• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.6
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• pp.465-481
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• 2022

Rock grouting is important to improve the waterproof efficiency and mechanical strength of rock medium with joint for utilizing the underground rock space such as tunnel. The grouting materials typically has been used the cement materials, which represent Bingham fluid model. This model can express the relationship of viscosity and yield strength. In addition, it is dependent with elapsed time. The grouting injection performance can be deteriorated with an increase of viscosity and yield strength in the grouting process if the time dependence is ignored. Therefore, in this study, the characteristics of viscosity and yield strength were investigated according to water-cement ratio and time dependence in the laboratory test. Numerical simulation was carried out to investigate the grouting performance according to the time dependence of characteristics in terms of the viscosity model. Given the results, the grouting injected distance and cumulative grout volume were significantly decreased when the time dependence of grouting material was considered. This study, considering the characteristics according to the time dependence of viscosity and yield strength, will be meaningful to the design of grouting injection in field applications.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.6
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• pp.1049-1060
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• 2018

Soil conditioning is one of the key factors for successfull tunnel excavations utilizing the earth pressure-balanced (EPB) shield tunnel boring machine (TBM) by increasing the tunnel face stability and extraction efficiency of excavated soils. In this study, conditioning agents are mixed with the weathered granite soils which are abundant in the Korean peninsula and the workability of the resulting mixture is evaluated through the slump tests to derive and propose the most suitable conditioning agent as well as the most appropriate agent mix ratios. However, since it is cumbersome to perform the slump tests all the time either in the laboratory or in-situ, a simpler test may be needed instead of the slump test; the fall cone test was proposed as a substitute. In this paper, the correlation between the slump value obtained from the slump test and the cone penetration depth obtained from the proposed fall cone test was obtained. Test results showed that a very good correlation between two was observed; it means that the simpler fall cone test can be used to assess the suitability of the conditioned soils instead of the more cumbersome slump test.

• Journal of the Korean GEO-environmental Society
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• v.12 no.7
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• pp.39-47
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• 2011

The objective of this study is to investigate the removal characteristics of cadmium(Cd) and lead(Pb) by adsorption on red mud and to study the adsorption characteristics of Cd and Pb using red mud activated by acid treatment and calcination. The adsorption of Cd and Pb on red mud was significantly achieved within 1hour and equilibrated after 5 hours. The adsorption capacity of Cd and Pb on red mud increased with increasing pH. The neutralization of red mud by distilled water or acid and the activation of red mud by acid treatment or calcination decreased the adsorption capacity of Cd and Pb on red mud, suggesting that Cd and Pb could be effectively eliminated by adsorption on red mud without any pretreatment or modification. Both Langmuir and Freundlich models were successfully applied to describe the adsorption behavior of Cd and Pb on red mud. The $q_m$ of Langmuir adsorption model and $K_F$ of Freundlich adsorption model were 5.230mg/g and 1.118mg/g for Cd and 22.222mg/g and 7.241mg/g for Pb, respectively.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.6
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• pp.79-85
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• 2023

Skid resistance pavement is an accessory to the road and is a facility for the safe driving of cars by increasing the skid resistance of road pavement. In particular, in bad weather conditions such as snow, rain, and black ice, the skid resistance performance of skid resistance pavement greatly affects the safety of road traffic and drivers. However, BPT(British Pendulum Tester) has a test area of only 0.009 m², making it difficult to represent the overall packaging surface. A reliable method of evaluating slip resistance performance is needed for maintaining non-slip packaging. In this study, the conventional BPT test and the skid resistance performance evaluation method of the PFT(Pavement Friction Tester) and µGT(Micro Grip Tester) tests were compared through guidelines and standard investigations and applied to the field skid resistance performance evaluation. In addition, skid resistance pavement with different skid resistance performance was installed at the test-bed and actual road demonstration sites to compare BPN(British Pendulum Number), SN(Skid Number), GN(Grip Number), and to derive correlations for each performance evaluation method. As a result of the experiment, SN and GN showed similar skid resistance performance, and the GN value was derived similar to BPN × 0.01.

• Journal of Korean Home Economics Education Association
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• v.15 no.4
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• pp.115-132
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• 2003

The purpose of this study is aimed at giving proof that helps the elementary practical arts education system accomplish as the effects are turned out experimentally. Two classes of the sixth grade of J elementary school in Dae-gu have been selected in order to be experimented. One was chosen as an experimental group, the other was done as a comparative group. The creative-problem-solving learning-model was applied to the experimental group, and the traditional way of teaching was applied to the comparative group. For four classes of the sixth grades, ‘chapter 8: Making with recycled materials’ was proceeded as the content. Then. tests about the way of environmental awareness and creativity were carried out twice. After that, the results of pre and after-test in the comparative and experiment groups were compared using the t-test method. Following the analysis of the data collected in this study. the following major observations were obtained: First, children who were educated the creative problem-solving in a practical arts education achieved higher scores than before. Therefore, it turns out that the CPS method is an effective way to improve the environmental awareness in children. It showed that it included lots of daily habits connected with daily life and it made the intention to carry out the environment-preservation stronger and children´s attitude towards the environment improved. Moreover, making with recycled materials was used to solve an environmental problem, affecting in a positive way in our life. It also made the positive recognition about the environment. Second. the application of the creative problem-solving class of the practical arts education can make positive results to children. It helped children to have more interest in the environment around them. Children´s fluency, flexibility and originality in their ideas were improved as much as possible while they were solving problems. Consequently, the application of the creative problem-solving class model of elementary practical arts environmental education lets children expand environment consciousness and creativity.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.2
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• pp.155-162
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• 2005

This paper presents an invetigation into the cause of deterioration of wet surrounding RC structures subjected to checmical attacks such as sewage. The antibacterial-reforming agent is developed after determining the permeability of the RC structure. After application of the anitbacterial-reforming agent through SEM, the permeability, compressive strength properties and the micro-structure of the concrete were evaluated for durability. In addition, the antibacterial-reforming agent was combined with a protective coating for the wet surrounding RC structure and evaluated for durability. The combined effect of the antibacterial-reforming agent and the protective coating were evaluated in field tests in both sewer system and tunnel sites.

• Journal of the Economic Geographical Society of Korea
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• v.14 no.3
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• pp.394-406
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• 2011

The retailing industry in Korea has developed with new store formats: supermarket, convenient store, discount Store, and super-super market. Also, there are confrontation and conflict between them, becoming a national issue. This study reviews the existing literatures in Korean geography of retailing and consumption and attempts to set forth the future research themes and topics. The review shows that the existing literatures disproportionately focus on location, diffusion, and market area of the new store formats. The future research themes and topics includes the marketplace combined with recreation, donation, environment-friendliness, or social welfare; marketplace as a part of global production and distribution system; expansion of marketplace into homes which are longstanding private space; spatial structure of retailing at various geographical scale.

• Journal of Korean Society of Steel Construction
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• v.28 no.5
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• pp.365-371
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• 2016

In the case of the superstructure which is consist of two I girders and slab, the section can behave as II section, so that the neutral axis with respect to out of plane direction flexure can be regarded as major axis. Therefore in-plane flexural mode might govern the free vibration mode. Meanwhile, horizontally curved girders always experience not only bending moments but also torsional moments although the primary load is usually supposed to be gravitational load. The interaction due to bending and torsional moments make the behavior complicated and torsional mode may govern the free vibration mode. In other words, structure can have different dynamic characteristic due to its initial curvature. In this research, using 3-dimensional sell elements, free-vibration analyses are carried out due to initial curvature. The analysis models are assumed to be composite and non-composite and finally natural frequency and eigen mode are discussed.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.2
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• pp.235-244
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• 2016

Grouting is frequently used before the construction of subsea tunnels to mitigate problems that can occur in weak ground zones such as joints, faults or unconsolidated settlements during construction. The grout material injected into rock mass often flows through the discontinuities present in the host rock and hence, joint properties such as its distribution, roughness and thickness greatly affect the properties of grouting-improved rocks. The grouting-improved zones near subsea tunnels are also subjected to high water pressures that can cause long-term weathering in the form of changes in grout microstructure and crack formation and lead to subsequent changes in ground properties. Therefore, an assessment method is needed to accurately measure changes in the grouting-improved zones near subsea tunnels. In this study, the elastic wave propagation characteristics in grouting-improved rocks were tested for various axial stress levels, curing time, joint roughness and thickness conditions under laboratory conditions and the results were compared with wave velocity standards in different Korean rock mass classification systems to provide a basis for inferring improvement in grouted rock-mass.

• Journal of the Korean Society of Hazard Mitigation
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• v.4 no.1 s.12
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• pp.51-56
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• 2004

In this study, the variation of water quality in Osan stream was investigated through continuous monitoring, and mass balance and metabolism occurred into water body were estimated to set up effective management plan for water quality of small urban stream. From the results of continuos investigation of water quality in Osan stream, the things written as follows must be previously done to improve water quality of main stream. Firstly, it need that effective management plan for tributaries must be set up to improve the water quality in main stream. Secondly, the counter plan for re-eruption of pollutants from sediment in main-stream is required to prevent inner pollution. In this study, we showed that small urban stream can be managed effectively by simple investigation to prevent deterioration of water quality. Therefore continuous monitoring for water quality in stream is important to improve water quality, furthermore matter cycle and mass balance happening in the stream environment must be correctly estimated to make up healthy stream environment.