• Title/Summary/Keyword: Borehole System

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Analysis of cross-borehole pulse radar signatures measured at various tunnel angles (다양한 투과 각도에서 측정된 투과형 펄스 시추공 레이더 신호 분석)

  • Kim, Sang-Wook;Kim, Se-Yun
    • Geophysics and Geophysical Exploration
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    • v.13 no.1
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    • pp.96-101
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    • 2010
  • A pulse radar system has been developed recently to detect dormant underground tunnels that are deeply located at depths of hundreds of metres. To check the ability of the radar system to detect an obliquely oriented tunnel, five different borehole pairs in the tunnel test site were chosen so that the horizontal lines-of-sight cut the tunnel axis obliquely, in $15^{\circ}$ steps. The pulse radar signatures were measured over a depth range of 20 m around the centre of the air-filled tunnel. Three canonical parameters, consisting of the arrival time, attenuation, and dispersion time were extracted from the first and second peaks of the measured radar signatures. Using those parameters, the radar system can detect obliquely oriented tunnels at various angles up to 45 from the transmitter-receiver line of sight.

A Foreign Cases Study of the Deep Borehole Disposal System for High-Level Radioactive Waste (고준위 방사성폐기물 심부시추공 처분시스템 개발 해외사례 분석)

  • Lee, Jongyoul;Kim, Geonyoung;Bae, Daeseok;Kim, Kyeongsoo
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.12 no.2
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    • pp.121-133
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    • 2014
  • If the spent fuels or the high-level radioactive wastes can be disposed of in the depth of 3~5 km and more stable rock formation, it has several advantages. For example, (1)significant fluid flow through basement rock is prevented, in part, by low permeability, poorly connected transport pathways, and (2)overburden self-sealing. (3)Deep fluids also resist vertical movement because they are density stratified and reducing conditions will sharply limit solubility of most dose-critical radionuclides at the depth. Finally, (4) high ionic strengths of deep fluids will prevent colloidal transport. Therefore, as an alternative disposal concept to the deep geological disposal concept(DGD), very deep borehole disposal(DBD) technology is under consideration in number of countries in terms of its outstanding safety and cost effectiveness. In this paper, for the preliminary applicability analyses of the DBD system for the spent fuels or high level wastes, the DBD concepts which have been developed by some countries according to the rapid advance in the development of drilling technology were reviewed. To do this, the general concept of DBD system was checked and the study cases of foreign countries were described and analyzed. These results will be used as an input for the analyses of applicability for DBD in Korea.

Electrical Resistivity Imaging for Upper Layer of Shield TBM Tunnel Ceiling (쉴드 TBM터널 상부 지반 연약대 전기탐사)

  • Jung, Hyun-Key;Park, Chul-Hwan
    • Proceedings of the Korean Geotechical Society Conference
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    • 2005.03a
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    • pp.401-408
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    • 2005
  • Recently shield TBM tunnellings are being applied to subway construction in Korean cities. Generally these kinds of tunnellings have the problems in the stability of ground such as subsidence because urban subway is constructed in the shallow depth. A sinkhole occurred on the road just above the tunnel during tunneling in Kwangju, so a survey for upper layer of the tunnel was needed. But conventional Ground Probing Radar can't be applicable due to the presence of steel-mesh screen in the shield segment, so no existent geophysical method is applicable in this site. Because the outer surface of each shield segment is electrically insulated, dipole-dipole resistivity method which is popular in engineering site investigation, was tried to this survey for the first time. Specially manufactured flexible ring-type electrodes were installed into the grouting holes at an interval of 2.4 m on the ceiling. The K-Ohm II system which has been developed by KIGAM and tested successfully in many sites, was used in this site. The system consists of 1000Volt-1Ampere constant-current transmitter, optically isolated 24 bit sigma-delta A/D conversion receiver - maximum 12 channel simultaneous measurements, and graphical automatic acquisition software for easy data quality check in real time. Borehole camera logging with circular white LED lighting was also done to investigate the state of the layer. Measured resistivity data lack of some stations due to failing opening lids of holes, shows general high-low trend well. The dipole-dipole resistivity inversion results discriminate (1) one approximately 4 meter diameter cavity (grouted but incompletely hardened, so low resistivity - less than $30{\Omega}m$), (2) weak zone (100-200${\Omega}m$), and (3) hard zone (high resistivity - more than 1000${\Omega}m$) very well for the distance of 320 meters. The 2-D inversion neglects slight absolute 3-D effect, but we can get satisfactory and useful information. Acquired resistivity section and video tapes by borehole camera logging will be reserved and reused if some problem occurs in this site in the future.

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Thermal Response Test (TRT) interpretation and the status in Korea (열응답 실험 해석 및 국내 현황)

  • Shim, Byoung Ohan;Choi, Choonghyun
    • 한국신재생에너지학회:학술대회논문집
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    • 2010.06a
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    • pp.168.2-168.2
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    • 2010
  • The growing market for geothermal heat pump system requires great consideration of quality control and assurance in design and construction. The borehole heat exchanger of GHP system should be sustainable, economical and ecological. Thermal Response Test (TRT) is a useful method for site investigation to obtain reliable data for a optimal system design from the technical and economical aspect. Intensive researches combined with exchange of experiences on an international level within the IEA ECES Annex 21 improved the technology. Major subjects on the interpretation of TRT are development of improved evaluation models, evaluation of the TRT with respect to geological layers and investigation of the influence of ground water. Current status of TRT in South Korea, as well as a new version of the Korean TRT standard test procedure was presented. TRT is mostly used for governmental supported projects with corresponds to more than 100 GCHP systems per year. More than 200 tests are applied, mostly on single U-tube heat exchangers (about 95%). Bentonite is the most common grouting to be used. KIGAM (Korea Institute of Geoscience & Mineral Resources) is also keeping a GIS geological and geothermal database. In the institute also laboratory measurements of rock properties are carried out. About 90% of the laboratory measurements of the rock heat conductivity shows higher values than the in-situ TRT.

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A Development and Utilization of Geotechnical Information System(GTIS) of the Rock Mass in A Seoul Metropolitan Area(1) (서울일대 암반을 대상으로 한 Geotechnical Information System(GTIS)의 개발 및 활용(1))

  • 김정엽;전효택;박형동
    • Tunnel and Underground Space
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    • v.5 no.4
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    • pp.336-346
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    • 1995
  • Geotechnical Information System (GTIS) for efficient management of three dimensional borehole data has been developed. Some problems were raised during the input process of borehole data, and alternative solutions were sought. According to the previous geotechnical reports, there is no unified weathering classification scheme. A criterion, 100 times/30cm from SPT, was turned out inappropriate to the discrimination of weathered rock from weathered soil. It has also been suggested that weathered soil, weathered rock, soft rock, and hard rock should be defined as CW, HW, MW, and SW~fresh condition. For better comparison of RQD, the use of NX size coring is recommended for the whole area although BX size coring has been used in excavated area. The limit of drilling depth up to 1 m from the top of surface of hard rock should be extended to avoid possible wrong interpretation of rock head due to the existence of corestone. The input data were analysed by geostatistical methods. It is found that the range in semivariogram is about 300m, and the variance of gneiss is greater than that of granite. It is because the granite data analysed came from almost single uniform rock mass(i.e.Seoul granite), but gneiss data came from the rock mass(i.e. Gyeonggi gneiss complex experienced several metamorphic metamorphic processes.

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Design of Web GIS for Geotechnical Data (지반데이터의 활용을 위한 Web GIS 설계)

  • Yu, Shik;Park, Hyeong-Dong
    • Tunnel and Underground Space
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    • v.12 no.4
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    • pp.284-290
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    • 2002
  • Over the past few decades, a considerable number of studies have been conducted on GIS(Geographic Information System) to process spatial date. As GIS comes to be used in many fields and used by many people, Web GIS which is a GIS system used on the internet, was proposed as a good tool to maintain the need. There is an increasing demand for Web GIS to provide more opportunity for users to manage and to analyze geotechnical data. This study mainly focused on the design and application of Web GIS particularly with geotechnical data, including design of efficient database structure for borehole data. A practical application of the Web GIS to tunnelling site has been successfully completed by the design of several analytical functions.

Development of a Three-Dimensional Numerical Model of the Vertical Ground-Coupled Heat Exchanger Considering the Effects of the Thermal Capacity (내부 열용량을 고려한 수직 지중열교환기의 3차원 수치 모델 개발)

  • Kim, Eui-Jong
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.28 no.7
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    • pp.293-298
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    • 2016
  • A three-dimensional (3D) numerical model of the vertical ground-coupled heat exchanger is useful for analyzing the modern ground source heat pump system. Furthermore, a detailed description of the inner side of the exchanger allows to account for the effects of the thermal capacity. Thus, both methods are included in the proposed numerical model. For the ground portion, a FDM (Finite Difference Method) scheme has been applied using the Cartesian coordinate system. Cylindrical grids are applied for the borehole portion, and the U-tube configuration is adjusted at the grid, keeping the area and distance unchanged. Two sub-models are numerically coupled at each time-step using an iterative method for convergence. The model is validated by a reference 3D model under a continuous heat injection case. The results from a periodic heat injection input show that the proposed thermal capacity model reacts more slowly to the changes, resulting in lower borehole wall temperatures, when compared with a thermal resistance model. This implies that thermal capacity effects may be important factors for system controls.

Analysis of Slope Stability in Slopes of Failed and not Excavated (붕괴된 사면과 굴착되지 않은 사면의 안정성 검토)

  • 유병옥;김경석;이용희
    • Proceedings of the Korean Geotechical Society Conference
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    • 2003.06a
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    • pp.129-144
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    • 2003
  • Generally, investigation methods of cut slope are conducted only geological surface survey to gain engineering geological data of cut slopes. These methods have many problems such as limitations of investigation for a special area. So geophysical investigations such as geotomography, seismic and electrical resistivity methods have been used to search for failure surface in potential failure slopes or failed slopes. But investigation method using the borehole camera is recently a used method and it is thought that this method is more reliable method than other investigation methods because of being able to see by the eyes. Therefore, this paper was conducted investigations of borings and BIPS(Borehole Image Processing System) to search for potential sliding surfaces and was applied to obtain information of discontinuity on failed and potential failure slope in highway. As the results of BIPS, we could decide potential sliding surface in the slope, conducted to check slope stability and decided slope stability measures.

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A Study to Calculate Inlet Fluid Temperature of the Borehole Heat Exchanger (BHE) using Modified TOUGHREACT (Modified TOUGHREACT를 이용한 지중 열교환기 내 순환 유체의 온도 분포 추정)

  • Kim, Seong-Kyun;Bae, Gwang-Ok;Lee, Kang-Kun;Shim, Byoung-Ohan;Song, Yoon-Ho
    • 한국신재생에너지학회:학술대회논문집
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    • 2007.11a
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    • pp.477-480
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    • 2007
  • Inlet fluid temperature of the BRE in the geothermal heat pump system depends on heat exchange rate between the refrigerant of the heat pump and the leaving fluid from the BRE. Because the outlet fluid temperature of the BHE varies with time, inlet fluid temperature has to vary with time. In this study, the module to calculate inlet fluid temperature is developed, which can consider the time-varying outlet fluid temperature and the heat exchange capacity of the heat pump. It is assumed that heat loss or gain of the leaving fluid from outlet to inlet of the BHE is negligible, except when the fluid contacts with the refrigerant of the heat pump. This module is combined with TOUGHREACT, a widely accepted three-dimensional numerical simulator for heat and water flow and geochemical reactions in geothermal systems and is applied to data analyses of the thermal response test.

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Monitoring water injection with borehole ERT: preliminary results of an experiment carried out in Sindos (N. Greece)

  • Tsourlos, Panagiotis;Kim, Jung-Ho;Vargemezis, George;Yi, Myeong-Jong
    • 한국지구물리탐사학회:학술대회논문집
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    • 2007.06a
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    • pp.87-92
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    • 2007
  • This work describes the installation and preliminary measurements of an electrical resistivity tomography (ERT) system to monitor the injection of recycled water into a confined aquifer in the area of Sindos (Thessaloniki N. Greece). The aim is to provide, through time-lapse ERT measurements and processing, geoelectrical images of rather increased volumetric sampling around and between the holes and to obtain improved understanding of the flow and transport of the injected water. The details about the general setting, the construction and installation of the ERT cables into the boreholes are explained in full. Preliminary measurements involving single and cross-hole ERT measurements were obtained and processed with a 2D inversion algorithm to produce images of the subsurface. Results depict a very good correlation between ERT images and the lithology and resistivity logs; an indication of the reliability of the approach.

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