Abstract
Many shallow foundations are constructed within the soil layer above the groundwater table, where the soil remains unsaturated, and the failure of shallow foundation is mostly related to shear failure. The shear strength of the unsaturated soil is one of the main engineering properties required in geotechnical designs. Previous researchers suggested that the shear strength of the unsaturated soil depends on matric suction in the soil. The shape of the soil–water characteristic curve (SWCC) has a significant effect on the characteristics of unsaturated shear strength with respect to matric suction. In this paper, a new model was proposed for the estimation of the unsaturated shear strength from SWCC. In this new model, meniscus was considered to transfer soil suction into both additional net normal stress and additional cohesion. Based on the categorization from soil science, water in soil can be categorized into three groups: (1) gravity water, (2) capillary water and (3) hygroscopic water. The elemental analysis on the contractile skin indicated that only the capillary water in the soil can transfer stress into soil skeleton. Consequently, the SWCC is modified by considering capillary water only for the estimation of unsaturated shear strength. In the derivation, unsaturated soil is considered as four-phase material. Finally, a new mathematical equation for the estimation of the unsaturated shear strength was proposed and verified with the experimental data from the published literature. In addition, the proposed equation does not consist of any empirical parameter and can be used to predict the shear strength of unsaturated soil.
Similar content being viewed by others
References
Alonso EE, Gens A, Josa A (1990) A constitutive model for partially saturated soils. Géotechnique 40(3):405–430
Bishop AW (1959) The principle of effective stress. Teknisk Ukeblad, Norwegian Geotech Inst 106(39):859–863
Bishop AW, Alpan I, Blight GE, Donald IB (1960) Factors controlling the shear strength of partly saturated cohesive soils. Paper presented at the research conference on shear strength of cohesive soils, ASCE, University of Colorado, Boulder, CO, pp 503–532
Cunningham MR, Ridley AM, Dineen K, Burland JB (2003) The mechanical behaviour of a reconstituted unsaturated silty clay. Géotechnique 53(2):183–194
Fredlund DG (1987) The stress state for expansive soils. In: Proceedings of the sixth international conference on expansive soils, New Delhi, pp 524–534
Fredlund DG, Morgenstern NR (1977) Stress state variables for unsaturated soils. J Geotech Eng Div 103(GT5):447–466
Fredlund DG, Morgenstern NR, Widger A (1978) Shear strength of unsaturated soils. Can Geotech J 15:313–321
Fredlund DG, Xing A (1994) Equations for the soil-water characteristic curve. Can Geotech J 31(3):521–532
Fredlund DG, Rahardjo H (1993) Soil Mechanics for unsaturated soil. Wiley, New York
Fredlund DG, Rahardjo H, Fredlund MD (2012) Unsaturated soil mechanics in engineering practice. Wiley, New York
Fredlund DG, Xing A, Fredlund MD, Barbour SL (1996) The relationship of unsaturated soil shear strength to the soil–water characteristic curve. Can Geotech J 33:440–448
Goh SG, Rahardjo H, Leong EC (2010) Shear strength equations for unsaturated soil under drying and wetting. J Geotech Geoenviron Eng 136(4):594–606. https://doi.org/10.1061/(asce)gt.1943-5606.0000261
Fung YC (1965) Foundations of solid mechanics. Prentice-Hall, Englewood Cliffs
Fung YC (1977) A first course in continuum mechanics, 2nd edn. Prentice-Hall, Englewood Cliffs
Gao Y, Sun DA, Zhu AC, Xu YF (2018) Hydromechanical behavior of unsaturated soil with different initial densities over a wide suction range. Acta Geotech. https://doi.org/10.1007/s11440-018-0662-5
Jennings JEB, Burland JB (1962) Limitations to the use of effective stresses in partly saturated soils. Géotechnique 12(2):125–144
Khalili N, Khabbaz MH (1998) A unique relationship for the determination of the shear strength of unsaturated soils. Géotechnique 48(5):681–687
Lloret-Cabot M, Wheeler SJ, Sánchez M (2017) A unified mechanical and retention model for saturated and unsaturated soil behavior. Acta Geotech 12:1–21
Lloret-Cabot M, Wheeler SJ, Jubert AP, Romero E, Sheng DC (2018) From saturated to unsaturated conditions and vice versa. Acta Geotech 13:15–37
Maâtouk A, Leroueil S, La Rochelle P (1995) Yielding and critical state of collapsible unsaturated silty soil\. Geotechnique 45(3):465–477
Plaster EJ (2009) Soil science and management. Delmar, Clifton Park
Pepper IL, Gerba CP, Gentry TJ, Maier RM (2009) Environmental microbiology, 2nd edn. Academic Press, New York
Rahardjo H, Ong BH, Leong EC (2004) Shear strength of a compacted residual soil from consolidated drained and constant water content triaxial tests. Can Geotech J 41(3):421–436. https://doi.org/10.1139/t03-093
Schnellmann R, Rahardjo H, Schneider HR (2014) Controlling parameter for unsaturated soil property functions: validated on the unsaturated shear strength. Can Geotech J 52:374–381. https://doi.org/10.1139/cgj-2013-0278
Sheng D, Fredlund DG, Gens A (2008) A new modelling approach for unsaturated soils using independent stress variables. Can Geotech J 45:511–534
Sheng D, Zhou A, Fredlund DG (2011) Shear strength criteria for unsaturated soils. Geotech Geol Eng 29:145–159
Sun DA, Sheng DC, Sloan SW (2007) Elastoplastic modelling of hydraulic and stress-strain behaviour of unsaturated compacted soils. Mech Mater 39(3):212–221
Sun DA, Sheng DC, Xu YF (2007) Collapse behaviour of unsaturated compacted soils with different initial densities. Can Geotech J 44(6):673–686
Sun WJ, Sun DA (2012) Coupled modelling of hydro-mechanical behavior of unsaturated compacted expansive soils. Int J Numer Analyt Methods Geomech 36:1002–1022
Sun DA, Sun WJ, Li X (2010) Effect of degree of saturation on mechanical behavior of unsaturated soils and its elastoplatic simulation. Comput Geotech 37:678–688
Terzaghi K (1936) The shear strength of saturated soils .In: Proceedings of the first international conference on soil mechanics and foundation engineering, Cambridge, MA, vol 1, pp 54–56
Toll DG (1990) A framework for unsaturated soil behavior. Géotechnique 40(1):31–44
Toll DG, Ong BH (2003) Critical state parameters for an unsaturated residual sandy clay. Géotechnique 53(1):93–103
Thu TM, Rahardjo H, Leong EC (2007) Critical state behavior of a compacted silt specimen. Soils Found 47(4):749–755
Thu TM, Rahardjo H, Leong EC (2008) Soil–water characteristic curve and consolidation behavior for a compacted silt. Can Geotech J 44:266–275
Vanapalli SK, Fredlund DG, Pufahl DE, Clifton AW (1996) Model for the prediction of shear strength with respect to soil suction. Can Geotech J 33:379–392
Vanapalli SK, Sillers WS, Fredlund MD (1998) The meaning and relevance of residual state to the unsaturated soil. In: Canadian geotechnical conference, October, pp 4–7
Wheeler SJ, Sivakumar V (1995) An elasto-plastic critical state framework for unsaturated soils. Geotechnique 45:35–53
Zhai Q, Rahardjo H (2012) Determination of soil–water characteristic curve variables. ComputGeotech 42:37–43
Zhai Q, Rahardjo H (2015) Estimation of permeability function from soil-water characteristic curve. Eng Geol 199(2015):148–156
Zhai Q, Rahardjo H, Satyanaga A (2017) Effects of residual suction and residual water content on the estimation of permeability. Geoderma 303:165–177
Acknowledgements
The first author would like to acknowledge the financial supports he received from the National Natural Science Foundation of China (No. 51878160), the National Key Research and development program of China (No. 2017YFC00703408) and the Fundamental Research Funds for the Central Universities (No. 2242018K41046).
Author information
Authors and Affiliations
Corresponding author
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Zhai, Q., Rahardjo, H., Satyanaga, A. et al. Estimation of unsaturated shear strength from soil–water characteristic curve. Acta Geotech. 14, 1977–1990 (2019). https://doi.org/10.1007/s11440-019-00785-y
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11440-019-00785-y