International Journal of Civil Engineering

, Volume 18, Issue 2, pp 161–168 | Cite as

Investigation of Soil Active Wedge Angle with Linear Matric Suction Distribution Below the Footing

  • Hasan GhasemzadehEmail author
  • Fereshteh Akbari
Research paper


In this paper, a theoretical approach is established to determine the active wedge angle of unsaturated soils, based on the limit equilibrium method, while matric suction varies linearly with respect to depth. In the previous researches, constant suction distribution profile within the soil has been pointed out, however, generally linear and nonlinear suction profiles develop above the ground water table. The range of suction value covers transition zone and residual zone of unsaturation. Sensitivity of the proposed model, with respect to different parameters, shows that the value of active wedge angle is more dependent on the internal friction angle, in comparison to other properties. Therefore, instead of a complex relation, simple equation can be used. The results show that the active wedge angle for unsaturated soils is equal to \(\frac{\pi }{6} + \frac{7}{8}\phi\). Comparisons between the presented model and experimental data show that, for some values of internal friction angle, the active wedge angle in unsaturated state is close to saturated state.


Active wedge angle Unsaturated soil Matric suction Limit equilibrium method Bearing capacity 


  1. 1.
    Mahmood Kh, Kim YM, Ashraf M, Urrehman Z (2016) The effects of soil type on matric suction and stability of unsaturated slope under uniform rainfall. KSCE J Civil Eng 20:1294–1299. CrossRefGoogle Scholar
  2. 2.
    Vanapalli SK, Mohamed FMO (2013) Bearing capacity and settlement of footings in unsaturated sands. Int J GEOMAT 5:595–604. CrossRefGoogle Scholar
  3. 3.
    Vanapalli SK, Mohamed FMO (2007) Bearing capacity of model footings in unsaturated soils. In: Experimental unsaturated soil mechanics. Springer, Berlin, pp 483–493.
  4. 4.
    Schanz T, Lins Y, Vanapalli SK (2010) Bearing capacity of a strip footing on an unsaturated sand. In: The 5th international conference on unsaturated soils. Barcelona, pp 1195–1200. CrossRefGoogle Scholar
  5. 5.
    Rassam DW, Williams DJ (1999) A relationship describing the shear strength of unsaturated soils. Can Geotech J 36:363–368. CrossRefGoogle Scholar
  6. 6.
    Oh WT, Vanapalli SK (2018) Modelling the stress versus settlement behavior of shallow foundations in unsaturarted cohesive soils extending the modified total stress approach. Soils Found 58:382–397. CrossRefGoogle Scholar
  7. 7.
    Lu N, Likos W (2004) Unsaturated soil mechanics. Wiley, New JerseyGoogle Scholar
  8. 8.
    Oloo SY, Fredlund DG, Gan JKM (1997) Bearing capacity of unpaved roads. Can Geotech J 34:398–407CrossRefGoogle Scholar
  9. 9.
    Vanapalli SK, Fredlund DG, Pufahal DE, Clifton AW (1996) Model for the prediction of shear strength with respect to soil suction. Can Geotech J 33:379–392. CrossRefGoogle Scholar
  10. 10.
    Fredlund DG, Xing A, Fredlund MD, Barbour SL (1996) The relationship of the unsaturated soil shear strength to the soil–water characteristic curve. Can Geotech J 33:440–448CrossRefGoogle Scholar
  11. 11.
    Oloo SY (1994) A bearing capacity approach to the design of low-volume traffic roads. PhD Thesis, University of Saskatchewan, CanadaGoogle Scholar
  12. 12.
    Bolton MD (1986) The strength and dilatancy of sands. Geotechnique 36:65–78. CrossRefGoogle Scholar
  13. 13.
    Uchaipichat A, Man-Koksung E (2011) Bearing capacity characteristic of unsaturated granular soils. Adv Mater Res 261–263:989–993. CrossRefGoogle Scholar
  14. 14.
    Rojas JC, Salinas LM, Sejas C (2007) Plate-load tests on an unsaturated lean clay. In: Experimental unsaturated soil mechanic. Springer, Berlin, pp 445–452.
  15. 15.
    Oh WT, Vanapalli SK (2013) Interpretation of the bearing capacity of unsaturated fine-grained soil using the modified effective and the modified total stress approaches. Int J Geomech. CrossRefGoogle Scholar

Copyright information

© Iran University of Science and Technology 2019

Authors and Affiliations

  1. 1.Faculty of Civil EngineeringK.N. Toosi University of TechnologyTehranIran

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