Journal of the Korean Society of Hazard Mitigation (한국방재학회 논문집)

Korean Society of Hazard Mitigation (한국방재학회)
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Evaluation of Debris Properties Using Numerical Analysis for USGS Debris Flume Tests

수치해석에 의한 USGS의 토석류 실험의 물성치 평가

  • Shin, Hosung (Dept. of Civil and Environmental Engrg., Univ. of Ulsan)
  • 신호성 (울산대학교 건설환경공학부)
  • Received : 2015.04.23
  • Accepted : 2015.05.28
  • Published : 2015.06.30
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Abstract

Despite of recent active research on movement mechanism of debris flow, development of constitutive model and its necessary properties to determine flow characteristics is under slow progress. Rheologic-mechanical properties of debris material containing coarse sediment is so difficult to determine in laboratory tests that inverse analysis and parameter study for field and model measurements are necessary to evaluate the physical properties to simulate flow characteristics accurately. Parametric numerical study is conducted on USDS debris flume experiments from 1994 to 2004 (SGM case with high clay content, SG case with very low clay content). Numerical program simulates a single-phase flow based on the total stress analysis, and uses rheologic-mechanical constitutive model. Physical properties for the debris flow is determined to minimize the error between experimental and numerical results for arrival time and residual thickness of the debris flow (SGM case: ${\mu}=1.0Pa{\cdot}s$, ${\phi}=8^o$; SG case: ${\mu}=0.6Pa{\cdot}s$, ${\phi}=11^o$). Suggested constitutive model and its determined properties shows significant improvement in numerical prediction compared to a previous numerical study. However, different initial configuration of debris and modeling difficulty for debris discharge device cause slight discrepancy between numerical and experimental results.

최근 토석류의 이동 메커니즘에 대한 활발한 연구에도 불구하고, 유동 흐름을 결정하는 구성모델과 이에 필요한 토석류의 물성치 평가에 대한 연구는 부진하다. 조립질 토사를 포함하는 토석류에 대한 유동-역학적 물성치는 실내 물성실험을 통하여 산정하기 어렵고, 모형실험과 현장 계측결과를 바탕으로 역해석이나 매개변수 연구를 통하여 토석류의 흐름특성을 정확히 모사할수 있는 물성을 평가하여야 한다. 본 연구는 1994~2004년에 USGS(United States Geological Survey)에서 수행되었던 토석류 모형실험 결과(점토 함유량이 높은 SGM 경우, 점토 함유량이 매우 낮은 SG 경우)에 대하여 매개변수적 수치해석을 수행하였다. 개발된 프로그램은 단상흐름에 대한 전응력 해석을 수행하고, 흐름특성을 정의하기 위한 구성모델은 유동-역학적 모델을 사용하였다. 토석류 실험에서 사면내 토석류 도달시간과 잔류 두께에 대한 오차를 최소화하는 전응력 기반의 토석류 물성치를 점성(${\mu}$)와 마찰각(${\phi}$)으로 결정하였다(SGM 경우: ${\mu}=1.0Pa{\cdot}s$, ${\phi}=8^o$; SG 경우: ${\mu}=0.6Pa{\cdot}s$, ${\phi}=11^o$). 제시된 구성모델과 결정된 물성치를 이용한 수치해석결과는 기존의 수치해석 결과에 대비하여 예측결과가 상당히 개선하였으나, 초기 토석류의 기하학적 차이와 토석류 방류장치에 대한 수치해석의 어려움으로 인하여 다소 차이가 발생하였다.

Keywords

Acknowledgement

Supported by : 국토교통과학기술진흥원

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