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Behavior and pillar stability of enlarged existing parallel tunnels

기존 병설터널의 확폭에 따른 터널 거동 및 필라 안정성 분석

  • Lee, Myeong-Han (Danwoo E&C, Geotechnical Department) ;
  • Kim, Bumjoo (Dongguk University, Department of Civil and Environmental Engineering) ;
  • Jang, Yeon-Soo (Dongguk University, Department of Civil and Environmental Engineering) ;
  • Yun, Ji-Nam (Posco E&C, Civil and Environmental Division, Design Group) ;
  • Park, Hyun-Gon (Korea Expressway Corporation, Expressway & Transportation Research Institute)
  • 이명한 ((주)단우기술단 지반공학부) ;
  • 김범주 (동국대학교 건설환경공학과) ;
  • 장연수 (동국대학교 건설환경공학과) ;
  • 윤지남 (포스코건설 토목환경사업본부 설계그룹) ;
  • 박현곤 (한국도로공사 도로교통연구원, 연구개발실)
  • Received : 2013.09.15
  • Accepted : 2013.09.29
  • Published : 2013.09.30

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.

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