Tunnel and Underground Space (터널과지하공간)

Korean Society for Rock Mechanics and Rock Engineering (한국암반공학회)
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A Study on Comparative Analysis of Hydraulic Conductivity in Injection and Recovery Phases of Constant Pressure Injection Tests in Deep Fractured Rock

심부 균열암반 정압주입시험 주입-회복 단계별 수리전도도 비교분석 연구

  • Hangbok Lee (Deep Subsurface Storage and Disposal Research Center, Korea Institute of Geoscience and Mineral Resources) ;
  • Chan Park (Deep Subsurface Storage and Disposal Research Center, Korea Institute of Geoscience and Mineral Resources)
  • 이항복 (한국지질자원연구원 심층처분환경연구센터) ;
  • 박찬 (한국지질자원연구원 심층처분환경연구센터)
  • Received : 2024.09.03
  • Accepted : 2024.09.19
  • Published : 2024.10.31
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Abstract

In the research project for the disposal of high-level radioactive waste, where the deep rock environment is considered as the main target for the disposal facilities, the hydrogeological characteristics of rock aquifers are utilized as the most important evaluation factor for the suitability of the disposal site, design/construction of facilities and stability analysis during operation. Such hydrogeological data are obtained by conducting in-situ hydraulic tests using deep boreholes located at the target sites. In this process, the reliability and accuracy of the investigation results are closely linked to various factors including the selection of the optimal testing methods, the performance of testing equipment, the standardization of testing procedures, and data interpretation methods. In this paper, to improve the reliability of the evaluation of hydrogeological characteristics in deep rock aquifers, we conducted a comparative analysis of the hydraulic conductivity characteristics derived from the injection and recovery phases of the most representative hydraulic test, the constant pressure injection test. A high-performance hydraulic testing equipment and standardized testing procedures were applied to deep boreholes in the fractured rock aquifers located in granite/volcanic rock areas in Korea, to obtain the downhole pressure-flow rate, and the hydraulic conductivity was derived by using various transient flow analysis solutions. The results of the study showed a high consistency between the hydraulic conductivity values obtained during the injection and recovery phases within the same test section, even under different permeability conditions (low-permeability/high-permeability). This research case, which precisely conducted a comparative analysis of two different phases (injection/recovery) within a single specific hydraulic testing process using actual field data from deep rock aquifers in Korea, is expected to help overcome the inherent limitations of in-situ field tests, where the validation and verification of measurement results are challenging, and ultimately contribute to enhancing the reliability of deriving in-situ hydrogeological characteristics information.

심부 암반 환경이 처분시설의 주요 대상으로 고려되는 고준위 방사성폐기물 처분 연구사업에서, 해당 암반 내 수리지질특성 정보들은 처분 부지의 적합성과 시설의 설계/건설 및 운영 중 안정성 분석에 이르기까지 가장 핵심적인 평가인자로 활용된다. 이 같은 수리지질특성 자료들은 대상 부지에 위치한 심부 시추공을 이용하여, 현장 원위치 수리시험 수행을 통해 획득하게 된다. 이 과정에서 조사 결과의 신뢰도와 정확도는 최적 시험방법 선택, 시험 장비 성능, 시험법 및 조사절차 표준화, 자료해석 방법 등 여러 항목들과 밀접하게 상호 연결된다. 본 논문에서는 심부 균열암반 수리특성평가 신뢰도 향상을 위해, 가장 대표적인 수리시험인 정압주입시험의 주입 및 회복 단계에서 도출된 수리전도도 특성을 비교분석하였다. 자체 개발된 고성능 현지수리특성 측정시스템과 표준시험법이 포함된 조사절차를 국내 화강암/화산암 지역 내 균열암반 대수층의 심부시추공 현장에 적용하여 현지 압력-유량 자료를 획득하였고, 다양한 비정상류 해석해들을 활용해 수리전도도를 도출하였다. 연구 분석 결과, 다른 투수성 환경 조건(저투수성/고투수성)에서 각각 단일 시험구간 내 주입과 회복 단계의 수리전도도가 서로 높은 일치성을 나타냈다. 이처럼 실제 국내 심부 균열암반의 현장자료를 활용하여 하나의 특정한 수리시험 과정에서 다른 두 단계(주입/회복)의 비교분석을 정밀하게 수행한 본 연구사례는, 본질적으로 측정 결과의 검증 및 타당성 확보가 어려운 원위치 현장시험 고유의 한계점을 보완하고, 궁극적으로 현지 수리지질특성 정보 도출의 신뢰도 향상에 기여할 수 있을 것으로 기대된다.

Keywords

Acknowledgement

본 연구는 한국지질자원연구원 기본사업인 "HLW 심층처분을 위한 지체구조별 암종 심부 특성 연구(과제코드 : GP2020-002, 과제번호 : 24-3115)" 및 "심지층 개발과 활용을 위한 지하심부 특성평가 기술개발(과제코드: GP2020-010, 과제번호 : 24-3414)" 지원을 받아 수행되었습니다.

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