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2019 Vol.21, Issue 6 Preview Page

Research Paper

A numerical study of the influence of rock mass classes boundary on tunnel stability

암반 등급 경계가 터널 안정성에 미치는 영향에 관한 수치해석적 연구

Gyeomyeon Kim1
,
Chanmook Jung2
,
Yongjun Lee3*
김 겸연1
,
정 찬묵2
,
이 용준3*
1General Manager, Honam Headquarters, Korea Rail Network Authority
2Professor, School of Railroad Civil System Engineering, Woosong University
3General Manager, Dept. of Geotechnical Engineering, DANWOO E&C
1비회원, 한국철도시설공단 호남본부 부장
2비회원, 우송대학교 철도토목시스템공학과 교수
3정회원, 단우기술단 지반공학부 상무
* Corresponding Author
30 November 2019. pp. 825-835
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Abstract

When the tunnel is designed, the ground is classified into several grades and the corresponding support system is applied according to the support pattern table. However, a simple pattern application based on rock grade does not take into account the longitudinal stress transitions occurring at rock grade boundaries. In this study, three-dimensional numerical analysis was performed to estimate the stress change in the longitudinal rock grade change of NATM tunnel, and the influence zone of load transfer was investigated using the influence line and trend line. As a result, the downward change of rock grade in the direction of tunnel excavation occurs in the range of 0.35~0.7D from low-strength rock to high-strength rock around the grade change boundary. It is necessary to apply a downward pattern of about 1.0D to the safety direction in consideration of the influence range of 0.35D to 0.7D.

Keywords
Rock mass grade
rock mass classes boundary
influence line
trend line
longitudinal stress transition

터널 설계 시 조사를 통하여 지반을 여러 개의 등급으로 분류한 후 지보패턴표에 따라 해당 지보시스템을 적용하게 된다. 그러나 암반 등급을 기준으로 한 단순한 패턴 적용방식은 암반 등급 경계부에서 발생하는 종방향 응력 전이를 고려하지 못한다. 본 연구는 NATM 터널의 종방향 암반 등급 변화부에서 응력 변화를 추정하기 위한 3차원 수치해석을 실시하였으며 Influence Line (영향선) 및 Trend Line (경향선)을 이용하여 하중 전이 영향권을 파악하고자 하였다. 연구 결과 터널 굴착방향으로 암반 등급이 하향 변화하면 등급변화 경계를 중심으로 강성이 약한 암반에서 강성이 큰 암반 방향으로 0.35~0.7D 범위에서 응력 전이가 발생하며 이를 고려하여 암반 등급의 종방향 하향 변화부에서는 연구결과의 0.35~0.7D 영향권을 감안하여 안전측으로 1.0D 정도의 하향패턴을 추가 적용하는 것이 필요하다.

키워드
암반 등급
등급 변화 경계
영향선
경향선
응력 전이
References
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Bang, J.H., Han, I.Y. (2006), "Prediction of ground condition changes ahead of tunnel face using three- dimensional absolute displacement analysis", Journal of Korean Tunnelling and Underground Space Association, Vol. 8, No. 2, pp. 101-113.
2
Gnilsen, R. (1989), Numerical Methods, Developments in Geotechnical Engineering, 59A, Underground Structures Design and Instrumentation, Elsevier, New York, pp. 84-128.
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3
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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 : 21
  • No :6
  • Pages :825-835
  • Received Date : 2019-09-10
  • Revised Date : 2019-10-08
  • Accepted Date : 2019-10-19
  • DOI :https://doi.org/10.9711/KTAJ.2019.21.6.825
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