A vertical borehole of 50m depth was drilled in the diatomaceous mudstone, which is classified as weak rock, at Horonobe, Hokkaido and stress measurement by the borehole deformation method was carried out at different depths. The rock is massive with density as low as 1.48 g/cm³, reflecting high porosity of 45%. Mean value of the compressive strength is 3.21MPa. Fresh water and bentonite was inevitably used as the drilling fluid to maintain the fragile borehole wall.
Stress measurements were tried at seven points along the borehole of 50m depth. At four measuring points, where the cores contained two types of fractures, longitudinal and cross, behaviors of the borehole deformations during overcoring deviated from the prediction based on the elastic theory. Results obtained at three measuring points, where cores contained little cracks, are judged to be reliable. Maximum principal stress directs EW and the stress is almost biaxial in the subsurface region of Horonobe district. This characteristic of stress condition is in harmony with the direction of the active folds distributed in the vicinity of this district.
The efficiency of measurement was highly dependent on the condition of borehole and three sets of measurements were taken within 8 hours working period, at sections where fewer cracks occurred. It has been proved that the stress meter is applicable in weak rock and that the measuring system adopted is practical, although the stress meter suffered some damages at sections where the core was highly fractured.

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It is well known that rock strength decreases with increasing of specimen size. Accurate knowledge for the size or scale effects in rock strength is very important to apply the small-scale experimental results to the large-scale underground space design. However, the investigation of the size effects requires tremendous efforts and expenses in most cases. In this study, a new method to estimate the size effects of rock based on the specific energy in excavation was proposed. The method needs minimum efforts without extra equipments. Through the careful examination of eleven excavation methods, it was found that the specific energy decreases with the excavation scale following the equation:
(Specific energy) ∝ (Excavation scale)^-2α with α=0.2.
Cutting spacing, penetration or geometrical mean of the two was found to be appropriate as excavation scale. Specific energy is roughly proportional to square of strength. Then, the following equation stands:
(Rock strength) ∝ (Excavation scale)^-α.
This result is very conformable to the size effects deduced by the results of the compression tests. The size of cuttings in excavation was examined and the close relation was found between the excavation scale and the size of cuttings. Relation between the specific energy and the work index in comminution was also discussed.

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Steel fiber reinforced mortar (SFRM), a composite material by compounding the short steel fibers in mortar uniformly, is considered to improve the resistance against the defect of cracks and toughness in plain mortar. SFRM is now getting more popularity in the application field of construction. The evaluation of durability and service life is important in wide ranges of application. However, only limited information is known concerning the durability of SFRM.
In this study, three sites were chosen to investigate the durability of SFRM. The first site is a tunnel in Garou mine (Hokkaido) where SFRM lining was sprayed 18 years ago. The steel fibers were found to be almost sound except the rusted fibers on/near the wall surface. The tensile and compressive strengths were found to be close to the initial values obtained 18 years ago.
The second site is a slope in Shizuoka Prefecture where plain mortar and SFRM were sprayed in 1994. Investigation of the slope in 1997 showed that mean crack-width on SFRM was considerably smaller than that on plain mortar. The number of cracks on SFRM was only 1/3 of that on the plain mortar.
The third site is seashore in Chiba Prefecture and exposure tests were started in 1996. The compressive strength of SFRM did not change so much for five years. Thereafter, the strength decreased considerably.

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Tensile fractures were nucleated and developed from a borehole, which was drilled at the center of a block of granite with two types of boundary conditions. Samples were then prepared from the blocks before the fracture penetrated throughout the block, in order to clarify the fracture surfaces in the original condition. Next, cross sectional photographs of the samples containing the fracture were taken by holding the fracture surfaces in the original opening condition. Based on the photographs, coordinate values of upper and lower boundaries of fracture profiles were measured at a regular interval. Moreover, fracture apertures, fracture angle, and closing direction of fracture surfaces were estimated at each local part of both fracture surfaces.
It was found that the fracture angle of the fracture surfaces tended to gradually decrease from the wall of the borehole to the fracture front. This result reveals that the upper and lower fracture surfaces can be assumed to be almost the same in direction with regards to approaching the fracture front.
Two patterns of the fracture propagation could be extracted from a distribution of closing direction vectors of the fracture surfaces. One is a linear pattern, and the other is a radial pattern. These patterns are similar in structure to a tree spreading out its branches. It was considered that such a structure is closely related to the fractal behavior for roughness evaluated by fracture profiles.
The aperture tended to gradually decrease with a distance from the wall of the borehole. Its decreasing direction harmonized well with the direction of the fracture propagation. It was recognized that macroscopic distribution of apertures was strongly related to the distribution of tensile stress induced in samples before the occurrence of fractures.

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To reduce the volume of precipitates generated by the neutralization of acid mine drainage (AMD) containing high concentrations of Fe and As, ferritization of the precipitates was attempted by a two-step neutralization process in which magnesium oxide (MgO) was used as the first neutralizer and sodium hydroxide (NaOH) as the second. Batch neutralization experiments with MgO and continuous flow experiments by the two-step neutralization were conducted in laboratories and an AMD treatment plant. The results showed that the precipitates by the neutralization were magnetized in the continuous flow experiments, although there was Al and Si that prevented the generation of ferrite in the AMD. This indicates that ferrite was formed from the precipitates after removing most of the soluble Al and Si by the first neutralization. In addition, aging of the precipitates under reducing conditions and returning the aged precipitates to a ferrite tank were required to form ferrite. The molar ratio of As to Fe in the precipitates reached a constant value at pH>3.5. This suggests the coprecipitation of As and Fe.

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Authors have been developing a thermal jet dryer for the purpose of weight and volume reduction and recycling of organic sludge dehydrated cake. A new sludge feeding system was introduced to avoid the compression of the sludge in a screw feeder. Sewage sludge was able to be dried by this improvement. The experimental results for the sewage sludge were compared with those of bean curd refuse and waste water sludge from a dye works. The simulations of the air-solid multiphase flow accompanying drying process were made using a CFD software and its results were compared with the experimental ones.
(1) There was little difference about the particles' average residence times in the drying tank for three samples, although experimental results showed large difference about the effective diameters of dried product. Therefore, there is little influence of disintegration, drying, kinds and physical properties of samples on the fundamental particles' flow.
(2) CFD calculations of particles' trajectories with heat transfer and drying were made by two-way coupling method. Similar calculation results were obtained with the experimental data for setting the vertical restitution coefficient between particles-wall to 1, and setting the horizontal one to 0.6-0.7. In order to carry out better predictions, development of the disintegration process model is needed.
(3) Unlike conventional pneumatic dryers or rotary dryers, the particles in the drying tank are in the almost same drying conditions through the drying process. Moreover, it turned out that a gas-solid multiphase flow in the drying tank is assumed to be a complete-mixing flow.

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Leaching rate of chalcopyrite in sulfuric acid solutions depends on a solution redox potential, determined by a concentration ratio of ferric to ferrous ions, and it become maximum at a certain potential (an optimum potential) depending on leaching conditions. In this study, factors affecting the optimum potential were investigated.
Shaking flask leaching experiments for two chalcopyrite concentrates were performed at 303 K under various pH values, pulp densities, and concentrations of ferrous and ferric ions with or without iron-oxidizing bacteria. The experimental results were analyzed based on a reaction model for the redox potential dependence of chalcopyrite leaching, which assumes the formation of an intermediate Cu2S from chalcopyrite. Plotting the leaching rate to a normalized potential in the model showed that the rate is controlled by the normalized potential and is independent of solution compositions, pulp densities, and iron-oxidizing bacteria when ferric ions do not precipitate. A maximum rate was achieved at a certain value of the normalized potential. Converting the normalized potential to the solution redox potential gives the optimum potential for chalcopyrite leaching as a function of cupric and ferrous ion concentrations. The optimum potential increases with increasing the cupric ion concentration and decreases with the ferrous ion concentration. Cupric ions affect stronger than ferrous ions on the optimum potential.

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Activated carbon is known as a catalyst for chalcopyrite leaching in sulfuric acid solutions. This paper compares the effects of six different activated carbon samples on copper extraction from a chalcopyrite concentrate by shaking flask leaching experiments at 303 K under atmospheric conditions. Eight different coals were also evaluated as an alternative to activated carbon.
Except for one activated carbon sample, activated carbon addition enhanced copper extraction. Increases in the weight ratio of activated carbon to the chalcopyrite concentrate caused increases in copper extraction.
The effects of the coals on copper extraction were related to the rank of the coals: Low rank coals like brown coal, which have low fixed carbon contents and high contents of volatile matter, suppress copper extraction, and high rank coals, which contain more fixed carbon and less volatile matter, enhance copper extraction. High rank coals stored under atmospheric conditions over long periods (more than 7 months) suppressed copper extraction, implying that oxidation of the coal surface and its products cause the suppression in copper extraction.
The experimental results are analyzed and discussed with a reaction model for the redox potential dependence of chalcopyrite leaching, which assumes the formation of intermediate Cu₂S by chalcopyrite reduction and a subsequent oxidation of the Cu₂S.

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Impurity bands in the infrared transmission spectra of Ge-S binary glasses are evaluated. Glass samples with various S concentrations were prepared by ordinary melt-quenching process using Ge and S raw materials and vacuumed fused quartz ampoules as containers. The infrared absorption bands of S-H, Si-O and Ge-O are observed in glasses with Ge-excess compositions over 66.7 at%S (GeS₂). In S-excess glasses from 66.7 at%S, the bands due to CS₂ and S-S bonds are additionally observed. All glasses have infrared transmission up to ∼ 10μm and the absorption edge is determined by the Ge-O impurity band. Possible origins of various impurities are qualititatively discussed.

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