Numerical Evaluation of Consolidation of Soft Foundations Improved by Sand–Deep-Mixed Composite Columns
Publication: International Journal of Geomechanics
Volume 17, Issue 8
Abstract
With the development of column technology, a new concept of composite columns has been proposed. Composite columns integrate two columns into one single column, which has a small inner column installed in the middle of a large column. The purpose of the composite column is to combine favorable features of these two constituent columns. The inner and outer columns can have different stiffness, strength, and permeability values and different combinations. In this study, a sand–deep-mixed column was investigated, which included a deep-mixed (DM) column in the middle of a sand column. Because two component columns work together in the composite column, the load-transfer mechanism of the foundation becomes complicated. The bearing capacity of the soft foundation improved by composite columns has been studied. However, the consolidation of the soil foundation improved by composite columns has not been investigated. In this study, a finite-element method was used to model the soft foundation improved by the sand–DM composite (SDMC) column subjected to rigid loading. The SDMC column was fully penetrated through the soft soil and keyed into a firm soil layer. The concept of a unit cell was adopted, and one-quarter of the unit cell was utilized due to the symmetry of the model. The SDMC column was modeled as a linearly elastic perfectly plastic material, and the surrounding soil was modeled as an elastic material. Two additional soft foundations improved by sand columns and DM columns were modeled as well for comparison purposes. The stress concentration ratio, excess pore-water pressure, column bulging, and consolidation settlement of the three soft foundations were analyzed and are discussed. The numerical results show that the vertical effective stress on the top of the SDMC column increased to the maximum value and then decreased to the steady-state value, whereas the vertical effective stress on the top of the soil decreased first and then slightly increased to the steady-state value. The maximum stress values of the columns and the steady-state stress values of the soil indicated the yielding of the columns and the completion of consolidation, respectively. The process of stress transfer in the foundation improved by the SDMC column can be divided into the following three phases: (1) the stress was transferred from the soil to the inner DM column and the outer sand column before the inner DM column yielded, (2) the stress was transferred from the inner DM column to the outer sand column after the inner DM column yielded, and (3) the stress was transferred from the outer sand column to the soil after the outer sand column yielded. The SDMC column had a larger stress concentration ratio than the sand column but a smaller ratio than did the DM column. In addition, the SDMC column resulted in larger bulging and settlement than the DM column but smaller ones than the sand column. The foundations improved by the SDMC column and the sand column had higher degrees of consolidation than did the DM column.
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Acknowledgments
The authors appreciate the financial support by the Natural Science Foundation of China for this study.
References
Abaqus [Computer software]. SIMULIA, Providence, RI.
Abusharar, S., and Han, J. (2011). “Two-dimensional deep-seated slope stability analysis of embankments over stone column-improved soft clay.” Eng. Geol., 120(1–4), 103–110.
Ahnberg, H. (2006). “Strength of stabilised soils—A laboratory study on clays and organic soils stabilized with different types of binder.” Rep. 72, Swedish Geotechnical Institute, Linköping, Sweden.
Alamgir, M., Miura, N., Poorooshasb, H. B., and Madhav, M. R. (1996). “Deformation analysis of soft ground reinforced by columnar inclusions.” Comput. Geotech., 18(4), 267–290.
Barksdale, R. D., and Bachus, R. C. (1983). “Design and construction of stone column.” RD-83/026, Federal Highway Administration, Washington, DC.
Barron, R. A. (1948). “Consolidation of fine-grained soils by drain wells.” Trans. Am. Soc. Civ. Eng., 73(6), 811–835.
Bhandari, A., and Han, J. (2009). “Evaluation of high-capacity composite spun piles.” J. Transp. Res. Rec., 2116, 53–61.
Biot, M. A. (1941). “General theory of three-dimensional consolidation.” J. Appl. Phys., 12(2), 155–164.
Castro, J., and Karstunen, M. (2010). “Numerical simulation of stone column installation.” Can. Geotech. J., 47(10), 1127–1138.
Castro, J., and Sagaseta, C. (2009). “Consolidation around stone columns–Influence of column deformation.” Int. J. Numer. Anal. Methods Geomech., 33(7), 851–877.
Castro, J., and Sagaseta, C. (2011). “Consolidation and deformation around stone columns: Numerical evaluation of analytical solutions.” Comput. Geotech., 38(3), 354–362.
Chai, J. C., Miura, N., Kirekawa, T., and Hino, T. (2010). “Settlement prediction for soft ground improved by columns.” Ground Improv., 163(2), 109–119.
Chai, J. C., and Pongsivasathit, S. (2009). “Prediction of consolidation settlements of floating column improved soft clayed subsoil.” Proc., Int. Symp. on Geotechnical Engineering, Ground Improvement and Geosynthetic for Sustainable Mitigation and Adaptation to Climate Change including Global Warming, Asian Institute of Technology, Khlong Nung, Thailand, 107–115.
Chen, J. S., Tang, T. Z., Zhao, W. B., and Yu, J. (2007). “Field tests on composite foundation with concrete-cored sand-gravel piles.” Chin. J. Geotech. Eng., 29(7), 957–962 (in Chinese).
Han, J. (2015a). Principles and practice of ground improvement, John Wiley & Sons, Hoboken, NJ.
Han, J. (2015b). “Recent research and development of ground column technologies.” Proc. Inst. Civ. Eng., 168(4), 246–264.
Han, J., Bhandari, A., and Wang, F. (2012). “DEM analysis of stresses and deformations of geogrid-reinforced embankments over piles.” Int. J. Geomech., 340–350.
Han, J., Chen, J. F., Hong, Z. S., and Shen, S. L. (2010). “Mitigation of levee failure using deep mixed columns and geosynthetics.” Geomech. Geoeng., 5(1), 49–55.
Han, J., and Gabr, M. A. (2002). “Numerical analysis of geosynthetic-reinforced and pile-supported earth platforms over soft soil.” J. Geotech. Geoenviron. Eng., 44–53.
Han, J., Parsons, R. J., Sheth, A. R., and Huang, J. (2005). “Factors of safety against deep-seated failure of embankments over deep mixed columns.” Proc., Deep Mixing 2005 Conf., Swedish Deep Stabilization Research Centre, Linköping, Sweden, 231–236.
Han, J., Yang, X. M., Chen, J. F., and Porbaha, A. (2009). “Settlement calculation of deep mixed foundations.” Proc., Int. Symp. on Deep Mixing and Admixture Stabilization, Port and Airport Research Institute, Yokosuka, Japan, 19–21.
Han, J., and Ye, S. L. (2001). “Simplified method for consolidation rate of stone column reinforced foundations.” J. Geotech. Geoenviron. Eng., 597–603.
Han, J., and Ye, S. L. (2002). “A theoretical solution for consolidation rates of stone column-reinforced foundations accounting for smear and well resistance effects.” Int. J. Geomech., 135–151.
Hansbo, S. (1981). “Consolidation of fine-grained soils by prefabricated drains.” Proc., 10th Int. Conf. On Soil Mechanics and Foundation Engineering, A. A. Balkema, Rotterdam, Netherlands, 3, 677–682.
Huang, J., Han, J., and Oztoprak, S. (2009). “Coupled mechanical and hydraulic modeling of geosynthetic-reinforced column-supported embankments.” J. Geotech. Geoenviron. Eng., 1011–1021.
Jamsawang, P., Bergado, D. T., and Voottipruex, P. (2010). “Field behaviour of stiffened deep cement mixing piles.” Proc. Inst. Civ. Eng., 164(1), 33–49.
Jiang, Y., Han, J., and Zheng, G. (2013). “Numerical analysis of consolidation of soft soils fully-penetrated by deep-mixed columns.” KSCE J. Civ. Eng., 17(1), 96–105.
Jiang, Y., Han, Y., and Zheng, G. (2014). “Influence of column yielding on degree of consolidation of soft foundations improved by deep mixed columns.” Geomech. Eng., 6(2), 173–194.
Jing, Z. D., Liu, L., Zheng, G., and Jiang, Y. (2008). “Numerical analysis of pile lateral behavior of pile supported embankment.” J. Central South Univ. Technol., 15(S2), 87–92.
Kitazume, M. (2008). “Stability of group column type DM improved ground under embankment loading.” Rep. 047-01-01, Port and Airport Research Institute, Yokosuka, Kanagawa, Japan, 3–56.
Kitazume, M., Okano, K., and Miyajima, S. (2000). “Centrifuge model tests on failure envelope of column type deep mixing method improved ground.” Soils Found., 40(4), 43–55.
Ling, G. R., An, H. Y., Xue, D. Z., and Wang, E. Y. (2001). “Experimental study on concrete core mixing pile.” J. Build. Struct., 22(2), 92–96 (in Chinese).
Lorenzo, G. A., and Bergado, D. T. (2006). “Fundamental characteristics of cement-admixed clay in deep mixing.” J. Mater. Civ. Eng., 161–174.
Oliveira, P. J. V., Pinheiro, J. L. P., and Correia, A. A. S. (2011). “Numerical analysis of an embankment built on soft soil reinforced with deep mixing columns: Parametric study.” Comput. Geotech., 38(4), 566–576.
Plaxis 3D Foundation [Computer software]. Plaxis, Delft, Netherlands.
Pulko, B., and Majes, B. (2005). “Simple and accurate prediction of settlements of stone column reinforced soil.” Proc., 16th Int. Conf. on Soil Mechanics and Geotechnical Engineering, IOS Press, Amsterdam, Netherlands, 1401–1404.
Qu, M., Xie, Q., Cao, X., Zhao, W., He, J., and Jin, J. (2016). “Model test of stone columns as liquefaction countermeasure in sandy soils.” Front. Struct. Civ. Eng., 10(4), 481–487.
Shen, S. L., Han, J., and Du, Y. J. (2008).“Deep mixing induced property changes in surrounding sensitive marine clays.” J. Geotech. Geoenviron. Eng., 845–854.
Tan, S. A., Tjahyono, S., and Oo, K. K. (2008). “Simplified plane-strain modeling of stone-column reinforced ground.” J. Geotech. Geoenviron. Eng., 185–194.
Tang, T. Z., Zhao, W. B., Chen, J. S., and Cheng, W. Z. (2010). “Experimental study on deformation and bearing capacity of composite foundation with concrete-cored sand-gravel piles under high embankment load.” Chin. J. Geotech. Eng., 32(12), 1829–1836 (in Chinese).
Terzaghi, K. (1943). Theoretical soil mechanics, John Wiley and Sons, New York.
Voottipruex, P., Bergado, D. T., Suksawat, T., Jamsawang, P., and Cheang, W. (2011a). “Behavior and simulation of deep cement mixing (DCM) and stiffened deep cement mixing (SDCM) piles under full scale loading.” Soils Found., 51(2), 307–320.
Voottipruex, P., Suksawat, T., Bergado, D. T., and Jamsawang, P. (2011b). “Numerical simulations and parametric study of SDCM and DCM piles under full scale axial and lateral loads.” Comput. Geotech., 38(3), 318–329.
Yapage, N., Liyanapathirana, D., Poulos, H., Kelly, R., and Leo, C. (2014). “Numerical modeling of geotextile-reinforced embankments over deep cement mixed columns incorporating strain-softening behavior of columns.” Int. J. Geomech., 04014047.
Ye, S. L., Han, J., and Ye, G. B. (1994). Ground improvement and underpinning technologies, 2nd Ed., China Building Industry Press, Beijing.
Yin, J. H., and Fang, Z. (2006). “Physical modelling of consolidation behaviour of a composite foundation consisting of a cement-mixed soil column and untreated soft marine clay.” Géotechnique, 56(1), 63–68.
Zhang, J., Cui, X., Huang, D., Jin, Q., Lou, J., and Tang, W. (2015). “Numerical simulation of consolidation settlement of pervious concrete pile composite foundation under road embankment.” Int. J. Geomech., B4015006.
Zhang, Z., Han, J., and Ye, G. B. (2014). “Numerical investigation on factors for deep-seated slope stability of stone column-supported embankments over soft clay.” Eng. Geol., 168(16), 104–113.
Zheng, G., Jiang, Y., and Han, J. (2014). “Consolidation of soft foundations treated with composite columns.” Proc., Geo-Shanghai 2014, ASCE, Reston, VA, 98–106.
Zheng, G., Jiang, Y., Han, J., and Liu, Y. F. (2011). “Performance of cement-fly ash-gravel pile-supported high-speed railway embankments over soft marine clay.” Mar. Georesour. Geotechnol., 29(2), 145–161.
Zheng, G., Liu, S. Y., and Chen, R. P. (2009). “State of advancement of column-type reinforcement element and its application in China.” Advances in Ground Improvement, Geotechnical Special Publication No. 188, J. Han, G. Zheng, V. R. Schaefer, and M. S. Huang, eds., Proc., U.S.-China Workshop on Ground Improvement Technologies, ASCE, Reston, VA, 12–25.
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International Journal of Geomechanics
Volume 17 • Issue 8 • August 2017
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© 2017 American Society of Civil Engineers.
History
Received: May 26, 2016
Accepted: Dec 19, 2016
Published online: Mar 15, 2017
Published in print: Aug 1, 2017
Discussion open until: Aug 15, 2017
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