Evaluation of bearing capacity methods for shallow foundations in unsaturated soils
DOI:
https://doi.org/10.24849/j.geot.2020.150.06Keywords:
Unsaturated soil, bearing capacity, shallow foundationsAbstract
This paper presents an experimental and numerical analysis of the behavior of an unsaturated soil with respect to the bearing capacity of shallow foundations. For this, the results of two plate load tests on a 30 cm diameter plate in the Experimental Field of Foundations of the Federal University of Ceará, with soil in two different conditions, one with a natural moisture profile and the other with pre-flood are presented. Soil samples were collected in each of the trials, and the soil was later characterized. The soil suction in both situations were estimated through the soil-water characteristic curve. Several soil suction profiles are presented in accordance with the methodology proposed by Lu and Likos (2004), followed by the proposals of Oloo et al. (1997), Vanapalli and Mohamed (2007), Briaud (2013), Vahedifard and Robinson (2016) and Tang et al. (2017) for the determination of bearing capacity of shallow foundations in unsaturated soils. The values obtained in the application of these methods showed values of bearing capacity quite coherent with the values determined by the extrapolation of the curve from the unsaturated plate load test.
Downloads
References
ASTM D 3080 (2011). Standard test method for direct shear test of soils under consolidated drained conditions. Annual Book of ASTM Standards 2011.
Arya, L. M.; Dierolf, T. S. (1989). Predicting soil moisture characteristics by particle-size distributions: an improved method to calculate pore radii from particle radii. Proc. of the Int. Workshop on Indirect Methods for Estimating the Hydraulic Properties of Unsaturated Soils, p. 115-124.
Briaud, J. L. (2013). Geotechnical Engineering: Unsaturated and Saturated Soils. Hoboken, New Jersey. Wiley.
Costa, Y. D.; Cintra, J.C.; Zornberg, J.G. (2003). Influence of matric suction on the results of plate load tests performed on a lateritic soil deposit. Geotechnical Testing Journal, vol. 26, nº 2, pp. 219-226.
Fredlund, D. G.; Morgenstern, N. R.; Widger, R. A. (1978). The shear strength of unsaturated Soils.
Canadian Geotechnical Journal, vol. 15, nº 3, pp.313-321.
Garakani, A.A.; Sadeghi, H.; Saheb, S.; Lamei, A. (2019). Bearing Capacity of Shallow Foundations on Unsaturated Soils: Analytical Approach with 3D Numerical Simulations and Experimental Validations. International Journal of Geomechanics, vol.20.
Gitirana Jr., G. F. N.; Camapum de Carvalho, J.; Cordao Neto, M. P. (2005). Previsão de curvas características de um perfil de solo colapsível de Brasília utilizando curvas granulométricas. Congresso Brasileiro de Mecânica do Solos e Engenharia Geotecnica, Curitiba, v. I, 6 p.
Hansen, J. B. (1970). A revised and extended formula for bearing capacity. Geoteknisk Inst., Bulletin 28, pp. 5-11.
Lu, N.; Likos, W. (2004). Unsaturated soil mechanics. John Wiley and Sons, New York, NY, USA. Meyerhof, G. G. (1951). The ultimate bearing capacity of foundations. Géotechnique, vol. 1, nº 4, pp. 351.
Oh, W. T.; Vanapalli, S. K. (2011). Modelling the applied vertical stress and settlement relationship of shallow foundations in saturated and unsaturated sands. Canadian Geotechnical Journal, 48, pp. 425-438.
Oloo, S. Y.; Fredlund, D. G.; Gan, J. K. M. (1997). Bearing capacity of unpaved roads. Canadian Geotechnical Journal, 34, pp. 398-407.
Pinto, C. S. (2006). Curso Básico de Mecânica dos Solos. 3. ed. São Paulo: Oficina de Textos, 354p.
Rojas, J. C.; Salinas, L. M.; Sejas, C. (2007). Plate-load tests on an unsaturated lean clay. Experimental Unsaturated Soil Mechanic, Edited by T. Schanz, Springer-Verlag, Berlin, Heidelberg, Germany, pp. 445-452.
Tang, Y.; Taiebat, H. A.; Senetakis, K. (2017). Effective stress based bearing capacity equations for shallow foundations on unsaturated soils. Journal of GeoEngineering, vol. 12, nº 2, pp. 59-64
Terzaghi, K. (1943). Theorical soil mechanics. New York: John Wiley & Sons.
Tristá, J.G.; Cristía, W.D.C.; Sotolongo, G.J.Q. (2017). Bearing capacity of footings in unsaturated soils employing analytic methods. Ingeniería y Desarrollo, vol. 35, nº 2, pp. 417-430.
Vahedifard, F.; Robinson, J. D. (2016). Unified method for estimating the ultimate bearing capacity of shallow foundations in variably saturated soils under steady flow. Journal of Geotechnical and Geoenvironmental Engineering, vol.142, nº 4, 04015095.
Van Der Veen, C. (1953). The bearing capacity of a pile. International conference on Soil Mechanics and Foundation Engineering, 3. Switzerland, vol.2, pp. 84-90.
Van Genuchten, M. TH. (1980). A closed form equation for predicting the hydraulic conductivity of unsaturated soils. Soil Science Society of America Journal, 44, pp. 892-898.
Vanapalli, S. K.; Fredlund, D. G. (2000). Comparison of empirical procedures to predict the shear strength of unsaturated soils using the soil-water characteristic curve. Advances in Unsaturated Geotechnics, Shackelford, C. D., Houston, S. L., and Chang, N. Y., eds., GSP n. 99, ASCE, Reston, VA, p. 195–209.
Vanapalli, S. K.; Mohamed, F. M. O. (2007). Bearing Capacity of Model Footings in Unsaturated Soils. Theoretical and Numerical Unsaturated Soil Mechanics, pp. 483-493.
Vanapalli, S. K.; Mohamed, F. M. O. (2013). Bearing capacity and settlement of footings in unsaturated sands. International Journal of Geomaterials, vol. 5, nº 1, pp. 595-604.
Vesic, A. S. (1963). Bearing capacity of deep foundations in sand. Highway Research Record, n. 39, pp. 112-153.
Vesic, A. S. (1969). Experiments with instrumented pile groups in sand. American Society for Testing and Materials. Performance of deep foundations. Philadelphia (ASTM Special Technical Publication, n. 444), pp. 177-222.
Vesic, A. S. (1973). Analysis of ultimate loads of shallow foundations. Journal Soil Mechanics and Foundations Division, ASCE, vol. 99, n. SM1.
Vesic, A. S. (1975). Bearing capacity of shallow foundations. Foundation Engineering Handbook, New York, McGraw-Hill, pp. 121-147.
Vo, T.; Russell, A.R. (2016). Bearing capacity of strip footings on unsaturated soils by the slip line theory. Computers and Geotechnics, vol. 74, pp. 122-131.
Zhang, C.; Gao, B.; Yan, Q.; Zhao, J.; Wu, L. (2019). Development of allowable bearing capacity for strip foundations in unsaturated soils. Computers and Geotechnics, vol. 114.
