All Issue

2017 Vol.33, Issue 3 Preview Page
3D Numerical Study on the Reinforcing Effect of Inclined System Bolting in NATM Tunnel

NATM 터널에서 경사 록볼트의 보강효과에 대한 3차원 해석

June Heo1
,
Byoung-Il Kim2*
,
Jea-Dug Lee3
,
Young-Geun Kim4
허 준1
,
김 병일2*
,
이 재덕3
,
김 영근4
1Staff, Geotechnical and Tunnelling Dept. Kyongdong Eng.
2Prof., Dept. of Civil & Environmental Engrg., Myongji Univ.
3Senior Researcher, Geotechnical Engrg. Research Institute
4Senior Managing Director, Geotechnical and Tunnelling Dept. Kunhwa Eng.
1동엔지니어링 사원
2명지대학교 토목환경공학과 교수
3대원토질 기술연구소장
4건화엔지니어링 전무
*교신저자. *Corresponding Author. 
31 March 2017. pp. 29-36
PDF XML Citation
Abstract

It has been known that rockbolt is one of important supports improving the support capacity with shotcrete in NATM tunnel. Also, it is necessary for the inclined system bolting to enhance the efficiency of installation in case of a narrow space such as cross passage and enlargement tunnel. However, there is no profound technical study for the effect of inclined rockbolt of systematic installation on the support mechanism and ground behaviour in NATM tunnel. In this study, the effects of the length and installation angle of rockbolt on the characteristics of support and ground reinforcement were analyzed by using 3D finite element numerical study. Through the numerical results for the parametric modelling of inclined rockbolt, the characteristics of mechanical behaviors between the axial force of rockbolt and the effect of ground reinforcement in regard to the various factors of the length and installation angle of rockbolt were verified and reviewed thoroughly. Also, it was shown that the installation angle of rockbolt for enhancing the arching effect in NATM tunnel was 45°, and the difference of the reinforcing effect for support between the installation angles of 75° and 90° was insignificant. The additional numerical studies for various condition would be carried out for practical design guideline of inclined rockbolt.

Keywords
3D Numerical analysis
Inclined rockbolt
Reinforcement effect
NATM tunnel

NATM 공법에서 터널을 확대하거나 피난갱과 같이 좁은 단면에 록볼트를 설치하는 경우에는 록볼트를 경사지게 설치하거나 또는 짧은 볼트를 연결하여 시공할 수밖에 없다. 국내외에서 실시된 경사 록볼트에 대한 연구는 아직 미흡한 실정이며 실제 현장에 적용하기 위해서는 경사 록볼트의 거동특성에 대한 연구가 필요하다고 사료된다. 본 연구에서는 3차원 유한요소해석을 사용하여 경사 록볼트 시공 시 록볼트의 설치각도와 설치길이에 따른 최대 중립점 발생위치의 변화를 확인하고 이에 따른 록볼트에 의한 원지반 아치형성영역의 두께 변화를 비교 분석하여 지반보강효과에 대해 확인하였다. 해석결과 표준지보패턴(설치길이 4m)에선 설치각도가 감소할수록 터널 주변지반의 변형범위는 증가하여 지반보강효과가 감소하는 것을 알 수 있었다. 또한, 설치길이가 증가함에 따라 설치각도에 의한 영향을 적게 받은 것으로 나타났으며 설치각도 45° 이하에서는 설치길이의 영향을 받지 않는 것으로 나타났다. 이러한 결과로부터 경사록볼트의 설치각도는 45°이상으로 하여 아칭영역을 확보하도록 하여야 하며, 설치각도 75°이상인 경우 직각으로 설치하는 경우와의 보강효과의 차이가 크지 않음을 확인하였다. 또한 추가적인 상세 검토를 통하여 NATM 터널에서의 경사록볼트 설계지침을 제시하고자 하였다.

References
1
Baek, K.H. (2011), “Ground Behavior Analysis and Protector Design during the Enlargement of a Tunnel in Operation”, Inha University, pp.1-3.
2
MLTMA (2010), “The Revision of the Road-Design Guideline-6th Tunnel”, Ministry of Land, Transport and Maritime Affairs, pp. 605.2-606.4.
3
Freeman, T.J. (1978), “The Behaviour of Fully-bonded Rock Bolts in Kielder Experimental Tunnel”, Tunnel & Tunnelling, pp.37-40.
4
Heo, J. (2016), “A 3D Numerical Analysis on the Reinforcing Effect of Inclined System Bolting”, Master Dissertation, Myongji University, pp.13-25.
5
Hyett, A.J., Moosavi, M., and Bawden, W.F. (1996), “Load Distribution along Fully Grouted Bolts, with Emphasis on Cable Bolt Reinforce-ment”, Int. J. Numer. & Anal. Meth. Geomech, Vol.20, pp.517-544.
6
Kim, U.G., Baek, K.H., Seo, K.W., Kim, D.K., and Woo, S.B. (2010), “Numerical Study on Effect of Ground Reinforcement with Installation Angle of Rockbolt”, Korean Society for Rock Mechanics Conference, pp.199-204.
7
KSGE (1997), “Geotechnical Engineering Series-7th”, Goomi Publisher, p.663.
8
Lee, J.D. (2012), “Effect of Installation Angle on Ground Reinforce-ment in System Bolting”, Ph.D. Dissertation, Myongji University, pp.1-119.
9
Lee, S.D. (2013), “Tunnel Mechanics”, CIR Publisher, pp.387-480.
10
Lee, Y.K., Song, W.K., Park, C.W., and Choi, B.H. (2010), “Numerical Study on the Behavior of Fully Grouted Rock Bolts with Different Boundary Conditions”, Journal of Korean Society for Rock Mechanics, Vol.20, No.4 pp.267-276.
11
Talobre, J. (1957), “La Mechanique des Roches : Appliquee aux travaux publics”, Dunod.
Information
  • Publisher :The Korean Geotechnical Society
  • Publisher(Ko) :한국지반공학회
  • Journal Title :Journal of the Korean Geotechnical Society
  • Journal Title(Ko) :한국지반공학회 논문집
  • Volume : 33
  • No :3
  • Pages :29-36
  • Received Date : 2016-12-01
  • Accepted Date : 2017-03-02
  • DOI :https://doi.org/10.7843/kgs.2017.33.3.29
Journal Informaiton Journal of the Korean Geotechnical Society Journal of the Korean Geotechnical Society
Archives
: Vol.23~28 (2007~2012)
  • NRF
  • KOFST
  • KISTI Current Status
  • KISTI Cited-by
  • crosscheck
  • orcid
  • open access
  • ccl
Journal Informaiton Journal Informaiton - close