Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Prediction and Assessment on Consolidation Settlement for Soft Ground by Hydraulic Fill

준설매립 연약지반에 대한 압밀침하 예측 및 평가

  • Jeon, Je-Sung (KIWE, Korea Water Resources Corporation) ;
  • Koo, Ja-Kap (Dept. of Civil Eng., Hankyong National University) ;
  • Oh, Jeong-Tae (Yeosu Regional Office, Korea Water Resources Corporation)
  • Published : 2008.09.30
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Abstract

This paper describes the performance of ground improvement project using prefabricated vertical drains of condition, in which approximately 10m dredged fill overlies original soft foundation layer in the coastal area composed of soft marine clay with high water content and high compressibility. From field monitoring results, excessive ground settlement compared with predicted settlement in design stage developed during the following one year. In order to predict the final consolidation behavior, recalculation of consolidation settlements and back analysis using observed settlements were conducted. Field monitoring results of surface settlements were evaluated, and then corrected because large shear deformation occurred by construction events in the early stages of consolidation. To predict the consolidation behavior, material functions and in-situ conditions from laboratory consolidation test were re-analyzed. Using these results, height of additional embankment is estimated to satisfy residual settlement limit and maintain an adequate ground elevation. The recalculated time-settlement curve has been compared with field monitoring results after additional surcharge was applied. It might be used for verification of recalculated results.

본 연구에서는 해안 준설매립지반에 대한 연약지반 개량사례를 이용하여 연적배수공법 적용시의 현장계측 및 압밀침하 해석을 실시하였다. 대상현장은 원지반위에 대략 10m의 준설매립을 통해 조성된 부지로서 고함수비 및 고압축성의 해성점토로 구성되어 있다. 1년 동안의 현장 계측결과, 당초 설계시의 예측침하량에 비해 매우 큰 압밀침하가 발생하였고, 이 조건에서의 향후 침하거동을 예측하기 위한 추가 압밀침하 해석 및 계측결과를 이용한 역해석을 실시하였다. 상부시공 영향 등에 의해 준설매립지반에는 과다한 전단변형이 발생하였으며, 이에 대한 현장 계측결과의 평가 및 보정을 실시하였다. 압밀해석 및 원지반 조건을 평가하기 위해 실내시험 결과를 이용한 물질함수분석을 실시하였으며, 최종적으로 부지 인도후의 잔류침하량 및 최종 지반고를 만족시키기 위한 추가 성토고를 산정하였다. 추가 성토이후의 현장 계측결과와 당초 예측했던 압밀침하 거동을 비교하였으며, 이를 통해 당초 예측내용에 대한 검증을 수행할 수 있었다.

Keywords

References

  1. Arulrajah, A, Nikraz, H, and Bo, M.W. (2004), "Observational method of assessing improvement of marine clay", Ground Improvement, Vol.8, No.4, pp.151-169 https://doi.org/10.1680/grim.8.4.151.41846
  2. Cargill, K.W. (1984), "Prediction of Consolidation of Very Soft Soil", J of Geotechnical Engineering, ASCE, Vol.110, No.6, pp.775-795 https://doi.org/10.1061/(ASCE)0733-9410(1984)110:6(775)
  3. Cargill, K.W. (1985), Mathematical model of the consolidation/ desiccation processes in dredged material, Technical Rep. D-85-4, U.S. Army Engineering Waterways Experiment Station
  4. Choa, V, Bo, M.W., and Chu, J (2001), "Soil improvement works for Changi East Reclamation Project", Ground Improvement, Vol.5, No.4, pp.141-153 https://doi.org/10.1680/grim.5.4.141.39988
  5. Chu, J, Bo, M.W., Chang, M.F., and Choa, V (2002), "Consolidation and Permeability Properties of Singapore Marine Clay", J Geotechnical and Geoenvironmental Engineering, Vol.128, No.9, pp.724-732 https://doi.org/10.1061/(ASCE)1090-0241(2002)128:9(724)
  6. Cousens, T.W., and Stewart, D.I. (2003), "Behavior of a trial embankment on hydraulically placed pfa", Engineering Geology, Vol.70, pp.293-303 https://doi.org/10.1016/S0013-7952(03)00097-8
  7. Gibson, R.E., Schiffman, R.L. and Cargill K.W. (1981), "The Theory of One-dimensional Consolidation of Saturated Clays II. Finite Nonlinear Consolidation of Thick Homomgeneous Layers", Canadian Geotechnical Journal, Vol.18, pp.280-293 https://doi.org/10.1139/t81-030
  8. Hansbo, S. (1981), "Consolidation of fine-grained soils by prefabricated drains", 10th Int Conf Soil Mechanics and Found Engineering, Stockholm, Sweden, Vol.3, pp.677-682
  9. Mesri, G., and Rokhsar, A. (1974), "Theory of Consolidation for Clays", Journal of the Geotechnical Engineering Division, ASCE, Vol.100, No.GT8, pp.889-904
  10. Poindexter, M.E. (1988), Behavior of subaqueous sediment mounds: Effect on dredged material disposal site capacity, Ph.D. Thesis, Texas A&M Univ., College Station, Tex
  11. Stark, T.D., Choi, H., and Schroeder, P.R. (2005), "Settlement of Dredged and Contaminated Material Placement Areas. II: Primary Consolidation, Secondary Compression, and Desiccation of Dredged Fill Input Parameters", J Waterway, port, coastal, and ocean engineering, Vol.131, No.2, pp.52-61 https://doi.org/10.1061/(ASCE)0733-950X(2005)131:2(52)
  12. Tan, S.A. (1993). "Ultimate Settlement by Hyperbolic Plot for Clays with Vertical Drains", J Geotechnical Engineering, Vol.119, No.5, pp.950-956 https://doi.org/10.1061/(ASCE)0733-9410(1993)119:5(950)
  13. Terzaghi, K, Peck, R.B., and Mesri, G. (1996), Soil Mechanics in Engineering Practice, 3nd Edition, John Wiley & Sons, New York, pp.71-121
  14. Yoo, N.J. (2007), Consolidation Characteristics of Dredged Fill Material Including Centrifuge Test, Research Rep., KSCE, pp.1-117