardness test, abrasion test and microscopic observation of three kinds (Cr: 4.1%, 1.6%, 0.8%) of test pieces prepared from the molten metal were performed. Their results were almost adequate.
(4) Possibility for making dechromiumed iron. By melting without solid reducing agent of the reduction product from CO gas reduction, the iron containing 0.06% of chromium was recovered. This chromium content is quite applicable value to make common steel.

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