The exploration activities play an important role for the steady supply of non-renewable resources such as copper. On the other hand, exploration activities will be very risky and vulnerable to the level of corporate financial situations. Its budget will be easily reduced at the time of depressed metal prices and economic recessions. This study focuses on the copper production cost from exploration to refining stages, and the reserves replacement of copper through exploration and project acquisition during 1992-2001, and examines the implications for the exploration strategies. The exploration cost or discovery cost can be defined by the exploration spending for the discovery of unit of metal. This paper includes (1) quantitative analysis of copper production cost, (2) reserves replacement by exploration and project acquisition, (3) exploration vs acquisition costs. Since copper prices rose record high level of 6,722 $/t in 2006, acquisition costs during 2006 were compared with the past during 1992-2001, and obtained the following results; (1) Exploration is the most economic strategies for the copper reserves replacement, (2) Acquisition costs are becoming higher along with the higher copper prices during 2006.
In order to develop a better practice for enhancing the cost performance and reducing the risk of construction of underground openings, the authors focus on the cablebolting. A field experiment was conducted during constructing an underground powerhouse to establish a construction practice of cablebolting, involving measuring an effectiveness of preset cablebolts for the rock stability. The conventional construction procedures and equipments for dowels are found to be applicable to cablebolting. The pre-mixed cement, which is commonly applied for conventional dowels, are also applicable to a grout material for cablebolting by adjusting the water-cement ratio of 40 to 45%, which can be controlled by the flow value of around 180. Through the back analysis considering the non-uniformity of rock elasticity around the underground powerhouse, it is found that the preset cablebolts alleviate the stress relax in the surrounding rock of the underground powerhouse due to its excavation. Such back analysis is useful during the excavation of an underground powerhouse to measure the effectiveness of preset cablebolts and to manage adequate arrangement of post-set supports such as dowels and pre-stressed anchors.
The tangent modulus method was applied to pre-loaded cylindrical specimens of Shikotsu welded tuff, Inada granite and Kimachi sandstone. It was clarified that the tangent modulus method could be applied to the rocks. A positive correlation was observed between the preloading duration and the maximum delay time at which the preloaded stress was determined with the error less than 20% for Shikotsu welded tuff and Inada granite although the correlation was not confirmed for Kimachi sandstone due to small number of specimens. The confirmed maximum delay time for each rock was 42 days for Shikotsu welded tuff, 21 days for Inada granite and 28 days for Kimachi sandstone based on clip gage. The stress at bending point in uniaxial cyclic loading for triaxially pre-loaded Kimachi sandstone decreased as confining pressure in the preloading increased. Kimachi sandstone and Shirahama sandstone were triaxially preloaded and triaxially cyclic loaded under decreased or increased confining pressure. The stress at bending point decreased with decrease of confining pressure for Shirahama sandstone. No apparent change was observed for Kimachi sandstone. Bending points were not observed for Shirahama sandstone under increased confining pressure. On the other hand, the stress at bending point decreased with increase of confining pressure for Kimachi sandtsone. The physical phenomena utilized to detect stress memory in tangent modulus method was explained based on a model which consisted of two springs and a slider. One spring represents the elasticity of rock. Another spring and the slider are connected in parallel and represent inelasticity due to irreversible closure of voids. Decrease of tangent modulus at the preloaded stress was well simulated by the model.
The fluid flow in a single rock fracture during shear processes has been an important issue in rock mechanics and is investigated in this study using the Finite Element Method (FEM), considering evolutions of aperture and transmissivity with shear displacement histories under different normal loading conditions. The distributions of fracture aperture and its evolution during shear were calculated from the initial aperture, based on the laser-scanned sample surface roughness features, and shear dilations measured in the laboratory coupled shear-flow tests. Three rock fractures with different roughness were used as parent samples from which nine replicas were made and tested under three normal loading conditions. For flow simulations, a special algorithm for treating the contact areas as zero-aperture elements was used to produce more accurate flow field simulations, which provide good agreement with the flow rate data obtained from the laboratory tests, showing that complex histories of fracture aperture and tortuous flow fields with changing normal stress and increasing shear displacements.
Platinum Group Metals (PGM) are usually recovered from pyrometallurgically concentrated and refined PGM concentrate. PGM concentrate is dissolved with highly concentrated hydrochloric acid with oxidants. Therefore PGM form the maximum coordinated chloro-complex, such as [MCl6]2-, [MCl6]3- (M: PGM) and they are easily extracted with some extractants1) or adsorbed with some ion exchange resins2) except for rhodium. However, concentration of chloride ion in leach solution of copper anode slime with chlorine gas is kept relative low level, around 3kmol/m3, to prevent dissolution of harmful impurities (ex: antimony, bismuth, lead, and tin). Therefore some parts of PGM exist as aquo- (or hydroxo-) chloro-complex, such as [MClx (H2O) 6-x]2-, [MClx (H2O) 6-x]3-. Since aquo chloro-complexes are difficult to extract or adsorb, co-extractant with anion exchange extractant is tested. Addition of TBP is successfully performs on extraction of PGM ions by synergic effect. Even chloro-complexes of rhodium which are not extracted with the conventional extractants can be extracted to the mixture of TOMAC and TBP. Since both PGM aquo-chloro complexes and are fully stable in the room temperature, it is important to change the all complexes to maximum coordinated chloro-complexes in chlorine leach step of copper anode slime with high concentrated chloride ion (≥7.3kmol/m3). Chloride ion concentration under low temperature (25°C), ORP, pH, both temperature and retention time under low concentrated chloride ion (≤2.8kmol/m3) do not affect the distribution coefficient of PGM. Under optimum condition, the extraction rates of iridium, ruthenium, rhodium are 92, 95, 85 (%) respectively with TOMAC and TBP (1:1) in five stages of extraction.
Wood samples (Japanese cedar, Sugi in Japanese) impregnated with 1 - 10wt% iron were pyrolyzed at 1000°C to study the influences of the impregnated iron on the distribution of the pyrolysis products and the structure of the char. The pyrolysis of wood sample without iron produced about 20% of char and about 32% of tar. In the pyrolysis of the wood samples impregnated with iron, the char yield increased to 35% and the tar yield decreased to a few percent. Both CO and CO2 yields were enhanced by the presence of the impregnated iron. The structure of char produced by pyrolysis of wood sample without iron was amorphous, whereas the turbostratic carbon was formed by the loading of iron. Surface areas of char increased from 30m2/g for the wood sample without iron to 230 - 270m2/g for the wood samples with iron.
Recently, many researches and studies of geosphere environments have been conducting to clarify regional variations and the anthropogenic or natural contamination by metals in soils. However, particularly in Japan, those results were held by individual research institute and nationwide database have not been systematized. In this study, an integration of geosphere environmental information and database architecture were carried out by using a geographical information system (GIS). Geosphere environmental information such as geology, topography, soil, vegetation, satellite image, position of mineral deposit, alteration and heavy metal's concentration in groundwater, in river-bed sediments and in soils was collected. In this study, we examined a hydrologic analysis considering the Pb concentration in river-bed sediments as an example use of the database. The topographic map, geologic map, position of mineral deposit and geochemical map in Japan published from the Geological Survey of Japan, AIST were overlaid on the GIS and evaluated Pb concentration distribution at each watershed. As the result, mineral deposits were the most probable main resource of Pb. We also evaluated the relationship between the Pb concentration and the geology at the backland of sampling points. After analyzing the exposed ratio of various types of rocks at each watershed and calculating the correlation coefficient between the ratio of rock exposure and the value of Pb concentration, we found that some sedimentary rocks exposed along rivers and a certain kind of metamorphic rock showed a little good correlation with Pb concentration. It is expected that the geosphere environmental information database can be used in a determination of anthropogenic pollution, determination of health risk, and reflection to national land use plan.