한국지반공학회논문집 (Journal of the Korean Geotechnical Society)

한국지반공학회 (Korean Geotechnical Society)
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지반내 세립토 유동에 대한 수치해석적 연구

Numerical Study on Fine Migration in Geo-materials

  • 신호성 (울산대학교 건설환경공학부)
  • Shin, Hosung (Dept. of Civil & Environmental Engrg., Univ. of Ulsan)
  • 투고 : 2018.10.03
  • 심사 : 2018.10.24
  • 발행 : 2018.11.30
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초록

지반의 내부침식은 유체 흐름에 의하여 입자골격에 부착된 세립토가 이탈하는 현상이며, 지속적인 세립토의 유동은 지반구조물의 수리-역학적 특성을 약화시킨다. 본 논문은 세립토의 유동에 관한 지배방정식을 정립하고 수치해석 기법을 제안하였다. 공극내의 세립토는 액상의 세립토($c_e$), 조립토에 부착된 입자(${\sigma}_a$) 그리고 조립토골격에 폐색된 세립토(${\sigma}_s$)로 구분하여 상관계를 제시하였다. 이를 바탕으로 세립토의 유동과 공극수의 흐름에 대한 수리학적 지배방정식들과 유한요소 수식화를 제시하였다. 세립토의 이탈, 부착 그리고 공극막힘에 대한 구성 모델들을 제시하였으며, 실내 1차원 침식실험으로부터 모델변수를 도출하는 방법을 제안하였다. 그리고 세립토의 공극 막힘 현상에 의한 지반의 투수계수 변화에 대한 추정식을 제안하였다. 기존의 침식실험 결과에 대한 수치해석을 통하여 개발된 해석기법과 세립토 유동 모델의 적정성을 검증하였다.

Soil internal erosion is a phenomenon in which fines attached to the solid skeleton are detached by fluid flow, and this continuous fine migration weakens the hydro-mechanical characteristics of the ground structure. This paper proposed governing equations for fine migration in pore spaces and its related scheme for the numerical analysis. Phase diagram for fine particles includes three different states: detached fines in the liquid phase ($c_e$), attached fines in the solid phase (${\sigma}_a$), and pore-clogged fines in the solid phase (${\sigma}_s$). Numerical formulations for finite element method are developed based on the hydraulic governing equations of pore fluid and fine migration. This study proposed a method of estimating model parameters for fine detachment, attachment, and clogging from 1D erosion experiments. And it proposed an analytical formula for hydraulic permeability function considering fine clogging. Numerical analysis of the previous erosion test developed the numerical scheme and verified the adequacy of fine migration models.

키워드

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Fig. 1. Schematic illustration of volume fractions of fine particles

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Fig. 3. Comparison of normalized hydraulic conductivity as a function of clogging fine particles (ø=0.37)

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Fig. 4. Numerical results for hydraulic gradient ih=0.55. (a) Variation of attached fines σa at different locations with time. (b) Change of fine concentration ce in the fluid with time

GJBGC4_2018_v34n11_33_f0004.png 이미지

Fig. 2. (a) Determination of maximum fine retention function from one dimensional seepage flow test (Sterpi, 2003). (b) Variation of fine erosion coefficient Kd with hydraulic gradient ih, (c) Comparison between experimental results and a developed model of fine particle erosions with time

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