A crack-detector has been developed for measuring the -distribution of open cracks and the change sonic velocity in rockmasses, and in-site measurements have been performed with it. This paper describes the in-site measurements at three site.
The results obtained in this study are as follows;
1) At I tunnel, the distribution of cracks and the sonic velocity in a borehole were measured by the crack-detector. Thedistribution of cracks at the inner surface of the same borehole was observed with a borehole television camera. Theresults of undetectable area by the crack-detector were found in good agreement with open cracks obtained by theborehole television camera.
2) At H quarry, Lugeon's tests and the measurements by the crack-detector were done in a borehole before and afterthe grouting to estimate the effect of the grouting operation. From the Lugeon's tests, the grouting operation hadlittle effect on filling the cracks. On the other hand, the position of the imcomplete filling-open crack was found withthe crack-detector.
3) In order to comfirm what part of a retaining wall was damaged by an earthquake, the distribution of open cracks andthe change of sonic velocity were measured by the crack-detector in a borehole drilled in the retaining wall. From theresults of measurement, it was clear that the crack zone in the retaining wall lies on the extension of the boundarybetween the natural ground and the banking.
These findings show that the use of the crack-detector is practical when the distribution of open cracks correspounds tothe undetectable area of the measurements for the design and maintenance of rock and concrete structures.

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It is verified that the basic equations used in the three dimensional displacement discontinuity method (3 dim. DDM) are coincided with the so-called physical dislocation solutions. There may occur slight error in the evaluated deformation whenthis method is applied to some special problems such as Cerruti's one (see Figs. 4, 5).
Formulation to solve tabular inclusion problem applying the 3 dim DDM is derived. Its validity is examined by solvingthe flat spherodial inclusion problem and by comparing with the analytical result, as shown in Fig. 8.
3 dim. DDM, which belongs to the category of the boundary element method, yields less accurate results when it is appliedto the problem where boundaries are adjacent to each other. Simplified model is proposed to treat the problem of closelyadjacent mining panels and its validity is confirmed by solving typical problem shown in Fig. 10.

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A simple 2-dimensional model based on stochastic theory has been applied to simulate time-dependent failure of an underground roadway in mine. In the calculation, FEM technique is used, and the obtained results are compared with the resultsmeasured at a mine in Akita prefecture. The road way considered in this study is U-shaped and supported by rockbolts installedin a square grid pattern at 1m interval. The calculated results of convergence and extension indicate a fairly good coincidence, at least in qualitative means, with measured ones.
By the virtue of the model versatility, the simulation has been carried out for various conditions changing bolt length, diameter, setting-time and so on. Through the calculation, it is found that grouted rockbolt support can retard the failure ingreat extent and are much superior to conventional point anchored bolt or steel arch support.
It can be said that the model showed a potential for application purpose. Simplicity of this model requires a minimummodification of a standard FEM program and also minimum experimental work to obtain necessary parameters. Application ofthis model to tunnel, dam, slope, underground storage and plant may be possible.

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This paper deals with the basic data on gas permeability and diffusion coefficients of coal and its correlation with the characteristics of the macropore such as Klinkenberg's constant, mean pore-radius, effective pore-area and porosity. Numerical researches on the flow and diffusion of gas in the coal seam have been extensively studies, however many numerical constants determined by experiments are necessary. This paper aims at stating the possibility of reduction the number of numerical constants of the numerical analysis by means of several relationship equations between the numerical parameters.
Two kinds of test pieces, made of lump coal and compressed fine coals, were prepared. Measurements were performed by flowing methane, nitrogen and other gases through the test pieces. On the basis of experimental results for compressed finecoals, the empirical equations between gas permeability and characteristics of macropore were obtained. For lump coal, thef actors were determined to express its heterogeneity in comparison with the equations for compressed fine-coals. Permeability flowing methane was less by 10-15% than that of nitrogen. This amount of reduction can be explained on the basis of the difference inmean free-pass of molecule. The effect of adsorption on macropore surfaces of coal was not evident for gas per-meability.

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An electromagnetic inspection instrument for stationary wire ropes up to 95 mm in diameter has been developed. This instrument utilizes two solenoidal coils coaxial with the rope for magnetizing it longitudinally close to saturation.
Because of the inconvenience of coiling up the conductor around the rope for each test, the solenoid type method of magnetization has not been adopted so widely. However, for large-diameter stationary ropes this method has been recognized to be better than yoke type method, as indicated in the facts which follow:
1) The instrument without iron core weighs 70 kgf and is lighter than that of yoke type.
2) Solenoidal magnetizing coils induce longitudinal magnetic field in the rope more effectively than yoke type electromagnet.
3) The distribution of flux density in the rope due to the coaxial solenoid is relatively uniform, and consequently the difference between the inspection sensitivity of a defect in the surface and that of an inner one is relatively small.
4) Inspection signal is satisfactorily stable with the solenoid type instrument, while the magnetic field in the rope is affected by the motion of the rope with the yoke type instrument, which results in a fluctuation on the inspection signal.
The instrument was applied in the field for inspecting the P.W.S.217 cables installed in a suspension roofing, and localized corrosion in these cables was successfully detected.

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Cationic flotation of coarse grained quartz (149-210 μm) from an artificial mixture (1: 1 by weight) with fine grained hematite (-10 μm) was investigated in alkaline media (pH 9.8) using dodecyl ammonium acetate as a collector. Individual flotation of quartz and hematite was also carried out for comparison. Flotationresults were discussed in terms of the adsorption density of DAA, zeta potential and scanning electron micrographs.
The results obtained are summarized as follows.
1) Individual flotation tests showed that complete flotation of quartz is achieved at a surface coverage of DAA of about 6%, while the complete flotation of hematite requires as much as 70% of surface coverage of DAA. This behavior of hematite may be explained by assuming that the adsorption of undissociated free amine molecules predominates on fine grained hamatite particles.
2) Negative zeta potential of hematite becomes zero at an adsorption density of DAA corresponding to about 100% of surface coverage. This supports the adsorption mechanism of undissociated free amine molecules on fine grained hematite particles.
3) Floatability of quartz decreased markedly in the presence of hematite fines in spite of the fact that quartz acquires a sufficient amount of surface coverage of DAA, indicating that the depression of quartz flotation can not be interpreted in terms of the collector consumption by hematite fines.
4) Depression of quartz flotation in mixed suspensions is considered to be due to the slime coating of quartz surfaces with hematite fines, where the hydrophobic interaction between quartz and hematite plays an important role.

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A new method of producing hard briquettes for the vertical retort has been developed. This method requires only zinc oxide calcine and coking coal, and can eliminate the use of spent liquor which has been becoming more expensive and less available. It can also considerably shorten the time to produce briquettes. The method includes mixing calcine and coal, preheating the mixture, briquetting the mixture into a cylindrical briquette of 1 cm in diameter, and coking the briquette. Effects of preheating time, briquetting force, coking temperature and time, particle sizes of calcine and coke, etc. have been examined to determine an appropriate condition under which briquettes of satisfactory strength have been obtained. More than 99% of zinc oxide in those briquettes is easily reduced in 60 min at 1050°C.

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Heat contents of calcium ferrite slags in the CaO-Fe₂O₃, CaO-FeO-Fe₂O₃ and CaO-Fe₂O₃-Cu₂O systems were determinedi n the temperature range up to 1660 K by using a drop-calorimeter. The heat contents in the liquid phase, referred to 1 g sample quantity, are of the same magnitude in these slag systems. Further, the CaO content in the slag phase does not give any serious effect to the heat content. The heat contents in the liquid Ca-Fe-O system are given in the following equations as functions of (FeO) of the slag and temperature;
-molten slag containing 20% CaO-
HT-H_{298. 15}=-590+2.06 (FeO)+1.38T-6×10^-4 (FeO)T(J·g^-1)
-molten slag containing 25% CaO-
HT-H^298.15=-600+2.50 (FeO)+1.39T-9×10^-4 (FeO)T (J·g^-1)

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