Modified Equivalent-Area Method for Calculating Factors of Safety against Deep-Seated Failure of Embankments over Deep-Mixed Foundations
Publication: International Journal of Geomechanics
Volume 20, Issue 3
Abstract
The limit equilibrium method (LEM) and the finite-element method (FEM) commonly have been used in design to calculate the factors of safety (FS) against deep-seated failure of deep-mixed (DM) column-supported embankments over soft clays. Previous studies showed that the LEM with the conventional equivalent-area method (EAM) for column foundations yields higher FS than the three-dimensional (3D) FEM with individual columns. This study investigated the FS against deep-seated failure of embankments over deep-mixed columns using the 3D individual column method and the LEM with the conventional EAM. The roles of DM columns and soft clays in the stability of DM column-supported embankments were assessed by performing a weighted analysis and examining the stress states of the DM columns and the soft clay at failure. The results showed that the conventional EAM had a higher possibility of overestimating the FS against deep-seated failure of embankments over deep-mixed foundations than did the 3D FEM with individual columns. The conventional EAM overestimated the contributions of DM columns to the slope instability because some DM columns had not fully mobilized their shear strengths when the embankment failed in the 3D FEM, especially for soil and DM columns with a large strength difference and for DM columns with a large area replacement ratio. Load transfer almost disappeared at failure in the 3D model. Accordingly, a modified equivalent-area method was proposed and verified by comparing its results with those in the literature.
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Data Availability Statement
The FS of all models created in this study are included in Table S1 in the Supplemental Data, including 2D LEM using conventional EAM, 2D FEM using conventional EAM, 3D FEM with individual columns, and 2D LEM using the modified EAM. The input code of the 3D numerical model in the 3D model validation section also is included in the Supplemental Data.
Acknowledgments
The authors appreciate the financial support provided by the Natural Science Foundation of China (NSFC) (Grant Nos. 51508408, 41772281, and 51478349) and the Fundamental Research Funds for the Central Universities (Grant No. 22120180106) for this research. This study was also financially supported by the Key Research and Development Project of Chinese Ministry of Science and Technology (Grant No. 2016YFE0105800).
References
Abusharar, S. W., and J. Han. 2011. “Two-dimensional deep-seated slope stability analysis of embankments over stone column-improved soft clay.” Eng. Geol. 120 (1–4): 103–110. https://doi.org/10.1016/j.enggeo.2011.04.002.
Ariyarathne, P., D. S. Liyanapathirana, and C. J. Leo. 2013. “Comparison of different two-dimensional idealizations for a geosynthetic-reinforced pile-supported embankment.” Int. J. Geomech. 13 (6): 754–768. https://doi.org/10.1061/(asce)gm.1943-5622.0000266.
Baker, S. 2000. Deformation behavior of lime/cement column stabilized clay, 30–39. Sweden: Goteborg Chalmers Univ. of Technology.
Broms, B. B. 1999. Can lime/cement columns be used in Singapore and Southeast Asia?. Singapore: NTU-PWD Geotechnical Research Centre, Nanyang Technological Univ.
CDIT (Coastal Development Institute of Technology). 2002. The deep mixing method: Principle, design and construction. Amsterdam, Netherlands: A.A. Balkema.
Chai, J. C., Y. Igaya, T. Hino, and J. Carter. 2013. “Finite element simulation of an embankment on soft clay—Case study.” Comput. Geotech. 48 (1): 117–126. https://doi.org/10.1016/j.compgeo.2012.10.006.
Chai, J. C., S. Shrestha, T. Hino, W. Q. Ding, Y. Kamo, and J. Carter. 2015. “2D and 3D analyses of an embankment on clay improved by soil–cement columns.” Comput. Geotech. 68 (Jul): 28–37. https://doi.org/10.1016/j.compgeo.2015.03.014.
Chai, J. C., S. Shrestha, T. Hino, and T. Uchikoshi. 2017. “Predicting bending failure of CDM columns under embankment loading.” Comput. Geotech. 91 (Nov): 169–178. https://doi.org/10.1016/j.compgeo.2017.07.015.
Chen, R. H., and J. L. Chameau. 1983. “Three-dimensional limit equilibrium analysis of slopes.” Géotechnique 32 (1): 31–40. https://doi.org/10.1680/geot.1983.33.1.31.
Christoulas, S., C. Giannaros, and G. Tsiambaos. 1997. “Stabilization of embankment foundations by using stone columns.” Geotech. Geol. Eng. 15 (3): 247–258. https://doi.org/10.1007/bf00880828.
Cooper, M. R., and A. N. Rose. 1999. “Stone column support for an embankment on deep alluvial soils.” Proc. Inst. Civ. Eng. Geotech. Eng. 37 (1): 15–25. https://doi.org/10.1680/gt.1999.370103.
Dawson, E. M., W. H. Roth, and A. Drescher. 1999. “Slope stability analysis by strength reduction.” Geotechnique 49 (6): 835–840. https://doi.org/10.1061/40512(289)8.
Griffiths, D. V., and P. A. Lane. 2004. “Slope stability analysis by finite elements.” Géotechnique 51 (7): 653–654. https://doi.org/10.1680/geot.1999.49.3.387.
Han, J., J. C. Chai, D. Leshchinsky, and S. L. Shen. 2004. “Evaluation of deep-seated slope stability of embankments over deep mixed foundations.” In Vol. 120 of Proc., Sessions of the GeoSupport Conf.—Innovation and Cooperation in Geo, 945–954. Reston, VA: ASCE. https://doi.org/10.1061/40713(2004)71.
Han, J., R. J. Parsons, A. R. Sheth, and J. Huang. 2005. “Factors of safety against deep-seated failure of embankments over deep mixed columns.” In Vol. 1.2 of Proc., Deep Mixing 2005 Conf., 231–236. Linkoping, Sweden: Swedish Geotechnical Institute.
Huang, J., and J. Han. 2008. “Critical height of a deep mixed column-supported embankment under an undrained condition.” In Proc., GeoCongress 2008: Geosustainability and Geohazard Mitigation, 638–645. Reston, VA: ASCE.
Huang, J., and J. Han. 2009. “3D coupled mechanical and hydraulic modeling of a geosynthetic-reinforced deep mixed column-supported embankment.” Geotext. Geomembr. 27 (4): 272–280. https://doi.org/10.1016/j.geotexmem.2009.01.001.
Huang, M., and C. Q. Jia. 2009. “Strength reduction FEM in stability analysis of soil slopes subjected to transient unsaturated seepage.” Comput. Geotech. 36 (1–2): 93–101. https://doi.org/10.1016/j.compgeo.2008.03.006.
Jamsawang, P., P. Voottipruex, P. Boathong, W. Mairaing, and S. Horpibulsuk. 2015. “Three-dimensional numerical investigation on lateral movement and factor of safety of slopes stabilized with deep cement mixing column rows.” Eng. Geol. 188 (Apr): 159–167. https://doi.org/10.1016/j.enggeo.2015.01.017.
Jamsawang, P., N. Yoobanpot, N. Thanasisathit, P. Voottipruex, and P. Jongpradist. 2016. “Three-dimensional numerical analysis of a DCM column-supported highway embankment.” Comput. Geotech. 72 (Feb): 42–56. https://doi.org/10.1016/j.compgeo.2015.11.006.
Kitazume, M., and K. Maruyama. 2007. “Centrifuge model tests on failure pattern of group column type deep mixing improved ground.” In Proc., Int. Offshore and Polar Engineering Conf., 1293–1300. Cupertino, CA: International Society of Offshore and Polar Engineers.
Marandi, S. M., M. Anvar, and M. Bahrami. 2016. “Uncertainty analysis of safety factor of embankment built on stone column improved soft soil using fuzzy logic -cut technique.” Comput. Geotech. 75 (May): 135–144. https://doi.org/10.1016/j.compgeo.2016.01.014.
Navin, M. P., and G. M. Filz. 2006. “Numerical stability analyses of embankments supported on deep mixed columns.” In Proc., ASCE GSP 152: Ground Modification and Seismic Mitigation, 1–8. Reston, VA: ASCE.
Navin, M. P., M. Kim, and G. M. Filz. 2005. “Stability of embankments founded on deep-mixing-method columns: Three-dimensional considerations.” In Proc., Int. Conf. on Soil Mechanics and Geotechnical Engineering, 1227–1230. Amsterdam, Netherlands: A.A. Balkema.
Oliveira, P. J. V., and L. J. L. Lemos. 2011. “Numerical analysis of an embankment on soft soils considering large displacements.” Comput. Geotech. 38 (1): 88–93. https://doi.org/10.1016/j.compgeo.2010.08.005.
Oliveira, P. J. V., J. L. P. Pinheiro, and A. A. S. Correia. 2011. “Numerical analysis of an embankment built on soft soil reinforced with deep mixing columns: Parametric study.” Comput. Geotech. 38 (4): 566–576. https://doi.org/10.1016/j.compgeo.2011.03.005.
Qiu, Y., B. Fu, J. Wang, and L. Chen. 2003. “Spatiotemporal prediction of soil moisture content using multiple-linear regression in a small catchment of the Loess Plateau, China.” Catena 54 (1): 173–195. https://doi.org/10.1016/s0341-8162(03)00064-x.
Qiu, Y., B. Fu, J. Wang, L. Chen, Q. Meng, and Y. Zhang. 2010. “Spatial prediction of soil moisture content using multiple-linear regressions in a gully catchment of the Loess Plateau, China.” J. Arid. Environ. 74 (2): 208–220. https://doi.org/10.1016/j.jaridenv.2009.08.003.
Shrestha, S., J. C. Chai, D. Bergado, T. Hino, and Y. Kamo. 2016. “3D FEM investigation on bending failure mechanism of column inclusion under embankment load.” Lowland Technol. Int. 17 (3): 157–166. https://doi.org/10.14247/lti.17.3_157.
Smith, M. 2009. Abaqus/Standard user’s manual, version 6.9. Providence, RI: Simulia.
Tan, S. A., S. Tjahyono, and K. K. Oo. 2008. “Simplified plane-strain modeling of stone-column reinforced ground.” J. Geotech. Geoenviron. Eng. 134 (2): 185–194. https://doi.org/10.1061/(ASCE)1090-0241(2008)134:2(185).
Terashi, M. 2003. “The state of practice in deep mixing methods.” In Proc., 3rd Int. Specialty Conf. on Grouting and Ground Treatment, 25–49. New Orleans: Lawrence.
Wei, W. B., Y. M. Cheng, and L. Li. 2009. “Three-dimensional slope failure analysis by the strength reduction and limit equilibrium methods.” Comput. Geotech. 36 (1): 70–80. https://doi.org/10.1016/j.compgeo.2008.03.003.
Yapage, N. N. S., D. S. Liyanapathirana, R. B. Kelly, H. G. Poulos, and C. J. Leo. 2014. “Numerical modeling of an embankment over soft ground improved with deep cement mixed columns: Case history.” J. Geotech. Geoenviron. Eng. 140 (11): 04014062 https://doi.org/10.1061/(asce)gt.1943-5606.0001165.
Ye, G. B., Z. Zhang, J. Han, H. F. Xing, M. S. Huang, and P. L. Xiang. 2013. “Performance evaluation of an embankment on soft soil improved by deep mixed columns and prefabricated vertical drains.” J. Perform. Constr. Facil. 27 (5): 614–623. https://doi.org/10.1061/(asce)cf.1943-5509.0000369.
Zhang, Z., J. Han, and G. Ye. 2014a. “Numerical analysis of failure modes of deep mixed column-supported embankments on soft soils.” In Proc., 2014 GeoShanghai Int. Congress on Ground Improvement and Geosynthetics-Selected Papers, 78–87. Los Angeles: Geotechnical Special Publication.
Zhang, Z., J. Han, and G. Ye. 2014b. “Numerical investigation on factors for deep-seated slope stability of stone column-supported embankments over soft clay.” Eng. Geol. 168 (2): 104–113. https://doi.org/10.1016/j.enggeo.2013.11.004.
Zheng, H., G. Sun, and D. Liu. 2009. “A practical procedure for searching critical slip surfaces of slopes based on the strength reduction technique.” Comput. Geotech. 36 (1): 1–5. https://doi.org/10.1016/j.compgeo.2008.06.002.
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Published In
International Journal of Geomechanics
Volume 20 • Issue 3 • March 2020
Copyright
©2019 American Society of Civil Engineers.
History
Received: Dec 11, 2018
Accepted: Aug 8, 2019
Published online: Dec 27, 2019
Published in print: Mar 1, 2020
Discussion open until: May 27, 2020
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