Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Coefficient of Earth Pressure at Rest Ko for Particulate Materials Under Repetitive Loading

장기간 반복하중을 받는 입자성 물질의 정지토압계수 Ko

  • Kim, Naewon (Dept. of Civil and Environmental Engineering, Incheon National Univ.) ;
  • Park, Junghee (Dept. of Civil and Environmental Engineering, Incheon National Univ.)
  • 김내원 (인천대학교 건설환경공학과 ) ;
  • 박정희 (인천대학교 도시환경공학부 )
  • Received : 2024.09.12
  • Accepted : 2024.09.30
  • Published : 2024.10.31
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Abstract

Soil undergoes numerous repetitive loads, making it crucial to estimate changes in effective horizontal stress for structural stability. This study investigates the variations in the coefficient of earth pressure at rest (Ko), void ratio, and shear wave velocity of granular materials during repetitive loading. Semi-cyclic compaction tests were performed under different initial stress-to-amplitude ratios throughout the loading history. The results indicate that the void ratio of all specimens decreases during cyclic compaction subjected to varying stress amplitude ratios, eventually stabilizing at a terminal void ratio-representing a stable deformation state. Variations in Ko under repetitive loading depend on the stress amplitude ratio and relative density, influenced by soil fabric and particle-scale mechanisms. Ko can be predicted through changes in shear wave velocity over the entire stress history as the number of cycles approaches infinity. This study presents new solutions for determining the resilient modulus in road pavement design and offers methods to estimate terminal settlement of foundation structures subjected to repetitive loading.

지반은 구조물로부터 장기간 다양한 형태의 반복하중을 받으며, 구조물의 안정성 확보를 위한 유효수평응력의 변화 예측이 필요하다. 본 연구는 장기간 반복하중을 받는 입자성 물질의 정지토압계수, 간극비, 전단파 속도의 변화를 실험을 통해 파악하였다. 기존 연구의 압밀셀을 개조하여 수평응력 및 전단파를 측정하기 위한 시스템을 구축하였고, 주문진 표준사를 다양한 상대밀도로 조성하여 초기 정하중, 반복하중, 추가 정하중, 그리고 하중 제하의 응력 이력 동안 일정 초기응력에서 다양한 응력 진폭으로 반복압축실험을 수행하였다. 실험 결과, 무한대에 근접한 반복압축에서 모든 시료의 간극비는 초기응력-진폭비 (= Δσ/σo)에 따라 감소하였으며, 시료의 최종 상태를 대변하는 최종 간극비 eT로 수렴하였다. 반복압축 중 정지토압계수는 상대밀도에 따라 변화양상이 달리 나타났으며, Soil fabric의 변화와 Particle scale mechanism에 따라 결정되는 것으로 판단된다. 응력 이력 동안, 전단파 속도의 변화를 통해 반복하중을 무한대로 받는 시료의 정지토압계수를 예측하였으며, 측정한 값과의 교차 검증을 통해 높은 신뢰도를 보여주었다. 실험결과로부터 무한대에 근접한 반복압축조건에서 흙의 도로포장설계 정수인 회복탄성계수의 새로운 산정 방법과 기초 구조물의 최종 침하량 예측방법을 제시하였다.

Keywords

Acknowledgement

이 성과는 정부(과학기술정보통신부)의 재원으로 한국연구재단의 지원을 받아 수행된 연구임(No. RS-2024-00334355).

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