Journal of the Korean Geosynthetics Society (한국지반신소재학회논문집)

Korean Geosynthetics Society (한국지반신소재학회)
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The Study on The Numerical Analysis Method for Ground Improved by Cement Mixing Method

시멘트혼합처리공법이 적용된 지반의 수치해석 방법에 관한 연구

  • Received : 2018.10.15
  • Accepted : 2018.11.09
  • Published : 2018.12.30
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Abstract

Since the composite ground design method is easy to apply for calculation or numerical analysis, it is applied to the design of cement mixing methods. However, the comparison studies between analysis and actual results such as a trial test and construction for the cement mixing method are few because the composite ground design method was developed for the compaction pile (SCP, GCP) methods. In this study, the results of various analysis methods, such as the composite ground analysis method (1 case) and the individual pile method (3 cases), were compared with actual measurements through a two-dimensional finite element numerical analysis. In case of the surface settlements, the results of study show that the individual plate method was larger than the actual measurements, while other methods are similar. The settlements at the under ground of the improved area is overestimated in all analysis methods. When comparing numerical analysis results for the horizontal displacement, and ground reaction forces, the individual pile method in equivalent wall concept was found to be the most similar to the measurements. The composite ground method was not able to predict the behavior of stress transfer (Arching effect) and it turned out that the prediction of horizontal displacement was too large.

복합지반 설계법은 계산이나 수치해석시 적용하기 편리하여 시멘트혼합처리공법의 설계시 많은 설계자들에 의해 적용되고 있다. 그러나, 복합지반 설계법은 다짐말뚝공법(SCP, GCP)에 관하여 개발된 것으로 시멘트혼합처리공법에 대한 시험시공 등의 실제 결과와의 비교 분석은 미미하다. 본 연구에서는 2차원 유한요소 수치해석을 통해 복합지반 해석법, 개별말뚝해석법 등 다양한 해석법의 결과를 실측과 비교 분석하였다. 본 연구 결과, 지표면에서의 침하는 Plate 요소만을 적용하는 방법의 침하량이 실측에 비해 크게 예측되었고, 기타 방법은 유사한 것으로 나타났다. 개량지반 직하부에서만 발생된 침하량의 크기가 크게 나타났고, 침하량, 수평변위 및 지반반력 등에 대하여 실측과 수치해석 결과를 비교하면 등가벽 개념의 개별말뚝 해석법이 가장 유사한 것으로 나타났다. 복합지반법의 경우 응력전이(지반아칭) 현상을 예측하지 못하였고, 수평변위를 과대 예측하는 것으로 나타났다.

Keywords

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Fig. 1. Trial test and numerical analysis section

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Fig. 2. Cross section of embankment for trial test and numerical analysis

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Fig. 4. Settlement with distance from center

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Fig. 3. Measurement plans (Settlement, Pore water pressure)

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Fig. 5. Time-settlement curve with depth

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Fig. 6. Settlement with depth

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Fig. 7. Horizontal displacement at the end of embankment

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Fig. 8. Stress with distance from center and depth

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Fig. 9. Time-stress curve with depth

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Fig. 10. Stress distribution

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Fig. 11. Shear and bending moment within improved pile

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Fig. 12. Time-EPWP curve with depth

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Fig. 13. EPWP distribution (Immediately after embankment)

Table 1. Soil properties

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Table 2. Improved pile properties

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Table 3. Composite ground properties

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Table 4. Plate properties

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Table 5. Description and constitutive model with analysis case

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Table 6. Comparison between measurements and numerical analysis

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