The Goyomatsu magnetite skarn deposit consists of large and small irregular massive bodies interlayered in upper Chichibu formations (limestone, sandstone, slate etc.), which have been metamorphosed by Miocene Omine acidic rocks (granodiorite).
On the basis of mineralogic observations and thermodynamic data, the principal conditions of formation of the skarns have been determined. Results are as follows:
1) Field evidence reveals that in the deposit hedenbergite is predominant in and near the granodiorite, and andradite is predominant in and near the limestone. This contrasting occurrence appears to show that the μO₂ in the limestone gradually increased away from the granodiorite-limestone contact, assuming these skarns were formed at nearly the same stage.
2) Generally, andradite rarely coexists with actinolite in skarns. This field evidence iswell in agreement with thermodynamic data, which shows that the andradite+actinolite phase cannot be a stable assemblage at constant temperature and pressure asseen in Fig. 3.
3) Fig. 3 suggests that in general, under constant μCO₂ conditions, the following mineral zonation formed with increasing μO₂: zones of hedenbergite+actinolite, hedenbergite+andradite, and andradite, respectively. However primary assemblages of hedenbergite+actinolite havenot been observed. On this point, we need more detailed examinations.
4) It is also found that in the skarns, hedenbergite has sometimes altered into aggregates of actinolite, calcite and quartz. Assuming constant temperature and pressure it can be interpreted that such alteration was caused by an increase in μCO₂ at low μO₂ environments.

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Thermal fracturing is one of the effective method for drilling and cutting the hard crystalline rocks. As for the thermal piercing rate, many workers proposed the theoretical, empirical and experimental equations. But these equations were derived in neglecting many actual conditions relating to thermal fracture process.
Based on the measured thermal and kinematic characteristics of jet flame impinging onto the flat plane, the thermal piercing rate of INADA granite was calculated by simulation and this calculation coincided closely with the experimental results. In the simulation the following conditions were considered;
i) temperature-dependence of rock properties,
ii) residual temperature in the rocks,
iii) size distribution of debris.
By the same method of simulation estimating thermal piercing rate, the procedure for calculating the thermal cutting depth was considered. This study makes it possible to forecast thermal piercing and cutting rate, if the properties of the rocks are known.

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Fracture mechanics solutions for hydraulic fracturing under confining pressure σ∞ are studied. Elastic problem of two symmetric cracks emanating from a hole in a plate is solved by utilizing Nishitani's method, under the assumption that the pressure along the crack is induced due to the steady-flow intrusion of fluid into the crack.
Attension is payed on the precise analysis of the crack opening process of closed cracks prior to the crack propagation, by adopting step-by-step procedure. Results are given both for the behaviors of long cracks (hydraulic fractures) when repressurized and for the behaviors of short cracks (pre-existing cracks) in terms of fracture initiation.
These findings for long cracks are (see Figs. 3 through 5);
1) Crack opening begins when the injection pressure reaches to 2σ∞. And the injection pressure achieves its maximum vaiue in the process of crack opening, that is, larger pressure is required to open the crack than to extend it, under the relatively high confining pressure condition.
2) The injection pressure at the final stage of crack opening, as well as the pressure at the onset of crack growth, approaches to σ∞ as a crack length increases.
And for short cracks are;
3) Maximuminjection pressure is always attained at the onset of unstable crack growth (seeFig. 6).
4) Fracture criterion curve, where the crack extension pressure is plotted as a function of the confining pressure, is obtained for five different flow rates. For infinitely large flow rate, the curve is given by the line of slope 2, while for null flow rate, by the line of slope 1. For moderate flow rates, bi-linear curves are obtained which lie in a range bounded by the two limiting lines (see Fig. 7).

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The fracturing fluid pressure to make the artificial reservior in hot dry rock has been studied. Hydraulic fracturing experiments are carried out for the triaxial loaded cylindrical specimen with outer diameter of 60mm, bore hole diameter of 4mm and length of 30, 60 and 90mm by applying pressure in bore hole. And the Brazilian tests with diameter of 60mm and length of 30mm are conducted under triaxial condition, too. Rock specimens used are Kofu andesite, Emochi andesite and Inada granite.
A summary of the results is shown below.
(1) The relations between the breakdown pressure and the confining pressure are obtained for both permeable and impermeable conditions of the fracturing fluid. As is shown in Fig. 4-6, the experimental results agreed with the theoretical ones.
(2) The breakdown pressure for permeable condition is about two-thirds as that for impermeable condition, as is evident from Fig. 4-5 and Fig. 12-13.
(3) The hydraulic fracturing results for the boring core of Yakedake geothermal zone are shown in Fig. 7 and Table 1. The breakdown pressure is more influenced by the confining pressure rather than the physical properties of rock.
(4) As is shown in Fig. 8-13, the breakdown pressure by hydraulic fracturing can be estimated from the failurel oad by Brazilian test under triaxial condition.

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A seismic method is one of tools to survey the state of the strata, and it is effective in especial to monitor the unstable rock failure caused by the change of stress and strain energy. From this point of view the field investigation has been carried out using the seismic method over eight years at four coal mines in Hokkaido. The investigation confirmed that the seismic method might be useful to examine the state of rock failures around underground excavations even if the measuring system was composed of primitive devices and an analogue recorder. But on the other hand it was realized that prompt and precise analysis of a large number of seismic events might be impossible unless an analogue measuring system was replaced by a computer system.
In 1976 the computer system was installed, whose main part was occupied by a 32-K words mini-computer. After the development of softwares for processing and analysing seismic data the system has been applied to a field investigation. In the present paper the measuring system including softwares will be described in detail.

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Experiments were made to estimate the loads acting on the steel arch support by means of the acoustic emission (AE) technique. By the bending test of the I-steel for arch support, the following results were obtained:
1) The impulsive AE signals of the I-steel began to generate from the level of half of its yielding stress and the AE activity became at a high degree during the process of its yielding. The AE activity of the I-steel formed into an arch at an ordinary temperature was very low. But the laggings on the steel arch displayed the high AE activity under a low load by the friction between laggings and steel or their collapse.
2) In the bending test, it was able to estimate the stress history of I-steel by Kaiser's effect and to locate the sources of acoustic emissions. But it was difficult to estimate the stress history of the I-steel used in mine arch supports, because its AE activity was degenerated due to the bending in the formation of an arch and the noises of the dispersal of rusts from the surface of the specimen were generated.
3) The yielding stress of the I-steel formed into an arch at an ordinary temperature decreased to nearly half of that of the original straight I-steel due to Bauschinger's effect.
4) By normalization the formed I-steel recovered nearly 90% of the original yielding stress and the AE activity slightly.
It will be able to estimate the direction of the load acting on the steel arch by the source location of AE generated between laggings and steel arch. And the I-steel formed into an arch at an ordinary temperature should be normalized.

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In this paper, the author described the crushing loadF_Hand the crushing coefficientκin the case that the rock is crushed.
The author presented the theoretical equation of the crushing loadF_Hby solving the mechanism of a single toggle jaw crusher.
The author carried out the crushing experiments of the cylindrical mortar blocks, the cylindrical concrete blocks and the various irreular rocks.
In these experiments, the author didn't only inquire the crushing loadF_Hof each sample, but also considered the relation between the crushing loadF_Hof each sample and the load p which was inquired by tne inner stress equation of each sample.
The principal results are shown below;
(1) In the case of a regular mortar block as a cylindrical shape and a homogeneous material, F_H/N·P=κis closely akin to 1, wnereNis tne number of the breaking sections. The value ofF_H/N·P=κis decided by the shape, the size and the material of the sample.pis generally found out by the radial compression intensityσ_x, the distance between two load pointsy, and the diameterdof the sample. In the case of using this crusher, if the diameter of each sample is only decided, yis usually obtained a constant value. So that, it seems thatF_His estimated by σ_xand d of the sample.
(2) In the case that the irregular rocks are crushed, the value ofF_H/N·P=κis influenced by not only the sort, the shape, the size and the number of cracks touching the rock, but also the rotary an le of the upper end at the movable jawθand the position at the teeth of the crusner touching the rock. But in the range of this experiment, namely, whenyof rock is in the range of from 90mm to 150mm, whenθof this crusher is in the range of from 250°to300°, and when this crusher is put in motion at the 316 r. p.m, κgenerally shows the constant value as showing in Table 2. So that, it seems that FH is estimated byσxandκ, of rocks.

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The equilibrium vapour pressure of the following reactions was measured, using the transpiration method.
As₂O₃(s) =1/2As₄O₆(g)
2Ag₃AsO₃(s) =6Ag (s) +1/2As₄O₆(g) +3/2O₂(g) 2FeAsO₃(s) =Fe₂O₃ (s) +1/2As₄O₆(g)
Both Ag₃AsO₃and FeAsO₃were prepared in a wet method by making a precipitate for each arsenite through the addition of metal ions to arsenite ions. The FeAsO₃obtained by the above method was found to hold the combined water, which can be removed by heating at 300°C. X-ray studies on the FeAsO₃indicated that the samples before and after heat treatment were all amorphous. The equilibrium constantKpof the above reactions in the innert gas flow can be estimated by measuring the equilibrium vapour pressure. The results obtained are as tollows.
As₂O₃;(180.2-275.0°C)
logKp(atm1/2) =4.302-2819.5/T
Ag₃AsO₃;(227.0-298.1°C)
logKp (atm1/2) =16.874-10.916×10³/T
FeAsO₃;(325.1-425.1°C)
logKp(atm1/2) =2.951-2794/T

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In order to clarify the reaction mechanism for the sulfatizing roasting between garnierite ores and jarosite in the mixture, the reaction between dehydrated garnierite and ferric sulfate in the absence or presence of alkaline sulfate was investigated. These reactions were studied under the atomospheric controlled heating condition by means of the techniques of differential thermal analysis and thermogravimetric analysis with the aid of X-ray diffraction analysis and infrared absorption spectra. Moreover, the thermal decomposition of magnesium sulfate formed at this time was studied kinetically.
Some of results obtained are as follows.
1) The reaction for dehydration and decomposition of garnierite ores seems to be as follows.
Me₃Si₂O₅(OH) ₄→2MeO+MeSi₂O₅+2H₂O↑
2) The maximum amount of MgO sulfated in garnierite ores in the absence of alkaline sulfate was approximately 60%, and this was agreed with the amount of amorphous oxide.
3) The sulfation of garnierite ores was promoted by the presence of potassium sulfate or sodium sulfate. Because not only amorphous oxide but also amorphous silicate was sulfated by the presence of alkaline sulfate. Accordingly, the jarosite is the most proper addition of the sulfatizing roasting of garnierite ores.
4) When the thermal decomposition of MgSO4 takes place in the presence of ferric oxide, it seems to be as follows.
MgSO₄+Fe₂0₃→MgO·Fe₂O₃+SO₃↑
In this experimental condition, the apparent activation energy of the above reaction is approximately 84.5kcal/mol, and the order of the reaction with respect to MgSO4 is about 0.7.

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