• Tunnel and Underground Space
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• v.26 no.2
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• pp.68-86
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• 2016

Understanding the frictional properties of rock discontinuities is crucial to ensure the stability of underground structures. In particular, the frictional behavior at depth depends on the complex interaction among mechanical, hydraulic, thermal and chemical characteristics and their coupled effects. In this study, a series of shear tests were carried out in a triaxial compression chamber to investigate the shearing behavior of saw-cut granite surface and rough shear surface of synthetic rocks. The test results were analyzed using Coulomb's shear strength criterion. The frictional behavior of saw-cut granite surface showed little variation at different confining, water pressures and temperature conditions, however in case of synthetic rocks, the frictional behavior showed different trend depending on normal stress level. In addition, the variation of stiffness and dilation at different testing conditions were analyzed, and the stiffness and dilation showed little variation at different water pressures and temperature conditions.

• Journal of the Korean GEO-environmental Society
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• v.4 no.2
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• pp.15-25
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• 2003

Time Domain Refletometry, or TDR, is a remote sensing electrical measurement technique that has been used for many years to determine the spatial location and nature of various objects, especially in the United States of America and Australia at mining industry. Since early on 1990, the TDR techniques have been applied to the geotechnical engineering such as : deformation measurement of rock slope and landslide, monitoring of ground water content and ground water level change, investigation of ground contamination and its movement. The first application of this technique, in 1996, to the domestic area is to determine the possibility of ground settlement caused by subsidence from abandoned underground mines at the Tongri and Gosari in Gangwon-d. In this paper, through the results of analysed deformation data between conventional measurements and the TDR, it was concluded that the TDR technique is a useful instrumentation method for the prediction of ground deformation.

• Tunnel and Underground Space
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• v.18 no.3
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• pp.219-225
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• 2008

To obtain the input data for the design and long-tenn performance assessment of a high-level waste repository, the thermal conductivities of several granite rocks which were taken from the rock cores from the declined borehole were measured. The rock specimens were sampled at the various depths from the surface, and the thermal conductivity was measured under the dry and water-saturated conditions. Under the dry condition, the thermal conductivities of the granite rocks decrease with increasing porosity and range from 2.1 W/mK to 3.1 W/mK. The water-saturated rock samples showed greater thermal conductivities than the dry samples, and the thermal conductivities of the granite rocks range from 2.9 W/mK 3.6 W/mK. The anisotropy effects on the thermal conductivity of granite of the site seem to be insignificant.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.4
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• pp.687-699
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• 2018

The construction of subsea tunnel differs from that of inland tunnel because of high water pressure due to sea water level and difficulties to reinforce the ground under construction. Therefore, it is very important to prevent trouble in advance when the subsea tunnel is constructed. In this paper, we established lots of databases about characteristics of geological and mechanical parameters on the construction of subsea tunnel using micro slurry TBM which depth is about 60 m. The correlation analysis is conducted to confirm the effect of thrust, torque and RPM among the excavation database on the net penetration rate. Also, An empirical formula is suggested to predict the net penetration rate through the correlation analysis between FPI (Field Penetration Index) and specific energy from the subsea tunnel excavation database.

• Journal of the Korean Institute of Landscape Architecture
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• v.26 no.3
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• pp.297-311
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• 1998

Landscaping on artificial ground is currently served as a means to imposing a greenery benefit on high-density and high-rise apartment sites. It functions as a sub-hierarchy in apartment planning such as ornamental element from the past. Major parking space tends to be allocated on the basement area in response to the required parking regulation. Therefore, competitive relatioinship between the parking and greenery space I limited outdoor of apartments leads to the development planning strategy and technology of artificial ground. This study aims at evaluating landscape planning on artificial ground of apartment complex through several approaches such as site survey, plan drawing analysis, and interview with related field experts. 15 survey apartment sites including Bundang Model, Shindaebang-dong, Pyoungchon Hyundai Apartments have been selected for conducting the research. Main results of this study are summarized below : First, scattering allocation of artificial ground between apartment building units is a dominant plan layout type among the survey sites. Even though unifying allocation type has an advantage to maximize underground parking space, it has a difficulty in maintaining proper soil ground base for nurturing plants. Therefore, underground parking space should be planned by unifying allocation type placed separately from apartment units. This plan type can provide a balanced planting between soil and artificial ground on surface level. Second, It is strongly recommended to integrate the whole planting base which involves architectural structure, drainage, and water proofing above the planting design. When considering that process as a professional subject dealing with natural material such as trees and shrubs, those tasks should be directed by landscape architectural divison and landscape architect. And planting area for artificial ground has to be specified in initial phase of architectural design. This step provides an opportunity to make a proper decision on structural load, drainage, and water proof design as an integrated part of the management.

• Geomechanics and Engineering
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• v.13 no.4
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• pp.671-683
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• 2017

Groundwater control is a significant issue in most underground construction. An estimate of the inflow rate is required to size the pumping system, and treatment plant facilities for construction planning and cost assessment. An estimate of the excavation-induced drawdown of the initial groundwater level is required to evaluate potential environmental impacts. Analytical and empirical methods used in current engineering practice do not adequately account for the effect of the jointed-rock-mass anisotropy and heterogeneity. The impact of geostructural anisotropy of fractured rocks on tunnel inflows is addressed and the limitations of analytical solutions assuming isotropic hydraulic conductivity are discussed. In this paper the unexcavated Zagros tunnel route has been classified from groundwater flow point of view based on the combination of observed water inflow and numerical modeling results. Results show that, in this hard rock tunnel, flow usually concentrates in some areas, and much of the tunnel is dry. So the remaining unexcavated Zagros tunnel route has been categorized into three categories including high Risk, moderately risk and low risk. Results show that around 60 m of tunnel (3%) length can conduit the large amount of water into tunnel and categorized into high risk zone and about 45% of tunnel route has moderately risk. The reason is that, in this tunnel, most of the water flows in rock fractures and fractures typically occur in a clustered pattern rather than in a regular or random pattern.

• Journal of the Korean Society of Safety
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• v.28 no.5
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• pp.35-40
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• 2013

Recently reclamation land is largely developed to utilize the land according to economic growth. The soil of landfill is soft, low shear strength, which makes it difficult to use the equipment. A large movement is occurred on the utility tunnel under construction. The inclined land with high water level and underground facilities are widely distributed and the excess pore water pressure may occur under construction similarly to this study. Some different conditions are made to design result, such as 4m of soil piling near the construction area, heavy rainfall during 2nd excavation that may cause flow liquefaction. To analyze the cause of transverse lateral movement, Three dimensional analysis are performed to four load cases, which is original design condition, flow liquefaction by heavy rainfall, unsymmetric lateral soil pressure, and both of them simultaneously. Ten steps of full construction stage, 1st excavation for utility tunnel, construction of utility tunnel, 1st refill, piling soil from 1m to 4 m, 2nd excavation for drainage culvert, liquefaction around the utility tunnel, construction of drainage culvert and 2nd refill, are take into account to investigate the cause of movement.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.418-418
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• 2021

신월 빗물저류배수시설은 2010년 집중호우로 침수피해가 발생한 강서구 및 양천구의 저지대 침수문제 해결을 위해서 양천구의 지하 50m 깊이에 설치한 직경 10m, 길이 3.6km, 저류량 32만톤 규모의 지하 대심도 저류 터널이다. 해당 시설은 강우 발생시 유역의 중상류 하수관에서 횡월류 수문을 통해 우수를 저류터널로 유입 및 저류하고, 하류에 위치한 목동 빗물펌프장과 연계하여 배수할 수 있도록 구성되어 있다. 현재 시설의 운영은 유입부 인근에 설치된 수위계를 통해 수문 가동 여부를 판단하고 있으며, 운영 기준 및 매뉴얼은 서울기술연구원에서 지속적인 모니터링을 통해 고도화하고 있다. 본 연구의 목적은 실측 수위 기반의 신월 빗물저류배수시설 운영을 자동화하기 위한 방편으로, 딥러닝 기반의 RNN, LSTM, GRU 등의 알고리즘을 이용하여 유입부 관거 수위를 예측하는 모델을 개발하는 것을 목표로 하였다. 모델의 개발 및 검·보정을 위해 2010년부터 유역 내 구축되어 있는 강우 및 하수관 수위 자료와 목동 빗물펌프장 운영자료를 활용하였다. 현재 신월 빗물저류배수시설은 2020년 5월 준공되어 절대적인 자료 축적 기간이 부족하기 때문에, 향후 지속적인 강우-수위 모니터링을 통해 모델을 고도화하여 시설의 운영에 활용할 수 있도록 개선해 나갈 예정이다.

• Nuclear Engineering and Technology
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• v.6 no.2
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• pp.97-111
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• 1974

The adsorption mechanism of Cs-137 in low level radioactive solution by vermiculite treated with Na ion is studied in order to investigate its effective utilization for the radioactive effluent treatment. The beneficial role of Na-vermiculite is that Na ion can induce the wider c-axis spacing in which Cs ion can be sorbed in vermiculite. Cation exchange capacity and distribution coefficient of cesium seems to be influenced by the variation of c-axis spacing of vermiculite. Comparative identification and detection with the characteristic analyses of X-ray diffraction and electron diffraction patterns, diffrential thermal analysis and electron microscopy of Na-, K- and Cs-vermiculite are studied for the phemomena of Cs adsorption by vermiculite. This importance of the utilization in terms of adsorption and fixation of cesium involving vermiculite is discussed. It is found that the Na-vermiculite is valuable outside charging material for high level radioactive liquid waste storage tank of underground to protect the pollution of the underground water.

• Journal of Korean Tunnelling and Underground Space Association
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• v.26 no.1
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• pp.79-89
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• 2024

Excessive inflow of groundwater during tunnel excavation not only affects the stability and constructability of the tunnel, but is also one of the main causes of ground settlement due to groundwater level drawdown. The most commonly applied measure against excessive groundwater inflow during tunnel excavation in soil or fractured zone is to reduce the ground permeability coefficient by injecting grout material. Generally, the grouting area is assumed to be same as the plastic zone that occurs during tunnel excavation, but injecting grout material in the area of plastic zone is appropriate only for reinforcement grouting. In order to determine the thickness of cutoff grouting, the amount of reduction in the water permeability coefficient due to the application of cutoff grouting must be considered. In this study, a method for estimating the range of cutoff grouting considering the reduction in permeability coefficient was mathematically derived and evaluated through computer numerical analysis.