Numerical Study of the Settlement of Rafts on Soft Soils Improved by Small Groups of Stone Columns

Document Type : Research Article

Authors

1 Department of Civil and Environmental Engineering, Amirkabir University of Technology, Tehran, Iran.

2 Department of Civil and Environmental Engineering, Amirkabir University of Technology, Tehran. Iran

Abstract

Stone column installation is used as an economical, simple, and efficient technique for soft ground improvement to reduce settlements, increase bearing capacity and accelerate the drainage of the foundation soil. While design approaches and analytical methods usually consider the condition of a very large loaded area by using unit-cell models, many practical stone column improvement projects deal with finite or semi-infinite loading areas (e.g. storage tank foundations and road embankments, respectively). In recent years, researchers drew attention to studying the behavior of small groups of stone columns. There are some recommendations in the literature for the prediction of settlements of small groups of stone columns (Sgroup) based on results of unit-cell models (Suc). However, these methods are developed for a specific soft soil or loading condition. This paper presents a relationship for the estimation of the ratio of settlement of a finite-sized stone column supported foundation (SCSF) to the settlement of an infinite group as obtained from a unit-cell model (Sgroup/Suc). The sub-soil and loading conditions are easily taken into account in the proposed relationship. For this purpose, the settlement of a large number of SCSFs having various geometrical and mechanical conditions is investigated using numerical FEM modeling.

Keywords

Main Subjects


  1. Ou Yang, J. Zhang, W. Liao, J. Han, Y. Tang, J. Bi, Characteristics of the stress and deformation of geosynthetic-encased stone column composite ground based on large-scale model tests, Geosynthetics International, 24(3) (2017) 242-254.
  2. S. Pugh, Settlement of floor slabs on stone columns in very soft clays, Proceedings of the Institution of Civil Engineers-Geotechnical Engineering, 170(1) (2017) 16-26.
  3. Ghazavi, A.E. Yamchi, J.N. Afshar, Bearing capacity of horizontally layered geosynthetic reinforced stone columns, Geotextiles and Geomembranes, 46(3) (2018) 312-318.
  4. T. Lima, M.S. Almeida, I. Hosseinpour, Field measured and simulated performance of a stone columns-strengthened soft clay deposit, International Journal of Geotechnical Engineering, (2019) 1-10.
  5. Hosseinpour, C. Soriano, M.S. Almeida, A comparative study for the performance of encased granular columns, Journal of Rock Mechanics and Geotechnical Engineering, 11(2) (2019) 379-388.
  6. K. Das, K. Deb, Experimental and 3D numerical study on time-dependent behavior of stone column–supported embankments, International Journal of Geomechanics, 18(4) (2018) 04018011.
  7. Castro, C. Sagaseta, Consolidation and deformation around stone columns: Numerical evaluation of analytical solutions, Computers and Geotechnics, 38(3) (2011) 354-362.
  8. Pal, K. Deb, Effect of clogging of stone column on drainage capacity during soil liquefaction, Soils and Foundations, 59(1) (2019) 196-207.
  9. Cengiz, E. Güler, Seismic behavior of geosynthetic encased columns and ordinary stone columns, Geotextiles and Geomembranes, 46(1) (2018) 40-51.
  10. Geng, L. Tang, S. Cong, X. Ling, J. Lu, Three-dimensional analysis of geosynthetic-encased granular columns for liquefaction mitigation, Geosynthetics International, 24(1) (2017) 45-59.
  11. W. Abusharar, J. Han, Two-dimensional deep-seated slope stability analysis of embankments over stone column-improved soft clay, Engineering Geology, 120(1-4) (2011) 103-110.
  12. Schnaid, D. Winter, A. Silva, D. Alexiew, V. Küster, Geotextile encased columns (GEC) used as pressure-relief system. Instrumented bridge abutment case study on soft soil, Geotextiles and Geomembranes, 45(3) (2017) 227-236.
  13. Yoo, D. Lee, Performance of geogrid-encased stone columns in soft ground: full-scale load tests, Geosynthetics International, 19(6) (2012) 480-490.
  14. Zhou, G. Kong, Deformation analysis of geosynthetic-encased stone column–supported embankment considering radial bulging, International Journal of Geomechanics, 19(6) (2019) 04019057.
  15. Murugesan, K. Rajagopal, Model tests on geosynthetic-encased stone columns, Geosynthetics International, 14(6) (2007) 346-354.
  16. Samanta, R. Bhowmik, 3D numerical analysis of piled raft foundation in stone column improved soft soil, International Journal of Geotechnical Engineering, 13(5) (2019) 474-483.
  17. Shivashankar, M.D. Babu, S. Nayak, R. Manjunath, Stone columns with vertical circumferential nails: laboratory model study, Geotechnical and Geological Engineering, 28(5) (2010) 695-706.
  18. Black, V. Sivakumar, M. Madhav, G. Hamill, Reinforced stone columns in weak deposits: laboratory model study, Journal of Geotechnical and Geoenvironmental Engineering, 133(9) (2007) 1154-1161.
  19. Zeydi, A. Boushehrian, Experimental and Numerical Study of Bearing Capacity of Circular Footings on Layered Soils With and Without Skirted Sand Piles, Iranian Journal of Science and Technology, Transactions of Civil Engineering, 44(3) (2020) 949-958.
  20. K. Nazir, W.R. Azzam, Improving the bearing capacity of footing on soft clay with sand pile with/without skirts, Alexandria Engineering Journal, 49(4) (2010) 371-377.
  21. J. Priebe, The design of Vibro replacement, Ground engineering, 28(10) (1995) 31.
  22. Raithel, H.-G. Kempfert, Calculation models for dam foundations with geotextile coated sand columns, in: ISRM International Symposium, OnePetro, 2000.
  23. Castro, C. Sagaseta, Influence of elastic strains during plastic deformation of encased stone columns, Geotextiles and Geomembranes, 37 (2013) 45-53.
  24. Zhou, G. Kong, Deformation analysis of a geosynthetic-encased stone column and surrounding soil using cavity-expansion model, International Journal of Geomechanics, 19(5) (2019) 04019036.
  25. Keykhosropur, A. Soroush, R. Imam, 3D numerical analyses of geosynthetic encased stone columns, Geotextiles and Geomembranes, 35 (2012) 61-68.
  26. M. Killeen, B.A. McCabe, Settlement performance of pad footings on soft clay supported by stone columns: a numerical study, Soils and Foundations, 54(4) (2014) 760-776.
  27. A. McCabe, M.M. Killeen, Small stone-column groups: mechanisms of deformation at serviceability limit state, International Journal of Geomechanics, 17(5) (2017) 04016114.
  28. Tabchouche, M. Mellas, M. Bouassida, On settlement prediction of soft clay reinforced by a group of stone columns, Innovative Infrastructure Solutions, 2(1) (2017) 1.
  29. Castro, Groups of encased stone columns: Influence of column length and arrangement, Geotextiles and Geomembranes, 45(2) (2017) 68-80.
  30. S. Ng, Settlement ratio of floating stone columns for small and large loaded areas, Journal of GeoEngineering, 12(2) (2017) 89-96.
  31. Castro, Modeling stone columns, Materials, 10(7) (2017) 782.
  32. Elshazly, D. Hafez, M. Mossaad, Reliability of conventional settlement evaluation for circular foundations on stone columns, Geotechnical and Geological Engineering, 26(3) (2008) 323-334.
  33. P. Balaam, Load-settlement behavior of granular piles, Ph.D. thesis, University of Sydney, Australia, (1978).
  34. G. Poulos, N.S. Mattes, Settlement of pile groups bearing on stiffer strata, Journal of the Geotechnical Engineering Division, 100(2) (1974) 185-190.
  35. Nash, J. Powell, I. Lloyd, Initial investigations of the soft clay test site at Bothkennar, Géotechnique, 42(2) (1992) 163-181.
  36. Hight, A. Bond, J. Legge, Characterization of the Bothkennaar clay: an overview, Géotechnique, 42(2) (1992) 303-347.
  37. Allman, J. Atkinson, Mechanical properties of reconstituted Bothkennar soil, Géotechnique, 42(2) (1992) 289-301.
  38. Castro, Numerical modeling of stone columns beneath a rigid footing, Computers and Geotechnics, 60 (2014) 77-87.
  39. G. Sexton, B.A. McCabe, Stone column effectiveness in soils with creep: a numerical study, Geomechanics and Geoengineering, 11(4) (2016) 252-269.
  40. Shehata, T. Sorour, A. Fayed, Effect of stone column installation on soft clay behavior, International Journal of Geotechnical Engineering, 15(5) (2021) 530-542.
  41. Brinkgreve, S. Kumarswamy, W. Swolfs, Plaxis 3D Reference Manual Anniversary Edition Version 1. Plaxis, Delft (2015), ISBN 978-90-76016-19-2.
  42. Khabbazian, V.N. Kaliakin, C.L. Meehan, Column supported embankments with geosynthetic encased columns: validity of the unit cell concept, Geotechnical and Geological Engineering, 33(3) (2015) 425-442.
  43. M. Killeen, B. McCabe, A numerical study of factors affecting the performance of stone columns supporting rigid footings on soft clay, in: 7th European Conference on Numerical Methods in Geotechnical Engineering, Taylor and Francis, 2010.
  44. Watts, D. Johnson, L. Wood, A. Saadi, An instrumented trial of Vibro ground treatment supporting strip foundations in a variable fill, Géotechnique, 50(6) (2000) 699-708.
  45. Elkasabgy, Performance of stone columns reinforced grounds, M.Sc. Thesis, Zagazig University, Egypt (2005).
  46. Benmebarek, A. Remadna, N. Benmebarek, Numerical modeling of stone column installation effects on performance of circular footing, International Journal of Geosynthetics and Ground Engineering, 4(3) (2018) 1-15.
  47. Schanz, P. Vermeer, P.G. Bonnier, The hardening soil model: formulation and verification, in: Beyond 2000 in computational geotechnics, Routledge, (2019), 281-296
  48. G. Sexton, B.A. McCabe, J. Castro, Appraising stone column settlement prediction methods using finite element analyses, Acta Geotechnica, 9(6) (2014) 993-1011.
  49. G. Sexton, B.A. McCabe, Modeling stone column installation in an elasto-viscoplastic soil, International Journal of Geotechnical Engineering, 9(5) (2015) 500-512.
  50. Yoo, Settlement behavior of embankment on geosynthetic-encased stone column installed soft ground–a numerical investigation, Geotextiles and Geomembranes, 43(6) (2015) 484-492.
  51. Jardine, B. Lehane, P. Smith, P. Gildea, Vertical loading experiments on rigid pad foundations at Bothkennar, Géotechnique, 45(4) (1995) 573-597.
  52. Pulko, B. Majes, J. Logar, Geosynthetic-encased stone columns: analytical calculation model, Geotextiles and Geomembranes, 29(1) (2011) 29-39.
  53. Balaam, J.R. Booker, Analysis of rigid rafts supported by granular piles, International journal for numerical and analytical methods in geomechanics, 5(4) (1981) 379-403.
  54. Barksdale, R. Bachus, Design and construction of stone columns volume I, Federal Highway Administration Washington, DC, USA, (1983).