The amplitude of the_free surface displacement due to plane SH waves incident were studied by means of HASKELL's layer matrices.Numerical computations were at first applied to a single layeredmodel and also carried out in the case of multilayered model.
From the results of the single layered case, it is shown that the amplitude at free surface is markedly affected by the thickness of upper layer and the impedance ratio of media. When the superficial stratum consists of more than two layers, the variationin amplitude of surface displacements in general becomes more complex. Especially from the results of five layered case, it is shown that the surface amplitude mainly depends upon the change of the thickness of first layer. A computer program is written to calculate the surface amplitude as a function of solid viscosity.

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In this paper, the failure process of the rock in compression issimulated in the electronic digital computer from the standpointof linear Fracture Mechanics.
Under compression, pre-existingcracks would be closed to allow normal and frictional stresses transmitted across the cracks and fracture cracks do not propagate in the direction of the pre-existing cracks. To take these characteristics into account, stress intensity factor is expressed in terms of the effective shear stress and Nuismer's hypothesis is adopted as the criterion of onset of propagation of fracture cracks.
Based on the above assumptions, the correlation between fracture propagation and stress-strain diagram of various rock types is simulated, and the number of fracture propagation of unstable type is accumulated which is considered as a model of acoustic emission.

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In the present paper, correlation coefficients between the numbers of outbursts which occurred in various collieries in IshikariCoal Field, Hokkaido, Japan from 1926 to 1970 and 13 types of geological characteristic values of each colliery are shown. According to the consideration of calculated correlation coefficients, it was confirmed that all characteristics which are of geological complex structure have a high correlation with the frequencyof outburst incidence.
Next blasting experiments were made ona small scale to study the back effect of blasting which is considered one of the important causes of outburst incidence. In theexperiments, the blasting conditions were selected to simulate asite where the geological structure has a crossed and complicated formation, with a fragile and weak coal seam located at the back of the charged hole tip.
As a result of the experiment, weobtained quantitative relations between the charged explosive volume and back effect and also between the charge hole length andback effect.
For example, when the charged explosive volume (L) and the length of charged hole (l) are increasedrespectively, the expansion rate of back material (η) which is one of the important measurement of the back effect was observed to increase in proportion to L ^0.35-0.4 and l^1.9-2.4
We are of the opinion that thesefacts indicate qualitatively that both over-charging and long length hole blasting may give rise to gas outburst at coal mines.

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In part 1, the traction distribution between the wedge and elastic body was determined using the photoelastic method. In this paper, as the tangential traction component is due to the frictionbetween the wedge and rock, the coefficient of friction was measured to apply the result obtained in part 1 to the penetration of the wedge into rock. The stress distribution in rock was calculated by the finite element method using the traction distribution obtained and the shear fracture path is assumed. And as the rock around the tip of the wedge is crushed and is in triaxial compression state, the plasticity analysis was applied.
These theoretical prediction is agreed well with the experimental results of the penetration of the wedge into rocks such as andesite, sandy tuff and marble.

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Activation of galena with copper ions and floatability of the copper-activated galena in the presence of sulfite have been investigated by means of adsorption measurements and floatation tests, in order to elucidate the floatation behavior of galena in black ore.
The results obtained are as follows:
Activation ofgalena with copper ions proceeds according to the following exc ange reaction, PbS+ Cu²⁺= CuS +Pb²⁺which is controlled by the parabolic rate law.
Copper activation leads to an increase of the galena floatability, which may be caused not by an increase of the uptake of collector, but by an increase of the native floatability of galena.
Copper activated galena is not so easily depressed by sulfite ion as unactivated one, and the large amount of sulfite is required for it s depression.
In galena-sphalerite mixture suspension, copper ion is abstracted by galena in preference to sphalerite, but the floatability of sphalerite remarkably increases with copper activation and galena cannot be separated by depressing sphalerite with sodium bisulfite.
In this case, galena can be floated from sphalerite by depressing the latter with sodium bisulfite together with zinc sulfate after a suitable extent of copper activation.

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The arsenic problem in nonferrous smelters should be solved as soon as possible. The present work was undertaken from the view point of hydrometallurgical treatment of by-products containing arsenic. It is well-known that the coprecipitation with ferric hydroxide is the most economical method of separating arsenic from aqueous solution. We found that arsenic in solution should be the pentavalent arsenic species for removing arsenic completely from solution over the wide range of pH by the ferric hydroxide coprecipitation. Accordingly, the oxidation of arsenite to arsenate by oxygen, hydrogen peroxide and ozone has been investigated. The results obtained are as follows:
1) The concentration of arsenic in the solution after coprecipitation is considerably reduced over the wide range of pH with increasing the relative amount of Fe (III) added to As (V). Atthe Fe (III) to As (V) molar ratio of 2, the concentration of arsenic in the solution was less than 0.3mg/lover the pH range of 3.1 to 5.0. At the Fe (III) to As (V) molar ratio of 5, the pH range over which the concentration of arsenic in the solution was less than 0.3mg/lwas 3.1 to 7.7.
2) Oxygen is not useful as an oxidizing agent for arsenite. Arsenite was oxidized to arsenate by oxygen only when cupric ion was present at high pH (11.2).
3) Arsenite is effectively oxidized to arsenate by hydrogen peroxide (H₂O₂/A_s (III) molar ratio=2) in ammoniacal solutions (pH>9.3), but the-oxidation was slowed down with a decrease in pH, because hydrogen ion liberated with the progress of the oxidation reaction. Therefore an addition of some buffers is effective in the oxidation of arsenite. The oxidation is accelerated with increasing temperature. At 80°C, arsenite was completely oxidized to arsenate even at low pH (3.0).
4) Ozone is an effective oxidizing agent. Arsenite was oxidized rapidly and completely to arsenate by ozone over the wide pH range of 1.0 to 11.0. The oxidation reaction was little affected by pH, temperature and the cupric ion presence.

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