Mining In Japan Research Articles

Supervisors' Work Engagement Is Associated With Interactivity and Carefulness in Supporting Subordinates: A Cross-sectional Study Using Text Mining in Japan.

This study aimed to structure supervisory support and clarify the relationship between supervisors' work engagement and support for their subordinates. We conducted a cross-sectional study in a manufacturing company using a questionnaire survey. Supervisors provided open-ended responses regarding the provision of support for their subordinates. Using text mining, we structured these descriptions into multiple categories, assigned words to them, and analyzed frequently mentioned categories by the level of work engagement. We obtained responses from 729 participants that included 13,968 words. We structured supervisory support by three categories (contents, direction, and attitude toward support) and 11 subcategories. As supervisors' work engagement increased, the rates of mentioning information retrieval, information transmission, and carefulness increased. Supervisors with work engagement could communicate with each other and be careful in providing support to their subordinates.

Examination of Source Control Measures by Applying Groundwater Flow Analysis to Abandoned Mines in Japan

Examination of Source Control Measures by Applying Groundwater Flow Analysis to Abandoned Mines in Japan

Effect-based water quality assessment of rivers receiving discharges from legacy mines by using acute and chronic bioassays with two cladoceran species

Abstract Information about the ecotoxicological impacts of surface waters that receive discharges from legacy mines is valuable to infer the ecological impacts on natural environment for managing mine discharges. In this study, we investigated behavioural and reproductive responses of two cladoceran species Ceriodaphnia dubia and Daphnia magna to water samples collected from metal-contaminated and reference rivers near legacy mines in Japan. The toxicity identification evaluation (TIE) of water samples that caused D. magna immobility was conducted to evaluate the key metals causing acute toxicity. The results of our water quality assessment performed using two cladoceran species demonstrated modest to significant adverse effects on their behaviour and reproduction, suggesting the potential for ecotoxicological impacts on natural populations and communities at several contaminated sites that received mine drainage. The results of TIE of water samples that caused D. magna immobility indicated likely contributions of Zn and Cu. These results imply that effect-based water quality assessments such as ours can provide direct and unique evidence of the ecotoxicological impacts of metals in river waters, which will be useful for better understanding and predicting the ecological effects of these metals in the natural environment.

Study on the Applicability of Passive Treatment for Mine Drainage Treatment at Abandoned Mines in Japan

Study on the Applicability of Passive Treatment for Mine Drainage Treatment at Abandoned Mines in Japan

Improvement in pH and Total Iron Concentration of Acid Mine Drainage after Backfilling: A Case Study of an Underground Abandoned Mine in Japan

If the excavated underground veins are not backfilled, they may be a factor in the continued outflow of acid mine drainage (AMD). The flow rate of AMD can be reduced by backfilling underground drifts from abandoned mines. In addition, the quality of AMD may be improved as the flow rate of AMD reduces. In this paper, the quality of the AMD after backfilling was evaluated by a three-dimensional geochemical analysis model when the groundwater level was recovered after backfilling. The measured dissolved iron (Fe) and sulfate ion (SO42−) concentrations and pH before backfilling the drift were reproduced by the calibration of the simulation. Using the calibrated model, the pH at the outlet of the drift was changed from about pH 3 before backfilling to about pH 4 to 5 after backfilling. When calcite was contained in the filling materials of the drift, the pH approached neutral. However, when gypsum was formed, the neutralization was inhibited. The Fe concentration discharged from the drift was calculated at approximately 0.002 mol/L before backfilling. The total Fe concentration was calculated at 0.0004 mol/L or less after backfilling, and the dissolved Fe concentration decreased by several orders of magnitude after backfilling. A geochemical model quantitatively evaluated the improvement in water quality after backfilling the drifts. This method can be applied to the other abandoned mines with similar hydrogeological conditions.

Projecting future changes in element concentrations of approximately 100 untreated discharges from legacy mines in Japan by a hierarchical log-linear model

Understanding future changes in the concentrations of elements such as Cd in mine drainages, which can cause severe environmental impacts, is crucial to strategically optimize the treatment and management of such drainages. In this study, on the basis of 17-year data (2003–2019) for 99 untreated drainages from legacy mines in Japan, we developed a Bayesian hierarchical log-linear model that can capture temporal changes in the concentrations of seven elements including six metals (Cd, Pb, As, Cu, Zn, Fe, and Mn) in individual mine drainages. We also projected future changes to understand the prospective trends nationwide. The modeling results showed that, during 2003–2019, although overall decreasing trends were observed for most elements across all the drainages evaluated, decreases in the concentrations of these elements were not evident in many mine drainages (5%–28% of drainages for individual elements); in addition, any rise in the number of mine drainages with element concentrations below nationwide drainage standards over the next 100 years will likely be limited (e.g., approximately 10 drainages for Zn and Fe at median estimates). These results have significant implications for future strategies to manage mine drainages: it is probably too optimistic to assume that the element concentrations of mine drainages will always decrease, or that these drainages will satisfy drainage standards (permits) in the not so distant future.

Identification of source mine using sulfur, mercury, and lead isotope analyses of vermilion used in three representative tombs from Kofun period in Japan

Vermilion, a precious red pigment that was used in ancient times, was believed to protect the dead from evil beings and was thus used in burial facilities in China and Japan. Vermilion was used frequently in tumuli in Japan during the expansion of the Yamato kingship (third to sixth centuries AD)—named the Kofun period. Until recently, the cinnabar used in tumuli in Japan was thought to have been imported from China, but evidence of its Japanese origin is gradually emerging. The purpose of this study is to evaluate the usefulness of S, Hg, and Pb isotope analyses for identifying the origin of the vermilion used in these tombs. Therefore, the S, Hg, and Pb isotope ratios of vermilion collected from three tumuli from the early Kofun period, namely, Sakurai-Chausuyama, Kurozuka, and Tenjinyama (which were built in the main area of the ancient Yamato kingship), were compared with those of cinnabar from the Yamato Mercury, Niu, and Suii mines in Japan and the Wanshan and Qingtongguo mines in China to identify the source of the vermilion. Each isotope indicates multiple possibilities about the origin of the vermilion used in each tumulus. Nonetheless, with the three isotopes considered at the same time, the results indicate that the red pigments from the Sakurai-Chausuyama tumulus come from the Yamato Mercury Mine, whereas the vermilion used in the Kurozuka and Tenjinyama tumuli is from the Niu Mine. Therefore, although single isotope analysis can be useful as a first approximation of the source mine of vermilion, analysis of all three isotopes yields considerably more accurate results. On the basis of these three isotope analysis methods, research on the distribution of ancient vermilion is expected to proceed from the identification of the origin of the vermilion used in the abovementioned ruins.

Investigation of Groundwater Flow Using Δ18O and ΔD in a Sulfur Mine in Japan

The A sulfur mine is located in the Iwate Prefecture of Japan. This mine has both surface and underground parts and was operatedfrom the late 1800s to the late 1900s. Since the early 1900s, acid mine drainage (AMD) has been reported in this mine, and the wastewater has been neutralized in a treatment plant since the mine was closed. Recently, reducing the AMD volume by decreasing waterinflow to the underground mine has been considered as a way to reduce the AMD treatment cost. The first step in such an approachis to understand in detail the groundwater flow around the mine. However, part of the study area is covered by lava and comprisescrystalline rocks with complicated structures, making it difficult to understand the groundwater flow. Therefore, the present studyinvestigated the groundwater flow around this mine by focusing on water quality, such as pH and electrical conductivity (EC), stableisotopes (i.e. δ18O and δD) and 3H in the surface and ground water. The spatial distributions of pH, Stiff diagrams, and δ18O and δDvalues in the surface and ground water indicated that the groundwater flow system was divided into three basins in the study area,as predicted from geomorphological information. Moreover, the spatial distribution of δ18O and δD in the surface and ground watersuggested that the groundwater recharged at the highest altitudes in the B mountain in the northwest of the mine might flow in theunderground mine. Furthermore, the 3H values in the waste water discharged from the underground part of mine implied that thegroundwater age was no more than approximately 60 years old.

Complete slaking collapse of dike sandstones by fresh water and prevention of the collapse by salt water

Slaking is a well-known process, in which the surface of rock masses consisting of rocks such as mudstone, shale, etc. show rapid and complete disintegration when they are subjected to drying and then wetting with fresh water. On the other hand, dried sandstones even if they contain clay minerals such as smectite, etc., usually do not exhibit complete disintegration when they are soaked in fresh water. Instead, they usually show a strength decrease. Their slaking durability is tested by rotating them in a drum which is partially immersed in fresh water and eventually measuring the decrease in weight. On the other hand, it was found that some of the Paleogene sandstones from Kushiro Coal Mine in Japan, were completely disintegrated when they were immersed in fresh water followed by drying, but they were not collapsed when saline water was used instead of the fresh water. It was also shown that sandstones containing calcite did not show the complete breakdown even in fresh water. To understand the complete collapse of sandstones in fresh water and prevention of the collapse by salt water, sandstones sampled from Neogene dikes and Cretaceous at the mine were immersed in pure and salt water with Shikotsu welded tuff for comparison. Only dike sandstones showed a complete collapse in pure water and 3% salt water. Dike sandstone further showed severe time-dependent damage in salt water whose salinity was less than 7%. The results were explained by the dissolution of halite, swelling pressure of montmorillonite, osmotic pressure, etc.

Forecast of AMD Quantity by a Series Tank Model in Three Stages: Case Studies in Two Closed Japanese Mines

There are about 100 sites of acid mine drainage (AMD) from abandoned/closed mines in Japan. For their sustainable treatment, future prediction of AMD quantity is crucial. In this study, AMD quantity was predicted for two closed mines in Japan based on a series tank model in three stages. The tank model parameters were determined from the relationship between the observed AMD quantity and the inflow of rainfall and snowmelt by using the Kalman filter and particle swarm optimization methods. The Automated Meteorological Data Acquisition System (AMeDAS) data of rainfall were corrected for elevation and by the statistical daily fluctuation model. The snowmelt was estimated from the AMeDAS data of rainfall, temperature, and sunshine duration by using mass and heat balance of snow. Fitting with one year of daily data was sufficient to obtain the AMD quantity model. Future AMD quantity was predicted by the constructed model using the forecast data of rainfall and temperature proposed by the Max Planck Institute–Earth System Model (MPI–ESM), based on the Intergovernmental Panel on Climate Change (IPCC) representative concentration pathway (RCP) 2.6 and RCP8.5 scenarios. The results showed that global warming causes an increase in the quantity and fluctuation of AMD, especially for large reservoirs and residence time of AMD. There is a concern that for mines with large AMD quantities, AMD treatment will be unstable due to future global warming.

Estimating the injury rates and causes of fatalities in the Japanese mining industry, 1924–2014

This article investigates the trends in injury rates and causes of fatalities in the Japanese mining industry. Accident data were collected from the Japan Statistics Yearbooks released by the Bureau of the Prime Minister. These data were analyzed to estimate the injury rates and accident causes in the Japanese mining industry. In Japan, the median injury, severe injury and fatality rates were 129.25, 5.44 and 2.99/1000 workers, respectively. A collapsing roof in an underground mine was the principal cause of fatal accidents, accounting for a median value of 21/1000 worker deaths during the entire period under study. In comparison with the accident experience of the USA and the Democratic Republic of Congo, countries with substantial mining industries, the median values of the fatality rates were 0.58 and 0.28/1000 workers, respectively. We conclude that Japanese mineworkers were most exposed to the risk of accidents during the prewar era.

Seismic response and stability of abandoned lignite mines in Japan

The 2003 Miyagi Hokubu and 2011 Great East Japan earthquakes induced severe damage to abandoned mines and resulted in many collapses. There is a growing concern on the seismic response and stability of areas situated above the abandoned lignite mines in Japan due to urbanisation in recent years. The authors had the chance to investigate some damage on abandoned lignite mines caused by the 2003 Miyagi Hokubu and 2011 Great East Japan earthquakes and some local instabilities in abandoned mines in Mitake Town, Gifu Prefecture. This paper describes the characteristics of damage induced on abandoned lignite mines by the 2003 Miyagi Hokubu and 2011 Great East Japan earthquakes. The authors also performed a series of shaking-table experiments on model abandoned mines to understand the response and stability of actual abandoned mines and explain the fundamental mechanism in the formation of sinkholes and subsidence. Furthermore, some discussions are given on the possible causes of the damage inflicted on the ground surface on the basis of some shaking-table model tests in the laboratory.

The status of KAGRA underground cryogenic gravitational wave telescope

KAGRA is a 3-km interferometric gravitational wave telescope located in the Kamioka mine in Japan. It is the first km-class gravitational wave telescope constructed underground to reduce seismic noise, and the first km-class telescope to use cryogenic cooling of test masses to reduce thermal noise. The construction of the infrastructure to house the interferometer in the tunnel, and the initial phase operation of the interferometer with a simple 3-km Michelson configuration have been completed. The first cryogenic operation is expected in 2018, and the observing runs with a full interferometer are expected in 2020s. The basic interferometer configuration and the current status of KAGRA are described.

A Century-Long Ex-Post Evaluation of a Countermeasure for a Serious Pollution Problem in Japan

Current environmental literature provides insufficient information and analysis on how today’s environmental state was shaped by countermeasures to pollution taken in the last century, which could be characterized as a century of environmental degradation. Such a look back is crucial to better understand and predict how policy and countermeasure choices today may shape the world in the future. Following this line of reasoning, the present work conducted a post audit on the long-term consequence of a countermeasure against a major heavy metal pollution case caused by the operation of the Ashio Copper Mine in Japan. It examined this issue from both environmental and societal perspectives by document analysis, field investigation on the heavy metal concentration in the soils of a heavy mental catchment area and questionnaire survey on the public knowledge with regard to the copper mining contamination case as well. It shed new light on how environment may evolve via the interaction with human activities by identifying drivers behind major changes. It also revealed a gap between the reality and the public perception towards the consequence of the copper contamination. Such insights will deepen the discussion on what is sustainability and motivate further study to pursue sustainable development.

Improving the T2K Oscillation Analysis With fiTQun: A New Maximum-Likelihood Event Reconstruction for Super-Kamiokande

A new event reconstruction algorithm, fiTQun, has been developed for the Super-Kamiokande detector. Super-Kamiokande is a ring-imaging water Cherenkov detector with a 22.5-kton fiducial volume located 1000 m underground in the Kamioka Mine in Japan. Neutrino events in the detector’s central volume produce charged particles whose Cherenkov rings are imaged by more than 11,000 photomultiplier tubes (PMTs) that line the walls of the detector. This new reconstruction software is able to reconstruct the detailed kinematics of the neutrino interaction from the charge and timing information of each PMT. In contrast to previous reconstruction algorithms that use image processing and pattern recognition techniques, fiTQun uses a maximum-likelihood approach that takes advantage of the known Cherenkov emission profiles and the detector response to evaluate the likelihood of a given reconstruction hypothesis. This approach provides a unifying framework for all aspects of the event reconstruction, including kinematics, ring counting, and particle identification. Using fiTQun to reconstruct neutrino events for the Tokai-to-Kamioka (T2K) experiment can greatly improve the current event selection by reducing pion backgrounds, improving separation of electrons and muons, and reconstructing the neutrino energy with greater precision. These improvements should significantly increase T2K’s sensitivity to the oscillation parameters.

Calculation method for light scattering caused by multilayer coated mirrors in gravitational wave detectors.

Scattered light in inteferometric gravitational wave detectors needs to be reduced so that it will not harm the actual signals coming from a gravitational wave. In this paper, we report on the application of the theory of light scattering from mirrors in interferometric detectors having multilayer coatings on their surfaces and compared the results with single-surface scattering theories, which are traditionally used in the field of gravitational wave detectors. For the first time in this field, we have calculated the scattering distributions of the power-recycling, the signal-recycling, and the beam-splitter mirrors in KAGRA (a cryogenic interferometric gravitational wave detector currently under construction in the Kamioka mine in Japan) by using models of their multilayer coatings. Furthermore, we have performed simulations to show the differences between multilayer scattering and single-surface scattering models in the back-scattering of mechanical structures close to the mirrors and the impact on the sensitivity of the KAGRA detector. We show that the back-scattering by using those coatings can be larger by up to almost two orders of magnitude and they also give rise to additional scattering features that should be taken into account for all optical applications in gravitational wave detectors.

Children’s Experiences of the Coal Mine Disaster: Analysis of Junior High School Students’ Essays in Yubari City

In 1981, a gas outburst accident occurred in the Yubari Shintanko coal mine, the only expectant mine in Japan, it caused 93 deaths. As a result, Yubari Shintanko closed in 1982. This major disaster was a turning point for sustainability of Yubari City, the largest coalfield in Japan. Finally, Yubari City was bankrupted in 2007. This paper aims to explore how miner’s children experienced this disaster and felt about region, family, and themselves, and to explain the relation between region declining and children’s lives. The data of this paper are the archived 600 essays, written by the junior high school students at the time of the disaster. There are three findings. First, the children who lost their father were the most shocked. They faced profound sadness. But they expressed that they had decided to overcome their sadness with surviving family. Second, the children who didn’t lose their father were also influenced. They were anxious about the future of Yubari, their family, and themselves. Furthermore, they decided to strive for their future. Third, they understood the disaster as a turning point of Yubari declining and looked ahead their future outside of Yubari. In conclusion, this disaster created their hopelessness to Yubari region and, as a result, promoted the decline of the city through their migration to other city. Furthermore, it is important to clarify that Yubari City has to continue the struggle to the regeneration.

Characterization of the room temperature payload prototype for the cryogenic interferometric gravitational wave detector KAGRA.

KAGRA is a cryogenic interferometric gravitational wave detector currently under construction in the Kamioka mine in Japan. Besides the cryogenic test masses, KAGRA will also rely on room temperature optics which will hang at the bottom of vibration isolation chains. The payload of each chain comprises an optic, a system to align it, and an active feedback system to damp the resonant motion of the suspension itself. This article describes the performance of a payload prototype that was assembled and tested in vacuum at the TAMA300 site at the NAOJ in Mitaka, Tokyo. We describe the mechanical components of the payload prototype and their functionality. A description of the active components of the feedback system and their capabilities is also given. The performance of the active system is illustrated by measuring the quality factors of some of the resonances of the suspension. Finally, the alignment capabilities offered by the payload are reported.

Large-scale cryogenic gravitational-wave telescope in Japan: KAGRA

KAGRA, the large-scale cryogenic gravitational-wave telescope (formerly known as LCGT), is a laser interferometric detector under construction at the Kamioka mine in Japan. We report on the current status of the project as well as the overview of the main features and the schedule. The construction has been underway since 2012, and the tunnel excavation in the mine for two 3-km arms finished at the end of March 2014. As with the other advanced terrestrial interferometers, KAGRA will have two long Fabry-Perot cavities to sense gravitational waves, but they are to be installed underground for lower seismic noise. KAGRA will be the first large interferometer having cryogenic cavities, the mirrors for which are planned to be cooled down to around 20 K for reducing thermal noise.

Carbon monoxide poisoning: clinical features of the victims of the explosion accident of Mitsui-Miike Mikawa coal mine 50 years ago

Clinical features of carbon monoxide poisoning have been described in 24 victims of an intense explosion accident of the Mitsui-Miike Mikawa coal mine in Japan 50 years ago; these victims were admitted to the Kyushu University Hospital as they suffered from severe poisoning. In the early stage of poisoning, all victims showed disturbed state of consciousness, varying in duration from 5.5 hours to 3 months, and the duration of unconsciousness was closely correlated to the clinical severity in the late stage. Some of the severely poisoned patients showed a transient stage of apallic syndrome. After recovery from unconsciousness, all patients presented with severe amnestic syndrome and loss of initiative. Neurologically, the extrapyramidal signs were prominent in the early stage, which gradually improved in the late stage. Variable types of agnosia and apraxia were apparent in some of the severely and moderately poisoned patients in the late stage, with prominent Gerstmann syndrome and visual-visuospatial agnosias. Since these signs showed poor improvement, the agnosia and apraxia, as well as impaired intellectual ability, remained as a sequela of the poisoning, and were one of the major causes of deficits of the patients in their daily life activities in the late stage.