The bacterial leaching of flotation concentrate of copper-nickel sulfide ores (Jinchuan mine in China) containing chalcopyrite and pentlandite was studied using Thiobacillus ferrooxidans. About 75 percent of nickel in the concentrate was dissolved after 42 days of bacterial leaching, but the extraction of copper was only 14 percent.
In order to enhance copper extraction, effect of silver ions on the bacterial leaching of copper-nickel flotation concentrate was investigated. Silver ions accelerated the leaching of chalcopyrite by Thiobacillus ferrooxidans. The leaching rate of copper increased as initial silver concentration was increased up to 38mg/l. A 59 percent of copper in the concentrate was dissolved after 10 days of bacterial leaching at initial silver concentration of 38mg/l. However, the leaching rate of nickel decreased as initial silver concentration was increased. The reason is that silver ions hinder the leaching of pentlandite with ferric ions.

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In this study hydrofracture propagation in discontinuous rocks were investigated by Acoustic Emission (AE) locations. Two kinds of rocks, Inada granite and Tako sandstone, were used in the experiments. Inada granite is an anisotropic rock with rift planes and Tako sandstone has discontinuous planes. AE measurements were carried out by 12 piezoelectric transducers.
Hydrofracture propagation in Inada granite were controlled by rift planes. Under unconfined condition hydrofractures were oriented to rift plane. Under confined condition, however, the initiation fracture were caused by the stress condition. In the stage of fracture extension, the fracture changed its direction depending on the rock anisotropy.
In the case of Tako sandstone discontinuous plane had a great influence on the propagation of hydrofracture. Discontinuous planes prevented fractures from propagating through these planes. And, the majority of the AE events were located below the discontinuous plane and predominant fracture growth was downwards.

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Adhesion of quartz particles (size 5-10μm) to various oil droplets (kerosene, hydrocarbons) in aqueous surfactant-free solutions was studied. Electrokinetic behavior of quartz particles and oil droplets, recovery of quartz with the oil phase and contact of oil drops with quartz surfaces in the aqueous solutions were examined. The results are summarized as follows:
(1) In the aqueous phase of pH3, hydrophilic quartz particles adhered to kerosene droplets, whereas kerosene drops did not contact with quartz surfaces.It was suggested that, on this condition, the negatively charged quartz particles and the positively charged kerosene droplets coagulate across water layers.
(2) In CaCl₂ solution of pH 11.5, where quartz particles adhered to droplets of hydrocarbons as well as those of kerosene, oil drops were found to contact directly with quartz surfaces. In this case, water layers between quartz particles and oil droplets should be removed by specific interaction, probably due to specific adsorption of [CaOH]⁺ on both quartz and oil surfaces.

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Effect of silver ions on iron-oxidizing activity of Thiobacillus ferrooxidans was investigated in order to examine the application of T. ferrooxidans in the leaching of silver sulfide.
The 6 strains of T. ferrooxidans used in this study were isolated from process waters of mine water treatment plants, a H₂S gas treatment plant and a flue dust treatment plant utilizing T. ferrooxidans, and drainage waters of sulfide mineral mines in Japan.
Silver ions inhibited iron-oxidizing activity of T. ferrooxidans. Oxidation rate decreased as silver concentration was increased. Critical silver concentrations at which each strain used could oxidize more than 90% of ferrous ions (initial concentration 4.0×10^-2 mol/l) were from 0.10m/g to 0.28mg/l. Addition of copper ions revived iron-oxidizing activity of T. ferrooxidans that was inhibited by silver ions. A Copper tolerant strain cultured in the mediums with gradually increasing copper concentration up to 13g/l had higher silver tolerance. The strain oxidized more than 90% of ferrous ions at the silver concentration of 1.04mg/l. A nickel tolerant strain cultured in the mediums with gradually increasing nickel concentration up to 10 g/l had less silver tolerance.

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This paper is concerned with a numerical experiment on the effect of shock waves on a square pillar in an underground space, as encountered in an explosion of high-pressure gas in a mining shaft or tunnel. A duct with a uniform sectional area is initially divided into two parts by a diaphragm, on the closed end side of which ther e is high-pressure stagnant gas, and on the open end side of which there is low-pressure stagnant gas. A square pillar stands as a support at the width center in the duct.
In such a situation the numerical experiment has been carried out, and various phenomena have been analysed as follows: As soon as the diaphragm is broken, a strong travelling shock wave propagates into the low-pressure gas region and then interacts with the pillar. Instantaneously the shock wave is separated into the wave reflected from the frontal pillar wall and the ones passing through the both sides of pillar. The former repeats the reflection on the closed end side and frontal pillar one, and weakens and disappears some time later. The latter two waves coalesce with each other downstream from the pillar, and then the wave with triple crossing point is formed, but goes away out of the duct.
In addition, it has been demonstrated that the force acting on the pillar reaches the peak state when the first shock wave from the high pressure side comes to the frontal pillar side and the reflected shock wave is formed. The force drops down a little and increases instantaneously by interaction between the reflected shock wave and the contact surface. Thereafter, the force continues to decrease by the strong flow around the pillar as well as the expansion wave, and disappears in a short time.

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Continuous measurements related to gas drainage and cuttings volume at boring were carried out at 20 in-seam boreholes of No.3 slope area in Minami-Oyubari coal mine, which contained the virgin area, influence area due to cross measure boreholes from another rock road, and influence area due to boreholes of previous boring base.
The results obtained were as follows.
1) The relationship between cuttings volume at boring and influence area due to cross measure borings were described.
2) Investigating the relationship between the influence area due to cross measure borings and gas drainage rate, it was recognized that the latter was smaller as the former was larger.
3) It was recognized that cumulative gas drainage volume was in proportion to thepeak value of gas drainage rate.
4) Typical gas drainage curves at each borehole could be divided into two patterns according to geological conditions and gas drainage rates.

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Oxidation state of Sb dissolved into copper electrolyte has been investigated to control the concentration of Sb (V) which relates to floating slime formation during copper electrorefining. The fractional determination of Sb (III) and Sb (V) was done by the atomic absorption spectrophotometry combined with the solvent extraction. Diethylammonium diethyldithiocarbamate (DDTC) in chloroform has used as an extractant in this work that extracted only Sb (III) from the sample solution selectively.
It was found that Sb (III) and Sb (V) in the solution were simply determined by this method. Since Cu and impurities such as Zn, Ni, Fe, Bi, As were extracted by DDTC, these influenced the fractional determination of Sb (III) and Sb (V). Sb (V) was coextracted with Sb (III) at high Cu concentration. Therefore, it was clarified that Cu concentration had to diluted up to 1, 200 ppm to prevent coextraction of Sb (V) under high Cu concentration.
Sb in the anode dissolved into electrolyte in trivalent state. It was confirmed that Sb mostly existed as Sb (III) form in electrolyte during Cu electrorefining, because of the very slow oxidation rate of Sb (1) to Sb (V) by dissolved oxygen.

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When phosphorus in wastewater is removed as calcium phosphate, the characteristics of calcium phosphate precipitate remarkably improved by adding dolomite powder. Generally speaking, zeta potential is an important factor for dispersion or flocculation of colloidal particles in water. Therefore, in this study, the relation between settling characteristics and zeta potential of calcium phosphate and dolomite is investigated. The results are as follows.
Ca²⁺ and HPO₄^2- ions act on calcium phosphate precipitate as potential-determining ions. As H⁺ or OHions influence the concentration (activity) of potential-determining ions in the solution, they are thought to play with the similar roles as potential-determining ions. Under the condition that phosphorus in wastewater can be removed as calcium phosphate, that is, in alkaline solution with excessive Ca²⁺, the zeta potential of calcium phosphate is positive and high, which corresponds to unfavorable settling characteristics of the calcium phosphate. Under the condition at which flocculation between calcium phosphate and dolomite occurs (that is, the settling characteristics of the precipitate is improved), both dolomite and calcium phosphate have positive zeta potentials. Therefore it becomes obvious that the flocculation between calcium phosphate and dolomite occurs not by electrostatic interaction, but by certain chemical interaction, in which calcium ion plays a important role.

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The fine particles in weathered granite were refined by hydrothermal method in order to utilize them as pottery clay.
Feldspar and vermiculite included in weathered granite were altered into kaolin mineral using 0.14mol/l hydrochloric acid adding aluminum chloride under the hydrothermal condition at 200°C. However, the values of pyrometric cone number and the whiteness of the refined samples were lower than that of the common pottery clay.
The concentration by HGMS (high gradient magnetic separator) using the fine particles are hydrothermally altered. The whiteness of the treated samples were improved, however, total yield of the refined products from the fine particles in weathered granite were low in the range of 27.8 to 48.7 wt%. Then two stages of hydrothermal treatment were performed. The first stage is to extract ferrous ions from the fine particles using 6 mol/l hydrochloric acid, and the second stage is that the treated fine particles is altered into kaolin mineral under the previous hydrothermal conditions. In addition to increasing the total yield of the refined products more than 60 wt%, the values of pyrometric cone number and the whiteness of the treated samples were improved similar to those of the common pottery clay.

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Rock breaker is widely used to break seabed rock. A force-penetration relationship appears to be closely related to deformation and fracture mechanism of rock.
Penetration test of rock breaker was conducted on seabed weathered granite at the base of Kurushima Bridge. The rock breaker weighs 46 tons and is 5m long. The angle of its cutting edge is 45 degrees. It is found that a linear relationship exists between force F and penetration u;
F=ku,
where k is a constant. This equation has been pointed out by many authors based on the experiments where typical penetration is 1mm or less. In this study, the penetration reaches as much as 500mm and it is found that this equation is still valid in case of such deep penetration.
The following equation is also obtained considering energy balance;
k (u-0.05) ²/2=m· a · h,
where m, a and h are respectively mass of the rock breaker, falling acceleration and falling height. This equation is consistent with the experimental results.

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