• Tunnel and Underground Space
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• v.27 no.6
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• pp.357-365
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• 2017

The mine subsidence prevention technology has been promoted based on the field test for design, construction, automation measurement and monitoring optimized for investigation, design and mine-filling efficiency customized in Korean mining environment. Based on the R&D roadmap ('07~'16) of the 1st and 2nd stage, mine reclamation technology development has been focused on developing method of evaluating subsidence stability, development of filling material and optimum filling technology, and development of measuring instrument. In the future, in order to systematic management for the subsidence risk areas, we intend to enhance technological capabilities and strengthen the technological infrastructure for business promotion in parallel with the discovery and introduction of new technology to prevent subsidence in the 4th Industrial Revolution era.

• Journal of Korean Society of Rural Planning
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• v.8 no.1 s.15
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• pp.3-14
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• 2002

Changes of chemical properties by times of the reclaimed tidal land soils and soil surface water, underground infiltration water with precipitation-runoff on natural meteological condition in the unripened tidal reclaimed paddy fields were investigated. This study was carried out to use environment-friendly farm land in the reclaimed tidal lands. The soils used in this study were saline-alkaline soils with the high $Na^+$ and $Mg^{++}$ content. As the results of investigation outflow loading of nutriments through outflow water in the unripened tidal reclaimed paddy fields by precipitation during the survey period, nutriments equivalent to T-N $1{\sim}2\;kg\;10a^{ -1}$ and T-P $0.01{\sim}0.02\;kg\;10a^{-1}$ from in the unripened tidal lands were discharged. Besides, the results of comparison losses of cation through outflow water showed $Na^+>\;K^+>\;Mg^{++}\;>\;Ca^{++}$, and the highest appeared water discharge of $Na^+$. In case of saemangeum reclaimed tidal land soils water discharge of cations showed $Ca^{++}$ 1.3 kg $10a^{-1}$, $Mg^{++}$ 1.6 kg $10a^{-1}$, $Na^+$ 17.7 kg $10a^{-1}$, and $K^+$ 3.2 kg $10a^{-1}$ respectively. On the other hand, in case of koheung reclaimed tidal lands soils water discharge of cations showed $Ca^{++}$ 18.1 kg $10a^{-1}$, $Mg^{++}$ 31.2 kg $10a^{-1}$, $Na^+$ 320.8 kg $10a^{-1}$ and $K^+$ 51.2 kg $10a^{-1}$ respectively.

• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.5
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• pp.68-79
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• 1998

In the years, the concern about high-strength concrete which is new material has been heightened as a result of active research and development. Recently, as the building structure has been being bigger, higher, longer and more specialized, the demand of material with high-strength concrete for building has been increasing. The demand of high -strength concrete is expected to increase with expansion of usage about the complex concrete structures such as bridge structure as well as nuclear plants, underground structures, hydraulic structures and arctic area sturctures. In this research, silica-fume was used as an admixture in order to get a high-strength concrete. Water/binder ration was limited no more than 18 percent and the amount of unit cement was increased. In this study, a number of trial in concrete mix was carried out to get optimal mix design, and the target slump with $10{\pm}2cm$ was set for in-situ construction. High-strength concrete with cylinder strength of 1,200kgf/$cm^2$ in the 28-days was produced and tested. The static test was carried out to measure the ultimate load, the initial load of flexural and diagonal cracking, crack patterns, fracture modes. The load versus strain and load versus deflection relations were obtained form the static test. The test results were compared with the shear strengths predicted by the equations of ACI code 318-89 and orther researchers. Based on the test results, shear strength equation of reinforced concrete beam using high strength concrete was proposed. Form an evaluation of the results of this experimental investigation, it was concluded that shear strength after diagonal tention cracking diminished with the increase in compressive strength for beams.

• The Journal of Engineering Geology
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• v.16 no.3 s.49
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• pp.265-273
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• 2006

Face mapping during tunnel construction is useful and critical to predict the characteristics and stability condition of following tunneling sections and to select optimum support pattern. Therefore, a detailed geological survey of the tunnel faces, as important as a routine underground survey and a RMR evaluation, should provide critical information of the tunnel face condition in terms of the engineering geological condition and the safety of working environment for the following tunneling section. But the results of the face investigation have not been applied satisfactorily during tunneling due to limitation of technique, experience and time. This study analyze problems of face mapping in tunnel construction site by using statistical results of face mapping sheets obtained from completed tunnels, and suggest several opinions to improve face mapping during tunnel construction.

• Journal of the Korean Society for Advanced Composite Structures
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• v.2 no.3
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• pp.18-24
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• 2011

In this paper, we present the load-deflection behavior of GRP pipes. GRP buried pipes are widely used in construction in the advantage of their superior mechanical and physical characteristics such as high chemical resistance, high corrosion resistance, right weight, smooth surface of the pipe, and cost effectiveness from soil-structure interaction. To design flexible pipes to be buried underground, it should be based on the ASTM D2412(2010). When applying ASTM D 2412(2010) to the design, pipe stiffness(PS) must be predetermined by the parallel-plate test which requires tedious and laborious working process. To overcome such problems, the finite element simulations for finding the load-deflection behavior of the GRP flexible pipes is installed at UTM testing machine. In the finite element simulations, basic data, such as the modulus of elasticity of the material and cross-sectional dimension, is used. From the investigation, we found that the difference between experimental result and analytical prediction is less than 15% when the pipe deflected 3% and 5% of its vertical diameter although the pipe material is not uniform across the cross-section.

• Journal of Forest and Environmental Science
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• v.10 no.1
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• pp.8-24
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• 1994

Because of the underground existence of roots, a few studies have been reported on root system. The developmental information of roots should be understood for the studies of specific tree traits and the influence of such traits on the soil surface fixation. In order to clarify the specific character of pine forest in Kangwon Province, the investigation on the form and distribution of root system of pine trees were carried out for 5 trees in the Campus Forest, Kangwon National Univ.. Root form was very well in flat root. As soil depth was approximatly 50cm, fine roots were very sparsly distributed(+), roots of 0.2cm in diameter were most common and roots > 0.2cm were very rare, also thickness thined. 60~70% all the roots were developed at the depth of 0~30cm, where big roots were below 0.9cm in diameter and fine roots were higly sparse(+).

• Geomechanics and Engineering
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• v.21 no.2
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• pp.111-122
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• 2020

In most cases in urban areas, construction of divergence tunnel should take into account proximity to existing tunnel in operation. This inevitably leads to deformation of adjacent structures and surrounding ground. Preceding researches mainly dealt with reinforcing of the diverging section for the stability including the pillar. This has limitations in investigating the interactive effects between existing structures and surrounding ground due to the excavation of the divergence tunnel. In this study, the complex interactive behavior of pile, the operating tunnel, and the surrounding ground according to horizontal offsets between the two adjacent tunnels was quantitatively analyzed based on conditions diverged from operating tunnel in urban areas. The effects on ground structures confirmed by analyzing the ground surface settlements, pile settlements, and the axial forces of the pile. The axial forces of lining in operating tunnel investigated to estimate their impact on existing tunnel. In addition, in order to identify the deformation of the surrounding ground, the close range photogrammetry applied to the laboratory model test for confirming the underground displacements. Two-dimensional finite element numerical analysis was also performed and compared with the results. It identified that the impact of excavating a divergence tunnel decreased as the horizontal offset increased. In particular, when the horizontal offset was larger than 1.0D (D is the diameter of operating tunnel), the impact on existing structures further reduced and the deformation of surrounding ground was concentrated at the top of the divergence tunnel.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.6
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• pp.87-94
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• 2002

As a section insulator dividing the electric railroad catenaries with different phases, the AC/DC section insulator which divides AC and DC railroad catenary have the complex structure, and suffer irregular abrasion on the surface or insulator rods when it is installed at the underground railroad. This paper intended as an investigation of the irregular abrasion of section insulators, provides the field measurements of abrasion level along insulator length and the abrasion patterns. The height variation of insulator parts and the balding length of insulators against pantograph's contact force are analysed experimentally, and the irregular abrasion mechanism is clarified with the help of theoretical analysis on the interaction between pantographs and section insulators. On the basis of experimental and theoretical analysis, the countermeasures to reduce the irregular abrasion are provided too.

• Tunnel and Underground Space
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• v.17 no.2 s.67
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• pp.83-89
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• 2007

Impact-echo test is a non-destructive testing method to determine dynamic properties of a material. This presentation introduces the experimental set-up and procedure of the test for rock specimens. In addition, the test results of domestic rocks collected in 5 different areas, a cement mortar and aluminium alloy are presented. The test results include resonance frequencies of P- and S-wave as well as damping ratios of the described 7 different materials. The differences between dynamic and static values of elastic moduli are about 10%, while the dynamic Poisson's ratios are greater than the static Poisson's ratios by at least 0.07. The damping ratio is dependent on the joint density and degree of weathering of a rock specimen.

• Tunnel and Underground Space
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• v.21 no.5
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• pp.341-348
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• 2011

As a result of the detailed site investigation performed for the design of a 4.3 km long tunnel, geological anomalies of four fault zones and a rock boundary were discovered on the tunnel route. Most of all, it was confirmed that pyrite, which may corrode steel material, is contained inside the geological anomalies, and pressured ground water flows out of the fault fractured zone. To overcome these geological conditions, antisulfur concrete for the concrete lining and anticorrosive swelling rock bolts are designed in the pyrite-containing sections. For the sections where a great amount of groundwater outflows, water blocking methods including grouting are applied according to the result of numerical analyses on the seepage. In addition, since the past earthquakes occurred around Korea have take place mainly near fault zones, seismic analyses were performed based on the Soil-Structure Interaction (SSI) concept and the strength of concrete tunnel lining is designed to be 27 MPa from 24 MPa in order to reinforce the tunnel structure.