Evaluation of the Response of Piled Raft Systems in Soft Soil Undergoing Consolidation and Pore Pressure Drawdown
Publication: Geo-Congress 2024
ABSTRACT
The paper presents the results of a numerical investigation to study the time-dependent settlement and structural behaviour of piled raft foundations due to consolidation and subsidence. It is well understood that structures constructed on soft soils undergo large deformations with time. Moreover, few researchers have concluded that due to consolidation and pore pressure drawdown (dewatering and pumping), there is a possibility of separation of the raft from the soil, which can lead the piles to take higher loads than the design loads. A 3D numerical model of a piled raft foundation using finite element approach was incorporated in this paper. The validation was done with the reported experimental results. A parametric study was conducted to study the variation in the distribution of axial load along the pile undergoing consolidation and drawdown, the increase in settlement with time, and the load transfer from the raft to the pile head due to the process of consolidation and drawdown with variation in the pile slenderness ratio. From the finite element simulations, it was observed that soil continues to settle as a result of pore pressure drawdown. Therefore, large drag force occurs in the piles. As the soil continues to settle, the contact pressure between raft and the soil reduces, thereby changing the working conditions of the piled raft. Pile takes additional load due to the loss in shearing strength of the soil at the raft-pile interface, which may result in the failure of the piles. The maximum axial force transmitted to the piles after drawdown is 1.02 to 1.77 times higher than that transmitted during structural service load. Therefore, the need to study the effect of consolidation and drawdown on the serviceability and structural aspects of piled raft is of utmost importance.
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REFERENCES
Alarcón Posse, A. J., J. F. Rodríguez Rebolledo, J. A. Buriticá García, B. Caicedo Hormaza, and E. Rodríguez-Rincón. 2021. “Validation of a 3D numerical model for piled raft systems founded in soft soils undergoing regional subsidence.” Soils and Rocks, 44 (1): 1–15.
Alnuaim, A. M., H. El Naggar, and M. H. El Naggar. 2014. “Performance of micropiled raft in sand subjected to vertical concentrated load: Centrifuge modeling.” Can. Geotech. J., 52 (1): 33–45.
Bhartiya, P., D. Basu, and T. Chakraborty. 2022. “Time-Dependent Response of Rectangular Piled Rafts in Clayey Soils.” 3 (5).
Bisht, R. S., and B. Singh, 2012. “Study on behaviour of piled raft foundation by numerical modelling.” SAITM Res. Symp. Eng. Adv., 15 (4): 23–26.
Cho, J., J. H. Lee, S. Jeong, and J. Lee. 2012. “The settlement behavior of piled raft in clay soils.” Ocean Eng., 53: 153–163.
Cui, Z. D., Y. Q. Tang, and X. X. Yan. 2010. “Centrifuge modeling of land subsidence caused by the high-rise building group in the soft soil area.” Environ. Earth Sci., 59 (8): 1819–1826.
Dinh, D., C. Nguyen, D. Kim, and S. Jo. 2013. “Settlement of Piled Rafts with Different Pile Arrangement Schemes via Centrifuge Tests.” J. Geotech. Geoenvironmental Eng.,139 (October): 1690–1698.
El-Garhy, B., A. A. Galil, A. F. Youssef, and M. A. Raia. 2013. “Behavior of raft on settlement reducing piles: Experimental model study.” J. Rock Mech. Geotech. Eng., 5 (5): 389–399. Taibah University.
Elwakil, A. Z., and W. R. Azzam. 2016. “Experimental and numerical study of piled raft system.” Alexandria Eng. J., 55 (1): 547–560. Faculty of Engineering, Alexandria University. https://doi.org/10.1016/j.aej.2015.10.001.
Goh, S. H., and L. Zhang. 2017. “Estimation of Peak Acceleration and Bending Moment for Pile-Raft Systems Embedded in Soft Clay Subjected to Far-Field Seismic Excitation.” J. Geotech. Geoenvironmental Eng., 143 (11).
Horikoshi, K., and M. F. Randolph. 1996. “Centrifuge modelling of piled raft foundations on clay.” Geotechnique, 46 (4): 741–752.
Mishra, A., and N. R. Patra. 2018. “Time-Dependent Settlement of Pile Foundations Using Five-Parameter Viscoelastic Soil Models.” Int. J. Geomech., 18 (5): 1–16.
Modak, R., and B. Singh. 2022. “A parametric study of large piled raft foundations on clay soil.” Ocean Eng., 262 (March): 112251.
Ng, C. W. W. 2014. “The state-of-the-art centrifuge modelling of geotechnical problems at HKUST.” J. Zhejiang Univ. Sci. A, 15 (1): 1–21.
Rincón, E. R., R. P. da Cunha, and B. C. Hormaza. 2020. “Analysis of settlements in piled raft systems founded in soft soil under consolidation process.” Can. Geotech. J., 57 (4): 537–548.
Rodríguez-Rincón, E. 2016. Experimental analysis of piled raft systems in consolidating soft soils (261 p.).
Sahraeian, S. M. S., J. Takemura, and S. Seki. 2018. “An investigation about seismic behavior of piled raft foundation for oil storage tanks using centrifuge modelling.” Soil Dyn. Earthq. Eng., 104 (November 2017): 210–227.
Sinha, A., and A. M. Hanna. 2017. “3D Numerical Model for Piled Raft Foundation.” Int. J. Geomech., 17 (2): 1–9.
Tang, Y. Q., X. Ren, B. Chen, S. Song, J. X. Wang, and P. Yang. 2012. “Study on land subsidence under different plot ratios through centrifuge model test in soft-soil territory.” Environ. Earth Sci., 66 (7): 1809–1816.
Wang, C., J. T. Han, and Y. E. Jang. 2019. “Experimental investigation of micropile stiffness affecting the underpinning of an existing foundation.” Appl. Sci., 9 (12): 1–14.
Watcharasawe, K., P. Kitiyodom, and P. Jongpradist. 2015. “Numerical analyses of piled raft foundation in soft soil using 3D-FEM.” Geotech. Eng., 46 (1): 109–116.
Watcharasawe, K., P. Kitiyodom, and P. Jongpradist. 2017. “3-D numerical analysis of consolidation effect on piled raft foundation in Bangkok subsoil condition.” Int. J.Geomate, 12 (31): 105–111.
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Published online: Feb 22, 2024
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