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Research Paper

A study on a reasonable modeling method of fully grouted rockbolt

전면접착형 록볼트의 거동 특성을 고려한 합리적인 모델링 방법에 대한 연구

Hong-Joo Lee1
,
Kyung-Nam Kang2
,
Ki-Il Song3*
,
Sang-Don Lee4
이 홍주1
,
강 경남2
,
송 기일3*
,
이 상돈4
1Master Student, Dept. of Civil Engineering, Inha University
2Post-Doctoral Researcher, Dept. of Geotechnical Engineering Research, Korea Institute of Civil Engineering and Building Technology
3Professor, Dept. of Civil Engineering, Inha University
4Research Fellow, KEC Research Institute, Korea Expressway Corporation
1비회원, 인하대학교 토목공학과 석사과정
2정회원, 한국건설기술연구원 지반연구본부 박사후연구원
3정회원, 인하대학교 토목공학과 교수
4정회원, 한국도로공사 도로교통연구원 연구위원
*Corresponding Author
31 January 2024. pp. 19-37
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Abstract

Rockbolts are the primary-supports in NATM tunnels and are widely used at tunnel construction sites. Among the rockbolts methods applied in domestic tunnel design, fully grouted rockbolts are the most representative and frequently used. Fully grouted rockbolts exhibit relative behavior between the bolt and the ground due to the grout material. However, during numerical analysis for tunnel design, fully grouted rockbolts are often modeled in a way that does not reflect their behavior characteristics. This may result in underestimating or overestimating the force of the supports. Based on a literature review, it was analyzed that fully grouted rockbolts are modeled using truss element or cable element. To analyze the effect of grout properties of cable elements on rockbolts behavior, this paper compared the behavior of rockbolts in two models: one estimating grout properties based on rockbolt pull-out test data, and another assuming complete adhesion between the rockbolts and the ground by applying large grout properties. Under identical tunnel conditions, the numerical analysis was conducted by modeling the fully grouted rockbolts differently using truss and cable elements, and the tunnel behavior was analyzed. The research results suggest that modeling fully grouted rockbolts as a function of the interface effect between the bolts and the ground, specifically considering grout, is desirable. The use of pull-out test data to simulate the behavior of actual fully grouted rockbolts was considered as a valid approach.

Keywords
Tunnel numerical analysis
Fully grouted rockbolts
Cable element
Truss element
Pull-out test

록볼트는 NATM터널의 주 지보재로서 터널공사 현장에 널리 이용되고 있다. 국내 터널 현장에서는 전면접착형 록볼트가 가장 많이 사용되고 있다. 전면접착형 록볼트는 그라우트에 의해 볼트체와 지반 간 상대적인 거동을 구현한다. 그러나 터널 수치해석 시 전면접착형 록볼트는 이러한 거동 특성이 반영되지 못한 방법으로 모델링되는 경우가 많다. 이러한 경우, 지보재의 부재력을 과소 혹은 과대 평가하는 요인이 될 수 있다. 본 연구에서는 전면접착형 록볼트의 합리적인 모델링 방법에 대한 연구를 수행하였다. 문헌 연구 결과, 전면접착형 록볼트는 Cable요소와 Truss요소로 모델링되는 것으로 분석되었다. Cable요소의 그라우트 물성치가 록볼트 거동에 미치는 영향을 분석하기 위해, 그라우트 물성치를 록볼트 인발시험 데이터를 통해 산정하여 적용한 모델과 록볼트와 지반 간 완전 접착을 가정하기 위해 임의로 크게 적용한 모델의 록볼트 거동을 비교하였다. 동일한 터널 조건에서 전면접착형 록볼트를 Truss요소와 Cable요소로 각각 다르게 모델링하여 수치해석을 수행하였고, 이에 따른 터널 거동을 분석하였다. 연구 결과, 록볼트와 지반 간 경계면 효과, 즉, 그라우트를 고려할 수 있는 요소로 전면접착형 록볼트를 모델링하는 것이 바람직한 것으로 검토되었다. 실제 전면접착형 록볼트의 거동을 모사하기 위해 인발시험 데이터를 활용하는 방법은 유효한 방법으로 검토되었다.

키워드
터널 수치해석
전면접착형 록볼트
Cable요소
Truss요소
록볼트 인발시험
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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 : 26
  • No :1
  • Pages :19-37
  • Received Date : 2023-12-08
  • Revised Date : 2024-01-19
  • Accepted Date : 2024-01-19
  • DOI :https://doi.org/10.9711/KTAJ.2024.26.1.019
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