Several characteristics of deformation of a rock slope due to excavation are clarified through a displacement measurement on Ikura limestone quarry for more than ten years. However, some causes of measured deformation have been still unknown. The rock slope behind the Tarumi face showed continuous contraction while the excavation was interrupted at this face. In this study, a cause of the continuous deformation was studied to evaluate stability of the rock slope by means of numerical analysis. Complex topography of the mining area on Ikura limestone quarry was modeled in three dimensions at several excavation stages. Then, an elastic analysis was carried out to estimate the deformation of the rock slope due to excavation in the whole mining area. Through the analysis, it was found that the rock slope could deform elastically while the excavation was interrupted at the Tarumi face. It was estimated to contract gradually due to progressive excavation at the Kawamukai face, which was located at 400m away from the rock slope. Analyzed results were consistent with the observed results under an adequate elastic constant. Therefore, this rock slope was evaluated to be stable because the continuous deformation caused by the excavation was elastic.

View full abstract

It is essential for underground development to understand the failure process of rock subjected to tri-axial compression. Okubo et al. developed a transparent tri-axial vessel made of an acrylic acid resin, and succeeded in observing the failure process of rock specimens in tri-axial compression test. In this study, tri-axial creep tests of Tage tuff were conducted within the transparent vessel.
A creep test usually requires longer time than a compression test and it is not feasible to take a photograph continuously at every predetermined time interval. Therefore, in this study, the photographing system was developed which cooperated with the existing loading and measuring apparatuses. This system made it possible to take a series of photographs of a specimen in the tertiary creep region. Photographs taken in a tri-axial test were processed to obtain axial and lateral deformations by the computer program developed in this study.
After careful examination of axial and lateral deformations, it was found that the creep strain (axial strain) just before failure was nearly equal to the cross sectional width of the stress-strain curve at the creep stress level, and that not only axial but also lateral strain-rates in the tertiary creep region were inversely proportional to the residual time up to the failure. And it was also found that ratio of the lateral and axial strain increases in the tertiary creep region were similar to those of the tri-axial compression test just after the strength failure point.

View full abstract

The crystalline aluminium hydroxides of hydrargillite-I (synonym of gibbsite) and II (H-I, II) and bayerite-I and II (B-I, II), in which I and II consist of the coarse and fine particles, respectively, were heated at 200-400°C under reduced pressure. The starting materials were checked up by electron microscopy and thermal analysis (TG and DTA), and then the resulting products were examined by x-ray diffraction study. Consequently, it was found that upon heating under reduced pressures at 0.667-6.67 Pa, amorphous alumina was formed from H-I and II bearing no relation to the heating rate at 1.25 or 5°C m^-1, and similarly amorphous alumina was also formed from B-I and II at the rapid heating rate of 5°C m^-1 ; while very poor crystalline alumina, which is regarded as the material corresponding to rho alumina (ρ-alumina) was obtained at the slow heating rate of 1.25°C m^-1 from B-II, and a mixture of boehmite and ρ-alumina was obtained from B-I at the same heating rate.
Accordingly it is seen that a ρ-alumina is prepared from the dehydration of bayerite which consist of fine particles by heating at 200-400°C at the slow rate under reduced pressure.

View full abstract

In cobalt-rich manganese crusts, valuable metals such as cobalt, nickel and copper are mainly contained as amorphous phases in the manganese oxides or iron oxyhydroxides without forming definite mineral phases. The mined ores, however, are expected to be likely accompanied with the substrate rock, e.g. basalt and limestone, because usually the cobalt-rich manganese crusts are found as pavement-like thin layers on seamounts. Thereby, mineral processing can be thought to be effective for separation of the metal-bearing crusts from the accompanied substrates.
On the basis of mineral processing experimental data acquired by the Deep Ocean Minerals Association (DOMA), the data qualification and re-evaluation by applying an economic evaluation model are presented in this paper. Using the data from gravity concentration, magnetic separation and froth flotation, their separation performances are estimated by Newton efficiency and technical efficiency methods. The relationships between the separation efficiencies and the internal rate of return calculated from the economic evaluation model are compared with the variation of some parameters.
As the results, it is shown that technical efficiency can be used effectively for the evaluation of mineral processing in some cases. Evaluating by Newton efficiency turns out to be an effective criterion in case of more than 66% substrate ratio in the mined ore, and the technical efficiency less than 52% substrate ratio. The applicability of the two efficiencies in 52 to 66% substrate ratio is case by case.

View full abstract

Since Ni is a valuable resources and its plating solution is costly, improvements in recycling technique from waste solution and slurry in the Ni plating process have been an necessity. In this paper, the retrieval of Ni from the electroless plating waste waters, especially worn-out ones with high concentration of Ni is considered. The compound precipitation method which retrieves Ni from waste waters as carbonate form or oxalate form is examined.
The results show that higher solution temperature is preferable, and that Fe can be removed by neutralization precipitation. Among carbonate, Na₂CO₃ turns out to be the more effective precipitator than NaHCO₃. When the double dose or more of the theoretical equivalent of Na₂CO₃ were added, and the initial pH was larger than 2, precipitation took the form of weak crystalline whose composition was Ni(CO)₃(OH)₄ · 4H₂O. When NaHCO₃ was used as precipitator, together with CO₂ bubbling, globular particles precipitated.
For oxalate, crystalline particles of NiC₂O₄ · 2H₂O precipitated. The method was tested for waste water from an actual plant and followings were suggested: Ni-B solution should be precipitated with carbonate, while Ni-P solution with oxalates.

View full abstract

Flow properties of paste were investigated by means of transport tests using pipelines of 4 and 8 inches in diameter at Toyoha Mine.
In addition to full-scale tests at the mime, laboratory tests using small-scale pipes and a viscometer were conducted. The experimental results show that the flow properties of the pastes could be approximated by the Bingham plastic model; however, the flow of the paste in the full-scale pipeline was different from the flow in the small-scale pipes due to the Schwedoff region at low shear velocity. In order to express the wall shear stresses over a wide range of shear velocity, the Papanastasiou's model was introduced. The shear stresses of paste flows over a wide range of shear velocity including the Schwedoff region were satisfactorily estimated by this model.

View full abstract