Rock stress is of great interest in cavern excavation, hot dry rock geothermal development and others. At great depth technically and economically usable methods for stress measurement are not many, and it is not rare that only methods based on laboratory core tests are available or stress induced rock failure phenomena like corediscing may give stress information. Stress induced failure phenomena like corediscing are straightforward information about stress state in a rock. On the other hand, core based methods have assumptions in their principles to some extent and hence they are not yet widely accepted. Whether the core based methods become to be truly reliable depends on the accumulation of the comparisons to other clear stress indicators.
This paper reports one of them. Corediscing was observed in a granite from 1,000 m depth at Akita pref., Japan. Test specimens for DSCA and AE methods were retrieved just adjacent to the discing point. Estimated rock stress state at the point were in agreement both in the maximum stress direction and the stress value with the corediscing criteria presented by Sugawara et al. and Matsuki et al. Also the spatial variation of stress state were observed in accordance with the structural condition of the rock. The average stress estimated by the core test was found to be in accordance also with shut-in pressure. Thus DSCA and AE methods were found to be basically reliable methods.
The specimens were tested about 6 years after the coring at the geothermal region and gave reasonable estimate of rock stress. Therefore it is also said that the effect of heat and the time from core retrieving to test can be not significant.

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The maximum tensile stress experienced by an HQ core in an arbitrary horizontal cross section was accumulated in equal area stereonet for 77 stress conditions. The maximum tensile stress accumulated for a central area of the core (57.1 % of the total area) was concentrated in a certain direction, which was nearly the direction of the minimum principal stress σ₃, for all stress conditions except those in which σ₂ = σ₃. Based on the assumption that a penny shaped crack is produced normal to the maximum tensile stress at each point of a horizontal cross section in proportion to the magnitude, the crack density in the core was analyzed by calculating strains under hydrostatic pressure as in Differential Strain Curve Analysis (DSCA). The direction of the maximum crack density was similar to that of the accumulated maximum tensile stress. Thus, the direction of the maximum crack density obtained by DSCA predicts the direction of the minimum principal stress rather than that of the maximum principal stress, if the distribution of pre-existing microcracks before stress relief is isotropic and if additional microcracks are produced by merely the tensile stresses during boring under in-situ stresses.
To verify this, the crack density was measured by DSCA for two cores of quartz diorite, which were taken by overcoring when a hemispherical ended borehole technique, one of stress relief method, was applied to measure in-situ stresses at Kanetsu tunnel. The direction of the maximum crack density obtained by DSCA was nearly that of the minimum principal stress for both cores.

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Recently, for the concern of safety in construction as well as for environmental and economical reasons, an efficient small-diameter shallow tunneling method has become increasingly important for outside plant engineering such as water supply, gas, electricity and telecommunications. In particular, for construction work near existing facilities, an underground tunnel excavated by the slurry pipe-jacking is becoming increasingly popular to avoid adverse effects.
The difference of the thrust between linear jacking and curved jacking is due to the frictional force of outside components of the curved area of thrust. It is considered that if the use of mud slurry on the face and over-cutting area is successful, lower increased ratio of the thrust is obtained in the curved jacking by in-situ data. However, in order to establish a more useful prediction equation in the curved jacking, more research and field data are needed. From this point of view, the purpose of this paper is to discuss the prediction equation in order to better explain the characteristics of the thrust and the friction resistance in the curved jacking by using laboratory testing and field data.

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Development of a powerful hydraulic rotary / percussive drill motivates improvement of drill rods and bits. Recently a button bit is preferably used for its durability and high maximum drilling rate. However, its penetration / rock-breaking mechanism is so complicated and many parameters are involved, then very few fundamental studies have been published up to now.
Very recently, authors had been carried out a series of button-chip penetration tests changing applied load, spacing and diameter of a button chip. In the first part of this paper, a computer program to simulate the static penetration test is stated. In case of Inada granite, it was found that the depth of groove produced by a series of static penetrations can be calculated by adding each depth / damage of a single penetration and making slight correction against the effect of unevenness of rock surface.
Finally, the simulation program was modified and computer simulation was carried out to estimate drilling rate by a button bit with six button chips. Simulation results were compared with results of drilling tests performed at various index angles.

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The authors proposed the mathematical model for the pulp layer in a flotation column by the two-stage axial diffusion with first order reaction model in the former paper. The Wehner and Wilhelm's as well as Danckwerts' boundary conditions have been partly modified and then applied to the feed point, the pulp level and the tailing point of the column. This model makes it possible to estimate the behaviors of particles that haven't yet attached (free particles) at the pulp level.
The proposed model has three unknown parameters, that is, the Peclet · Bodenstein number, the collection rate constant and the concentration of drainage particles from the froth layer. From the sensitivity analysis, it was found that the proposed model has little sensitivity to the Peclet · Bodenstein number, but some sensitivity to other parameters, especially to the concentration of drainage particles. In this study, the Peclet · Bodenstein number was assumed from the empirical expression derived by Mankosa et al.(1992), and the collection rate constant and the concentration of drainage particles were estimated by a least squares regression fit to the data sampled from an industrial operation, concerning the superficial concentration of attached particles as well as free particles. It is estimated by investigation of those parameters that the cleaning effect prevails exclusively not in the pulp layer but in the froth layer.

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Removal of cadmium and zinc ions from diluted solutions of their sulfate solutions with manganese dioxide, produced by ozone oxidation-precipitation reaction (OMD) under different conditions, has been investigated paying particular attention to correlation between the ion-uptake and the water content of OMD.
Uptake of Cd²⁺ which is demonstrated to be an ion exchange reaction increases with an increase in the water content of OMD. The adsorbed water, which is liberated at lower temperature up to 200 ^°C, as well as the structural water of MnO₂ takes part in the ion exchange reaction. One of the most outstanding features of OMD over both electrolytic MnO₂ and chemically precipitated one is that OMD has a higher water content and shows fairly stronger ion exchanger nature than the other types of MnO₂.
For removal of Cd²⁺ with a reduced amount of Cd-contaminated MnO ₂ residues, a two-stage treatment is considered to be effective. The first stage is addition of OMD in a small excess with respect to Cd²⁺ to uptake this ion at high efficiency and the second stage is addition of a small amount of OMD to make a high OMD / Cd²⁺ mole ratio to capture the remaining Cd²⁺ down to an adequately low concentration.
Zinc ion was observed to be removed from its dilute solution by OMD addition in a similar manner to cadmium ion.

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Now the Advisory Committee for Energy has taken up the security problem of several kinds of energy as the preferred issue and is undergoing revising work of energy supply and demand outlook toward the goal in less than a year. This work will emboss opaqueness and uncertainty of energy and environment though surrounding condition of energy such as oil price increase is changing considerably. This time at first I outlooked the present state of coal energy and environmental problems, followed by new condition related coal, third, CCT's ability to fixing up coal energy and environmental problems, fourth, how the condition of coal use will change according to the development of CCT, fifth, importance of international cooperation and finally noble use of coal in 21 century.

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Deployment of Technology Strategies for Coal Use
Coal generates high emission on volumes of CO₂ on combustion and thus exerts a relatively large burden on the environment as compared with petroleum and natural gas. On the other hand, however, coal energy offers great supply security for the 21st century in view of the relatively large reserves in comparison with other energies such as petroleum. The strategic target is therefore to achieve a coal use that will lessen the environmental load in 21st century further.
If we take the technology development that has been pursued up to the present, that is, up to the year 2000 as the first generation of development toward higher efficiency, the second generation of efficiency upgrading will extend to the year 2010 and be targeted at a 20 % reduction in CO₂ emission through the utilization of combined cycle power generation technology by the use of coal combustion and gasification process technology. "The hybrid generation" of efficiency upgrading that comes after this will span the decade from 2010 through to 2020 and its target will be a 30 % reduction in CO₂ emissions to through the practical application of fuel cell power generation based on the gasification of coal. The objective for the period from 2020 to 2030 will then be a decisive leap in technological development to the attainment of "the zero emission goal" that will bring about the turn to "zero emissions of pollutant" such as CO₂ into the atmosphere on the basis of core technologies involving the production of hydrogen from coal and the total separation and recovery of by-product CO₂.
Deployment of Technology Strategies for Coal Development
Although there are abundant coal reserves in the world. amidst the present trend of increasing coal demand primarily in the Asian region and the existing forecasts of dwindling deposits capable of being economically mined, the strategic targets adopted by Japan in an effort to achieve supply security are to make use of the wealth of technologies Japan has acquired and deploy them in and for the benefit of overseas coal fields, as well as to develop coal in a safe, low-cost and environment-friendly manner.
At present, the coal producing countries are facing a steady contraction of economically minable coal deposits and the challenging prospects of an ever-greater need to increase productivity, turn from open-cast to underground mining, and proceed to increasingly deeper depths and remoter seams. In view of these present-day realities, the development targets for the period of up to the year 2010 will primarily focus on "more advanced technology development" in the areas of existing exploration, evaluation, production, and safety technology and their application to field conditions in the coal producer countries. After this until the year 2020, priority will focus on "technology development in new fields" involving the use of low-grade coal and the recovery and utilization of coal mine methane gas. From then to the year 2030, the thrust of development will be directed toward the development of "next-generation technology" that will permit the utilization of unused energy resources , including coal in ultra-deep strata by use of coal production techniques based on automation and unmanned miming operations as well as in-situ underground coal gasification.

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Taiheiyo Coal Mine is located on the southeast part of Kushiro-city in Hokkaido prefecture, Japan. The Mine, which is an underground coal mine, was established in 1920. The total output of clean coal during its 80 years of operation was more than 100 million tons. Its mining fields gradually expanded into sea beds in the Pacific Ocean from land areas ; and since 1951 its entire mining fields have been under the sea bed. Currently, the main fields for mining are areas located 600 to 700 meters under sea level. The production of clean coal in 1999 was 2.13 million tons and R.O.M was 4.08 million tons.
The Coal Mine has commenced present directional drilling system applied in Australia for in-seam gas drainage since 1997. However, due to the coal seam condition in the Mine that collapse easier than in Australia and contain clay parting, it was difficult to keep the borehole in open. Hence we modified drilling system, in order to drill both in the coal seam and in the rock strata. This change required some modification on bit, bent sub and rod and also development of new drilling machine. After these modifications, three directional drilling systems have been installed for gas drainage and exploration underground, and another two systems will be installed by the end of March 2001.
In this paper, outline of the directional drilling system and the typical result of trials for in-seam gas drainage and exploration drilling by the system are descried.

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An original underground wireless communication system was developed at Ikeshima coal mine. This system uses a UHF frequency band of 800 MHz wave and consists of a surface center station, underground stations and portable stations. Operatioanl tests indicated that this system was possible to communicate with high articulation of clear voice without influences of electric noise even in travelling and to keep high grade maintenance. Also this is can be used for emergency communication system and large effect in safety area is expected. These merits are going to introduce to overseas countries.

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