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2025 Vol.35, Issue 4 Preview Page

Original Article

Evaluation of Shear Creep Behavior of Granite Joints by Direct Shear Test

직접전단시험에 의한 국내 화강암 절리면의 크리프 거동 특성 평가

Hyun-Sik Kim1
,
Seung Bum Choi2
,
Sung-Jun Ha2
,
Hoyoung Jeong3*
김 현식1
,
최 승범2
,
하 성준2
,
정 호영3*
1MS Course, Department of Energy Resources Engineering, Pukyong National University
2Senior Researcher, Korea Atomic Energy Research Institute
3Associate Professor, Department of Energy Resources Engineering, Pukyong National University
1부경대학교 에너지자원공학과 석사과정
2한국원자력력연구원 방사성폐기물처분부 선임연구원
3부경대학교 에너지자원공학과 부교수
*Corresponding Author
31 August 2025. pp. 385-400
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Abstract

This study was conducted to quantitatively analyze the shear creep behavior of granite joint surfaces in Korea. Hwangdeung granite was used in the tests, and direct shear creep tests were performed on discontinuity specimens created through wedge-type tensile splitting. The shear creep tests were carried out under stepwise shear stress levels ranging from 85% to 65% of the peak shear strength. Prior to and following the tests, a portable 3D scanner was used to measure the statistical roughness parameter (Z2), from which the JRC and peak shear strength were calculated using Barton’s empirical equation. The results revealed localized degradation of surface roughness, with the degree of degradation varying depending on the applied shear stress level. At stress levels above 75%, tertiary creep was observed, indicating a potential reduction in structural stability due to exceedance of the critical stress threshold. The shear creep rate increased in the order of tertiary > primary > secondary, suggesting differences in deformation mechanisms across creep stages. Among the creep models applied, the Burger model showed the best fit with the experimental data, while the Kelvin model tended to underestimate the creep deformation. However, the derived creep parameters did not exhibit a clear trend under the limited test conditions, indicating the need for further studies under various rock and stress conditions. This study is expected to provide fundamental data applicable to long-term shear behavior assessment of discontinuities and verification of creep model applicability.

Keywords
Shear creep test
Joint roughness
Creep model

본 연구는 국내 화강암 절리면의 전단 크리프 거동을 정량적으로 분석하기 위한 목적으로 수행되었다. 시험에는 황등화강암을 사용하였으며, 쐐기형 인장파괴를 통해 생성된 불연속면 시험편에 대해 직접 전단 크리프 시험을 수행하였다. 크리프 시험은 최대 전단강도의 85%에서 65%까지 단계적으로 응력을 변화시켜 진행하였으며, 시험 전 및 시험 후에는 휴대용 3D 스캐너를 이용하여 Z2(통계적 거칠기 파라미터)를 측정하고, Barton 식을 통해 JRC 및 최대 전단강도를 산정하였다. 본 연구에서는 특정 영역에 국한하여 국소적으로 거칠기 감소가 발생했으며, 전단응력 수준에 따라 거칠기 감소정도가 다른 것이 확인되었다. 75% 이상의 응력 수준에서 3차 크리프가 발생하였으며, 이는 임계 응력 초과 시 구조적 안정성 저하 가능성을 시사하였다. 전단 크리프 속도는 3차 > 1차 > 2차 순으로 증가하였으며, 이는 크리프 단계별 변형 메커니즘의 차이에 기인한 것으로 판단된다. 크리프 모델 중 Burger 모델이 실험 데이터와의 적합성이 가장 높게 나타났으며, Kelvin 모델은 크리프 변형을 과소평가하는 경향을 보였다. 한편, 도출된 크리프 파라미터는 제한된 시험 조건 하에서 명확한 경향성을 나타내지 않아, 향후 다양한 암반 조건 및 응력 수준에 대한 추가 연구가 필요할 것으로 판단되었다.

키워드
전단 크리프 시험
절리면 거칠기
크리프 모델
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Information
  • Publisher :Korean Society for Rock Mechanics and Rock Engineering
  • Publisher(Ko) :한국암반공학회
  • Journal Title :Tunnel and Underground Space
  • Journal Title(Ko) :터널과 지하공간
  • Volume : 35
  • No :4
  • Pages :385-400
  • Received Date : 2025-05-29
  • Revised Date : 2025-06-28
  • Accepted Date : 2025-06-30
  • DOI :https://doi.org/10.7474/TUS.2025.35.4.385
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