In this study, we measured properties of natural ventilation in a closed Arakawa mine and considered those properties theoretically. The natural ventilation pressure was estimated from the ratio of leakage airflow to the airflow when the ventilation door is fully opened, and the differential pressure between the front and the back of the door. We used a simple calculation method based on the average density of humid air in a simple ventilation circuit model．The measured natural ventilation pressure agreed very well with the results of simple calculation method. Therefore, if the modeling of the ventilation network is performed appropriately, simple calculation method is effective. In addition, seasonal changes in the quantity of ventilation agreed well with the results using the measured nature ventilation pressure, ratio of airflow, and average ventilation resistance value. The direction of airflow, natural ventilation pressure, and quantity of ventilation showed a change approximately every six months.
Compared to uniaxial or triaxial compression tests on rocks, direct tension tests on rocks are not common in practice. As is well known, the reasons are because underground rock masses are usually under compressive stress state and/or because the direct tension test on rock is rather difficult and time-consuming. However, the direct tension test is important to understanding mechanical characteristics of rocks under tensile stress state. Moreover, the number of case examples requiring accurate tensile strength of rock is recently increasing in rock engineering. This paper summarized the methods and points of attention for the direct tension test on rock, based on the previous studies and the authors' experiences. The direct tension tests on rock have adopted a variety of specimen shape, loading apparatus and testing conditions. This paper presented some important factors affecting the deformation and failure of rocks under tensile stress state. The relations of the direct tensile strength to the other mechanical properties, such as the Young's modulus, the elastic wave velocity and the compressive strength, was discussed. The rock tests related to the direct tension test were explained: tension test using centrifugal action, tension test under confining pressure, dynamic tension test and in situ tension test on rock masses. This paper introduced the authors' ongoing standardization activity for the direct tension test on rock.
In this study, we conducted a follow-up survey of brick cracking on a brick wall in the parking space of JR Kitami Station and installed temperature sensors on the surface of the brick wall in order to measure changes in the brick wall temperature during late winter. In addition, we attempted to reproduce the brick cracking observed on the brick wall by conducting an indoor freeze-thaw experiment. The field investigation confirmed that the brick cracking on the brick wall occurred on the south-facing wall in the period from the coldest season to late winter. It was also confirmed from the records of the measured surface temperatures of the brick wall that, even in winter, the bricks could thaw in daytime and re-freeze at night, depending on the weather, solar radiation, and depth of snow coverage. Furthermore, we were successful in reproducing the brick cracking observed on the brick wall in the parking space of JR Kitami Station in the indoor freeze-thaw experiment. Our experience outlined above has demonstrated that frost damage can occur on the brick wall at JR Kitami station by a mechanism caused by the phenomenon of closed-system freeze-thaw, which the authors propose.
It is important to understand the distribution mechanism of heavy metal elements in environmental systems, because the toxicities of various metals and metalloids significantly affect health risks. The heavy metals concentrations are controlled by a wide of variety environmental factors. This study aims to clarify main influence factors on the heavy metal distribution in sediment, soil, river in the Natori River, Sendai City. We firstly produced geochemical maps for heavy metal concentrations (As, Pb and Cr) of river sediment, neighboring soil (bulk component, soluble component in 1N HCl and in pure water) and river water. The heavy metals concentrations in river water increase from upper stream to down stream, whereas heavy metal concentrations in river sediments and soil vary little from upper stream to downstream. There are no anomalous distributions of heavy metals in the studied area, although many anthropogenic materials are found in sediment, soil and river water. The correspondence analysis was applied to investigate relationships of heavy-metal concentrations between sediment, soil and river water. The results indicate that the heavy metals (As, Pb Cr and Zn) in sediment, soil and river water are dominantly controlled by natural sedimentary processes, such as denudation and sedimentation. The proposed method could be further applied for other pollutants in various environment systems. From a viewpoint of risk assessment of heavy metals, it is suggested by the presence of closer relationship of heavy metals that contains the risk information of heavy metals.
In recent years, global environmental problems, such as climate change and global warming, are receiving too much attention. Especially, the importance of biodiversity has been recognized since COP10, which was held in Japan in 2010. The aim of this study is to evaluate the gold extraction and recovery from waste materials in the context of Life Cycle Impact Assessment methodology, based on endpoint modeling. In this research, aqua regia, cyanide solution and ammonium thiosulfate solution were employed as leaching reagents. The gold exudation and recovery system were evaluated by LIME2, which is the Japanese version life cycle impact assessment method based on endpoint modeling. The system boundary includes pretreatment of the scrap, manufacturing process of leaching solution, Au recovery, processing of waste fluid and residual substances. Moreover, two scenarios for the pretreatment of a scrap were taken into consideration:(1) chelating resin was used in case of the low concentration, and (2) electrolytic winning was performed in case of the high concentration. Consequently, one of the main findings is that waste showed the largest load at influence domains in any case, and the rate of the load to social property was the largest at damage evaluation. Furthermore, the environmental load, in the case of using electrolytic winning was lower, when compared with the case where chelating resin adsorption was used. In other words, in order to lower the environmental burden, the grade of Au in the product exiting the pretreatment process should be increased.