Determination of the Displacement of Shallow Foundations Sitting on Unsaturated Soils Using Analytical and Numerical Analysis Methods

Yıl 2024, Cilt: 28 Sayı: 6, 1202 - 1216

Mohammad Osama Fawwaz Alsmadi , Aşkın Özocak , Sedat Sert , Ertan Bol , Emre Akmaz

https://doi.org/10.16984/saufenbilder.1488083

Öz

The bearing capacity of a foundation is crucial for ensuring the stability and safety of structures. However, shallow foundations on unsaturated soils pose challenges due to the complicated behavior of such soils. To address this issue, engineers have developed analytical and numerical methods of analysis, which can be used to determine the bearing capacity of these foundations. This study explored the advantages and disadvantages of these methods, offering a thorough understanding of their role in ensuring the safety and longevity of structures built on unsaturated soil. The analysis in this study was conducted using finite element method simulations on soil sections with varying groundwater levels and degrees of saturation. The results obtained from PLAXIS 2D simulations revealed the effects of fluctuations in groundwater levels and changes in saturation degree on foundation displacements, emphasizing aspects often overlooked in empirical approaches. Under unsaturated conditions, as the degree of saturation decreased, the soil was better able to maintain its structural integrity, resulting in reduced foundation displacements. However, at near-complete saturation (%99), displacements increased significantly, highlighting the risks to foundation stability in soils with high saturation levels, particularly in flood-prone areas. Variability in excess pore water pressure in sections with high saturation indicated potential soil instability under high stresses, impacting structural integrity. Furthermore, finite element analyses showed that classifying soil as drained or undrained impacted foundation displacements. In conclusion, the comprehensive analysis provided by numerical methods emphasized the limitations of empirical approaches and underscored the importance of advanced simulation tools in modern geotechnical practices.

Anahtar Kelimeler

Plaxis 2D, Strip foundation, Bearing capacity, Settlement, Unsaturated soil

Kaynakça

• K. Terzaghi, R. B. Peck, G. Mesri, Soil mechanics in engineering practice. John Wiley & Sons, 1996.
• V. Kumbasar, F. Kip, Soil mechanics problems. Çağlayan Publishing, 1999.
• J. E. Bowles, Y. Guo, Foundation analysis and design. McGraw-Hill New York, 1996.
• A. S. Vesić, "Analysis of ultimate loads of shallow foundations," Journal of the Soil Mechanics and Foundations Division, vol. 99, no. 1, pp. 45-73, 1973.
• B. M. Das, Principles of foundation engineering, SI Edition, Cengage learning, 2010.
• B. B. Broms, "The effect of degree of saturation on the bearing capacity of flexible pavements," Highway Research Record, vol. 71, no. 1, pp. 1-14, 1963.
• J. Steensen-Bach, N. Foged, J. Steenfelt, "Capillary induced stresses―fact or fiction?," in European Conference on Soil Mechanics and Foundation Engineering. 9, 1987, pp. 83-89.
• J. Gan, D. Fredlund, H. Rahardjo, "Determination of the shear strength parameters of an unsaturated soil using the direct shear test," Canadian Geotechnical Journal, vol. 25, no. 3, pp. 500-510, 1988.
• D. G. Fredlund, H. Rahardjo, Soil mechanics for unsaturated soils. John Wiley & Sons, 1993.
• A. Önalp, Geotechnical Knowledge I: Soils and Mechanics. Sakarya University, 1997.
• D. Fredlund, N. R. Morgenstern, R. Widger, "The shear strength of unsaturated soils," Canadian Geotechnical Journal, vol. 15, no. 3, pp. 313-321, 1978.
• R. Noorzad, E. Manavirad, "Bearing capacity of two close strip footings on soft clay reinforced with geotextile," Arabian Journal of Geosciences, vol. 7, pp. 623-639, 2014.
• B. Hough, "Compressibility as the basis for soil bearing value," Journal of the Soil Mechanics and Foundations Division, vol. 85, no. 4, pp. 11-40, 1959.
• M. Aytekin, Experimental soil mechanics. Akademi Yayınevi, 2000.
• B. Jeremic, "by: Boris Jeremic Department of Civil and Environmental Engineering University of California, Davis," 2008.
• D. P. Coduto, M. Mollamahmutoğlu, K. Kayabalı, Foundation Design: Principles and Applications. Gazi Publishing, 2005.
• B. M. Das, Shallow foundations: Bearing capacity and settlement. CRC press, 2017.
• J. B. Hansen, (1970). A revised and extended formula for bearing capacity.
• Meyerhof, G. (1951). The ultimate bearing capacity of foudations. Geotechnique, 2(4), 301-332.
• H. G. Poulos, Tall building foundation design. CRC Press, 2017.
• A. Akbari Garakani, H. Sadeghi, S. Saheb, & A. Lamei (2020). Bearing capacity of shallow foundations on unsaturated soils: analytical approach with 3D numerical simulations and experimental validations. International Journal of Geomechanics, 20(3), 04019181.
• N. Ravichandran, V. Mahmoudabadi, & S. Shrestha (2017). Analysis of the bearing capacity of shallow foundation in unsaturated soil using Monte Carlo simulation. International Journal of Geosciences, 8(10), 1231-1250.
• Du, D., Zhuang, Y., Sun, Q., Yang, X., & Dias, D. (2021). Bearing capacity evaluation for shallow foundations on unsaturated soils using discretization technique. Computers and Geotechnics, 137, 104309.
• D. M. Potts, L. Zdravković, T. I. Addenbrooke, K. G. Higgins, N. Kovačević, Finite element analysis in geotechnical engineering: application. Thomas Telford London, 2001.
• D. L. Logan, A First Course in the Finite Element Method, Enhanced Edition, SI Version. Cengage, 2022.
• R. Brinkgreve, S. Kumarswamy, W. Swolfs, D. Waterman, A. Chesaru, P. Bonnier, "PLAXIS 2016," PLAXIS bv, the Netherlands, pp. 1-16, 2016.
• M.R. Mahmood, S.F. Al-Wakel, and M.S. Mohammed, Effect of partial saturation on ultimate bearing capacity of skirted foundations. Engineering and Technology Journal, 2022. 40(05): p. 710-721.
• Z. Safarzadeh, and M.H. Aminfar, Experimental and numerical modeling of the effect of groundwater table lowering on bearing capacity of shallow square footings. International Journal of Engineering, 2019. 32(10): p. 1429-1436.
• Y. Tang, H.A. Taiebat, and A.R. Russell, Bearing capacity of shallow foundations in unsaturated soil considering hydraulic hysteresis and three drainage conditions. International Journal of Geomechanics, 2017. 17(6): p. 04016142.