Geomechanics and Engineering

Techno-Press (테크노프레스)
권호 표지
DOI QR코드

DOI QR Code

Calculation model for the shear strength of unsaturated soil under nonlinear strength theory

  • Deng, Dongping (School of Civil Engineering, Central South University) ;
  • Wen, Shasha (School of Civil Engineering, Central South University) ;
  • Lu, Kuan (School of Civil Engineering, Central South University) ;
  • Li, Liang (School of Civil Engineering, Central South University)
  • Received : 2020.01.17
  • Accepted : 2020.03.16
  • Published : 2020.05.10
⟨ Previous Next ⟩

Abstract

The shear strength of unsaturated soils, a research hotspot in geotechnical engineering, has great guiding significance for geotechnical engineering design. Although kinds of calculation models for the shear strength of unsaturated soil have been put forward by predecessors, there is still need for new models to extensively consider the nonlinear variation of shear strength, particularly for the nonlinear effect of the net normal stress on the shear strength of unsaturated soil. Here, the shear strength of unsaturated soils is explored to study the nonlinear effects of net normal stress with the introduction of a general nonlinear Mohr-Coulomb (M-C) strength criterion, and the relationship between the matric suction (or suction stress) and degree of saturation (DOS) constructed by the soil-water characteristics curve (SWCC) of van Genuchten is also applied for unsaturated soil. Then, two calculation models (i.e., an envelope shell model and an effective stress model) are established for the shear strength of unsaturated soils under the nonlinear strength theory. In these two models, the curve of the shear strength of unsaturated soils versus the net normal stress exhibits a tendency to gently. Moreover, the proposed formulas have flexibility and convenience with five parameters (for the effective stress model) or six parameters (for the envelope shell model), which are from the M-C strength parameters of the saturated soil and fitting parameters of SWCC of van Genuchten. Thereafter, by comparison with the classical theory of the shear strength of unsaturated soils from some actual cases, the rationality and accuracy of the present models were verified.

Keywords

Acknowledgement

Supported by : National Natural Science Foundation of China, Natural Science Foundation of Hunan Province

The research described in this paper was financially supported by the National Natural Science Foundation of China (No. 51608541) and the Natural Science Foundation of Hunan Province, China (Grant No. 2019JJ50772).

References

  1. Al-Aqtash, U. and Bandini, P. (2015), "Prediction of unsaturated shear strength of an adobe soil from the soil water characteristic curve", Constr. Build. Mater., 98(11), 892-899. https://doi.org/10.1016/j.conbuildmat.2015.07.188.
  2. Al-Mahbashi, A.M., Elkady, T.Y. and Alrefeai, T.O. (2015), "Soil water characteristic curve and improvement in lime treated expansive soil", Geomech. Eng., 8(5), 687-696. https://doi.org/10.12989/gae.2015.8.5.687.
  3. Baker, R. (2004), "Nonlinear mohr envelopes based on triaxial data", J. Geotech. Geoenviron. Eng., 130(5), 498-506. https://doi.org/ 10.1061/(ASCE) 1090-0241(2004)130:5(498).
  4. Bao, C.G., Gong, B. and Zhan, L. (1998), "Properties of unsaturated soils and slope stability of expansive soil", Proceedings of the 2nd International Conference on Unsaturated Soils, Beijing, China, August.
  5. Bao, G.B., Li, H., Zhang, Y., Zhang, W.Y. and Jiang, N.S. (2018), "Experimental study on soil water characteristic curve of unsaturated loess in Xining area", IOP Conf. Ser. Earth Environ. Sci., 189(5), 052045.
  6. Bi, J., Chen, W.W., Dai, P.F. and Lin, G.C. (2018), "Influence of correction factor on fitting parameters of various types of Van Genuchten model", Rock Soil Mech., 39(4), 155-163. https://doi.org/10.16285/j.rsm.2016.1170.
  7. Bishop, A.W. (1959), "The principle of effective stress", Tecnisk Ukeblad, 39, 859-863.
  8. Bishop, A.W. and Blight, G. (1963), "Some aspects of effective stress in saturated and partly saturated soils", Geotechnique, 13(3), 177-197. https://doi.org/10.1680/geot.1963.13.3.177.
  9. Burdine, N.T. (1953), "Relative permeability calculations from pore size distribution data", J. Petrol. Technol., 5(3), 71-78. https://doi.org/10.2118/225-G.
  10. Chiorean, V.F. (2017), "Determination of matric suction and saturation degree for unsaturated soils, comparative study - numerical method versus analytical method", IOP Conf. Ser. Mater. Sci. Eng., 245(10), 32-74. https://doi.org/10.1088/1757-899X/245/3/032074.
  11. Deng, D.P. and Li, L. (2019a), "Failure modes and a calculation method for a stability analysis on a layered slope with a focus on interlayer sliding", Arab. J. Geosci., 12(6), 182. https://doi.org/10.1007/s12517-019-4308-1.
  12. Deng, D.P. and Li, L. (2019b), "Limit equilibrium analysis of slope stability with coupling nonlinear strength criterion and double-strength reduction technique", Int. J. Geomech., 19(6), 04019052. https://doi.org/10.1061/(ASCE)GM.1943-5622.0001431.
  13. Deng, D.P., Li, L. and Zhao, L.H. (2019a), "Stability analysis of slopes under groundwater seepage and application of charts for optimization of drainage design", Geomech. Eng., 17(2), 181-194. https://doi.org/10.12989/gae.2019.17.2.181.
  14. Deng, D.P., Li, L. and Zhao, L.H. (2019b), "Stability analysis of a layered slope with failure mechanism of a composite slip surface", Int. J. Geomech., 19(6), 04019050. https://doi.org/10.1061/(ASCE)GM.1943-5622.0001417.
  15. Deng, D.P., Li, L. and Zhao, L.H. (2019c), "Stability analysis of slopes reinforced with anchor cables and optimal design of anchor cable parameters", Eur. J. Environ. Civ. Eng., 1-16. https://doi.org/10.1080/19648189.2019.1631216.
  16. Deng, D.P., Lu, K. and Li, L. (2019), "LE analysis on unsaturated slope stability with introduction of nonlinearity of soil strength", Geomech. Eng., 19(2), 179-191. https://doi.org/10.12989/gae.2019.19.2.179.
  17. Deng, D.P., Zhao, L.H. and Li, L. (2015), "Limit equilibrium slope stability analysis using the nonlinear strength failure criterion", Can. Geotech. J., 52(5), 563-576. https://doi.org/10.1139/cgj-2014-0111.
  18. Estabragh, A.R. and Javadi, A.A. (2012), "Effect of suction on volume change and shear behaviour of an overconsolidated unsaturated silty soil", Geomech. Eng., 4(1), 55-65. https://doi.org/10.12989/gae.2012.4.1.055.
  19. Fredlund, D.G. (1995), "The stability of slopes with negative pore-water pressures", Proceedings of the the Ian Boyd Donald Symposium on Modern Developments in Geomechanics, Melbourne, Australia, June.
  20. Fredlund, D.G., Morgenstern, N.R. and Widger, R.A. (1978), "The shear strength of unsaturated soils", Can. Geotech. J., 15(3), 313-321. https://doi.org/10.1139/t78-029.
  21. Fredlund, D.G. and Xing, A. (1994), "Equations for the soil-water characteristic curve", Can. Geotech. J., 31(4), 521-532. https://doi.org/10.1139/t94-061.
  22. Hoyos, L.R., Velosa, C.L. and Puppala, A.J. (2014), "Residual shear strength of unsaturated soils via suction-controlled ring shear testing", Eng. Geol., 172(4), 1-11. https://doi.org/10.1016/j.enggeo.2014.01.001.
  23. Houston, S.L., Perez-Garcia, N. and Houston, W.N. (2008), "Shear strength and shear-induced volume change behavior of unsaturated soils from a triaxial test program", J. Geotech. Geoenviron. Eng., 134(11), 1619-1632. https://doi.org/10.1061/(ASC E)1090-0241(2008)134:11(1619).
  24. Johari, A., Hooshmand, N.A. and Mousavi, S. (2018), "Probabilistic model of unsaturated slope stability considering the uncertainties of soil-water characteristic curve", Sci. Iran., 25(4), 2039-2050. https://doi.org/10.24200/sci.2017.4202.
  25. Jokar, M.H. and Mirasi, S. (2018), "Using adaptive neuro-fuzzy inference system for modeling unsaturated soils shear strength", Soft Comput., 22(8), 4493-4510. https://doi.org/10.1007/s00500-017-2778-1.
  26. Kankanamge, L., Jotisankasa, A., Hunsachainan, N. and Kulathilaka, A. (2018), "Unsaturated shear strength of a Sri Lankan residual soil from a landslide-prone slope and its relationship with soil-water retention curve", Int. J. Geosynth. Ground Eng., 4(7), 20. https://doi.org/10.1007/s40891-018-0137-7.
  27. Khalili, N. and Khabbaz, M.H. (1998), "A unique relationship for $\chi$ for the determination of the shear strength of unsaturated soils", Geotechnique, 48(5), 681-687. https://doi.org/10.1680/geot.52.1.76.40832.
  28. Konrad, J.M. and Lebeau, M. (2015), "Capillary-based effective stress formulation for predicting shear strength of unsaturated soils", Can. Geotech. J., 52(12), 2067-2076. https://doi.org/10.1139/cgj-2014-0300.
  29. Lee, I.M., Sung, S.G. and Cho, G.C. (2005), "Effect of stress state on the unsaturated shear strength of a weathered granite", Can. Geotech. J., 42(2), 624-631. https://doi.org/10.1139/t04-091.
  30. Likos, W., Wayllace, A., Godt, J. and Lu, N. (2010), "Modified direct shear apparatus for unsaturated sands at low suction and stress", Geotech. Test. J., 33(4), 286-298. https://doi.org/10.1520/GTJ102927.
  31. Lin, H.D., Wang, C.C. and Wang, X.H. (2018), "A simplified method to estimate the total cohesion of unsaturated soil using an UC test", Geomech. Eng., 16(6), 599-608. https://doi.org/10.12989/gae.2018.16.6.599.
  32. Lu, N., Godt, J. and Wu, D. (2010), "A closed form equation for effective stress in unsaturated soil", Water Resour. Res., 46(5), W05515. https://doi.org/10.1029/2009WR008646.
  33. Lu, N. and Likos, W.J. (2004), Unsaturated Soil Mechanics, John Wiley & Sons, Inc., Hoboken, New Jersey, U.S.A.
  34. Lu, N. and Likos, W.J. (2006), "Suction stress characteristic curve for unsaturated soil", J. Geotech. Geoenviron. Eng., 132(2), 131-142. https://doi.org/10.1061/(ASCE)1090-0241(2006)132:2(131).
  35. Mualem, Y. (1976), "A new model for predicting the hydraulic conductivity of unsaturated porous media", Water Resour. Res., 12(3), 513-522. https://doi.org/10.1029/WR012i003p00513.
  36. Naghadeh, R.A. and Toker, N.K. (2019), "Exponential equation for predicting shear strength envelope of unsaturated soils", Int. J. Geomech., 19(7), 04019061. https://doi.org/10.1061/(ASCE)GM.1943-5622.0001435.
  37. Oh, W. and Vanapalli, S. (2018), "Undrained shear strength of unsaturated soils under zero or low confining pressures in the vadose zone", Vadose Zone J., 17(1). https://doi.org/10.2136/vzj2018.01.0024.
  38. Patil, U.D., Puppala, A.J., Hoyos, L.R. and Pedarla, A. (2017), "Modeling critical-state shear strength behavior of compacted silty sand via suction-controlled triaxial testing", Eng. Geol., 231(12), 21-33. https://doi.org/10.1016/j.enggeo.2017.10.011.
  39. Pedrotti, M. and Tarantino, A. (2018), "Effective stresses for unsaturated states stemming from clay microstructure", Geomech. Energy Environ., 15(9), 74-84. https://doi.org/10.1016/j.gete.2018.03.003.
  40. Pham, H.Q. and Fredlund, D.G. (2005), "A volume-mass constitutive model for unsaturated soils in terms of two independent stress state variables", Proceedings of the 58th Canadian Geotechnical Conference and the 6th Joint CGS and IAH-CNC Groundwater Specialty Conference, Saskatoon, Canada.
  41. Roopnarine, R., Eudoxie, G. and Gay, D. (2014), "Estimation of soil strength using the adsorption soil-water characteristic curve", Caribb. J. Earth Sci., 47(9): 1-8.
  42. Schnellmann, R., Rahardjo, H. and Schneider, H.R. (2013), "Unsaturated shear strength of a silty sand", Eng. Geol., 162(7), 88-96. https://doi.org/10.1016/j.enggeo.2013. 05.011.
  43. Schnellmann, R., Rahardjo, H. and Schneider, H.R. (2014), "Controlling parameter for unsaturated soil property functions: validated on the unsaturated shear strength", Can. Geotech. J., 52(3), 374-381. https://doi.org/10.1139/cgj-2013-0278.
  44. Sheng, D., Zhou, A. and Fredlund, D.G. (2011), "Shear strength criteria for unsaturated soils", Geotech. Geol. Eng., 29(2), 145-159. https://doi.org/10.1007/s10706-009-9276-x.
  45. Tarantino, A. (2007), "A possible critical state framework for unsaturated compacted soils", Geotechnique, 57(4), 385-389. https://doi.org/10.1680/geot.2007.57.4.385.
  46. Terzaghi, K. (1943). Theoretical Soil Mechanics, John Wiley & Sons.
  47. Vanapalli, S., Fredlund, D.G., Pufahl, D.E. and Clifton, A.W. (1996), "Model for the prediction of shear strength with respect to soil suction", Can. Geotech. J., 33(3), 379-392. https://doi.org/10.1139/t96-060.
  48. Van Genuchten, M.T. (1980), "A closed form equation for predicting the hydraulic conductivity of unsaturated soils", Soil Sci. Soc. Am. J., 44(5), 892-898. https://doi.org/10.2136/sssaj1980.03615995004400050002x
  49. Vilar, O.M. (2006), "A simplified procedure to estimate the shear strength envelope of unsaturated soils", Can. Geotech. J., 43(10), 1088-1095. https://doi.org/10.1139/t06-055.
  50. Wang, J.P., Hu, N., François, B. and Lambert, P. (2017), "Estimating water retention curves and strength properties of unsaturated sandy soils from basic soil gradation parameters", Water Resour. Res., 53(7), 6069-6088. https://doi.org/10.1002/2017WR020411.
  51. Xu, Y. and Cao, L. (2015), "Fractal representation for effective stress of unsaturated soils", Int. J. Geomech., 15(6), 04014098. https://doi.org/10.1061/(ASCE)GM.1943-5622.0000446.
  52. Zhai, Q., Rahardjo, H., Satyanaga, A. and Dai, G. (2019), "Estimation of unsaturated shear strength from soil water characteristic curve", Acta Geotech., 14(3), 1977-1990. https://doi.org/10.1007/s11440-019-00785-y.
  53. Zhang, L.L., Fredlund, D.G., Fredlund, M.D. and Wilson, G.W. (2014), "Modeling the unsaturated soil zone in slope stability analysis", Can. Geotech. J., 51(12), 1384-1398. https://doi.org/10.1139/cgj-2013-0394.
  54. Zhao, H.F., Zhang, L.M. and Fredlund, D.G. (2013), "Bimodal shear-strength behavior of unsaturated coarse-grained soils", J. Geotech. Geoenviron. Eng., 139(12), 2070-2081. https://doi.org/10.1061/(ASCE)GT.1943-5606.0000937.
  55. Zhou, B.C., Kong, L.W., Chen, W., Bai, H. and Li, X.W. (2010), "Analysis of characteristic parameters of soil-water characteristic curve (SWCC) and unsaturated shear strength prediction of jingmen expansive soil", Chin. J. Rock Mech. Eng., 29(5), 1052-1059.
  56. Zhou, W.H., Xu, X. and Garg, A. (2016), "Measurement of unsaturated shear strength parameters of silty sand and its correlation with unconfined compressive strength", Measurement, 93(9), 351-358. https://doi.org/10.1016/j.measurement.2016.07.049.

Cited by

  1. Water retention behaviour of tailings in unsaturated conditions vol.26, pp.2, 2020, https://doi.org/10.12989/gae.2021.26.2.117