A new scheme for field measure in rock engineering is proposed. The core technology in the new scheme is the use of light emitting sensors capable of 1) measuring data and 2) presenting them simultaneously by color of light using LED or other form of light emitting devices. Unlike in a conventional method of data acquisition, the use of these new devices enables real-time data processing and visualization on-site, so that the state of deformation, strain, inclination and etc. for a rock structure in concern is grasped with no delay in time and is shown visually to anyone nearby. Rational use of the new scheme On Site Visualization offers a new stage whereby visually shared real-time information about the rock structures in concern could lead to a new paradigm of field measurement in rock engineering. This paper introduces the experiences of OSV application in civil engineering projects and discusses its potential to be applied in mining and resources engineering.
The geomechanical response of the seabed layers to gas extraction from a methane-hydrate reservoir has not been sufficiently clarified, although they are essential to ensure sustainable production of methane hydrate in marine sediments. In particular, the time-dependent behaviors of methane-hydrate-bearing sandy sediment have great significance in the long-term prediction of the geomechanical behaviors of sub-seabed layers. The results of laboratory tests indicate that methane-hydrate-bearing sand has strong time dependence. In this paper, the timedependent behaviors of artificial methane-hydrate-bearing sand samples obtained in the three types of triaxial compression tests, e.g., creep test, constant-strain-rate test and constant-stress-rate test, are reviewed and discussed, and a nonlinear viscoelastic constitutive equation is proposed for methane-hydrate-bearing sand based on the creep properties. The stress-strain relationship predicted by the present constitutive equation appears to fit qualitatively the result of constant-strain-rate and constant-stress-rate tests. The present constitutive equation can be incorporated in a numerical simulator for the long-term prediction of geomechanical behaviors.
In hydrothermal alteration area, arsenic and metals included in rocks can be expected to leach out from the outcrops. In order to perform risk assessments of leaching arsenic and metals, it is important to systematically understand the leaching behavior of arsenic and metals from rocks and soils. In this study, the geochemical behavior of arsenic and metals, which were leached out from rocks in a hydrothermal alteration area, was investigated. Monolith of outcrop was classified into layer A (weathered rocks), layer B (intermediate), and layer C (host rocks) based on soil classification, and then extraction experiments of arsenic and metals for individual layer were conducted. The results showed that in the hydrothermal alteration zone, arsenic and metals readily leached into the water from the rocks of layer C as ionic forms, while arsenic and metals from the rocks of layer A were relatively stable. That is, the leaching concentrations were lower, and leached arsenic and metals were colloidal. In addition, the arsenic leaching from the layer C into the water increased at a lower temperature. By considering the chemical forms of arsenic and metals and their geochemical behaviors under several environmental conditions, we can evaluate the risks of natural arsenic and metals and apply such knowledge to the treatment procedures.
Distribution behaviors of non-ferrous metals of copper, lead, nickel, cobalt and sodium between matte and slag were studied using slags with a composition similar to industrial copper matte smelting of low grade secondary materials. The distribution ratios of copper, lead and nickel increased with the increasing copper concentration in matte, i.e., matte grade. In contrast, those of cobalt and sodium decreased with the increasing matte grade. Two interesting effects of sodium were found out in the present study. One is to reduce copper, lead and nickel concentration in slag; and the other is suppression of lead evaporation from matte. Both effects results in the increasing distribution ratios of copper, nickel and lead; however, sodium has no influence on the distribution ratio of cobalt. The effect of silicate degree, SD, of slags on the concentration of non-ferrous metals in slag was also found out. Distribution ratios of copper, nickel, lead and cobalt in present study, in which the SDs of slags were comparatively low (0.7 ～1.3), were 2 ～4 times higher than those in the previous study using silica-saturated iron silicate slag (SD ≃ 1.5). Variation in copper and nickel concentration in slag with matte grade was also dependent on the SD. These decreased with the increasing matte grade for the slag with low silicate degree. In conclusion, we proposed that the efficient recovery of rare metals, such as nickel and cobalt, in the copper matte smelting of low grade secondary materials is expected when the influences of sodium in secondary materials and a slag with low silicate degree are effectively utilized.
In order to develop a new method for the high-pressure acid leach (HPAL) process, which is a hydrometallurgical processing technology, the sulfurization of Ni and Co in a leach solution of nickel laterite ore was investigated. Ni and Co, which are the valuable metals present in the nickel laterite ore, are recovered as a mixed sulfide (NiS + CoS). Among the impurities present in the nickel laterite ore, Fe, Mn, Mg, and Al can be separated from Ni and Co by dissolving and leaving in a leach solution. Ni and Co, which are the target metals, can be selectively recovered by precipitation. Process parameters, which affect the sulfurization reaction of Ni and Co, are analyzed in this study. These process parameters include the relationship between the Ni concentration and the H2S concentration, and the relationship between the H2S concentration and redox in the solution. H2S, which is the precipitant for sulfurization reaction, should be dissolved in the leach solution by achieving an equilibrium between the gas phase and the aqueous phase in order to achieve homogeneous dissolution. In addition, optimum conditions for temperature and pH are established. Scaling on the reactor was minimized by controlling the seed addition rate. Based on these findings, a process for the effective recovery of Ni and Co from a solution containing impurities such as Fe was developed.