A Numerical Study on the Behavior of Disconnected Composite Piled Raft, Composite Piled Raft, and Unpiled Raft under Axial Load
Publication: IFCEE 2021
ABSTRACT
The unpiled raft foundation may not provide safe and economical design for highly compressible subsoil strata. The effectiveness of rafts is improved by the addition of piles as settlement reducers. However, the load distribution in piled raft is such that axial stress and bending moments are carried by the piles with minimum contribution from raft and subsoil. To mobilize the strength of subsoil in the load transfer mechanism, the concept of disconnected composite piled raft with cushion was considered. The present study aims at understanding the behavior of disconnected composite piled raft with cushion using 3D FEM analysis, by considering pile and raft as linearly elastic and non-associated Mohr–Coulomb elasto-plastic behavior for cushion and subsoil. In this study, the raft and piles were disconnected using a layer of granular material referred to as a cushion (load transfer platform). This cushion layer helped in the redistribution of the axial stress ratio amongst piles and subsoil as compared to the connected piled raft and unpiled raft. The results indicated that the bending moment, axial force, and settlements of disconnected composite piled raft were substantially modified by the cushion thickness under varying vertical pressure.
Get full access to this article
View all available purchase options and get full access to this chapter.
REFERENCES
Baziar, M. H., Rafiee, F., Lee, C. J., and Saeedi Azizkandi, A. (2018). “Effect of superstructure on the dynamic response of nonconnected piled raft foundation using centrifuge modeling.” International Journal of Geomechanics, 18(10), 04018126.
Cao, W., Chen, Y., and Wolfe, W. E. (2014). “New load transfer hyperbolic model for pile-soil interface and negative skin friction on single piles embedded in soft soils.” International Journal of Geomechanics, 14(1), 92-100.
Cao, X. D., Wong, I. H., and Chang, M. F. (2004). “Behaviour of model rafts resting on pile-reinforced sand.” Journal of geotechnical and geoenvironmental engineering, 130(2), 129-138.
Chen, R. P., Zhou, W. H., and Chen, Y. M. (2009). “Influences of soil consolidation and pile load on the development of negative skin friction of a pile.” Computers and Geotechnics, 36(8), 1265-1271.
Comodromos, E. M., and Bareka, S. V. (2005). “Evaluation of negative skin friction effects in pile foundations using 3D nonlinear analysis.” Computers and Geotechnics, 32(3), 210-221.
Dezfouli, M. G., Dehghani, M., Asakereh, A., and Kalantari, B. (2019). “Behaviour of Geogrid Reinforced and Unreinforced Non-Connected Pile Raft Foundation.” International Journal of Civil Engineering, 17(6), 709-722.
Fioravante, V., and Giretti, D. (2010). “Contact versus noncontact piled raft foundations.” Canadian Geotechnical Journal 47(11), 1271-1287.
Ghalesari, A. T., and Rasouli, H. (2014). “Effect of Gravel Layer on the Behaviour of Piled Raft Foundations.” In Advances in Soil Dynamics and Foundation Engineering (pp. 373-382).
Hor, B., Song, M. J., Jung, M. H., Song, Y. H., and Park, Y. H. (2016). “A 3D FEM analysis on the performance of disconnected piled raft foundation.” Japanese Geotechnical Society Special Publication, 2(34), 1238-1243.
Ko, K. W., Park, H. J., Ha, J. G., Jin, S., Song, Y. H., Song, M. J., and Kim, D. S. (2019). “Evaluation of dynamic bending moment of disconnected piled raft via centrifuge tests.” Canadian Geotechnical Journal 56(12), 1917-1928.
Lee, Y. S., and Hong, S. H. (2006). “An Experimental Study on the Load-settlement Behaviour and Settlement-reducing Effect of the Disconnected Piled Raft Foundation.” Journal of the Korean Geotechnical Society, 22(4), 95-104.
Liang, F. Y., Chen, L. Z., and Shi, X. G. (2003). “Numerical analysis of composite piled raft with cushion subjected to vertical load.” Computers and Geotechnics, 30(6), 443-453.
Ni, P., Song, L., Mei, G., and Zhao, Y. (2017). “Generalized nonlinear softening load-transfer model for axially loaded piles.” International Journal of Geomechanics, 17(8), 04017019.
Ottaviani, M. (1975). “Three-dimensional finite element analysis of vertically loaded pile groups.” Geotechnique, 25(2), 159-174.
Rasouli, H., Ghalesari, A. T., Modarresi, M., and Hasanzadeh, A. (2017). “Numerical study of non-contact piled raft interaction under static loads.” Civil engineering and urban planning, 750-762.
Saeedi Azizkandi, A., Baziar, M. H., Rasouli, H., Modarresi, M., and Shahnazari, H. (2015). “Centrifuge modeling of non-connected piled raft system.” International Journal of Civil Engineering, 13(2), 114-123.
Shahu, J. T., Madhav, M. R., and Hayashi, S. (2000). “Analysis of soft ground-granular pile-granular mat system.” Computers and Geotechnics, 27(1), 45-62.
Tradigo, F., Pisanò, F., Di Prisco, C., and Mussi, A. (2015). “Non-linear soil–structure interaction in disconnected piled raft foundations.” Computers and Geotechnics, 63, 121-134.
Xu, R., and Fatahi, B. (2018). “Geosynthetic-reinforced cushioned piles with controlled rocking for seismic safeguarding.” Geosynthetics International 25(6), 561-581.
Zhu, X. J. (2017). “Analysis of the load sharing and cushion failure mode for a disconnected piled raft.” Advances in Materials Science and Engineering, 2017.
Zhu, X. J., Fei, K., and Wang, S. W. (2018). “Horizontal loading tests on disconnected piled rafts and a simplified method to evaluate the horizontal bearing capacity.” Advances in Civil Engineering, 2018.
Information & Authors
Information
Published In
Copyright
© 2021 American Society of Civil Engineers.
History
Published online: May 6, 2021
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.