In this paper, a coupled Boundary Element-Characteristics method has been successfully applied to the elasto-plastic analysis of a single rectangular opening and parallel circular openings, and the effect of the geometrical condition, such as the shape of opening, the number of parallel openings and the interval between parallel openings, on the elasto-plastic behaviour of rock surrounding the openings has been analyzed.
From the analysis of the parallel circular openings of a regular interval in the horizontal direction, it is made clear that the critical interval of openings, namely the maximum interval in order that the plastic area around each opening may continue one another, depends on the number of parallel openings as given by equation (7). In the case that the interval between parallel openings is greater than the critical one, the closer the interval to the critical one, the smaller the effect of the horizontal initial stress becomes. So that, in the critical state, the stress distribution between the parallel openings is dependent upon the vertical initial stress.
From the analysis of the parallel circular openings of a regular interval in the horizontal direction, it is made clear that the critical interval of openings, namely the maximum interval in order that the plastic area around each opening may continue one another, depends on the number of parallel openings as given by equation (7). In the case that the interval between parallel openings is greater than the critical one, the closer the interval to the critical one, the smaller the effect of the horizontal initial stress becomes. So that, in the critical state, the stress distribution between the parallel openings is dependent upon the vertical initial stress.

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The coal-production workings of Korean coal mines descend to greater depths every year, making the establishment of the measures for the maintenance of deep gangways urgently needed. In order to prepare the basic data for the research into roof support, rock stress have been measured in the two mines located in the central area of Korea, namely, Bongmyung Coal Mine and Daesung Coal Mine.
In-situ rock stress measurements were carried out by the Leeman method, a type of the overcoring method, to determine the complete state of stress in deep rock. The locations where the measurements were made were 701 m level of Bongmyung mine and 854 m level of Daesung mine. The measurements resulted in obtaining stress components and principal stress of two mines.

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Uniaxial compression creep tests were conducted under comparatively high stress level (90-95% of strength) on Inada-granite, Tako-sandstone, cement-mortar and Akiyoshi-marble. The following results are obtained;
1) In all samples, the primary creep follows the logarithmic creep law.
2) The secondary creep where strain rate is nearly constant is apparent only forcement-mortar. For other samples, the strain rate continuously decreases at first, and increases after taking its minimum.
3) For Tako-sandstone and Akiyoshi marble, the value of creep strain at the minimum strain rate is nearly equal to half of the width of the complete-stress-strain curve cross-sectioned at corresponding creep stress. In case of granite, the creep strain at minimum strain rate is rather small, whereas, in case of cement-mortar nearly double of the width.
4) Strain rate at an arbitrary time in tertiary creep is inversely proportional to the residual time up to final failure. If this law is applied to rock mass, the failure of underground constructions may be predicted.
5) Except cement-mortar, the creep strain just before final failure (1 sec before failure) is nearly equal to the cross-sectional width of the complete-stress-strain curve. In case of cement-mortar, the creep strain just before final failure is as much larger than the width.

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In this study, the control performance of servo-controlled testing machine applied to creep test was investigated.
Firstly, supposing a linear rock model, the characteristic polynomial of machine-rock system was obtained and examined. It was found that the system is stable in primary and secondary creep regions, but unstable in tertiary creep region.
Secondly, the computer simulation was conducted for tertiary creep region, using a non-linear visco-elastic rock model which was recently proposed by authors. The results of simulation are summarized as;
1) The control performance is mainly influenced by natural frequency of testing machine, gain of servosystem and rigidity of hydraulic ram.
2) Complete creep curve of Class II rock can be obtained more easily than that of Class I rock.
Finally, Creep testing under uniaxial compression was conducted using Inada-granite, Sanjome-andesite and Kawazu-tuff as rock samples. It is found that the result of the simulation agrees with the result of experiment.

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The authors have already proposed a practical node potential method for ventilation network analysis, which is today used in all major coal mines in Japan. However, in the course of experience with this method it was found that two major problems must be solved for the calculation to be sped up: converge retardation by inadequate selection of an initial value of pressure to be given to the nodes and by extraordinarily small resistances of airway.
The present paper describes the improved method by which the calculation time is reduced to about one second to one fourth of that by the previously proposed method, the new techniques being introduced to solve the above problems. Also, the effect of natural ventilation pressure on the forced ventilation system and a problem of ventilation control in emergency are discussed, using the newly proposed method.

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The braking characteristics of pneumatic capsule in the pipeline with the closed end were analyzed numerically by the unsteady and the quasi-steady analyses for the combinations of two capsule diameters and two capsule initial speeds. The unsteady analyses were carried out by the method of characteristics under the twocases of polytropic change and irreversible adiabatic change based on the energy equation.
These analytical results were compared with the experiments and then the following conclusions were obtained.
(1) The analytical results based on the polytropic change with n =1.2 agree best with those of the experiment for the both of the pressure-time curve and the capsule position-time curve.
(2) In the quasi-steady analysis, a degree of agreement with the experiment is comparatively good for the capusle position-time curve, but the analytical results based on the irreversible adiabatic change don't agree with those of the experiment for the both of pressure-time curve and capsule position-time curve.

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Many attempts to date have been directed to develop a relationship for the prediction of the hydraulic gradient im in heterogeneous flow of settling slurry having coarse solid particles. This fact indicates clearly that existing correlations lack the universality, and often provide poor im prediction results due to the great diversity of flow conditions.
In this paper a heterogeneous suspentions model was developed for the flow simulation and scale-up of slurry pipelines in the deposit regime. Our analytical work has two main steps: In the first part, the modified O'Brien's equation for distribution of suspended particles above the bed was derived, and solved mathematically. Secondly, the mean velocity-hydraulic gradient correlation was determined in theory.
The predictions for the concentration distributions and the hydraulic gradient from the model were in good agreement with experimental results taken from the published literature for a variety of flow conditions of slurries. Based on the above analyses, we also discussed specific energy, Batchelor's dimensionless number, and Durand-Condolios equation.
As a result, it was confirmed that in the design of slurry pipelines for the commercial transportation of any materials our study made possible to predict the hydraulic gradients precisely in the deposit regime without laboratory flow loon tests.

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As part of a study regarding the recovery of fine mineral particles by liquid-liquid extraction, concentration of -44μm monazite particles at iso-octane/water interface was investigated under various conditions of pH and the concentration of sodium dodecylbenzenesulfonate (SDBS). Maximum recovery was obtained under conditions of pH around 7.0 and SDBS concentration of 1×10^-4mol·dm^-3. In alkaline solutions, the monazite recovery decreased rapidly regardless of SDBS concentrations. An increase in SDBS concentration up to 1×10-4mol·dm^-3 at pH 5 resulted in an increased in the monazite recovery. Since the zpc of monazite is 7.5, monazite particles are positively charged in acidic solution. It was considered that in the pH range below 7, an increase in SDBS concentration brought about higher coulombic adsorption density of the surfactant anion on monazite with its surface being of higher hydrophobicity, and resulted in higher recoveries. In order to examine a relationship between the oil-wettability and the recovery, contact angles of iso-octane/water/monazite system and iso-octane/water interfacial tensions were also measured in terms of pH and SDBS concentration. The work of adhesion for iso-octane onto monazite surface was calculated on the basis of the result of both contact angle and interfacial tension. It was found that the work of adhesion should be considerably related to the recovery of liquid-liquid extraction.

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Strains of Acidiphilium sp. resistant to four heavy metals, such as 10 mM Co²⁺, 100 mM Ni²⁺, 10 mM Cd²⁺, and 0.01 mM Hg²⁺, were obtained. An addition of ferrous or ferric ions in culture medium of Acidiphilium sp. markedly increased Co²⁺, -resistance of the cells. The mechanism of Co²⁺-resistance was studied with Acidiphilium sp.35. Cobaltous ion (50 mM) inhibited uptake of¹⁴C-glucose into intact cells and the acitivity of glucose oxidation. The activity of glucose oxidation was restored by adding ferrous or ferric ions (4 mM) in the reaction mixture, but¹⁴C-glucose uptake activity was not. Ferrous or ferric ions strongly inhibited an accumulation of Co²⁺in the strain, suggesting that inhibition of Co²⁺ uptake by ferrous and ferric ions is responsible for the improvement of Co²⁺ -resistance by those ions.

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As a fundamental study on an iron-reduction process to make crude antimony from its sulfide ore, phase relations and distribution of minor elements in the Fe-Sb-S and Fe-Sb-S-Na₂S systems were determined experimentally at 1200°C.
The phase relation in the Fe-Sb-S system was characterized by a wide miscibility gap composed of crude antimony, which contains small amounts of iron and sulfur, and matte phase whose main constituent is FeS. The addition of Na₂S to the Fe-Sb-S ternary resulted in a much wider immiscible region between crude antimony and matte phase whose main constituent is a double sulfide of mFeS·nNa₂S, and is very effective to increase recovery of antimony in the iron-reduction process.
The distribution ratios of tin, lead and arsenic between matte and crude antimony, L^m/c_x, in the Fe-Sb-S system scattered at about unity. However, those of lead and arsenic decreased significantly with increasing Na₂S in the Fe-Sb-S-Na₂S system, and it was clarified that the addition of Na₂S caused a severe problem in the elimination of arsenic and lead from crude antimony.
The phase relations as well as the distribution of minor elements observed in the present experiments could be reasonably explained by taking into account activity coefficients of the components in the matte phase.

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