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2013 Vol.15, Issue 5 Preview Page
Behavior and pillar stability of enlarged existing parallel tunnels

기존 병설터널의 확폭에 따른 터널 거동 및 필라 안정성 분석

Myeong-Han Lee1
,
Bumjoo* Kim2*
,
Yeon-Soo Jang3
,
Ji-Nam Yun4
,
Hyun-Gon Park5
이 명한1
,
김 범주*2*
,
장 연수3
,
윤 지남4
,
박 현곤5
1Danwoo E&C, Geotechnical Department, Engineer
2Dongguk University, Department of Civil and Environmental Engineering, Associate Professor
3Dongguk University, Department of Civil and Environmental Engineering, Professor
4Posco E&C, Civil and Environmental Division, Design Group, Deputy General Manager
5Korea Expressway Corporation, Expressway & Transportation Research Institute, Researcher
1㈜단우기술단 지반공학부, 기사
2동국대학교 건설환경공학과, 부교수
3동국대학교 건설환경공학과, 교수
4포스코건설 토목환경사업본부 설계그룹, 차장
5한국도로공사 도로교통연구원, 연구개발실, 연구원
*교신저자. *Corresponding Author. 
30 September 2013. pp. 537-546
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Abstract

Traffic congestion in existing tunnels has increased due to increased traffic volume and enlarged vehicles. Enlarging existing tunnels has advantages over constructing new tunnels by reducing land purchasing costs as well as minimizing natural environment destruction. In fact, many overseas projects for enlarging existing tunnels have been reported. Thus, it appears that the demand on enlarging existing tunnels continues to rise in Korea in near future. Nonetheless, the studies related to the enlarged tunnels have been relatively rare since there have been few tunnel enlargement projects in Korea. In the present study, the tunnel behavior and the stability of rock pillar when enlarging existing parallel tunnels were investigated by performing FE analysis and using existing theory and empirical relationships. Four different enlarging cases, depending on the enlargement types and directions, were examined in the study. According to the results, for the tunnels with the same pillar width after enlarged, the uni-laterally enlarged tunnel indicated 5 to 20% higher crown settlement compared to the bi-laterally enlarged tunnel, and for the tunnel with the narrowest pillar, the highest shotcrete stress was observed. Also, the strength/stress ratio for rock pillar was more than 1.0 for all four enlargement cases, and the Matsuda’s method was found to give higher strength/stress ratio by about 50% compared to the Peck’s method.

Keywords
Tunnel enlargement
Parallel tunnels
Pillar stability
Crown settlement
Strength/stress ratio

최근 교통량의 증가와 차량의 대형화로 인해 기존 터널에서 상습적인 정체가 발생되는 경우가 증가하고 있다. 이러한 문제 해결의 일환으로 기존 터널을 확폭하는 경우는 신설 터널을 건설하는 경우와 비교하여 용지매입 비용의 절감과 자연환경의 훼손을 최소화 시킬 수 있다는 장점이 있다. 실제로 일본과 유럽 등 해외에서는 기존 터널을 확폭 시공하는 사례가 많이 보고되고 있다. 이러한 흐름에서 국내에서도 향후 기존터널의 확폭 시공에 대한 수요는 꾸준히 증가할 것으로 예상되나, 현재까지는 기존 터널의 확폭에 관한 실적과 경험이 많지 않아 이에 관한 기반 연구가 필요한 상황이라고 볼 수 있다. 본 연구에서는 유한요소해석과 기존의 이론, 경험식 등을 이용하여 기존 병설터널을 확폭하는 경우 확폭방식과 그에 따른 필라폭 변화가 터널의 거동과 필라 안정성에 미치는 영향을 평가하였다. 조사 결과, 필라폭은 동일하나 편측과 양측으로 확대하는 경우의 차이에 따라 편측 확대 터널의 천단침하는 양측 확대 터널에 비해 약 5~20%의 큰 값을 보이는 한편, 최소 필라폭을 갖게되는 편측 확대 터널에서 숏크리트 응력이 최대를 보이는 것으로 나타났다. 또한, 강도/응력비의 경우 조사된 네 종류의 확폭 패턴에 대하여 모두 1.0 이상을 나타내었고 Matsuda의 방법이 Peck의 방법에 비해 약 50% 정도 강도/응력비를 크게 산정하게 됨을 확인하였다.

키워드
터널 확폭
병설터널
필라 안정성
천단침하
강도/응력비
References
1
1.Baek, K.H., Roh, J.R. (2007), “Case study on the widening construction of tunnel under use”, Korean Society of Civil Engineers Conference, pp. 2935-2938.
2
2.Byun, Y.S., Kim, H.G., Lee, S.S, Chun, B.S. (2010), “A study on pillar behavior of twin parallel tunnels by numerical approach”, Korean Geo-Environmental Society, Vol. 11, No. 8, pp. 49-55.
3
3.Choi, H.J., Kim, D.K. (2011), “A study on the enlargement of 2-Lane road tunnel under construction”, Korean Tunnelling and Underground Space Association, Vol. 13, No. 1, pp. 33-50.
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4.Hoek, E., Brown, E.T. (1980), “Empirical strength criterion for rock masses”, J. Geotech Engineering Div. ASCE 106, pp. 1013-1035.
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5.Jung, Y.J., Song, H.C., Lee, S.H., Shin, S.H. (2007), “A study on the reinforcing method and the evaluation of stability for pillar in closely-spaced tunnel.”, Korean Society for Rock Mechanics Symposium, pp. 486-500.
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6.Kang, C.M. (2008), “Big close reinforce parallel tunnel section applies pilla and reliability evaluation”, Master these, Kyungpook National University., pp. 14-18.
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7.Matsuda, T. (1998), “Ground behavior and settlement control of twin tunnels in soil ground” Tunnels and Metropolises, Vol. 16, No. 2, pp. 1193-1198.
8
8.Peck, R.B. (1969), “Deep excavations and tunneling in soft grounding”. 7th Internation Conferences, Soil Mechanics and Foundation Engineering., pp. 225-290.
9
9.Seo, K.W., Baek, K.H., Roh, J.R. (2008), “An analyzing overseas cases about enlargement of a tunnel in operation(I)”, Korean Tunnelling and Underground Space Association, Vol. 10, No. 1, pp. 40-50.
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10.Tunnel Design Criteria (2007), Construction and Transportation Ministry, KTA, pp. 17.
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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 : 15
  • No :5
  • Pages :537-546
  • Received Date : 2013-09-15
  • Revised Date : 2013-09-23
  • Accepted Date : 2013-09-29
  • DOI :https://doi.org/10.9711/KTAJ.2013.15.5.537
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