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2020 Vol.22, Issue 4 Preview Page

Research Paper

A numerical study on the behavior of existing and enlarged tunnels when widened by applying the pre-cutting method

Pre-cutting 공법을 적용한 터널 확폭 시 기존 및 확폭터널의 거동에 관한 수치해석적 연구

Han-Eol Kim1
,
Kyoung-Min Nam2
,
Sang-Gui Ha2
,
Han-Kyu Yoo3*
김 한얼1
,
남 경민2
,
하 상귀2
,
유 한규3*
1Ph.D. Student, Dept. of Civil and Environmental Engineering, Hanyang University
2Ph.D. Student, Dept. of Civil and Environmental Engineering, Hanyang University
3Professor, Dept. of Civil and Environmental Engineering, Hanyang University
1학생회원, 한양대학교 건설환경공학과 박사수료
2정회원, 한양대학교 건설환경공학과 박사수료
3정회원, 한양대학교 건설환경공학과 교수
* Corresponding Author
31 July 2020. pp. 451-468
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Abstract

Aging tunnels with small cross-sections can cause chronic traffic jams. This problem can be solved by widening the tunnel. In general, when the tunnel is expanded, the outer portion of the existing tunnel is excavated through a mechanical or blasting method. Such excavation affects not only the surrounding ground but also the existing tunnel. The application of the pre-cutting method can be a solution to these problems effectively. Therefore, if the widening of tunnel is performed by applying pre-cutting method, analysis of the impact of this method must be performed. In this study, in order to analyze the effect of applying pre-cutting in tunnel widening, numerical analysis is performed at six ground grades, from grade I to weathered rock. The analysis is performed with the expanding lane and the excavation length of pre-cutting as variables. In addition, the analysis is focused on the displacement of crown of the existing tunnel and the enlarged tunnel. As a result, the crown displacement of the enlarged tunnel is confirmed to converge at the same value regardless of the excavation length of the pre-cutting when the tunnel widening is completed. In the case of existing tunnels, uplift of crown occurs within 5 m of the front of the tunnel surface, and the shorter the excavation length of pre-cutting is found to be effective in preventing the occurrence of uplift.

Keywords
Tunnel enlargement
Pre-cutting method
Crown settlement
Enlarged tunnel
Existing tunnel

단면이 작게 만들어진 노후화된 터널은 만성적인 교통정체를 유발한다. 이는 터널의 확폭을 통하여 해결할 수 있다. 일반적으로 터널을 확폭할 경우, 기계식 또는 발파식 굴착방법을 통하여 기존터널의 외곽부를 굴착하게 된다. 이러한 굴착은 주변 지반뿐만 아니라 기존터널에도 영향을 미치게 된다. Pre-cutting 공법의 적용은 이러한 문제를 효과적으로 해결할 수 있는 방법이 될 수 있다. 따라서 Pre-cutting을 적용하여 확폭을 수행할 경우, 이에 따른 영향분석은 필수적으로 수행 되어야 한다. 본 연구에서는 터널 확폭에서 Pre-cutting을 적용할 경우, 이에 따른 영향을 분석하기 위하여 6가지의 지반등급에서 수치해석을 수행하였다. 해석에서는 확대차로와 Pre-cutting의 굴착길이를 변수로 하여 수행하였으며, 기존터널과 확폭터널의 천단침하에 주목하여 분석하였다. 그 결과, 확폭터널의 천단침하는 확폭이 완료가 되면, Pre-cutting의 굴착 길이와 상관 없이 동일한 값으로 수렴하는 것을 확인하였다. 기존터널의 경우, 굴진면의 전방 5 m 내에서 융기가 발생하였으며, Pre-cutting의 굴착 길이가 짧을수록 융기 발생 예방에 효과적인 것으로 나타났다.

키워드
터널 확폭
Pre-cutting 공법
천단침하
확폭터널
기존터널
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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 :4
  • Pages :451-468
  • Received Date : 2020-06-13
  • Revised Date : 2020-07-08
  • Accepted Date : 2020-07-09
  • DOI :https://doi.org/10.9711/KTAJ.2020.22.4.451
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