A practical method for predicting underground climate has been already proposed by the authors, where wetness factor of a airway is defined as the value which can be determined from measured change of moisture content in air current flowingin the airway. In this method, specific resistance and factor of time passage of each airway must be given in prediction calculationbut problem in practice has been how to estimate these parameters. Hence, a more improved system has been dveloped through works in the Research Committee on Development of Design system for Underground Ventilation which has been settled in the MMIJ.
All of the input data for prediction calculation in the system are estimated from measured values of rate of flow in the airways and dry bulb and wet bulb temperatures measured at the both ends of the airways. All of calculations in the system can be performed in a personal computer. Heat exchange between air and drinage is programmed in the system. Furthermore, temperature variations of underground air currents, due to cyclic variation of surface temperature can be evaluated by calculation in the system.

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This paper describes a constitutive equation of rock which undergoes strain-softening deformation beyond its strength failure. The equation consists of stress-strain relations in elastic, strain-softening and residual strength regions. The stress-strain relation in strain-softening region was idealized to be linear and expressed in terms of a few parameters that are related to postfailure characteristics and fracture criterion of rock. For an illustrative example was demonstrated an analytical solution of displacement and stress around a circular hole under hydrostatic pressure. The solution shows that three annuli which correspond to elastic, plastic and flow regions, will be formed around it if hydrostatic pressure exceeds a critical value. The plastic zone is decayed with increase of the negative slope in the post-failure region, and ceases to exist as the negative slope gets infinitive. Both the radii of elastic-plastic and plastic-flow boundaries are given by analytical formulae. The formula for elastic-plastic boundary is reduced to one of the elastic-perfectly plastic model when the negative slope gets flat. while it is coincident with one of the elastic-flow model when the negative slope gets infinitive. The formula also suggests that the raidius of elastic-plastic boundary is much greater than that predicted by elastic-perfectly plastic model. This implys that the formula allows us to estimate a rational elastic-plastic boundary for a circular tunnel in rock or a relief boring in coal seam.

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The purpose of this report is to discuss how to account for the fracture behaviors in re-opening, shut-in and circulation. Some laboratory re-opening and shut-in tests were conducted under various stress condition, and circulation tests were conducted under various flow rate and stress condition for single and cross hydro-fractures created in Inada granite and Kofu andesite.
The results of re-opening tests show that the values of re-opening pressure are of high application to stress evaluation because of the smaller influences of flow rate and permeation. The values of shut-in pressure were recognized to be equal to the normal stresses to fracture with 20% of accuracy for created fractures in 30 cm cubical specimens.
The relationship between steady flow pressure and square root of injected flow rate was obtained to be linear by circulation tests for single fracture, and for cross fractures, steady flow pressure were recognized to be limited in spite of increasing of injected flow rate. It is suggested from the comparison of the results of circulation tests and numerical analyses through coupled F. E. M. and D. D. M. on finite element that the existences of the residual aperture of fracture under stressed condition which comes from asperities of the fracture must be taken into consideration in the model for more precise simulation.

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A portable acoustic emission counter has been developed to observe seismoacoustic phenomena during boring in coal seam. This original equipment is intrinsically safe and its weight is 0.35kg with the dimentions of 200×100×40mm. The acoustic emission activity is indicated as the total number of acoustic emission ring down counts in digits on, the front pannel of this equipment with LCD display. The acoustic emission activities occured in coal seam during boring were able to be observed with this equipment. This provided usefull information for locating the unstably stressed zone in the coal seam, and eventually presented the results to indicate the possibility of detection of the impending outburst hazard, and of the jamming on borehole.

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Parallel Wire Strand (P. W. S.) ropes are used as major elements in suspension roofings and bridges. Long-term exposure to weather conditions deteriorate them by corrosion internally rather than on the surface. There has been a great need to evaluate this deterioration to decide whether or not they require replacement.
Some electromagnetic inspection instruments are available mainly for wire strand ropes which move, such as mine hoisting ropes. However, for stationary ropes, such as suspension cables and mooring cables, there is no equipment available for inspection work, and no prior experience in this area outside of visual examination.
A new electromagnetic inspection device for P. W. S. ropes up to 50mm in diameter was developed. This device consists of a exciting coil with two annular poles which magnetizes the rope longitudinally to saturation, and a detector unit which has twin annular arrays of Hall effect elements to sense the radial leakage flux produced by defects. This detector unit has two new features which follow:(1) The inspection sensitivity is independent of the relative rope speed, as required for inspecting stationary ropes.(2) The annular arrays are divided into 6 segments, and each segment can deliver the individual output, enabling us to detect the cross sectional location of defects.
This newly implemented instrument was used to inspect P. W. S. 75 suspension ropes. Evaluated degradation of those ropes in terms of loss in the cross sectional area was proved accurate by results of disassembling inspection.

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The problem of cold shortness of mine tub couplers, arose in winter at a coal mine in Hokkaido, Japan. Regarding this problem, the acoustic emission method was applied to the tensile test of the stud link and the fracture toughness test of same material at a low temperature.
Some stud links were tested under tention at a temperature of -30-20°C. The positions of fracture were classified as follows:(1) the loading part, (2) the corner and (3) the smallest section of link as shown in Photo. 1. Two of them broke brittlely and it was possible to locate defects by the method of acoustic emission. The results of fracture toughness test were concluded as follows: Forged carbon steel containing a fatigue crack breakes brittlely below a temperature of -10°C. Fracture toughness and crack growth factor reduce and the acoustic emission becomes active as the temperature declines The method of acoustic emission generally gives us low values of fracture toughness because it detects the acoustic signals caused by the void growth prior to the slow crack growth.

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Interfacial properties of particles-water-oil system and their effects on agglomerates formation have been studied using BaSO₄, sodium oleate (Na01) and kerosene as model particles, surface active reagent and bridging liquid, respectively. Prior to the experiments on agglomeration, adsorption isotherm for BaSO₄ /Na01 system, interfacial tension of kerosene in NaOl aqueous solution, contact angles of BaSO₄-kerosene-Na01 aqueous solution system, and zeta potential of BaSO₄and kerosene in NaOl aqueous solution were measured under the various conditions. The variations of contact angles with NaOl concentration and pH were explained in terms of the adsorption amount of oleate on BaSO₄, the interfacial tension and the potential barrier.
In addition to agglomeration experiments, phase inversion tests were also carried out. In the present system, spherical and/or lumpy agglomerates were obtained in the Na01 addition range of 2.19x10^-3-4.75x10^-3mol/lunder natural pH conditions and in the pH range of 7.3-11.9 at 3.65x10^-3mol/ lNa01 addition. And it was shown that agglomerates formation was possible within water-in-oil emulsion region in the phase inversion tests. From these results, it was found that particleparticle cohesive force due to negative capillary force was a necessary condition for agglomerates formation and contact angles on the surface of aggregate particles were more important than those on smooth surfaces.
Phase inversion method was effective for determing the best suitable reagent and its dosage for agglomeration.

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The problem to be solved in a direct lead smelting process is the considerable lead losses in dust and slag. The dissolution of lead in ferrite slag is approximately 10 times lower than that in silicate slag, affording a possibility to produce low sulfur bullion with high lead recovery by changing the slag from a silicate to a ferrite type and by using oxygen enriched air to decrease the dust loss. To investigate the usability of the proposed new process by use of ferrite slag and oxygen, an apparatus with a laboratory scale was constructed in this study to make lead bullion by injecting PbS reagents or concentrates and oxygen gas onto a layer of calcium ferrite slag.
The lead content of the produced calcium ferrite slag was quite low, being at most 5% at the sulfur content of bullion of 2%. On the other hand, the dissolution of lead in the iron silicate slag was extremely high, amounting to about 40% at the same sulfur content of bullion. The lead loss as chemical dust decreased considerably with increasing oxygen concentration of input gas, resulting in the high recovery of lead as bullion.

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