Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Characteristics of Bentonite Filter Cake on Vertical Cutoff Walls Evaluated by Modified Fluid Loss Test

수정 fluid loss 시험을 이용한 연직 차수벽에 생성된 벤토나이트 필터케익 특성 평가

  • Nguyen, The-Bao (School of Civil, Environmental, and Architectural Engrg., Korea Univ.) ;
  • Park, Moon-Seo (School of Civil, Environmental, and Architectural Engrg., Korea Univ.) ;
  • Lim, Jee-Hee (School of Civil, Environmental, and Architectural Engrg., Korea Univ.) ;
  • Choi, Hang-Seok (School of Civil, Environmental, and Architectural Engrg., Korea Univ.) ;
  • Han, Shin-In (R&D Center, Seoyeong Engrg. Co., Ltd.)
  • 웽테바오 (고려대학교 건축.사회환경공학부) ;
  • 박문석 (고려대학교 건축.사회환경공학부) ;
  • 임지희 (고려대학교 건축.사회환경공학부) ;
  • 최항석 (고려대학교 건축.사회환경공학부) ;
  • 한신인 ((주)서영엔지니어링 연구소)
  • Received : 2010.10.01
  • Accepted : 2011.01.06
  • Published : 2011.02.28
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Abstract

During the construction of vertical cutoff walls, filtration of bentonite slurry into the adjacent soil formation fabricates a layer of bentonite filter cake on the wall surface. The bentonite filter cake possesses much lower hydraulic conductivity compared to that of backfill materials in the cutoff wall. Hydraulic conductivity of bentonite filter cakes formed with three different types of bentonites has been measured by performing the modified fluid loss test under various pressure levels. Three different mixture ratios, 4, 6, and 8%, were selected for fabricating bentonite filter cakes to represent common field conditions. Two analysis methods for interpreting the experimental data from the modified fluid loss tests were employed to estimate hydraulic conductivity of the bentonite cakes. The range of hydraulic conductivities of the three bentonite cakes is between $2.15{\times}10^{-11}\;m/s$ and $2.88{\times}10^{-10}\;m/s$ which is 1 to 2.7 orders of magnitude lower than that of the design cutoff wall backfill. The stress distribution and thickness of the bentonite cakes were also evaluated in this paper.

연직 차수벽 시공 시, 벤토나이트 슬러리는 토양층으로 여과되면서 차수벽의 측벽 표면에 필터케익 층을 형성하고 이렇게 형성된 필터케익은 차수벽의 자체 투수계수보다 매우 낮은 값을 갖는다. 본 연구에서는 수정 fluid loss 시험을 수행하여 다양한 작용압력 하에서 슬러리월 시공현장에서 주로 사용되는 세 가지 종류의 벤토나이트로 형성된 필터케익의 투수계수를 평가하였다. 수정 fluid loss 시험에서는 일반적인 연직 차수벽 시공 조건을 반영하기 위해 중량비 4, 6, 8% 농도의 벤토나이트 슬러리를 적용하였다. 벤토나이트 필터케익의 투수계수를 예측하기 위해 수정 fluid loss 시험 결과를 기존에 제안된 두 가지 방법을 이용하여 해석하였다. 본 연구결과로부터 평가된 세 가지 벤토나이트 필터케익의 투수계수는 $2.15{\times}10^{-11}m/s$와 $2.88{\times}10^{-10}m/s$ 범위로 이는 일반적인 연직차수벽 뒤채움재의 설계값 보다 10-1000배 가량 작음을 알 수 있다. 또한, 필터케익 내 응력분포와 필터케익의 두께가 각 조건에 대해 비교되었다.

Keywords

Acknowledgement

Supported by : 학술진흥재단, 한국건설교통기술평가원

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