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Research Paper

Derivation and verification of electrical resistivity theory for surrounding ground condition prediction of TBM

TBM 주변 지반상태예측을 위한 전기비저항 이론식 유도 및 검증

Chang-Ho Hong1
,
Minhyeong Lee2
,
Gye-Chun Cho3*
홍 창호1
,
이 민형2
,
조 계춘3*
1Postdoctoral Researcher, Dept. of Civil and Environmental Engineering, KAIST
2Ph.D. Student, Dept. of Civil and Environmental Engineering, KAIST
3Professor, Dept. of Civil and Environmental Engineering, KAIST
1정회원, 한국과학기술원 건설및환경공학과 박사후연구원
2학생회원, 한국과학기술원 건설및환경공학과 박사과정
3정회원, 한국과학기술원 건설및환경공학과 교수
* Corresponding Author
31 January 2020. pp. 135-144
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Abstract

Since the depth of tunneling with tunnel boring machine (TBM) becomes deeper and deeper, the expense for site investigation for coring and geophysical survey increases to obtain the sufficient accuracy. The tunnel ahead prediction methods have been introduced to overcome this limitation in the stage of site investigation. Probe drilling can obtain the core and borehole images from a borehole. However, the space in TBM for the probe drilling equipment is restricted and the core from probe drilling cannot reflect the whole tunnel face. Seismic methods such as tunnel seismic prediction (TSP) can forecast over 100 m ahead from the tunnel face though the signal is usually generated using the explosive which can affect the stability of segments and backfill grout. Electromagnetic methods such as tunnel electrical resistivity prospecting system (TEPS) offer the exact prediction for a conductive zone such as water-bearing zone. However, the number of electrodes installed for exploration is limited in small diameter TBM and finally the reduction of prediction ranges. In this study, the theoretical equations for the electrical resistivity survey whose electrodes are installed in the face and side of TBM to minimize the installed electrodes on face. The experimental tests were conducted to verify the derived equations.

Keywords
TBM
Electrical resistivity survey
Side electrode

국내에서 TBM 공법을 활용한 터널건설 시 점차 건설심도가 깊어지고 있으며, 이로 인해 상부 지반조사 단계에서 충분한 예측 정확도를 획득하기 위해서는 시추조사 및 물리탐사 비용이 증가하게 된다. 이러한 문제를 극복하기 위해 터널 시공 중 터널 굴착면 전방 예측을 위한 방법들이 제시되었다. 프로브 드릴링을 활용한 굴착면 전방 예측은 코어회수, 시추공 내부 이미지 등을 활용할 수 있는 장점이 있지만 실제 TBM 내에 설치가 어렵고 터널 막장 전체가 아닌 국부적인 지반만을 파악할 수 있다. TSP 등 탄성파를 활용한 방법은 100 m 이상의 긴 탐사거리를 가지지만 신호발생을 위해 발파를 사용하므로 세그먼트 라이닝, 백필 등의 안정성에 영향을 미칠 수 있다. TEPS를 포함한 전자기파 탐사는 지하수 층 등 전도성 있는 이상대를 파악하는 데 적합하지만 소구경 TBM에 설치할 수 있는 전극의 개수가 한정적이며 이는 탐사 범위의 감소 등을 야기한다. 본 연구에서는 전기비저항 탐사 시 굴착면에 설치되는 전극의 개수를 최소화하기 위해 TBM의 굴착면과 측면에 전극이 설치되었을 때에 대한 탐사 이론식을 제시하고 실내실험을 통해 검증하였다.

키워드
TBM
전기비저항탐사
측면전극
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Information
  • Publisher :Korean Tunneling and Underground Space Association
  • Publisher(Ko) :한국터널지하공간학회
  • Journal Title :Journal of Korean Tunnelling and Underground Space Association
  • Journal Title(Ko) :한국터널지하공간학회 논문집
  • Volume : 22
  • No :1
  • Pages :135-144
  • Received Date : 2020-01-02
  • Revised Date : 2020-01-09
  • Accepted Date : 2020-01-10
  • DOI :https://doi.org/10.9711/KTAJ.2020.22.1.135
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