Behavior of Single Pile and Mono Pile-Raft Foundation under Hydraulic Loading Considering Hysteresis in Unsaturated Soils
Publication: Geo-Congress 2023
ABSTRACT
This paper presents the load-mobilization mechanism of single pile (SP) and mono pile-raft foundation (MPRF) embedded in unsaturated sand subjected to hydraulic loading. A finite element-based computer program Plaxis3D was used to develop and discretize the numerical model of soil, SP and MPRF. The solution to the boundary value problem was obtained by implementing a fully coupled flow deformation numerical scheme. The soil was modeled using an elastic perfectly plastic Mohr-Coulomb constitutive model modified by extending Bishop’s effective stress concept. The hysteretic hydro-mechanical properties of sand were incorporated using drying and wetting soil water retention curves (SWRC). The load-settlement (P-δ) response of SP under saturated and unsaturated conditions was validated with 1-g physical model test results available in the literature. The validated numerical model was extended to the case of MPRF. After subjecting foundations to their respective service loads, hydraulic loading in terms of infiltration/evaporation was simulated by applying time-dependent net moisture flux boundary conditions. The obtained results indicated a marked dependency on SWRC and the intensity of hydraulic loading in dictating the settlement and load-bearing responses of SP and MPRF. The hysteretic SWRC influenced the pile-soil relative movement where a higher movement was observed during the infiltration as compared to evaporation, mainly due to the confinement of evaporation within a shallow depth. This phenomenon also affected the mobilization of axial force along the length of SP where higher forces were mobilized up on infiltration (up to 2.7%) compared to evaporation (up to 1.9%). The load shared by the pile component of MPRF increased during evaporation and attained an equalized value, mainly due to the reduction in contact pressure of the raft associated with the reduction in suction stress within the shallow depth. However, a fluctuating load-sharing response for MPRF was observed during infiltration. The outcome of this study provides benchmarking evidence for the mobilization of loads within SP and MPRF considering the coupled mechanical and hydraulic loading.
Get full access to this article
View all available purchase options and get full access to this chapter.
REFERENCES
Al-Khazaali, M., and Vanapalli, S. K. (2019). “Experimental investigation of single model pile and pile group behavior in saturated and unsaturated sand.” J. Geotech. Geo. Eng., 145(12), 04019112.
Alonso, E. E., Gens, A., and Josa, A. (1990). “A constitutive model for partially saturated soils.” Géotechnique, 40(3), 405–430.
Biot, M. A. (1941). “General theory of three-dimensional consolidation.” J. Appl. Phys., 12, 155–164.
Bishop, A. W., and Blight, G. E. (1963). “Some aspects of effective stress in saturated and unsaturated soils.” Géotechnique, 13, 177–197.
BIS. (2013). Indian Standard Code of Practice for Design and Construction of Pile Foundations, Manak Bhavan, 9 Bahadur Shah Zafar Marg, New Delhi 110002.
Cerato, A. B., and Lutenegger, A. J. (2007). “Scale effects of shallow foundation bearing capacity on granular materials.” J. Geotech. Geo. Eng., 133(10), 1192–1202.
Fredlund, D. G., Sheng, D., and Zhao, J. (2011). “Estimation of soil suction from soil-water characteristic curve.” Can. Geotech. J., 48, 186–198.
Georgiadis, K., Potts, D. M., and Zdravković, L. (2003). “The influence of partial soil saturation on pile behavior.” Géotechnique, 53(1), 11–25.
Goh, S. G., Rahardjo, H., and Choon, L. E. (2010). “Shear strength equations for unsaturated soil under drying and wetting.” J. Geotech. Geo. Eng., 136(4), 594–606.
Han, Z., Vanapalli, S. K., and Kutlu, Z. N. (2016). “Modeling behavior of friction pile in compacted glacial till.” Int. J. Geomech., 16(6), D4016009.
Horikoshi, K., and Randolph, M. F. (1997). “On the definition of raft-soil stiffness ratio for rectangular rafts.” Géotechnique, 47(5), 1055–61.
Kumar, A., and Choudhury, D. (2018). “Development of new prediction model for capacity of combined pile-raft foundations.” Comp. and Geotech., 97, 62–68.
Kumar, A., Kumar, S., and Kumar, A. (2022). “Behavior of laterally loaded mono-piled raft foundation in sloping ground.” Chapter 24 in Advances in sustainable materials and resilient infrastructure, Reddy, K. R., Pancharathi, R. K., Reddy, N. G., Arukala, S. R., eds. Springer, Singapore, 357–372.
Kumar, S., and Kumar, A. (2022). “Effect of infiltration on single pile and mono pile-raft foundation embedded in unsaturated sand.” Int. J Geomech., Doi: https://doi.org/10.1061/IJGNAI/GMENG-7908, (Forthcoming).
Lee, J. H., and Salgado, R. (1999). “Determination of pile base resistance in sands.” J. Geotech. Geo. Eng., 125(8), 673–683.
PLAXIS 3D V20.04 [Computer software]. Delft, Netherlands.
Sheikhtaheri, M. (2014). Experimental and numerical modeling studies for interpreting and estimating the p-d behavior of single model piles in unsaturated sands. M.S. thesis, Univ. of Ottawa, Ottawa, Canada.
Van Genuchten, M. T. (1980). “A closed-form equation for predicting the hydraulic conductivity of unsaturated soils.” Soil Sci. Soc. Am. J., 44, 892–898.
Vanapalli, S. K., Fredlund, D. G., Pufahl, D. E., and Clifton, A. W. (1996b). “Model for the prediction of shear strength with respect to soil suction.” Can. Geotech. J., 33(3), 379–392.
Vanapalli, S. K., and Oh, W. T. (2010). “A model for predicting the modulus of elasticity of unsaturated soils using the soil-water characteristic curve.” Int. J. Ge. Eng., 4(4), 425–433.
Information & Authors
Information
Published In
Geo-Congress 2023
Pages: 228 - 239
History
Published online: Mar 23, 2023
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.