The mechanical characteristics for soft rocks are influenced by water. And the behaviors of clay minerals in soft rocks are one of primary factors on the influence of water. Well, it is known that the force acting between clay grains are changed by the kinds and concentration of pore fluid.
In this studies, by way of soft rocks, Ohya Tuff and Shirakawa Tuff are chosen, and the influence of NaCl concentration in its acqueous solution to mechanical characteristics and its mechanism are investigated.
The main results obtained in this studies are as follows;
(1) When NaCl concentration in its acqueous solution becomes dilute, longitudinal wave velocity and uniaxial compressive strength for Ohya Tuff and Shirakawa Tuff indicated the tendency of a decline.
(2) We considered that the tendency of the change of mechanical characteristics for soft rocks are the results of the change of the degree of union in soft rocks. That is to say, when the NaCl concentration in its acqueous solution in soft rocks changes, the force based on the repulsive force and attractive force between clay grains changes, and its force causes the change of the degree of union in soft rocks, and that's change of the degree of union in soft rocks influence the mechanical characteristics for the soft rocks.

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Sidewall softening technique is based on the transference of the high stress concentration further away from the roadway sides. This technique is accomplished by softening the parts of sidewalls of mine roadway by drilling holes, explosions or cutting slots into the sidewalls.
The effectiveness of sidewall softening in maintaining mine roadway is studied using finite element analyses and model tests. The results obtained in this study are as follows.
(1) Sidewall softening improves the stress states around mine roadway. But it must be noted that under certain geological or ground pressure conditions softening would produce the tensile stresses in the roof or floor of the roadway.
(2) Floor lift and side closure could be controlled effectively by sidewall softening, especially when the roadway has a weak fl oor.
(3) Good results of controlling floor lift could be obtained by softening the large parts of sidewalls.
(4) Main failures which occur in the vicinity of the top of softened parts are accompanied by large roof lowering without roof falls. So, in practice, one should take necessary steps to control the roof lowering.

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A simple heat balance equation was used to obtain the relation under the explosion limit condition. However, equations consequently obtained (Eqs.(8) and (9)) for fuel lean and rich sides, respectively, do not include important parameters such as particle size of coal dust and rock dust, and volatile content. Then the conditions that Eq.(8) must satisfy were introduced.
These are:
1) when the coal dust concentration is the lower explosion limit coal dust concentration, the rock dust mixed for suppressing explosions must be zero, that isR= 0 atC=C_L.
2) when the coal dust concentration is the apparent stoichiometric coal dust concentration, that is ca. 250 g/m³, the rock dust mixed for suppressing explosions must be the maximum, that is atC= C_st, R=Rm.
As a result Eqs.(14)-(17) were obtained. These equations were tested by comparing with the experimental data obtained by Ishihama and Cybulski, and a very good agreement was obtained as shown in Figs. 1 and 2, respectively. Eq.(18) can be used to estimate the lower explosion limit concentration of coal dust-rock dust mixture, in which the percentage of rock dust mixed isR.

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On the high mountain the partial pressure of oxygen becomes low in proportion to the atmospheric pressure with the altitude. It is important, therefore, for the health and safety of mine workers working in the underground mine to know the accurate and correct oxygen content in the environmental atmosphere. However, the availability of portable oxygenmeter on the high mountain, hitherto, has been hardly concerned about.
To make clear the availability of oxygenmeter on the high mountain, the indication accuracy of some galvanic cell type portable oxygenmeters under the low atmospheric pressure was studied in a low pressure testing apparatus which was made by way of trial for the purpose as well as on a high mountain of the 3000 meter class.
The tests in the laboratory and on the field revealed that the indication accuracy of oxygenmeters hithertofore in use were not enough for the use on high mountain and the main reason was found chiefly to be the inadequacy of membrane characteristics of galvanic cell used in the oxygenmeter.
The new oxygenmeter modified with an improved membrane works fairly good in the scope up to 5000m high and the indications coincide with the standard oxygen concentration calculated on each altitude.

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The purposes of this investigation are to measure the pipe pressure drop of fly ash slurry containing coarse particles and to measure the torque of a rotating cylinder in the packed coarse particles submerged with the fine slurry.
In order to make a comparison between flow pressure drop of the fly ash slurry and that of the fly ash slurry with coarse particles in pipes, some experiments were carried out in horizontal 2B and 4B pipe lines.
The result shows that under the same total volumetric concentration of solids the pressure drop decreases by adding coarse particles, especially at higher velocity and at higher conventration of coarse particles.
It is well known that some of fine particles as an additive to settling slurry bring the reduction of the pressure loss. Experimental results are also analyzed from this point of view.
The same result was obtained throughout the concentration of fly ash from 10 vol.% to 40 vol.% at low velocity, however, the most effective reduction of the pressure drop was achieved at lower fly ash concentration and at higher coarse particle concentration.
One the assumption that the reduction is due to the lubricant effect of fine particle, the torque of the rotating cylinder in the packed coarse particles mixed with fine slurry was measured.
The reduction of torque was very similar to the decrease of the pressure drop in pipes presented by several researchers.

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The writer, in this report, has discussed the improvements on the pelletizing property in oil agglomeration method of coal based on the reformation of the wettability of solid-liquid surface by surfactants.
As surfactant suitable for coal, especially low-rank coal, alkanol amide type one has been selected from various ones by the screening tests.
He has placed great importance on the affinity between the carboxyl functional group in brown coal and hydrophilic functional one of this type surfactant, namely alcohol OH.
Besides, as the pre-treatment method of O.A. one, he brought forward and discussed the usage of electrolyte in order to improve de-ash efficiency.

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The effect of particle size on the reverse flotation of quartz from hematite was examined in alkaline media (pH-10), where both quartz and hematite were negatively charged whereby neither heterocoagulation nor slime coating took place.
Results obtained are as follows.
1) In the case of coarse particles system (149-210μm for both quartz and hematite) fairly good separation of quartz was obtained.
2) Reverse flotation of quartz became difficult (both recovery and grade of quartz decrease) with decreasing the particle size: For intermediate particles system (44-53μm) the flotation results were tolerable, but for fine particles system (-10μm) no satisfactory results were obtained because of the concurrent flotation of hematite, though the recovery of quartz was improved as compared to that in acidic media.
3) In the system consisting of coarse quartz and fine hematite, no reverse flotation of quartz was achieved, which may be due to the lack of collector (DAA) concentration for quartz'flotation as a result of adsorption of DAA onto surfaces of hematite fine particles.
4) With the system consisting of fine quartz and coarse hematite no difficulty existed with the reverse flotation of quartz.

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In order to make clear the mechanism of liberation of NiO from garnierite are by means of the adding iron steam roasting, high temperature solid reactions have been investigated with the coupling of Mg-Ni olivine and FeO and the coupling of garnierite are and iron powder. Moreover, the reactions were examined by means of X-ray diffraction and chemical analysis, and the mechanism was discussed kinetically. The results obtained are as follows.
(1) A large quantity of NiO were detected at the contacting surface of Mg-Ni olivine and FeO and that of garnierite are and iron powder. Ni rich points were found everywhere in the reaction layer, and the concentration of Mg and Si decreased remarkably at these points.
(2). X-ray diffraction peak of (222) plane of olivine in the roasted ores shifted from Mg₂SiO₄side to Fe₂SiO₄side with increasing the roasting temperature. This phenomenon seems to be due to increase of mol fraction of Fe2SiO4 in olivine.
(3) The reaction of liberation of NiO from garnierite are by means of the adding iron steam roasting seems to be expressed as follows.
(Mg_1-xNi_x) ₂Siat+2x FeO→(Mg_1-xFex)₂SiO₄+2x NiO
The selective extraction of nickel seems to become possible, because Mg and Fe in olivine are insoluble and free NiO is soluble in the dilute sulfuric acid.

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