AE (Acoustic Emission) or MS (Microseismicity) is a very useful method to understand fracture mechanism and to predict serious rock fracture like rockburst. This method can be applied to monitor reservoirs where water and gas are injected, for example, in underground sequestration of carbon dioxide and in EOR (Enhanced Oil Recovery) of petroleum industry. If a numerical simulation helps to interpret AE monitoring results, AE monitoring would become much more powerful tool for the rock engineering. Thus, in this paper, the authors review various methods that can simulate occurrence of AE events incorporating inhomogeneity of rock. A code of Finite Element Method (FEM) developed by Tang et al., those of Boundary Element Method (BEM) by Napier's and Stephansson's groups and those of Distinct Element Method (DEM) by Shimizu et. al, Fakhimi et al. and Cai et al. are briefly introduced as simulation methods of brittle fracture like rockburst. For simulation of AE events induced by water or gas injection, DEM incorporating Fluid Flow Algorism by Shimizu et al. are introduced, with showing their simulation results of hydraulic fracturing.
Open pit mine production scheduling can be formulated as an integer programming problem, which is well-known for demanding enormous storage capacity and a lot of calculation time. In order to avoid these problems, in this paper, 4-D network relaxation method is applied. The 4-D network relaxation method relaxes a few constraints with Lagrange multiplier method and allows us to apply the Lerchs-Grossman (LG) method, which gives the optimal solutions for the ultimate pit design of open pit mine, and find good suboptimal solution. However, previous studies reported the problem of huge calculation time. Therefore, we propose the algorithm to reduce calculation time. With the reduced calculation time, we examine the effect of price changes as a case study. In this study, we calculate the production schedules with three price scenarios; upward trend, constant and downward trend. A lot of price changes, which do not necessarily correspond to three scenarios, are applied onto the obtained schedules and calculate and examine the realized NPVs. The variance of realized NPVs in upper scenario is bigger than those of other two scenarios, but the probability of the realizing highest NPV is also highest. Therefore, it is better to schedule with upward trend, if mining companies can accept the risk. Furthermore, the reduced calculation time allows us to include capacity constraints not only for mill but also mining, this also means that the results become more realistic one.
The quantitative estimation for the amount of storage and leakage of injected CO2 under the environment of underground is necessary for risk assessment of carbon dioxide capture and storage (CCS) . In addition, permeability characteristics of supercritical CO2 and water in porous media are very important parameter in order to predict migration of injected CO2 dependent on time and space. In this study, using sand column, we conducted experimental study on flow behavior of supercritical CO2 and water in porous media. Grain size and temperature were changed as an experimental parameter. Using experimental data for flow behavior such as discharge rate of fluids, differential pressure between inlet and outlet of sand column, we conducted a numerical simulation for this laboratory-scale experiment in order to clarify permeability characteristics of supercritical CO2 in porous media. As relative permeability model for simulation, the extended Corey model that Nkrg and Nkrw as indexes were introduced into the original one was used. By changing the values of Nkrg and Nkrw, history matching of flow behavior and pressure change during both of CO2 and water injection processes was carried out and the shapes of relative permeability curves that allowed us to reproduce CO2-water multi-phase flow behavior were optimized. Comparison of the optimized relative permeability curves in the process of CO2 injection indicated that 1) water mobility was relatively high compared with that of CO2 when grain size was large and 2) relative permeability to CO2 became higher under the condition below critical point of CO2. In addition, we interpreted transport phenomena of CO2 after shutoff of CO2 injection on the basis of relative permeability curves obtained for water injection process. As a result, it was found that 1) liquid CO2 easily migrated into geological formation in the cases of small grain size and low temperature and 2) dissolved CO2 migration due to groundwater flow contributed to the change of CO2 distribution under the condition of high water saturation.
In this research the behavior of Sapporo soft rock was investigated under the effect of repeated one-dimensional freeze-thaw. As indicators of the rate of deterioration, the AE (Acoustic Emissions) , porosity, and elastic wave velocity under dry conditions were used. It is considered that the microscopic destruction that occurred inside Sapporo soft rock, which doesn't show significant effect of freezing, can be analyzed in detail by measuring the AE. Main results obtained in our research are summarized as follows: (1) No deterioration of the test pieces was apparently observed even after 40 cycles of one-dimensional freeze-thaw. This experimental result implies that the effects of one-dimensional freezing on rock are significantly different from those resulting from three-dimensional freezing. (2) It was observed that the total number of occurrences of AE was the highest in the first cycle of freeze-thaw, and decreased thereafter. However, the number was converging to an almost constant value. (3) It was confirmed that the number of occurrences of AE decreased during freezing (processes 1, 2, and 3) after several freeze-thaw cycles, but increased during thawing (process 4) . (4) It was confirmed that the displacement of expansion during freezing and shrinking during thawing increased with repetition of the freeze-thaw cycle. The increase in the number of occurrences of AE during thawing mentioned above was due to this increase in the displacement of shrinking during thawing. The mechanism of deterioration caused by one-dimensional freeze-thaw on Sapporo soft rock revealed in this research is of great value in engineering for the examination of methods for the maintenance of architecture made of Sapporo soft rock, which is currently being re-evaluated as historical architecture.
The recovery of copper wires from automobile shredded residues (ASR) has been investigated using a new dry shaking table that we had developed. The shaking table is shaken in lateral direction while conventional shaking tables such as wet shaking tables and air table in the longitudinal direction. Heavier particles move preferentially in the direction perpendicular to the shaking direction, resulting in the separation of heavier particles from light one. In this study, we have carried out the separation experiments to recover copper wires from ASR which contained plastics, glasses, rubbers and copper wires. The size fraction of -2+1.18mm was mainly used for this study. The effects of several parameters such as tilts of table, shaking speed and copper content and so forth were examined on the recovery of copper wires from ASR. At the batch experiment using the sample with Cu grade of 15%, Cu grade and recovery were 50% and 64% under optimum conditions. For continuous separation experiments with 6 time addition of samples, Cu grade and recovery were 56% and 61%.
In the dental laboratories, powdery waste containing precious metals such as gold (Au) , silver (Ag) and palladium (Pd) is generated during the polishing process of dental alloy. For the recovery of precious metals, powdery waste is treated by dissolution with nitric acid and / or aqua regia. Similar wastes containing precious metals are also treated in copper smelting process as secondary resources. In general, the precious metal content of powdery waste is less than 1%, and therefore, it is difficult to economically and technologically recover these precious metals in the conventional process. In this research, a separation and recovery method using flotation was investigated. It was observed that selective recovery of the precious metals from powdery dental waste was obtained giving; 87.4% Au, 90.3% Pd and 88.5% Ag in a two stage flotation using sodium isopropyl xanthate (SIPX) as a collector. In addition, the values of enrichment of precious metals obtained by 1st flotation and 2nd flotation were 9.2-9.6 and 8.1-8.3 respectively. According to the series of these experiments, it was found that precious metals are effectively concentrated from the powdery dental waste. Therefore, we suppose this flotation process to be useful for the improvement of conventional recycling process.
The selective separation and recovery method of gold(Au) was developed with polymer bead containing epoxy group. Under strongly acidic condition at pH 1 or less, Au was adsorbed 82% to polymer bead. Namely, it is Au 3.2mg per polymer bead one gram. And, Au was desorbed from polymer bead about 90% under buffer solution of the pH 10 at room temperature or acidic condition using 0.5M hydrochloric acid solution at 80°C. Moreover, based on above experimental condition, Au was separated from other 64 kinds of ion contained at the same concentration of Au.
Electrodeposition of Cu was conducted at a current density of 260 A/m2 for 48 h in a Cu electrorefining solution at 60°C to investigate the effect of glue, thiourea, and chloride ions on the morphology and texture of the deposited Cu. The texture was evaluated using electron back scatter diffraction patterns. The chloride ions promoted growth in the <110> direction of the deposited Cu, and glue and thiourea maintained the field-oriented texture type of the crystals. In a solution containing the appropriate amount of glue, thiourea, and chloride ions, the deposited Cu showed a smooth surface without salient edges due to anomalous deposition. However, an increase in the concentration of glue and chloride ions in the solution caused a locally anomalous salient. With an increase in the concentration of thiourea, the surface became smooth and the concentration of current at the edge was suppressed. In an additive-free solution or in a solution containing two or less additives, the deposited Cu initially showed unoriented dispersed or field-oriented texture type of crystals, and with increasing deposition duration, it showed epitaxial growth. This is attributed to the decrease in the actual current density due to an increase in the surface roughness of the deposited Cu with deposition time. The continuous epitaxial growth increased the grain size of the deposited Cu, resulting in an increase in the asperity.