The concrete plug must be strong enough to support the hydrostatic pressure of mine water to seal the pit mouth of abandoned mines. In previous report, the test result of model plugs which were installed in hard rock was reported, and suggested that the conical plug is strong enough to support the pressure. In this report, the result of elastic F.E.M. analysis using the elastic constants obtained in previous report is reported. Furthermore, test results of model plugs installed in soft rock are reported. In order to explain these test results, elasto-plastic F.E.M. analysis considering tensile crack are performed.
The results of analysis obtained are as follows;
1. A remarkable tensile stress concentration is generated at the corner part of the rear end face of the plug.
2. Caused by this stress concentration, tensile crack is initiated and propagates to the free surface of rock, forming a conical fracture surface.
3. In the case of permitting the pressurized fluid to intrude along this fracture surface (experimental condition of previous report), stress field varies extremely, and elastic analysis become no more adequate to explain the fracture of the plug.
4. In the case of inhibiting the intrusion (experimental condition of this report), the formation of conical fracture conspicuously reduces the supportability of rock to the pressure.
5. Thus, the plug must be designed to reduce this stress concentration. One example of plug shape which can reduce stress concentration is also shown.

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This paper shows the mechanism of fracture formation of a granite caused by thermal stress in the case of applying the impulsive CO₂ laser beam to its surface.
The equation for heat conduction in solid according with the conditions of the laser beam irradiation is solved, and the temperature distribution in the rock for each time elapsed is calculated by making use of its thermal properties in various temperature surroundings by employing the laser flush method.
Applying the temperature distribution to the common axi-symmetric finite element method, the thermal stresses in the rock can be obtained.In this process for setting up external forces of the nodal points the ‘thermal’ Young's modulus is used instead of conventional Young's modulus.
Appropriateness of above temperature calculation is confirmed experimentally by two ways.One is to observe the distribution of the surface temperature by infra-red ray TV camera, and the other is to measure the surface displacement perpendicular to it by He-Ne laser holography.
The simulation is made for the fracture propagation with time elapsed.The Griffith theory is adopted for the evaluation of fracturing in each element mesh in FEM.
In this simulation it has become clear that the greater part of the fractured elements occurs at tensile stress region, and the fractured region caused only by the thermal stress is limited.

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In order to predict the temperature of ventilation air in mines it is essential to calculate accurately the temperature distribution in rocks around a roadway and the heat flow into the air current. Many authors have considered the problem of unsteady heat conduction., However, in previous studies many assumptions were made to simplify the problem, and some of the assumptions have never been discussed quantitatively. Consequently, there are uncertainties about the validity of these assumptions.
In this point of view, the authors examined the following assumptions by means of finite difference method, forcusing on the problem in coal mines;
(a) circular roadway
(b) isotropic rock, and
(c) homogeneous rock.
Examination of these assumptions leads to the following conclusions;
(a) To a good approximation the total heat flow is the same as that for a circular roadway having the hydraulic diameter of the actual roadway.
(b) The anisotropy of coals and shales are not negligible. However, a good approximation is obtained by calculating the heat flow for a roadway driven in isotropic rock whose thermal conductivity is the geometric mean of the thermal conductivities parallel and vertical to the bedding plane.
(c) When a roadway is driven into the coal seam, the coal seam has a great effect upon the temperature distribution in rocks and the total heat flow. In the present paper a method is proposed for modifying the equation for prediction of air current temperature to take into consideration the effect of the coal seam.

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In this paper a one-dimensional fully established annular flow analysis on a drag coefficient could be developed and compared with the results of the boundary layer theory as described in the previous paper and with experimental results for various factors of capsules which were freely suspended in a vertical tube with water.
The drag coefficient could be shown as follows:
_??_
l;length/diameter ratio of capsule
R_e;Reynolds number U_m d/v
Um;superficial mean flow veiocity to freely-Suspended capsule
v;kinematic viscosity of the fluld
d;capsule/pipe diameter ratio
ddiameter of capsule
It was apparent that the drag coefficient charagteristics curve obtained from the above equatlon could be apPilcable for the range of characteristics number l/(1/d-1) ²R_e<0.01.

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Three kinds of surface active agents as collectors for bubble separation were synthesized by malonic ester synthesis. They are di-sodium lauryl malonic acids, di-sodium hexadecyl malonic acid, and di-sodium stearyl malonic acid.
Generally, micelles are formed in a concentrated surface active agent aqueous solution. Although, it is said that micelles decrease collectabilities of collectors (surface active agents). Electro conductivities and CMC_s of the synthetic surface active agents were measured at 20°C in a constant temperature bath. These measurements were continued on same solutions for one week. One week later, the most concentrated solution of them were diluted into various concentrations. Then electro conductivities and CMC_s were measured. These values of fresh, of aging, and. of old solutions were not different. It is thought that micelles of these synthetic agents are dispersed quickly in dilute solution below CMC and that micelles do not disturb collectabilities of agents.
By using these synthetic surface active agents, bubble separation experiments were performed on heavy metal ions, cadmium, zinc, lead and nickel. Definite removal results were gotten by using of these synthesized agents respectively; LMD removed cadmium, zinc and nickel, HMD removed zinc, lead and nickel, and SMD removed zinc, lead and nickel effectively.
A simple bubble separation apparatus and a Kyodai flotation machine were used for the experiments. Better separation effects were shown by the Kyodai flotation machine than by the bubble separation apparatus.

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Precipitation of molybdic acid from aqueous molybdate solutions with the addition of hydrochloric acid was investigated through the solubility measurements of molybdic acid in hydrochloric acid solutions and the precipitation experiments of molybdic acid from artificial aqueous molybdate solutions.
The solubility of molybdic acid in an aqueous hydrochloric acid solution is greatly increased with the increase in the concentration of hydrochloric acid in the range of 0.01-3mol/l. A small increase in the solubility of molybdic acid with temperature elevation was observed. Solubility of molybdic acid in a hydrochloricacid solution containing sodium chloride or ammonium chloride decreases to some extent.
The precipitation of molybdic acid from artificial aqueous molybdate solutions is sometimes greatly influenced by the presence of certain electrolytes. Particularly, the presence of sulphates or the co-existence of sulphates and sodium chloride causes the decrease in molybdic acid precipitation. Because of the sensitive response of the molybdic acid precipitation to the concentration of hydrochloric acid, the careful control of acid addition is important to achieve a better precipitation.

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Activities of liquid Pb-Sb and Sn-Sb alloys have been determined between 700°C and 900°C by means of the cell (I) and (II), and especially, the cell (III) was used for liquid Sn-Sb alloys in the temperature range of 950°C to 1100°C.
Pb (l) |PbCl₂-NaCl-KCl (l) |Pb-Sb (l)(I)
Sn (l) |SnCl₂- NaCl- KCl (l) | Sn-Sb (l)(II)
Sn (l) |SnO -SiO₂ (1) SiO₂ (s)|Sn-Sb (l)(III) The obtained results are summarized as follows
(1) The activities of both systems exhibited negative deviations from the ideal behavior, and inPb-Sb system, the activities varied very little with the temperature changes, but in Sn-Sb system, it was shown clearly that activities came near to the ideal behavior with the rise of temperature.
(2) Both systems did not show the lregular solution behavior.
(3) In Sn-Sb system, the extrapolated values at 900°C from the observed activities at the temperature range of 950°C to 1100°C by the Cell (III) Were in good agreement with the activities measured at 900°C by the cell (II).
(4) From the thermodynamic considerations based on the obtained activities of Sn-Sb system, it is disclosed that the vaponzatlon process would not be hopeful for removal of Sbcontained as an impurlty in crude tin.

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