• Tunnel and Underground Space
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• v.25 no.3
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• pp.275-283
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• 2015

Excavation of underground space in soft ground implicate to the structure, such as subsidence. As a result, it has been acting as a serious risk to the stability of the roads and facilities. Therefore, in order to stabilize the soil stabilization and reinforcement of the structure, we have been using a number of methods and injecting material. In this study, we compared and analyzed the amount of subsidence regarding the ground reinforcement during underground excavation in soft ground by performing model test. And three-dimensional numerical analysis was performed using FLAC 3D. The subsidence was simulated numerically according to the tunnel excavation. The subsidence results of the model tests and numerical analyzes were relatively consistent. Thus comparing the ground subsidence by varying the reinforcement area on the numerical analysis was analyzed. As a results, three-dimensional numerical simulation could be regarded to simulate better on the ground subsidence by various kinds of underground excavation and it can be used as a material of subsidence prevention methods.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.2
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• pp.117-127
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• 2010

Gound excavation is frequently executed in unsaturated soil conditions. In this paper, the effect of apparent cohesion in unsaturated soils on the ground behavior during underground excavation is studied. The VPPE (Volumetric Pressure Plate Extractor) test, the unsaturated triaxial test and the trap-door test were carried out to figure out how the behavior of soils varies depending on the variation of apparent cohesion. The test results show that the ground behavior is almost identical if the soil is either fully dry or fully saturated. However, if the soil is partially-saturated with the increase of water content, the ground behaves quite differently. In summary, the apparent cohesion in unsaturated soils plays key roles when excavating underground structures.

• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.3
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• pp.219-226
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• 2005

The result that analyze for 6 years a groundwater influx quantity of total 60 catch-pit established in subway line 5 appeared with $0.77m^3/min$. When comparing design approaches of the catch-pit with design approaches of the box structure $2m^3/min$ and the tunnel structure $3m^3/min$, it is found that it has a surplus. Red sedimentation substance contains large portion of Fe. The earth retaining structure of a tunnel and groundwater containing more portion of Fe than other area rue the major factor of this substance. In case of white sedimentation substance, the most frequently founded ingredient is CaO, which is occurred in case grouting injection materials for ground reinforcement is transmitted into a tunnel system by ground water. This substance is doesn't affect safety of a tunnel.

• 지반과기술
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• v.4 no.4
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• pp.70-77
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• 2007

• Journal of the Korean Geotechnical Society
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• v.15 no.4
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• pp.235-246
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• 1999

Some of the underground structures such as subway tunnels are constructed by open cut method, in which the ground is excavated, a structure installed, and after that the excavated space is backfilled. In this case, because of their narrow and constrained boundary conditions, the earth pressure induced by self-weight of the backfilled soil acting on the underground structures is different from that of the classical theory. The vertical and horizontal earth pressures acting on upper slab and side wall of the underground structures constructed by open cut method are affected by the backfill geometry. The laboratory model tests were performed in the conditions of a variety of the shapes of backfill geometry and wall friction. And their results were compared with those from theories. As a result, it was observed that the distribution of the earth pressure acting on the underground structure is affected by the shapes of backfill geometry, the width of backfill, the angle of excavation and the wall friction.

• Explosives and Blasting
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• v.39 no.4
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• pp.22-33
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• 2021

Recently, the frequent occurrence of ground subsidence in urban areas has caused increasing anxiety in residents and incurred significant social costs. Among the causes of ground subsidence, the rupture of old water and sewer pipes not only halts the operation of the buried pipes, but also leads to ground and water pollution problems. However, because most pipes are buried after construction and cannot be seen with the naked eye, the importance of maintenance has underestimated compared to other structures. In recent years, integrated physical exploration has been applied to the maintenance of underground pipes and structures. Currently, to investigate the internal conditions and vulnerable portions of the ground, consolidated physical surveys are executed. Consolidated physical surveys are analysis techniques that obtain various material data and add existing data using multiple physical surveys. Generally, in geotechnical engineering, consolidated physical surveys including electrical and surface wave surveys are adopted. However, it is difficult to investigate time-based changes in under ground using these surveys. In contrast, surveys using cosmic-ray muons have been used to scan the inner parts of nuclear reactors with penetration technology. Surveys using muons enable real-time observation without the influence of vibration or electricity. Such surveys have great potential for available technology because of their ability to investigate density distributions without requiring as much labor. In this paper, survey technologies using cosmic ray muons are introduced, and the possibilities of applying such technologies as new physical survey technologies for underground structures are suggested.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.3
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• pp.69-75
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• 2014

The priority of repair areas are chosen with the probability distribution of 0.3mm wide crack and carbonation induced corrosion. Data is analyzed and evaluated based on the 28 section of Precise Inspection for Safety and Diagnosis (PISD) in seoul. As the crack is distributed in log-normal, the carbonation and cover are in normal distribution. To have rational in repair sections among 503 sheets of underground structure, it is adopted the reliability index as well as the environment factors: strength, sonic speed, $CO_2$ concentration, corrosion, and content of chloride.

• Journal of the Korean Association of Geographic Information Studies
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• v.24 no.4
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• pp.1-25
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• 2021

In order to respond and prevent underground safety accidents, the Korean government has been preparing a submitting completion drawing web system project for converting the current manual-based 3D Underground Geospatial Map construction and its update system to an automation-based 3D underground information construction. However, research on standard drawings required for the automatic update of 3D underground structures is insufficient, so detailed research is needed. In this research paper, a standard map-based 3D underground structure construction plan was presented for the six types of underground structures constituting the 3D Underground Geospatial Map, enabling rapid and accurate drawing data creation and systematically 3D underground structure drawing data could be managed. In addition, we developed a 3D construction drawing tool that can be used in underground information practice so that ordinary CAD program users can easily produce processing drawings. The results derived from this paper are expected to be major reference materials for the establishment of standard frameworks and practical application guidelines for the construction of 3D underground structures in the future.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.3
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• pp.183-190
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• 2022

The construction of an underground silo structure was the first stage of erecting the Gyeongju low-and-intermediate-level radioactive waste disposal facility. The facility, completed in 2014, has a scale of 100 000 drums and is currently in operation. The underground silo structure, 25 and 50 m in diameter and height, respectively, consists of cylindrical (for storing waste packages) and dome parts. The dome is divided into lower (connected to the operation tunnel) and upper parts. The wall of the underground silo structure is an approximately 1-m-thick reinforced concrete liner. In this study, finite element analysis was performed for each phase of the construction sequence and operation of the underground silo structure. Two-dimensional axial symmetric finite element analysis was implemented using the SMAP-3D program. Three-dimensional finite element analysis was also performed to examine the reliability of the two-dimensional axial symmetric finite element model. The structural behavior of the underground silo structure was predicted, and its structural safety was examined.

• The Journal of the Convergence on Culture Technology
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• v.8 no.6
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• pp.727-732
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• 2022

Applying the calculated cross-sectional reduction due to the corroded rebar investigated in the field to the numerical analysis model, the damage pattern and delamination of concrete in the field showed a tendency relatively similar to the numerical analysis results. It was analyzed that when the expansion pressure due to corrosion of the reinforcing bar is greater than the tensile stress of the concrete, cracks are generated and the concrete cover can be fracture. As a result of this study, the correlation between the corrosion rate of reinforcing bars and the crack occurrence of the concrete cover of the subway box structure was verified based on the numerical analysis and field test results. To prevent rebar corrosion, the corrosion rate can be reduced by applying rust prevention to the reinforcing bar and changing the material. In the case of exposed to a corrosive environment, the tensile strength of the concrete is improved by adjusting the concrete compressive strength to secure durability against the expansion pressure caused by the corroded rebar.