X-ray Computed Tomography (CT) is successfully applied to the visualization of water infiltration into dry rock, and to the quantitative determination of the permeability in rock. A multi-stage pressurization procedure is applied to a one-dimensional horizontal water infiltration test under low pressure conditions, and in which the volumetric water content at each point within a rock specimen is precisely monitored by means of X-ray CT. Case examples make clear that the subtraction of X-ray CT images is an effective procedure available for the flow field analysis dependent on the pore structure. Applying the Green-Ampt model, the coefficient of permeability and water entry pressure was evaluated. The result was consistent with the pore size distribution obtained by the mercury intrusion porosimeter.
In this study, effect of confining pressure on mechanical properties of artificial methane hydrate sediment was experimentally investigated and discussed. Two kinds of drained triaxial compression tests were conducted for artificial sediment specimens containing Toyoura sand and synthetic methane hydrate under a pore water pressure of 8 MPa and a temperature of 278 K; “constant confining pressure test” and “two-stage confining pressure test”. In the former test, confining pressure was kept constant at 8.5 MPa, 9 MPa, 10 MPa or 11 MPa during axial loading process. In the latter test, confining pressure was altered from 8.5 MPa to 11 MPa during axial loading process. The findings can be summarized as follows. (1) A specimen was restrained from deforming laterally by confining pressure. (2) Strength and stiffness of a specimen were enhanced by confining pressure. (3) Two strengths under different confining pressures could be obtained from a single specimen by two-stage confining pressure test. (4) Strength was formulated as a function of confining pressure and methane hydrate saturation based upon earlier findings. These findings concerning the effect of confining pressure seem to be of considerable help for a proposal of constitutive equation and numerical simulation in the future.
In-situ stress measurement by means of the Downward Compact Conical-ended Borehole Overcoring (DCCBO) technique, which one of the overcoring method, was carried out at Kamaishi mine to aim at practical use of this technique. Prior to in-situ stress measurement, measuring apparatus (conical bit, strain cell insertion tool and data logging equipment built-in tilt-azimuth meter) for HQ-size borehole were developed by improving apparatus for PQ-size borehole. Then, the measurement method based on the determination of strain coefficients depending on the estimation of the elastic properties of the adhesive under in-situ measured temperature was proposed. Performing in-situ tests, we verified that improved measuring apparatus for HQ-size borehole works well in a water-filled vertical borehole. Moreover, it was confirmed that the proposed measurement method could estimate the in-situ stresses relatively consistent with those by other measurement method near this test site. It was concluded that in-situ stresses measured by the proposed measurement method have sufficient reliability.
The Hida Tunnel for Tokai-Hokuriku Highway was excavated by a world-largest-class TBM with the diameter of 12.84 m. The TBM have bored over 4.3 km of the tunnel through Nouhi Rhyolite, Granite Porphyry and Hida Gneiss. The uniaxial compressive strength of these rocks was found to be extremely high. Such high strength resulted in significantly not only high wear rate of the disc cutters but also failure of those mounted on the TBM. In this study, cutter wear and failure were carefully measured and recorded together with the operation conditions such as thrust force, penetration rate, cutter-head rotation rate and rock strength. It was found that the extent of cutter wear largely depends on position of the disc cutter; cutter wear per unit tunnel length near the fringe of cutter head was extremely larger than that near the center of cutter head. The number of cutter replacements was found to show a good correlation with the cumulative cutter wear. It was found that the interval distribution of cutter replacements follows the exponential distribution and the number of cutter replacements follows the Poisson distribution.
As a fundamental study for support design of underground space using cable bolt, a series of laboratory pull-out tests with fully-grouted seven-wire plane and bulb strand cable bolt were conducted. Based on the test results, a constitutive law is suggested using Shear Resistance Model (SRM) . The resistance shear stress is induced between cable bolt and grout annulus due to bond failure in this model. Its value is mainly dependent on Young's modulus of surrounding rock mass and is formularized as a power function of Young's modulus of rock mass. Showing the simulations of the laboratory pull-out tests is successfully performed using the SRM, it is confirmed that the SRM is appropriate for explaining the pull-out behavior of cable bolts. Finally the SRM is applied to the support design of cable bolt for rock mass with various Young's modulus. Then the effect of the embedment length of cable bolt and Young's modulus of rock mass on the pull-out load and the region of resistance are shown. Then the method of support design using the SRM is discussed.
In recent years, high quality zinc ore in hydrometallurgy is decreasing because of stable demand of material, depletion of domestic mine and increased usage of recycling waste material. Therefore the impurity contained in the ore rose to the inexperienced level. Especially, SiO2 in zinc concentrate produced Zn2SiO4 in roasting process and Zn2SiO4 is easily leached in leaching process to form the supersaturated silica in the solution. As a result, silica turns into a gel to make complicates the solid-liquid separation difficult after leaching process. Several methods was proposed to solve this problem. However the factors affecting the silica polymerization have not been clearly understood. In previous paper, authors classified silica into three forms, and investigated the influence of several factors. The purpose of this paper is to obtain the knowledge for the effects of organic condense agents and inorganic compounds on the silica polymerization of colloidal silica. (1) The colloidal silica in the solution was charged negatively and could be removed by addition of cationic condensing agents. (2) The inorganic additives such as MnO2, PbSO4, ZnS,CaSO4 and ZnFe2O4 had no effect on the form of Silica existing in the solution. In the case of the addition of Al (OH) 3 and Fe (OH) 3, the concentration of colloidal silica decreased and the concentration of solid silica increased. (3) In the case of addition of solid silica, the concentration of colloidal silica decreased and the concentration of solid silica increased. This effect was promoted with increasing solid silica loading. (4) At high sulfuric acid concentration, the colloidal silica was stable. The solid silica added in the solution efficiently removed the colloidal silica also at high sulfuric acid concentration.
For the recovery of nuclear materials from the spent nuclear fuel by the sulfide process, fission products such as rare-earths are selectively sulfurized by CS2 at temperatures below 500 °C. However, sulfurization at lower temperatures would be favorable from the safety handling of CS2. In this paper, low temperature sulfurization of neodymiumu oxide Nd2O3 by mechanochemical method in the presence of CS2 was studied. When Nd2O3 powder was milled with CS2 by planetary mill in argon atmosphere followed by heatreatment in Ar, the broaden peaks for Nd2O2S phase were found by XRD analysis. These peaks for Nd2O2S became sharpened by the heat treatment at temperatures 500 — 600 °C in argon atmosphere. The relative intensity ratio of Nd2O2S peaks to Nd2O3 peaks increased with increasing milling time as well as the increasing CS2 amount . Finally, the experimental results were in good agreement with those of thermodynamic consideration.
The purpose of this work is to present processing and function of the sulfide phosphor. Phosphors of rock salt structure such as SrS and CaS and alkaline earth thiogallates with the formula MIIGa2S4, where MII=Ca, Sr and Ba have been investigated for full-color inorganic thin film electroluminescence. More recently sulfide phosphors were used as phosphors in phosphor converted light emitting diodes for solid state lighting. Various Eu2+ doped phosphors were prepared by solid state reactions between alkaline earth carbonates and gallium oxides mixed in stoichiometric compositions. Phosphors were treated at 900°C for 5h under a H2S stream, then doped with Eu2+ luminescent center and retreated at 1100°C under similar conditions. The emission spectra of YAG:Ce3+, SrGa2S4:Eu2+ and CaS:Eu2+ are presented as a function of the temperature from 20°C to 100°C. The emission intensities of phosphors slightly decreased with increasing temperature.
Hydrogen gas can be effectively synthesized from the electrochemical and/or photochemical decomposition process of H2S because of its low electrochemical potential. However, decomposition rate was gradually decreased with increasing the amount of poly sulfide ion, such as S22-, which simultaneously synthesized as the by-product during the reaction. Thus, poly sulfide ion should be removed from the solution, nevertheless it could not be removed from the solution by without loss of basic solution and/or dissipation of metal ion. In this study, the idea based on the interaction between fullerenes and sulfur was introduced into the development of collection method for poly sulfide ions from basic solution. Fullerenes was dissolved into toluene, and mixed with aqueous solution contained S22- ion. After 6 hours agitation, the color of the aqueous phase was changed from yellow to transparent in the case of fullerene/toluene solution treatment. Additionally, during every treatment, elemental sulfur was produced in the aqueous phase, and fullerene-sulfur compounds, such as C60S16 and C70S16, were formed in the toluene phase after 4th treatment. Thus, extracting and separating of poly sulfide ion from aqueous solution was succeeded.
Photocatalytic decomposition of hydrogen sulfide (H2S) into hydrogen (H2) by using the stratified type photocatalyst is considered as efficient route for the conversion of natural energy (solar energy) into clean energy (H2) . This reaction obeyed to next formula; 2HS-→2H+ + S22- + 2e-→H2↑+ S22-. To construct the continuous system, effective conversion route from S22-ion into H2S gas should be developed. In other word, sulfur cycle system should be constructed. In this report, conversion route from sulfur compounds (elemental sulfur and Na2SO4) into H2S by utilizing biological reaction was studied. H2S gas was stably synthesized until c.a.5% in the case of elemental sulfur addition, while it was c.a. 2% in the case of Na2SO4. Rate of biological reaction was seriously decreased if concentration of H2S was over these values because of its toxicity. Conversion efficiency was higher in the case of elemental sulfur addition since impediment of sodium ion was not progressed.
This paper describes hydrogen sulfide generation, isolation and characterization of sulfate-reducing bacteria in the activated sludge obtained from wastewater treatment plant. The sludge, collected from aerobic treatment system, was used as inoculums for hydrogen sulfide generation and for isolation of sulfate-reducing bacteria. Hydrogen sulfide was generated when the sludge was inoculated into a pH controlled medium. Two strains G2 and G3 of sulfate-reducing bacteria were isolated from the sludge. The characteristics and identification of these isolates was based on culture of the experiments and molecular analysis. Reduced sulfate rates in G2 and G3 is 0.39 and 0.41 mmol/dm3 respectively. Two isolates located in the genus Desulfovibrio in the phylogenetic tree based. First one was 16S rRNA gene analysis with the highest homology, 96.6 %, as Desulfovibrio carbinoliphilus (DSM 17524T) . However, the branch of the isolates was separated from the relatives and no strain was recognized in this branch. Also the dsr gene of isolate G3 had the highest homology with Desulfovibrio fructosovorans (DSM 3604T) , 92.7 %. The isolates G2 and G3 belonged to the genus Desulfovibrio as confirmed by the results of these analyses, however, these isolates oxidized organic compounds to carbon dioxide completely although relative strain oxidized it completely. Therefore, these isolates have high possibility that they should be recognized as a new strain.