DOI QR코드

DOI QR Code

하중 및 기초조건에 따른 GCP 복합지반의 거동분석

Analysis of Behavior on GCP Composite Ground Considering Loading and Foundation Conditions

  • 투고 : 2018.03.02
  • 심사 : 2018.03.22
  • 발행 : 2018.03.30

초록

쇄석다짐말뚝(Gravel Compaction Pile, 이하 GCP)는 느슨한 사질토지반이나 연약한 점토지반에 쇄석을 다지고 압입하여 원지반에 말뚝을 조성함으로써 지반을 개량하는 공법이다. 국내 GCP공법은 많은 연구자들이 실내실험, 현장실험 등을 이용해 GCP 복합지반의 응력거동을 분석하였으나, GCP 복합지반의 상부에 재하되는 매트기초의 강성 차이에 따른 거동분석은 다소 미미한 실정이다. 따라서 본 연구에서는 수치해석을 통해 기초의 강성 차이에 따라 응력분담비를 규명하고자 하였다. 이를 위해 유한요소 해석프로그램인 ABAQUS를 이용하여 치환율을 변화시켜 모델링하고, 강성 차이에 따라 복합지반의 응력분담비와, 침하량 및 최대 수평변위량을 분석하였다. 분석 결과, 강성기초의 하중재하시 응력분담비는 연성기초의 하중재하보다 높게 평가되었으며, 연성하중재하조건에서의 침하량은 강성조건에서 보다 다소 높은 경향이 나타났다. 이는 상부기초의 강성 차이에 대한 응력거동 특성을 명확히 규명해야 할 필요성이 있다고 판단된다. 또한, 최대 수평변위는 강성의 차이에 상관없이 일정한 위치에서 최대 변위가 발생하였다.

Gravel Compaction Pile (hereinafter referred to as GCP) is a ground improvement technique by packing crushed stones on fragile clay ground, pressing it, and forming stakes on the foundation. Although many researchers have analyzed stress behavior of GCP composite ground on domestic GCP technique using laboratory experiment and field experiment, analyses of stress behavior according to the difference of stiffness of mat foundation loaded on the upper foundation of GCP composite ground have not been done actively. Therefore, this study aimed to identify the stress concentration ratio in accordance with the difference of basis stiffness by interpreting figures. To perform this, replacement ratio was changed and modelled using ABAQUS, software for finite element analysis and analyzed the stress concentration ratio, amounts of settlement, and maximum amounts of horizontal displacement of composite ground in accordance with the difference of stiffness. An analysis showed that the stress concentration ratio of rigid foundation was highly assessed than unloading of flexible foundation in case of unloading, while amounts of settlement under flexible unloading condition were slightly higher than under rigid condition. This indicates that the characteristic of stress behavior on the different stiffness of upper foundation needs to be clarified. In addition, the maximum horizontal displacement was generated in a constant level regardless of the difference of stiffness.

키워드

참고문헌

  1. Aboshi, H., Ichimoto, E., Enoki, M. and Harada, K. (1979), "The Composer, a Method to Improve Characteristics of Soft Clays by Inclusion of Large Diameter Sand Columns", Proceeding of International Conference on Soil Reinforcement, Paris, France, Vol.1, pp.211-216.
  2. Bae, W. S., Kim, J. W. and Kwon, Y. C. (2007), "Finite Element Analysis for The Effects on The Stiffness of The Embankment and Sandmat on The Deformation Property and The Safety of Road Embankment", International journal of safety. Vol.22, pp.57-65.
  3. Barksdale, R. D. and Bachus, R. C. (1983), "Design and Construction of Stone Column", Georgia Institute of Technology, Atlanta, Vol.1.
  4. Busan New Port Corp. (1999), Report of North Container Terminal, pp.6.50-6.59.
  5. Choi, J. W. (2013), "Characteristics of Geogrid-encased Stone Column", Sungkyunkwan University, Master Thesis.
  6. Chun, B. S., Choi, H. S. and Lee, Y. H. (2000), "A Study on Bearing Capacity Characteristics of Gravel Piles", Journal of The Civil Engineering Conference Contents, Vol. 2000, pp.493-496.
  7. Dassault Systemes. (2008), Abaqus Version 6.12 Documentation. Providence, RI: Dassault Systemes.
  8. Goughnour R. R. and Bayuk A. A. (1979), "A Field Study of Long-Term Settlement of Loads Supported by Stone Columns in Soft Ground", Proceedings, International Conference on Soil Reinforcement: Reinforced Earth and Other Techniques, Vol. 1 Paris: 279-286.
  9. Greenwood, D. A. (1970), "Mechanical Improvement of Soil below Ground Surface", Proceeding of Ground Engineering Conference, Institute of Civil Engineers, pp.9-20.
  10. Greenwood, D. A. (1970), "Mechanical Improvement of Soil below Ground Surface", Proceeding of Ground Engineering Conference, Institute of Civil Engineers, pp.9-20.
  11. Heo, Y., Zheong, Z., Lee, C. K. and Ahn, K. G. (2006), "Centrifuge Modeling on Displacement Shapes of Composite Ground Improved by SCP and GCP", Journal of Korean Geotechnical Society, Vol.7, No.5, pp.57-66.
  12. Jeong, G. S., Park, B. S., Lee, J. H. and Yoo, N. J. (2005), "Centrifuge Model Experiments of Footing Behavior on Layered Sandy Soil", Korean Society of Civil Engineers, Vol. 25, No.1, pp.27-34.
  13. Kim, K. M. (2005), The Characteristics of Bearing Capacity of Rammed Aggregate Pier in Cohesionless Soils, Hanyang University, Ph. D. Thesis.
  14. Kim, M. S. (2016), The Behavior of Soft Ground Reinforced with Granular Compaction Pile, Chosun University, Master Thesis.
  15. Lee, C. H., Lim, H. D. and Lee, W. J. (2005), "Finite Element Analysis of GCP Ground with Replacement Ratio", Korean Society of Civil Engineers.
  16. Lee, M. H. (2004), A Study on the Load Support Mechanism and Stress Distribution Characteristic of Crushed-Stone Compaction Piles, Busan University, Ph. D. Thesis.
  17. Moon, I. J., Yoo, W. K. and Kim, B. I. (2012), "A Study on the Settlement and Bearing Capacity of the SCP, GCP Method with Low Replacement Ratio by 1g Model Tests", Journal of The Civil Engineering Conference Contents, Vol. 2012, No.10, pp.1187-1190.
  18. Nagahara, H., Fujiyama, T., Ishiguro, T. and Ohta, H. (2004), "FEM Analysis of High Airport Embankment with Horizontal Drains", Geotextiles and Geomembranes, Vol.22, pp.49-62. https://doi.org/10.1016/S0266-1144(03)00051-7
  19. Priebe, H. (1976), "Estimating Settlements in a Gravel Column Consolidated Soil", Die Bautechnik 53, pp.160-162.
  20. Shin, H. M. and Lee, J. H. (2007), Reinforced Concrete, Dongmyeongsa, pp.15-18.
  21. Song, M. G., Bae, W. S. and Ahn, H. Y. (2011), "Centrifugal Model Test on Stress Concentration Behaviors of Composition Ground under Flexible/Stiff Surcharge Loading", Journal of Korean Geotechnical Society, Vol.12, No.6, pp.5-15.
  22. Yoo, C. S., Song, A. R., Kim, S. B. and Lee, D. Y. (2007), "Finite Element Modeling of Geogrid-Encased Stone Column in Soft Ground", Journal of Korean Geotechnical Society, Vol.23, No.10, pp.133-150.
  23. Yoon, I. S., Lee, J. Y., Cho, B. Y. and Kim, Y. G. (2008), "Time Evolution of Water Permeability Coefficient of Carbonated Concrete", Journal of The Annual Research Conference in Fall 2008 Contents.
  24. Yoon, J. S. (2007), Evaluation of Behavior Characteristics on Granular Compaction Piles with Foundation Stiffness, Hongik University, Ph. D. Thesis.
  25. You, S. G. (2003), "Experimental Study on Stress Behavior of Composition Ground Improved by Sand Compaction Piles with Low Replacement Area Ratio", Journal of Korean Geotechnical Society, Vol.19, No.5, pp.253-261.