In the previous paper, the authors proposed the method, so-called compact shear test, for determining ModeII fracture toughness of rocks.
In this study, the compact shear tests are conducted under confining pressure in order to evaluate theeffect of confining pressure on the Mode II fracture toughness for six kinds of rocks, i. e., Kimachi sandstone, Ogino tuff, Emochi welded tuff, Inada granite, Akiyoshi marble and Tohoku marble. The specimen is 110mm wide, 60mm high and 30mm thickwith two 20mm pre-cracks as shown in Fig. 1.
K_IIC of the various rocks are found to increase with confining pressure. For example, the ratios of K_IIC under the confining pressure of 240kg/cm² to that under atmosphere are 3.4 for Kimachi sandstone, 4.1 for Ogino tuff, 2.3 forboth Emochi welded tuff and Inada granite, 2.8 for Akiyoshi marble, and 2.5 for Tohoku marble. For each confiningpressure, a consistent relationship is found between secant Young's moduli and K_IIC of the rocks employed as shown in Fig. 8.
Although the ratio of Mode II fracture toughness obtained in this study to Mode I fracture toughnessevaluated with the splitting testing method is about 1.1 at atmospheric pressure, this ratio (K_IIC/K_IC) increases more orless with confining pressure for four examined rocks as shown in Fig. 9. This shows that Mode II fracture toughness is more affected bythe confining pressure than Mode I fracture toughness.

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The pressure of shock wave measured and calculated from its velocity is able to be estimated as described in former report.
And also, temperature (T₅) at the end of shock tube can be calculated using pressure ratio P₂₁ in the following equation.
T₂₁=T₅/T₁=[(2+α₁) P₂₁-1](α₁-1+2P₂₁)/(1+α₁P₂₁)(α₁+1)
where P₂₁=P₂/P₁, α₁=(γ₁+1)/(γ₁-1) and P₁, T₁ areinitial pressure and temperature.
The studies described in this paper is the investigation of ignition of methane-air mixture by shock wave using the shock tube apparatus.
Reaction between methane and oxygen is considered to advance rapidly, when concentration of methyl group ([CH₃]) exceeds a certain threshold value. The time elapsed before reaching to the threshold is called a delay time (γ) for ignition. And, in the experiment, practically ignition is recognized by ascending of pressure and flames sensed by a photo cell.
Experimental conditions that are set up are as follows;
(1)Velocity of shock waves: 2.3 Mach-3.1 Mach
(2) Concentration of CH₄ in the air: 3.5-20%
(3)Ignition will be appeared only at the neighborhood of end of shock tube, wherethe shock waves are reflected back and turn their propagation direction.
Results obtained from the experiments are
(1) Ignitions of CH4-air mixture are sometimes yielded by shock waves
(2) When the gas mixture is ignited, the delay time from excitation to ignition is usually between 0.3 and 1.0 milli-seconds, and ignition temperature is assumed also 1, 100 and 2, 000K.
(3) I gnition will be produced by adiabatic compression of gas mixture.

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The development of the blind raise boring machine was a joint undertaking by the Dowa mining Co. Ltd. and the Koken boring machine Co. Ltd. The first machine was introduced into Matsumine mine in 1976 and more than 30 raises were completed until the end of 1981. Basically the unit consists of a boring machine and a segment erection component. The segments of the shield frame are installed and jacked upward immediately after each boring cycle is over to keep the wall stable. Boring capacity of this machine was limited to 30m, and within this limit drill rods are strong enough with only one stabilizer located just beneath the cutter head.
This study was started to improve the boring capacity up to the depth of 60m. First of all, the data was collected in-situ, such as thrust, torque and horizontal load to the stabilizer. The theoretical examination on the basis of the in-situ measurement indicates that an additional stabilizer is necessary to prevent the buckling of the drill rod.
After the comprehensive study including experimental work by a 1/40-scale model rig to certify the safety of the new system, two test borings, where upper and middle stabilizers were used, were carried out to complete 39 and 43m raises. Though the depth of 43m is a new record for this machine, high increase rate of segment jacking force encountered at the depth more than 30m is a new source of trouble remained for future research.

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Through analysis of the data obtained from the plant test in the Kamioka-Shikama concentrator, which includes a 2, 700mm dia.×3, 600mm length rod mill and a 3, 900mm dia.×5, 700mm length ball mill in a closed circuit with 2 or 3 hydrocyclones of 600mm in diameter, a comminution mathematical model has been deduced from making use of a selection function under the assumption of plug flow material transport. ln the rod mill, the said selection function “s (x) =Kx” is 1.871×10^-4x^0.7151 (s^-1) and that in the ball mill is 1, 179×10^-5x^0.9891 (s^-1).
As a cyclone classification-model, the logarithmic cumulative normal distribution function has been found to give a best fit to the true partition curve. Several regression equations for the prediction of the fraction of water β, separation size D₅₀, and the sharpness of σ separation a have been made up as the functions of the feed to the cyclone. Combining the mill models with those regression classification models, many simulations have been carried out to find out the most accurate cyclone model to be applied for simulating the real operation.
Making use of the optimum models, the comminution in the mills and classification in the cyclones have been simulated in a wide range of operating conditions to obtain information on the conditions of the plant. The results of the simulations indicate that it is possible to gain higher throughput in the mill-cyclone circuit without changing the characteristics of the cyclone overflow (i. e. the feed to the flotation circuit).

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Effects of sulfuric acid, thiourea, ferric ions, leaching time, and temperature on the extraction of gold and silver from ground carbonate are were investigated.
The sulfuric acid concentration did not seem to have a substantial influence on the extraction, except at the early stage, as long as the amount of sulfuric acid was a little more than the equivalent amount of calcium carbonate in the ore. The effect of thiourea was unambiguous and the extraction of both gold and silver was enhanced with the increasing addition of thiourea, and it was considered that concentrations of more than 1% thiourea would be necessary for efficiently extracting more than 90% of gold and more than 80% of silver. The effect of ferric ions was similar to that of thiourea, though it was suspected that at higher concentrations of ferric ions, thiourea might be deteriorated through a reaction with ferric ions to form complex ions When the leaching solutions contained 1.0% thiourea, 0.3% ferric ions, and 1.0% sulfuric acid, the extraction of silver gradually increased, while that of gold gradually decreased, after having reached a maximum of more than 98% at 5h of leaching, withth e prolonged leaching time. The effect of temperature was also apparent and activation energies of the dissolution of gold and silver were calculated from their dissolution curves at 10° and 28°C.
From the obtained activation energies it was considered that, at the beginning of the leaching, the dissolution of the both metals was controlled by the diffusion of thiourea, ferric ions, or sulfuric acid in are particles, but chemical reaction-controlled processes might become predominant after 40% extraction had been attained for gold and 20% extraction for silver, respectively, probably because of the slight passivation of metal particle surfaces in the ore.

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For better understanding of the semiconducting properties of particulate minerals, thermoelectric power (α) of 4 samples of sulfideare and 12 samples of flotation products supplied from the Hanaoka mine were measured. It was found that 2 samples of yelloware and one of blackare were n-type semiconductors. Only one sample of yelloware showed p-type behaviour. It was only possible to measure 4 of the 12 flotation samples; of these, 3 concentrates (Cu-Pb, Pb, and Py) were p-type semiconductors and one concentrate (Cu) was n-type. The other 8 samples had too high a resistance to measure.
At a later date (Jan. 1983) a further 10 samples of each concentrate were obtained. Cu-Pb and Cu concentrates showed large variations in α 50-150 and 80-180μV/deg, respectively.
It was found that, except for a few samples, measured values followed the relation.
α=±E_α/2eT
where E_α, e, and T are the activation energy for α, the charge of an electron, and absolute temperature, respectively. The electric conductivity was also measured'as a function of temperature. When E_α was less than 0.1eV, there was a linear correlation between the activation energies for the thermoelectric power and conductivity. A negative correlation between α and the copper content was found for the Pb concentrate, i. e., α=180 and 100μV/deg for Cu concentrations of 0.15 and 0.18 mol fraction, respectively.

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When the intermediate products such as dust, dross and slime formed in smelting process are melted in a reduction furnace to recover lead, the speiss is often formed because of a presence ofarsenic, and it equilibrates with metallic lead phase in molten state. To clarify the behavior of speiss in the process, the distribution of gold between molten speiss and lead in Pb-Fe-As, Pb-Cu-As and Pb-Fe-Cu-As systems has been determined at 1200°C, following the preceding papers on the miscibility gap and the distribution of silver.
In Pb-Fe-As ternary system, the values between 0.2 and 0.3 were obtained for the distribution ratio of gold, L^sp/Pb_Au defined by [wt%Au in speiss/wt%Au in lead], in the composition range of 25-50 wt%As in speiss phase. In Pb-Cu-As system, gold distributes 3 or 4 times in the speiss phase more than in the lead phase. In quarternary system which is added copper to Pb-Fe-As system, the distribution ratio of gold increases and approaches that of Pb-Cu-As ternary system with increasing copper content in the speiss phase. From the behavior of the distribution ratio of gold and the analysis of speissby EPMA, it is supposed that copper takes part in the dissolution of gold in the spiess.
For the purpose of recovery of precious metals dissolved in the speiss, it is considered that the speiss ismelted with the lead which is free from impurities, then the precious metals dissolve into lead from the speiss phase and those can be recovered in the refining process of lead. The recovery of silver and gold by this method is able to estimate by using the experimental results on the distribution ratio and the miscibility gap. The results of check tests were found to be in good agreement with the estimated values for both silver and gold.

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