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2025 Vol.35, Issue 6

Technical Note

Measurement and Mitigation Strategies of Borehole Deviation in Deep Drilling for High-Level Radioactive Waste Disposal Site Study

고준위방사성폐기물 처분부지연구를 위한 심부 시추공 공곡 측정 및 공곡도 향상 방안

Dae-Sung Cheon1
,
Jai-Yong Park1
,
Seong Kon Lee2*
,
Ki Seog Kim3
천 대성1
,
박 재용1
,
이 성곤2*
,
김 기석3
1Principal Researcher, Geological Safety Division, Korea Institute of Geoscience and Mineral Resources
2Principal Researcher, Resource Exploration and Development Research Division, Korea Institute of Geoscience and Mineral Resources
3CEO, Heesong Geotek, Co., LTd.
1한국지질자원연구원 국토안전연구본부 책임연구원
2한국지질자원연구원 자원탐사개발연구본부 책임연구원
3(주)희송지오텍 대표이사
*Corresponding Author
31 December 2025. pp. 667-688
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Abstract

Borehole deviation refers to the degree of curvature that occurs during actual drilling relative to the intended drilling direction. Since borehole deviation affects the accuracy of deep geological repository design for high-level radioactive waste, precise measurement and proper management are required. This article introduces the types and principles of instruments used for borehole deviation measurement both domestically and internationally, presents case studies from Finland and Sweden, and discusses the causes of borehole deviation and methods for its reassessment. In addition, borehole deviation results obtained from boreholes drilled at depths of approximately 750 m in various rock types during site study for a domestic high-level radioactive waste repository are presented. Most deep boreholes exhibited deviations of around 1°, with relatively larger deviations observed in rock types with stratification, foliation, or schistosity. However, in gneissic rock boreholes where drilling equipment was set on poor ground conditions and multiple weak zones were encountered during drilling, deviations exceeding 7° occurred. The excessive deviation was attributed to the influence of large boulders in the ground where drilling equipment was installed and to frequent weak and fractured zones encountered during drilling. Based on domestic deep drilling experience and international case studies, potential strategies for mitigating and improving borehole deviation include multi-stage drilling, installation of protective casing, placement of concrete pads for drill rig positioning, use of horizontal and vertical measurement devices for drill rig alignment at the start or during drilling, maintaining appropriate drilling rates, and employing drill collars or stabilizers during drilling.

Keywords
Borehole deviation
Multi-stage drilling
Concrete pad
High-level radioactive waste
Site study

공곡은 수직, 수평, 경사 등을 포함하는 시추 방향 기준으로 실제 굴진할 때 시추공의 휜 정도를 뜻하며, 고준위방사성폐기물 심층 처분시설 설계의 정확도에 영향을 주기 때문에 정밀한 측정과 적절한 공곡 관리가 요구된다. 본 보고에서는 국내·외 공곡 측정에서 활용되는 장비의 종류와 원리를 소개하고, 핀란드와 스웨덴의 공곡 측정 사례와 공곡 발생 원인, 공곡의 재산정 등에 대해 소개하였다. 또한 국내에서 고준위방사성폐기물 처분장의 부지연구에서 수행되었던 약 750 m 심도의 암종별 시추공에서 획득한 공곡 결과를 제시하였다. 대부분 심부 시추공에서 1° 전후의 공곡이 발생하였으며, 층리와 엽리, 편리 등이 있는 암종에서 공곡이 상대적으로 약간 크게 발생하는 것을 알 수 있었다. 그러나 시추장비가 위치한 지반 상태가 열악하고, 시추 중 다수의 연약대와 만났던 편마암반의 시추공에서는 7°를 넘는 공곡이 발생하였고, 공곡 초과 발생 원인은 시추장비가 위치한 지반 내 존재했던 큰 규모의 전석들과 시추 과정에서 자주 나타난 연약대와 파쇄대 등에 의해 영향을 받은 것으로 파악되었다. 국내 심부 시추 경험과 국외 사례 조사에 기반하여 심부 시추공의 공곡 완화 및 향상 방안으로 다단식 시추와 보호 케이싱 설치, 시추장비 위치의 콘크리트 패드 설치, 시추 시작 또는 시추 중 시추장비에 대한 수평, 수직계를 이용한 측정 및 관리, 적절한 시추 속도 유지, 시추 중 드릴칼라나 스테빌라이져의 이용 등을 제시하였다.

키워드
공곡
다단식 시추
콘크리트 패드
고준위방사성폐기물
부지연구
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2

Cheon, D.S. Park, J.Y., Song, W.K., and Kim, K.S., 2024b, The Evaluation of Rock Mass Deformation Characteristics at Deep Depth in Granite using a Pressuremeter Test, Tunnel & Underground Space, 34(6), 636-649.

3

Cheon, D.S., Park, J.Y., Song, W.K., and Kim, K.S., 2024c, A Study on Fracture Characteristics based on Deep Boreholes by Tectonic Regimes and Rock Types for Characterization of High-Level Radioactive Waste Disposal Site, Tunnel & Underground Space, 34(6), 750-770.

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Cheon, D.S. and Park, J.Y., 2024d, Procedure of Drilling Operations for Site Characterization of High-Level Radioactive Waste Disposal Facility Tunnel & Underground Space, 34(5), 477-502.

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Cho, S.H., Jung, H.K., Lee, H., and Kim, Y., 2019, Development of real-time borehole deviation and magnetic gradient logging system and its preliminary field test, Journal of Korean Society of Mineral and Energy Resource Engineers, 56(1), 23-32.

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Information
  • Publisher :Korean Society for Rock Mechanics and Rock Engineering
  • Publisher(Ko) :한국암반공학회
  • Journal Title :Tunnel and Underground Space
  • Journal Title(Ko) :터널과 지하공간
  • Volume : 35
  • No :6
  • Pages :667-688
  • Received Date : 2025-10-01
  • Revised Date : 2025-11-20
  • Accepted Date : 2025-11-20
  • DOI :https://doi.org/10.7474/TUS.2025.35.6.667
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