• Journal of the Korean GEO-environmental Society
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• v.19 no.2
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• pp.13-21
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• 2018

The magnitude and distribution of earth pressure on the excavation wall in jointed rock mass were examined by considering different wall permeability conditions as well as rock types and joint inclination angles. The study was numerically extended based on a physical model test (Son & Park, 2014), considering rock-structure interactions with the discrete element method, which can consider various characteristics of rock joints. This study focused on the effect of the permeability condition of excavation wall on the earth pressure in jointed rock masses under a groundwater condition, which is important but has not been studied previously. The study results showed that the earth pressure was highly influenced by wall permeability as well as rock type and joint condition. Earth pressure resulted from the study was also compared with Peck's earth pressure in soil ground, and the comparison clearly showed that the earth pressure in jointed rock mass can be greatly different from that in soil ground.

• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.2
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• pp.93-103
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• 2004

In trench excavation, essential factor of earth-retaining temporary work structure should be easy taking to pieces and movement, and dead weight must be less. This paper studies about the light weight material and application as earth-retaining structure to prevent the slope failure of sand soil ground caused by the variation of groundwater level in trench excavation. That is, light weight earth-retaining structural is proposed and a simulation with FEM on application of proposed structural in sandy soil is presented. The results are summarized as follows; (1) The study proposed FRP H-shaped pannel for the light weight member, and also presented estimation method about stability. (2) Mechanical property (bending moment, shear force, axial force, displacement) were changed according to groundwater level, but these values had been within enough safety rate and allowable stress. Therefore, proposed light weight pannel with FRP is available for bracing structure in trench excavation.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.2
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• pp.141-147
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• 2013

Permanent magnet (PM) motors that employ rare-earth magnets containing dysprosium (Dy) are used in electric and hybrid electric vehicles. However, it is desirable to reduce the amount of Dy used since it is expensive. This study investigates the rotor structure of a PM synchronous motor with a Dy-free rare-earth magnet. Flux barrier shapes and PM thicknesses that enhance the irreversible demagnetization are investigated. In addition, a rotor structure that improves the irreversible demagnetization is proposed. We demonstrate that the proposed rotor structure without Dy improves the irreversible demagnetization.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.05b
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• pp.21-24
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• 2009

This study deals with the application of USN wireless inclinometer sensor for earth retaining structure safety measurement, The application of wireless inclinometer sensor has great advantage about real-time monitoring of earth retaining structure, It allows a construction manager to monitor movement data from anywhere connected through internet during the process of excavation for substructures of buildings, To validate the applicability of the wireless inclinometer sensor. laboratory and field tests have been performed, The results have shown that the measured values of wireless inclinometer sensor represent the behavior of H-pile well, Both convenience of sensor installation and real-time monitoring of earth retaining structure are confirmed, The proposed wireless measurement system provides a good basis for exact measurement of temporary substructures, More measurements and application are expected for the other excavation sites with various conditions.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.1324-1329
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• 2009

Needs for underground space development and utilization have been increasing in urban area. The conventional strutting method in excavation is effective to restrain the ground movements and displacements of earth structures but inefficient for workers because of small working space. The conventional earth reinforcement methods such as earth-anchor and soil-nailing also have limitation to apply in urban area due to threats to stability of adjacent buildings around excavation boundaries. Recently, many types of earth retaining structures are being developed to overcome disadvantages of conventional excavation methods in urban area. In this study, a series of numerical analyses were performed with MIDAS GTS, geotechnical analysis program and MIDAS Civil, structural analysis design program to evaluate behavior and stability of the new type of non-supporting earth retaining structure, called Temporary Tower System (TTS), consisting of tower truss structures with much economical and spatial advantage.

• Journal of the Korean earth science society
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• v.41 no.4
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• pp.405-414
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• 2020

In this study, we analyzed the development of high school students' argumentation through their writings on socio-scientific Issues (SSI) related to the Climate Change Unit in the Earth Science I curriculum. Pre- and post-writing assignments on the two main causes of global warming were analyzed and compared. In addition, an in-depth interview of the focus group was conducted with 7 students who showed a distinct change in the level of argumentation. According to the results, 16 of 52 students remained at the same argumentation level in pre- and post-writing assignments, and students remaining at Level 2 among five levels had difficulty in understanding the Toulmin's argument pattern (TAP) structure. Using the TAP structure, 29 of 52 students demonstrated increased argumentation levels in the post-writing assignments. The conclusions include that writing lessons on SSI using the TAP in Earth science classes can improve the level of high school students' argumentative writing, and that the level of students' argumentation can develop with the elaboration of their level of falsification. Also, it is suggested that the science curriculum should increase students' science writing competencies by specifying science writing as one of the goals.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.10
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• pp.1796-1801
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• 2007

This paper presents electric potential rise on the surface of the earth due to ground currents. It is the aim of this paper to propose fundamental data relevant to the earth surface potentials depending on the soil structures. The earth potential rise, touch and step voltages in the immediate vicinity of the ground rod of a distribution pole were measured and analyzed. The results described in this paper are based on laboratory measurements which were intended to simulate conditions existing in actual installations. As a result, the earth surface potential rise, touch and step voltages strongly depend on the soil structure. The highest earth surface potential occurred in the vicinity of the top of ground rod. When the ground rod was installed in the distance range of $1{\sim}1.5\;m$ from distribution pole, the highest touch voltages appeared near the place of 1 m on the straight line connecting the distribution pole to ground rod.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.141-157
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• 2008

Since 1984, block-type reinforced earth wall with geogrid reinforcement has been widely used for retaining wall applications till now in Korea. The use of geogrid as a reinforcement in the reinforced earth wall is steadily increased in an amount over $6,500,000m^2$ in a year. However, still need exists that some problems in design and construction practices should be made to review. Therefore, this paper reviewed current state and development items of geosynthetics-reinforced earth wall technology on design and construction point of view.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.2
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• pp.23-31
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• 2008

Dynamic earth pressure acting on geotechnical structures can be driving force or resisting force for the displacement of the structure according to the phase relation between the dynamic earth pressure and inertia force of structures. In this research, the evaluation procedure of the phase relation between the dynamic earth pressure and the inertia force was proposed. According to the procedure, numerical analyses on caisson foundation of bridges were performed and the phase relation was analyzed. The analysis results showed that the dynamic earth pressure becomes the driving force, which increases the displacement of the structure, if the displacement amplitude of ground is larger than that of structure due to the low stiffness of the ground, and the dynamic earth pressure becomes the resisting force against the displacement of the structure if the displacement amplitude of ground is smaller than that of structure due to the high stiffness of the ground.

• Journal of Digital Convergence
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• v.17 no.3
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• pp.205-213
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• 2019

In a construction site, excavation work has a close relation with temporary earth retaining structure. In order to build the underground structure most effectively in a narrow space, prevent soil relaxation of the external behind ground in excavation work, and maintain a ground water level, it is required to install a temporary earth retaining structure that secures safety. To prevent soil washoff in underground excavation work, the conventional method of temporary earth retaining structure is to make a temporary wall and build the internal support with the use of earth anchor, raker, and struct for excavation work. RSB method that improves the problem of the conventional method is to remove the internal support, make use of two-row soldier piles and bracing, and thereby to resist earth pressure independently for underground excavation. This study revealed that through the field application cases of RSB method and the measurement result, the applicability of the method for installing a temporary earth retaining structure, the assessment result, and displacement all met allowable values of measurement, and that the RSB method, compared to the conventional method, improved constructability and economy.