Standing on the economical point of view, the optimum sampling density for wide range prospecting of the ocean floor manganese nodules was derived using a geostatistical method. A variogram was calculated from the existing sampling data of the ocean floor manganese nodules. Consequently the weak-stationarity of the area was certified, and the abundance distribution of the manganese nodules was calculated by means of Kriging. It was found that the frequency distribution of the abundance of the manganese nodules presented a lognormal distribution. The data used had been acquired from the ocean floor south of Hawaii.
The relation between Kriging deviation and the economical loss induced by estimation error was calculated. Also the relation between the sampling density and the expected value of Kriging deviation was calculated. From the both relations, we obtained the relation between the sampling density and the loss induced by estimation error. Considering the relation between the sampling density and the total sampling cost, the optimum sampling density from economical aspect was calculated for each cutoff values.

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Theoretical conditions for the stability of discontinuous rock slopes against flexural and rotational toppling failure areproposed depending upon the various arrangements and number of discontinuity sets. In addition, the stabilization of suchslopes against toppling by grouted rockbolts is studied and basic principles for the introduction of the reinforcement effect ofthe bolts are laid and their applications to some typical cases of toppling are shown.
The stability conditions are then applied to predict the stability of slopes with various arrangement and number of discontinuity sets. Good agreement has been found among the results of in-situ observations and of model tests and those calculated by the developed theoretical stability conditions. The developed conditions are deemed to be capable of predicting the stability of slopes against toppling very accurately and to enable a designer to evaluate the stability of a slope in question in a very short period of time.

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This paper describes calculations concerning temperature-rise and the oxygen diffusion processes of a coal seam in the low temperature range.
The temperature rise of coal occurs by the accumulation of the heat produced by oxidation on the coal surface. The heat generation rate is a function of temperature, oxygen concentration and the exposure time of coal in an oxygen atmosphere.
For the case where the oxygen concentration and the temperature around the coals vary with time, we have proposed a new method for estimating heat generation rate. We have called this new method “exposure equivalent-time”. This new method was applied successfully to simulate the temperature and the oxygen concentration in the coal seam model whose open-ends are exposed to the air. The finite-difference method was used to solve the equations of heat conduction and diffusion of air.

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Deformations of gate roadways located under previous workings are measured and compared to the theoretical values obtained by quasi-three dimensionalstress analysis.
The results of measurement show that roadways deform less and supports keep more stable under the goaf of old workings than under pillar or rib, where roadways deteriorate significantly requring constant repair. The advance of current longwall faces also promotes roadway deformation.
The stress analysis shows that the amount and the trend of redistributed stresses along gate roadway are major contributory factors to deformation of gate roadways. Moreover, it is shown that using the stress increases derived from stress analysis and closure factors, the vertical closure of gate roadways caused by longwall mining can be predicted well. This means that the analysis can be used as an aid to rational planning of mining layouts and roadway maintenance under more complicated conditions.

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Flow characteristics of slug flow for air-water mixtures upward flowing, including gas slug velocity, gas slug length, liquid slug length and void fraction profile, are discussed experimentally and/or analytically in present report. The experiments were carried out in three sizes of pipe that were used in the previous work (2nd Report) and the analysis were done using the equations presented in the previous paper (3rd Report). The results are summarized as follows.
(1) The gas slug velocity was represented by Eq.(10), however it was shown that the coefficient C₁ is influenced slightly by the void fraction in the liquid slug region.
(2) The distribution of lengths of the gas and liquid slugs was described by a logarithmic normal distribution.
(3) The mean value and the standard deviation of gas slug length were expressed by empirical equations (11) and (12) respectively.
(4) The liquid slug length was insensitive to the gas and liquid flow rates and almost constant for a given tube diameter.
(5) The void fraction profile in the overall slug was denoted by the power law distribution as Eq.(15).
(6) It was suggested from the analysis of liquid-phase velocity profile that the presence of small bubble in the liquid slug region brings a flattening effect on the velocity profile.
(7) It was found that the void fraction profile in the gas slug is denoted by Eq.(44) in general.

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In order to establish available process for utilization of manganese nodule production light weight aggregate from their residue which were treated with hydrochloric acid solution have been investigated.
The relation of some properties to bloating of pelletized sample have been inquired by chemical analysis, X-ray diffraction analysis, size distribution and by measuring specific gravity, water absorption, strength under compression etc. Further, the effects of bentonite to bloating of pelletes have been also examined.
The main results obtained were summarized as follows;
1) By proper arrangement of bentonite, the chemical components were found to be in the Riley expansion range of system SiO₂-Al₂O₃-Flux.
2) The mineral contents of residue were primarily quartz, with the presence of feldspars and magnetite, and these ofb entonite were primarily montomorillonite, with quartz and feldspars. Furthermore, mineral constituents of bloated pellets of the mixture of residue and bentonite were cristobalite, together with feldspars and iron oxide.
3) In the case of residue, the contraction of pelletes started at 750 C, and larger contractibility was showed with risingof temperature from 1000°to 1250°. In the case of bentonite, the expansion of pelletes started at 850°, and larger expansibility was showed with rising of temperature from 1000°.
When the rising rate of heating temperature was 80°/min and bloating temperature was 1250°, and expansion ratio of mixed pelletes (residue 60%+bentonite 40%) was about 60%. On such bloating condition for pelletes, the production of light weight aggregates could be expected.

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Thin layer radiochromatography is a useful means to investigate into intermediateoxyacid species of sulphur in low concentrations formed during aqueous reactions involving elemental sulphur and metal sulphides. In this study, 0.1-0.5 mol/dm3 standard solutions of commercial Na₂ SO₄ and Na₂ S₂O₃, synthesized Na₂ S₃O₆ and Na₂S₄O₆ were used to ensure identification of the anions. In an Ar glove box, 1-5×10^-3 cm³ of the solutions were dropped on a thin layer plate and dried. Development experiments were conducted in a glass cylinder in Ar at 22°C. It was found that a solvent containing ethanol, butanol, and water in the ratio 1: 1: 1 (vol.) and 0.5wt.-% KCH₃COO (pH 8.3), and the plate, TLC plastic sheets Cellulose No.5577 (Merk) gave best results for separating the thionate anions. Rf values obtained were 0.11, 0.20, 0.38, and 0.49 for SO₄^2-, S²O₃^2-, S₃O₆^2-, and S₄O₆^2-, respectively. From optical density measurements using films exposed to the developed plates, it was shown that the area of absorption peak (peak value x full width at half maximum) was proportional to the amount of S taken for all species. Two examples of the development were presentedbriefly. Sample solutions were taken from an ammoniacal copper solution where elimination of the copper was conducted by adding activated sulphur containing S. It was shown that S₃O₆^2- and S₄O₆^2- were formed during the reaction, whereas only S₂O₃^2- was found after completion of the elimination.

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In this study the behaviour of arsenic and oxygen in anode during copper electrorefining has been investigated. The form of anode slime and the dissolution state of anode surface after electrolysis as well as the effect of dissolved oxygen in electrolyte have been revealed.
In case of the arsenic concentration in anode was lower than 3%, the major part of it was homogeneously distributed inthe copper matrix, and then that was dissolved as As³⁺ ions into the electrolyte during electrolysis. These ions produced concurrently anode slime on the anode surface. These slime delayed the diffusion of the As³⁺ ions from the vicinity of anode to the short distance area from anode, and the anode was passivated after the drastic increasing of the As³⁺ ions in the vicinity of anode. The anode passivation was greatly accelerated with increasing concentration of the arsenic in anode and the As³⁺ ions in electrolyte. The form of anode slime showed mostly Cu₃As compound and a slight amount of copper powder, irrespective of the concentration of arsenic and oxygen in anode or dissolved oxygen in electrolyte.
It was clarified that the anode slime was produced by the secondary reaction of the dissolved Cu²⁺ and As³⁺ ions on the anode surface, and the anode passivation was caused by the development of the structure of anode slime from the granule to the lamella.

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