The concrete plugs installed in underground petroleum stockpiling bases must be strong enough to support the hydraulic pressure of the stored crude oil and fairly impermeable against both of oil and gas. In order to test and confirm the mechanical competence of the concrete plugs, in-situ tests were carried out in three underground petroleum stockpiling bases; Kuji, Kikuma and Kushikino.
In each case, an lm thick concrete plug was installed in a 2m wide by 2m high test adit and pressed as high as 10kg/cm²by four 200 ton hydraulic jacks. Deformations of the concrete plug and stresses induced in reinforcing rods as well as displacements of the surrounding rock were measured continuously while loading and unloading. Following results were obtained and discussed in details.
(1) None of visible damages such as cracks was found on the surfaces of the tested plugs and the pressure durability of the plugs was certified.
(2) Careful and scrupulous construction rather than geological condition affected the performance of the concrete plug more favorably.
(3) Although due to the time-dependent behavior of the surrounding rock applied pressure-displacement relations of the tested plugs showed slight non-lineality and creep deformation while holding constant pressure, the elastic deformations of the plugs showed fairly good coincidence with the results of FEM calculations.

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A numerical analysis is presented which predicts the fracture behavior of granite under high confining pressures. The numerical simulation uses a modified boundary element method, and incorporates the tension-softening model developed for characterizing the growth of the fracture process zone in rock.
Fracture toughness tests of granite have been conducted under confining pressures of 15.68 MPa and 26.46 MPa using compact tension specimens which were jacketed with urethane coating to eliminate the pore pressure effect.
It is demonstrated that the numerical method developed in this investigation can well simulate the experimentally obtained load-displacement records under a wide range of confining pressure from a knowledge of the tension-softening law. Based on the result the tension-softening law is found to be independent material property. Furthermore, source mechanism for the pressure sensitive fractures of the granite is discussed by exaamining the growth behavior of the fracture process zone simulated using the numerical method.

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An iterative calculation method for quantitative analysis of solid-liquid two phase flows is presented based on the momentum equation of the solid phase, the liquid phase, and the mixture of the two. This method yields the momentum diffusion coefficients for the three phases, the specific interaction forces, the slip velocity between the liquid and the solid phase, and velocities of the liquid and the mixture phase.
Data necessary for the calculation are the velocity, the concentration distribution of the solid phase measured with a conductive probe, and the pressure loss gradient of solid-liquid flows.
The results f the calculation supply a quantitative means of calculation of the iteraction between dispersed particles and a carrier liquid.

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A drilling model which consists of drill-body, piston, rod and bit is presented. The model is based on onedimensional stress-wave theory for piston, rod and bit. A force/penetration relationship with hysteresis is assumed for bit/rock interaction. A computer program based on the model is also developed which allows continuous simulation of drilling, that is, not restricted to just one blow.
The simulation for a heavy drifter is carried out to test the proposed model. The calculated results of piston displacement, force applied to piston, stress-wave in rod, force applied to rock etc. are presented and discussed. displacement, force applied to piston, stress-wave in rod, force applied to rock etc. are presented and discussed.
It can be said that the calculated resultsare reasonable and the model is able to use in research and development of rock drills. However, two points are still open to discussion: 1) bit/rock interaction and 2) attenuation of stress-wave in piston, rod and bit.

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Critical coagulation concentration (C.C.) of cations and anions was determined using monodispersed spherical hematite hydrosols (Metijevic colloids) having a median diameter of 0.13μm. Anions used tested were NO₃^-and SO₄^2-, each being as potassium salt, and tested at an acidic pH (3.3) where hematite particles were positively charged and cations used were K⁺, Ba²⁺, and La³⁺, each being as nitrate, and tested at an alkaline pH (10.4) where hematite particles were negatively charged. In both cases of acidic and alkaline solutions, the C.C. decreased with increasing valence of counterions in accordance with the Schulze-Hardy rule.
Concurrent measurements of zeta potential were carried out and the double-layer interaction energy, V_R, between particles was calculated at the C.C. The van der Waals energy of interaction, V_A, was calculated for various values of the Hamaker constant. An appropriate value of the Hamaker constant of hematite embedded in aqueous media was evaluated on the basis of the DLVO theory in such a way that the energy barrier height in the total interaction energy curve (V_R+V_A) becomes zero. The Hamaker constant obtained with NO₃^-was found to be 4.0×10^-13erg in agreement with a literature value (4.5×10^-13erg) evaluated on the basis of the dispersion component of surface tension. The less value (1.6×10^-13erg) was obtained with K⁺. The Hamaker constant increased with the increase of the valence of counterions in both cases of cations and anions.

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Separation of fine quartz (-10μm) from a mixed suspension (1: 1 by weight) with fine hematite (-10μm) was investigated using a Denver-type laboratory flotation machine (250ml capacity). The collector used was dodecyltrimethylammonium bromide which is characterized by its complete dissociation at all tested pH conditions. The results are summarized as follows:
1) At acidic condition pH=5, where quartz is negatively charged and hematite is positively charged, it was difficult to separate quartz because its floatability was significantly depressed in the presence of hematite fines. This was probably due to the heterocoagulation between the mineral particles.
2) At alkaline condition pH=10, where both minerals are negatively charged, selective flotation of quartz was also difficult because of concurrent flotation of hematite, as in the case where dodecylamine acetate (DAA) was used as a collector.
3) Fairly good results were obtained at pH 7-8, where quartz carries a relatively large number of negative charges and hematite carries a moderate number of negative charges. The case where both quartz and hematite carry negative charges provides the condition under which the heterocoagulation between the mineral particles is prevented. Where quartz carries more negative charges than hematite, the condition is set under which the adsorption of dodecylammonium cations in excess amounts onto hematite surfaces is avoided, thus preventing the concurrent flotation of hematite.
4) The principle stated above is also applicable to the case where DDA was used. Better separation results were obtained at pH 7.2 than at pH 10.

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The phase diagrams for the binary systems LiCl-NbCl₅and KCl-NbCl₅, and the ternary system LiCl-KCl-NbCl₅have been determined because of interest in molten salt electrolysis of niobium from its chlorides, by means of thermal analysis, visual observation and X-ray analysis.
LiCl-NbCl₅system has one incongruently melting compound LiNbCl₆, which is stable at the temperature range from 206°Cto 257°C.
KCl-NbCl₅system has one congruently melting compound KNbCl₆, the melting point of which is 398°. KCl and KNbCl₆form an eutectic at NbCl₅47.5mol%, 368°. There is a two-liquid region in the composition range from NbCl₅, 60mol% to NbCl₅, 100mol%.
LiCl-KCl-NbCl₅system has two miscibility regions in the composition ranges less than NbCl₅50mol% and more than NbCl₅60mol%, respectively. The former two-liquid region forms an island curve. This island curve can be explained by the high negative deviation of LiCl-KCl system and the positive deviations of both LiCl-NbCl₅and KCl-KNbCl₆systems.

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An application of the alkaline hydrothermal process to the extraction of rare earth elements from complex ores was studied. A typical rare earth ore, bastnaesite, was reacted with NaOH solution under a high temperature and pressure to produce a mixture of rare earth hydroxides. The recovery of rare earth elements was measured as a function of temperature (373-723K) and NaOH concentration (1-5 mol/l). The results obtained were as follows;
1. The optimum conditions for this process were 523-573K and 4-5 mol/l NaOH.
2. Fluorine and silica in the are where extracted into the alkaline solution.
3. The recovery of rare earth was decreased when the temperature exceeded 573K, which was assumed to be caused by the formation of cerium and praseodymium oxides.

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