• Tunnel and Underground Space
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• v.30 no.6
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• pp.573-590
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• 2020

This study presents the current status of DECOVALEX-2023 project Task G and our research results so far. Task G, named 'Safety ImplicAtions of Fluid Flow, Shear, Thermal and Reaction Processes within Crystalline Rock Fracture NETworks (SAFENET)' aims at developing a numerical method to simulate the fracture creation and propagation, and the coupled thermohydro-mechanical processes in fracture in crystalline rocks. The first research step of Task G is a benchmark simulation, which is designed for research teams to make their modelling codes more robust and verify whether the models can represent an analytical solution for displacements of a single rock fracture. We reproduced the mechanical behavior of rock and embedded single fracture using a three-dimensional grain-based distinct element model for the simulations. In this method, the structure of the rock was represented by an assembly of rigid tetrahedral grains moving independently of each other, and the mechanical interactions at the grains and their contacts were calculated using 3DEC. The simulation results revealed that the stresses induced along the embedded fracture in the model were relatively low compared to those calculated by stress analysis due to stress redistribution and constrained fracture displacements. The fracture normal and shear displacements of the numerical model showed good agreement with the analytical solutions. The numerical model will be enhanced by continuing collaboration and interaction with other research teams of DECOVALEX-2023 Task G and validated using various experiments in a further study.

• Tunnel and Underground Space
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• v.31 no.4
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• pp.270-288
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• 2021

We proposed a numerical method to simulate the hydro-mechanical behavior of rock fracture using a grain-based distinct element model (GBDEM) in the paper. As a part of DECOVALEX-2023 Task G, we verified the method via benchmarks with analytical solutions. DECOVALEX-2023 Task G aims to develop a numerical method to estimate the coupled thermo-hydro-mechanical processes within the crystalline rock fracture network. We represented the rock sample as a group of tetrahedral grains and calculated the interaction of the grains and their interfaces using 3DEC. The micro-parameters of the grains and interfaces were determined by a new methodology based on an equivalent continuum approach. In benchmark modeling, a single fracture embedded in the rock was examined for the effects of fracture inclination and roughness, the boundary stress condition and the applied pressure. The simulation results showed that the developed numerical model reasonably reproduced the fracture slip induced by boundary stress condition, the fracture opening induced by fluid injection, the stress distribution variation with fracture inclination, and the fracture roughness effect. In addition, the fracture displacements associated with the opening and slip showed good agreement with the analytical solutions. We expect the numerical model to be enhanced by continuing collaboration and interaction with other research teams of DECOVALEX-2023 Task G and validated in further study experiments.

• Tunnel and Underground Space
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• v.31 no.6
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• pp.593-609
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• 2021

We proposed a numerical method for the thermo-mechanical behavior of rock fracture using a grain-based distinct element model (GBDEM) and simulated thermally induced fracture slip. The present study is the benchmark simulation performed as part of DECOVALEX-2023 Task G, which aims to develop a numerical method to estimate the coupled thermo-hydro-mechanical processes within the crystalline rock fracture network. We represented the rock sample as an assembly of Voronoi grains and calculated the interaction of the grains (blocks) and their interfaces (contacts) using a distinct element code, 3DEC. Based on an equivalent continuum approach, the micro-parameters of grains and contacts were determined to reproduce rock as an elastic material. Then, the behavior of the fracture embedded in the rock was characterized by the contacts with Coulomb shear strength and tensile strength. In the benchmark simulation, we quantitatively examined the effects of the boundary stress and thermal stress due to heat conduction on fracture behavior, focusing on the mechanism of thermally induced fracture slip. The simulation results showed that the developed numerical model reasonably reproduced the thermal expansion and thermal stress increment, the fracture stress and displacement and the effect of boundary condition. We expect the numerical model to be enhanced by continuing collaboration and interaction with other research teams of DECOVALEX-2023 Task G and validated in further study experiments.

• Tunnel and Underground Space
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• v.32 no.6
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• pp.568-585
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• 2022

In the present study, we proposed a numerical method for simulating thermally induced fracture slip using a grain-based distinct element model (GBDEM). As a part of DECOVALEX-2023, the thermo-mechanical loading test on a saw-cut rock fracture conducted at the Korea Institute of Civil Engineering and Building Technology was simulated. In the numerical model, the rock sample including a saw-cut fracture was represented as a group of random Voronoi polyhedra. Then, the coupled thermo-mechanical behavior of grains and their interfaces was calculated using 3DEC. The key concerns focused on the temperature evolution, thermally induced principal stress increment, and fracture normal and shear displacements under thermo-mechanical loading. The comparisons between laboratory experimental results and the numerical results revealed that the numerical model reasonably captured the heat transfer and heat loss characteristics of the rock specimen, the horizontal stress increment due to constrained displacement, and the progressive shear failure of the fracture. However, the onset of the fracture slip and the magnitudes of stress increment and fracture displacement showed discrepancies between the numerical and experimental results. We expect the numerical model to be enhanced by continuing collaboration and interaction with other research teams of DECOVALEX-2023 Task G and validated in further study.

• Journal of Korea Water Resources Association
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• v.56 no.11
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• pp.823-835
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• 2023

Recently, due to the increase in abnormal climate, rainfall intensity is increasing and drought periods are continuing. These environmental changes lead to prolonged drought conditions and difficulties in real-time recognition. In general, drought can be judged by the amount of precipitation and the number of days without rainfall. In determining the impact of drought, it is divided into meteorological drought, agricultural drought, and hydrological drought and evaluation is made using the drought index, but environmental drought evaluation is insufficient. The river water quality managed through the total water pollution cap system is vulnerable to the effects of such drought. In this study, we aim to determine the drought impact on river water quality and quantify the impact of prolonged drought on water quality. The impact of rain-free days and accumulated precipitation on river water quality was quantitatively evaluated. The Load Duration Curve (LDC), which is used to evaluate the water quality of rivers, was used to evaluate water pollution occurring at specific times. It has been observed that when the number of consecutive rainless days exceeds 14 days, the target water quality in the mid-basin is exceeded in over 60% of cases. The cumulative rainfall is set at 28 days as the criteria, with an annual average rainfall of 3%, which is 32.1 mm or less. It has been noted that changes in water quality in rivers occur when there are 14 or more rainless days and the cumulative rainfall over 28 days is 32.1 mm or less in the Gamcheon Mid-basin. Based on the results of this study, it aims to quantify the drought impact and contribute to the development of a drought water quality index for future environmental droughts.

• Economic and Environmental Geology
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• v.38 no.2 s.171
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• pp.101-111
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• 2005

The objectives of this study we to assess the extent and degree of environmental contamination and to draw general conclusions on the fate of toxic elements derived from mining activities in Korea. 인t abandoned mines with four base-metal mines and four Au-Ag mines were selected and the results of environmental surveys in those areas were discussed. In the base-metal mining areas, the Sambo Pb-Zn-barite, the Shinyemi Pb-Zn-Fe, the Geodo Cu-Fe and the Shiheung Cu-Pb-Zn mine, significant levels of Cd, Cu, Pb and Zn were found in mine dump soils developed over mine waste materials, tailings and slag. Furthermore, agricultural soils, stream sediments and stream water near the mines were severely contaminated by the metals mainly due to the continuing dispersion downstream and downslope from the sites, which was controlled by the feature of geography, prevailing wind directions and the distance from the mine. In e Au-Ag mining areas, the Kubong, the Samkwang, the Keumwang and the Kilkok mines, elevated levels of As, Cd, Cu, Pb and Zn were found in tailings and mine dump soils. These levels may have caused increased concentrations of those elements in stream sediments and waters due to direct dis-charge downstream from tailings and mine dumps. In the Au-Ag mines, As would be the most characteristic contaminant in the nearby environment. Arsenic and heavy metals were found to be mainly associated with sulfide gangue minerals, and mobility of these metals would be enhanced by the effect of oxidation. According to sequential extraction of metals in soils, most heavy metals were identified as non-residual chemical forms, and those are very susceptible to the change of ambient conditions of a nearby environment. As application of pollution index (PI), giving data on multi-element contamination in soils, over 1.0 value of the PI was found in soils sampled at and around the mining areas.

• Tunnel and Underground Space
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• v.28 no.5
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• pp.400-425
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• 2018

This study presents the research results and current status of the DECOVALEX-2019 project Task B. Task B named 'Fault slip modelling' is aiming at developing a numerical method to simulate the coupled hydro-mechanical behavior of fault, including slip or reactivation, induced by water injection. The first research step of Task B is a benchmark simulation which is designed for the modelling teams to familiarize themselves with the problem and to set up their own codes to reproduce the hydro-mechanical coupling between the fault hydraulic transmissivity and the mechanically-induced displacement. We reproduced the coupled hydro-mechanical process of fault slip using TOUGH-FLAC simulator. The fluid flow along a fault was modelled with solid elements and governed by Darcy's law with the cubic law in TOUGH2, whereas the mechanical behavior of a single fault was represented by creating interface elements between two separating rock blocks in FLAC3D. A methodology to formulate the hydro-mechanical coupling relations of two different hydraulic aperture models and link the solid element of TOUGH2 and the interface element of FLAC3D was suggested. In addition, we developed a coupling module to update the changes in geometric features (mesh) and hydrological properties of fault caused by water injection at every calculation step for TOUGH-FLAC simulator. Then, the transient responses of the fault, including elastic deformation, reactivation, progressive evolutions of pathway, pressure distribution and water injection rate, to stepwise pressurization were examined during the simulations. The results of the simulations suggest that the developed model can provide a reasonable prediction of the hydro-mechanical behavior related to fault reactivation. The numerical model will be enhanced by continuing collaboration and interaction with other research teams of DECOLVAEX-2019 Task B and validated using the field data from fault activation experiments in a further study.

• Journal of Korean Public Health Nursing
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• v.6 no.1
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• pp.32-45
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• 1992

An important role of community health nurses in health centers is to solve community health problems found through data collection methodology which has been used to identify the health needs of the community, diagnose the health problems and to plan health programs suitable for the health problems. Also community health nurses must be prepared to know the community health needs and to participate in the planning process. Since 1956 when the health center law was established, community health nurses have really implemented only the services which the government has asked them to do. This has kept them busy enough. But these days as society is in rapid change, community health nurses should have the flexibility to deal with the social change and demands that are unique to their community each which has different health needs and demands. So community health nurses need to identify what community health problems exist in their particular communities. The purposes of this study were as follows. 1) To explore the suitability of the health programs which the government has asked the community health nurses to do for their own communities and if these programs are not suitable, to explore the reasons why. 2) To explore the degree to which the community health nurses have the ability to identify health problems in their own communities and activate the community diagnostic process. 3) To identify the degree that the community health nurses have the ability to implement plans related to community diagnosis. 4) To find out how much data related to community health problems, the community health nurses have and how they are utilizing it. 5) To measure the community health nurses self-confidence concerning diagnostic activities for community health. The study subjects were 454 Community Health Nurses working in Health Centers in Seoul, Korea. The period of data collection was 6 days(Nov. 9th 1991-Nov. 15th 1991). A questionnaire used for data collection was composed of three different items; general characteristics, community health diagnostic activities and self-confidence in performing diagnostic activities. The results of the study are as follows. First, over one third of the respondents replied that the government required activities for their communities are not appropriate. Of these activities the most frequent reply $(51.2\%)$ indicated that many of the activities in the community were inappropriate to the actual situation. Further, $25\%$ of the replies indicated that many activities were only administratively oriented and as such not appropriate. Second, $49.8\%$ of the respondents replied that they had done general assessments and had a general idea of the health problems of their community. Effective solutions to health problems could be found with an increase in health personnel and management ability according to $41.5\%$ of the respondents. Third, to the question as to whether they had ever independently implemented a plan towards solving community diagnosed problems, $52\%$ of nurses replied 'never', $40\%$ 'occasionally' but only $7.5\%$ replied that they did it frequently. Actually there was very little done even in the basic work of collecting the necessary data. Fourth, when asked how much of basic information they had collected that might be used in community diagnosis activity, of 26 items in 5 areas, there was hardly one for which complete data had been collected. Fifteen percent did have data on the geographical aspects of their area, housing distribution and types of housing, while $17.8\%$ knew the frequency with which the health center was used. Concerning community resources, even with a list of community resources, only $12.3\%$ had data on any of these resources, and this data was incomplete. Further, information about social work institutions, and facilities was also incomplete, only $14.2\%$ of the respondents had any data and even it was incomplete; that is, in general, the nurses did not have this information. Fifth, concerning the confidence of the community health nurse in their ability to carry out community diagnoses activities, $60\%$ replied that they were very or at least nominally confident, indicating that although they were not doing community diagnostic activities they felt they could do so, as they were carrying out home visits and program planning as part of their official duties. The following recommendations are made based on the results of this study. First; since the community health nurses have a high perception of the need for community diagnostic activities and. high confidence in their ability to carry out this activity and high percentage of respondents replied that with a little training they could do this even better it is recommended that community diagnostic activity training be included in the continuing education program for community health nurses. Second, in order for the Community Health Nurses to successfully solve the health problems of their respective community they reported to a need to increase the number of health personnel, improve the facilities and the system of managing their work. Considering this, it is recommended that ways be sought to remedy these deficits.

• Tunnel and Underground Space
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• v.28 no.6
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• pp.670-691
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• 2018

This study presents the research results of the BMT(Benchmark Model Test) simulations of the DECOVALEX-2019 project Task B. Task B named 'Fault slip modelling' is aiming at developing a numerical method to predict fault reactivation and the coupled hydro-mechanical behavior of fault. BMT scenario simulations of Task B were conducted to improve each numerical model of participating group by demonstrating the feasibility of reproducing the fault behavior induced by water injection. The BMT simulations consist of seven different conditions depending on injection pressure, fault properties and the hydro-mechanical coupling relations. TOUGH-FLAC simulator was used to reproduce the coupled hydro-mechanical process of fault slip. A coupling module to update the changes in hydrological properties and geometric features of the numerical mesh in the present study. We made modifications to the numerical model developed in Task B Step 1 to consider the changes in compressibility, Permeability and geometric features with hydraulic aperture of fault due to mechanical deformation. The effects of the storativity and transmissivity of the fault on the hydro-mechanical behavior such as the pressure distribution, injection rate, displacement and stress of the fault were examined, and the results of the previous step 1 simulation were updated using the modified numerical model. The simulation results indicate that the developed model can provide a reasonable prediction of the hydro-mechanical behavior related to fault reactivation. The numerical model will be enhanced by continuing interaction and collaboration with other research teams of DECOVALEX-2019 Task B and validated using the field experiment data in a further study.

• The Journal of Korean Medicine
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• v.28 no.3 s.71
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• pp.1-12
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• 2007

Objectives : The purpose of this study was to explore the perceptions of health promotion programmes using traditional Korean medicine among public health centre staff in charge of running such programmes. To do so, we examined and analysed the current situation of implementing the programmes in the public health centre. Methods : A survey was designed to collect information on perception of the health promotion programmes using traditional Korean medicine by public health centre staff in charge of running such programmes. The survey, using a structured questionnaire designed for this study, was conducted on 161 public health centre staff attending an annual meeting to presenting the results of activity evaluation related to public health programmes using traditional Korean medicine in public health centres. The participants were asked about the most successful programme, the benefits of the programmes, the positive aspects of the programmes, the most desirable outcomes of the programmes and so on. The data were analysed using SPSS system 12.0 for Windows. Results : Of the 161 questionnaires, 121 were analysed. The main findings of this research were as follows. Of the health promotion programmes using traditional Korean medicine implemented in public health centres, qigong and stroke preventive health promotion programmes were perceived as the most successful. The major benefits of the programmes were having merit for health promotion and expecting a positive performance outcome. The major positive aspects of the programmes for health promotion were cultivating community citizen's support and showing consistency between the philosophy of the programmes and the direction of existing health promotion programmes. The most desirable outcomes of the programmes were spreading community understanding of the programme and establishing an effective and unique health promotion model for implementing the programme. Two major causes of implementation difficulties were lack of material resources such as manpower, facility, and equipment, and methods of performance evaluation. One of the most urgent needs for activating the implementation of programmes was continuing financial and technical support from the central government. Conclusions : To promote the role of traditional Korean medicine in the public health sector in order to integrate traditional medicine into the public health system, government should develop some measures for solving the identified causes of implementation difficulties and coping with the most urgent needs for activating the implementation of programmes.