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

암반 등급 경계가 터널 안정성에 미치는 영향에 관한 수치해석적 연구

  • Kim, Gyeomyeon (Honam Headquarters, Korea Rail Network Authority) ;
  • Jung, Chanmook (School of Railroad Civil System Engineering, Woosong University) ;
  • Lee, Yongjun (Dept. of Geotechnical Engineering, DANWOO E&C)
  • 김겸연 (한국철도시설공단 호남본부) ;
  • 정찬묵 (우송대학교 철도토목시스템공학과) ;
  • 이용준 (단우기술단 지반공학부)
  • Received : 2019.09.10
  • Accepted : 2019.10.19
  • Published : 2019.11.30

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.

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