Geomechanics and Engineering

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Effect of degree of compaction & confining stress on instability behavior of unsaturated soil

  • Received : 2020.08.03
  • Accepted : 2022.06.06
  • Published : 2022.08.10
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Abstract

Geotechnical materials such as silt, fine sand, or coarse granular soils may be unstable under undrained shearing or during rainfall infiltration starting an unsaturated state. Some researches are available describing the instability of coarse granular soils in drained or undrained conditions. However, there is a need to investigate the instability mechanism of unsaturated silty soil considering the effect of degree of compaction and net confining stress under partially and fully drained conditions. The specimens in the current study are compacted at 65%, 75%, & 85% degree of compaction, confined at pressures of 60, 80 & 120 kPa, and tested in partially and fully drained conditions. The tests have been performed in two steps. In Step-I, the specimens were sheared in constant water content conditions (a type of partially drained test) to the maximum shear stress. In Step-II, shearing was carried in constant suction conditions (a type of fully undrained test) by keeping shear stress constant. At the start of Step-II, PWP was increased in steps to decrease matric suction (which was then kept constant) and start water infiltration. The test results showed that soil instability is affected much by variation in the degree of compaction and confining stresses. It is also observed that loose and medium dense soils are vulnerable to pre-failure instability i.e., instability occurs before reaching the failure state, whereas, instability in dense soils instigates together with the failure i.e., failure line (FL) and instability line (IL) are found to be unique.

Keywords

Acknowledgement

The Saitama University Japan and Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT) is gratefully acknowledged for research facilities and financial assistance

References

  1. Andrade, J.E., Ramos, A.M. and Lizcano, A. (2013), "Criterion for flow liquefaction instability", Acta Geotechnica, 8, 525-535. https://doi.org/10.1007/s11440-013-0223-x.
  2. ASTM D2487 (2011), Standard Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System), ASTM International.
  3. Chang, D.S., Zhang, L.M., Xu, Y. and Huang, R.Q. (2011), "Field testing of erodibility of two landslide dams triggered by the 12 May Wenchuan earthquake", Landslid., 8(3), 321-332. https://doi.org/10.1007/s10346-011-0256-x.
  4. Chen, M., Zhou, Z., Sleep, B., Kuang, X., Mingwei, L. and Shi, A. (2019), "Experimental study of water infiltration in unsaturated horizontal sand columns under various air confinement conditions", Geofluid., 2019, 4270358. https://doi.org/10.1155/2019/4270358.
  5. Chen, P., Wei, C., Liu, J. and Ma, T. (2013), "Strength theory model of unsaturated soils with suction stress concept", J. Appl. Math., 2013, Article ID 756854. https://doi.org/10.1155/2013/756854.
  6. Chu, J., Leong, W.K., Loke, W.L. and Wanatowski, D. (2011), "Instability of loose sand under drained conditions", J. Geotech. Geoenviron. Eng., 138, 207-216. https://doi.org/10.1061/(ASCE)GT.1943-5606.0000574.
  7. Chu, J., Leroueil, S. and Leong, W.K. (2003), "Unstable behaviour of sand and its implication for slope instability", Can. Geotech. J., 40(5), 873-885. https://doi.org/10.1139/t03-039.
  8. Chu, J. and Wanatowski, D. (2009), "Effect of loading mode on strain softening and instability behavior of sand in plane-strain tests", J. Geotech. Geoenviron. Eng., 135(1), 108-120. https://doi.org/10.1061/(ASCE)1090-0241(2009)135:1(108).
  9. Consoli, N.C., Da Silva Lopes, L., Consoli, B.S., Festugato, L., Di Sante, M., Fratalocchi, E. and Mazzieri, F. (2015), "Mohr-coulomb failure envelopes of lime-treated soils", Geotechnique, 65(10), 866-868. https://doi.org/10.1680/jgeot.15.D.001.
  10. Desai, C.S., Pradhan, S.K. and David, C. (2005), "Cyclic testing and constitutive modeling of saturated sand-concrete interfaces using the disturbed state concept", Int. J. Geomech., 5(4), 286-294. https://doi.org/10.1061/(ASCE)1532-3641(2005)5:4(286).
  11. Dong, Q., Xu, C., Cai, Y., Juang, H., Wang, J., Yang, Z. and Gu, C. (2016), "Drained instability in loose granular material", Int. J. Geomech., 16(2), 04015043. https://doi.org/10.1061/(ASCE)GM.1943-5622.0000524.
  12. Farooq, K., Rolando, O. and Ikuo, T. (2004), "Response of unsaturated sandy soils under constant shear stress drained condition", Soil. Found., 44(2), 1-13. http://doi.org/10.3208/sandf.44.2_1.
  13. Fredlund, D.G., Rahardjo, H. and Fredlund, M.D. (2012), Unsaturated Soil Mechanics in Engineering Practice, John Wiley & Sons, Inc.
  14. Gao, Y., Sun, D., Zhou, A. and Li, J. (2018), "Effect of stress state on soil-water retention and its application on the strength prediction", Geotechnique Lett., 8(4), 324-329. https://doi.org/10.1680/jgele.18.00159.
  15. Gao, Y., Li, Z., Sun, D. and Yu, H. (2021), "A simple method for predicting the hydraulic properties of unsaturated soils with different void ratios", Soil Tillage Res., 209, 104913. https://doi.org/10.1016/j.still.2020.104913.
  16. Gui, M.W. and Wu, Y.M. (2014), "Failure of soil under water infiltration condition", Eng. Geol., 181, 124-141. https://doi.org/10.1016/j.enggeo.2014.07.005.
  17. JGS 0527 (2020), Method for Triaxial Compression Test on Unsaturated Soils, Japanese Geotechnical Society Standard, 1-12.
  18. Jotisankasa, A., Coop, M. and Ridley, A. (2009), "The mechanical behaviour of an unsaturated compacted silty clay", Geotechnique, 59(5), 415-428. https://doi.org/10.1680/geot.2007.00060.
  19. 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.
  20. Labuz, J.F. and Zang, A. (2012), "Mohr-Coulomb failure criterion", Rock Mech. Rock Eng., 45(6), 975-979. https://doi.org/10.1007/s00603-012-0281-7.
  21. Lashkari, A. (2016), "Prediction of flow liquefaction instability of clean and silty sands", Acta Geotechnica, 11, 987-1014. https://doi.org/10.1007/s11440-015-0413-9.
  22. Leong, W., Chu, J. and Teh, C. (2000), "Liquefaction and instability of a granular fill material", Geotech. Test. J., 23(2), 178-192. https://doi.org/10.1520/GTJ11042J.
  23. Liu, J., Yang, C., Gan, J., Liu, Y., Wei, L. and Xie, Q. (2017), "Stability analysis of road embankment slope subjected to rainfall considering runoff-unsaturated seepage and unsaturated fluid-solid coupling", Int. J. Civil Eng., 15(6), 865-876. https://doi.org/10.1007/s40999-017-0194-7.
  24. Marinho, F.A.M. and Oliveira, O.M. (2012), "Unconfined shear strength of compacted unsaturated plastic soils", Proc. Inst. Civil Eng.: Geotech. Eng., 165(2), 97-106. https://doi.org/10.1680/geng10.00027.
  25. Meilani, I., Rahardjo, H. and Leong, E.C. (2005), "Pore-water pressure and water volume change of an unsaturated soil under infiltration conditions", Can. Geotech. J., 42(6), 1509-1531. https://doi.org/10.1139/t05-066.
  26. Melinda, F., Rahardjo, H., Han, K.K. and Leong, E.C. (2004), "Shear strength of compacted soil under infiltration condition", J. Geotech. Geoenviron. Eng., 130(8), 807-817. https://doi.org/10.1061/(ASCE)1090-0241(2004)130:8(807).
  27. Mirzaii, A., Yasrobi, S.S. and Hefzi, E. (2018), "Critical state behaviour of an unsaturated clayey sand along constant water content direct shear and triaxial loading conditions", Int. J. Geotech. Eng., 14(3), 286-294. https://doi.org/10.1080/19386362.2018.1438151.
  28. Monkul, M., Yamamuro, J. and Lade, P. (2011), "Failure, instability, and the second work increment in loose silty sand", Can. Geotech. J., 48, 943-955. https://doi.org/10.1139/t11-013.
  29. Mroz, Z., Boukpeti, N. and Drescher, A. (2003), "Constitutive model for static liquefaction", Int. J. Geomech., 3(2), 133-144. https://doi.org/10.1061/(ASCE)1532-3641(2003)3:2(133).
  30. Qi, S., Vanapalli, S.K., Yang, X., Zhou, J. and Lu, G. (2019), "Stability analysis of an unsaturated expansive soil slope subjected to rainfall infiltration", Geomech. Eng., 19(1), 1-9. https://doi.org/10.12989/gae.2019.19.1.001.
  31. Rahardjo, H., Kim, Y. and Satyanaga, A. (2019), "Role of unsaturated soil mechanics in geotechnical engineering", Int. J. Geo-Eng., 10(1), 1-23. https://doi.org/10.1186/s40703-019-0104-8.
  32. Rahman, M.M., Baki, M.A. and Lo, S.R. (2014), "Prediction of undrained monotonic and cyclic liquefaction behavior of sand with fines based on the equivalent granular state parameter", Int. J. Geomech., 14(2), 254-266. https://doi.org/10.1061/(ASCE)GM.1943-5622.0000316.
  33. Rasool, A.M. and Aziz, M. (2019), "Shear infiltration and constant water content tests on unsaturated soils", Geomech. Eng., 19(5), 435-445. https://doi.org/10.12989/gae.2019.19.5.435.
  34. Rasool, A.M. and Aziz, M. (2020), "Advanced triaxial tests on partially saturated soils under unconfined conditions", Int. J. Civil Eng., 18(10), 1139-1156. https://doi.org/10.1007/s40999-020-00530-7.
  35. Rasool, A.M. and Kuwano, J. (2018), "Influence of matric suction on instability of unsaturated silty soil in unconfined conditions", Int. J. GEOMATE, 14(42), 1-7. https://doi.org/10.21660/2018.42.7115.
  36. Rasool, A.M. and Kuwano, J. (2020a), "Shearing infiltration tests to study mechanical behavior and failure mechanism of shallow slopes", Iran. J. Sci. Technol.-Trans. Civil Eng., 45(2), 1089-1098. https://doi.org/10.1007/s40996-020-00403-y.
  37. Rasool, A.M. and Kuwano, J. (2020b), "Effect of constant loading on unsaturated soil under water infiltration conditions", Geomech. Eng., 20(3), 221-232. https://doi.org/10.12989/gae.2020.20.3.221.
  38. Rasool, A.M. and Kuwano, J. (2020c), "Effect of constant loading on unsaturated soil under water infiltration conditions", Geomech. Eng., 20(3), 221-232. https://doi.org/10.12989/GAE.2020.20.3.221.
  39. Rasool, A.M. and Kuwano, J. (2021), "Instability of unsaturated soils under constant deviatoric stress in drained conditions", Iran. J. Sci. Technol.-Tran. Civil Eng, 46(1), 419-434. https://doi.org/10.1007/s40996-021-00582-2.
  40. Rasool, A.M. and Kuwano, J. (2022), "Effect of wetting stress paths on mechanical behavior and instability of unsaturated soil in stress state space", Eur. J. Environ. Civil Eng., 1-20. https://doi.org/10.1080/19648189.2022.2025909.
  41. Rasool, A.M. and Kuwano, J. (2019), "Effect of water infiltration on the mechanical behaviour of unsaturated soil", E3S Web Conf., 92, 1-6. https://doi.org/10.1051/e3sconf/20199207002.
  42. Rasool, A.M., Kuwano, J. and Tachibana, S. (2015), "Behavior of compacted unsaturated soil in isotropic compression, cyclic and monotonic shear loading sequences in undrained condition", Deformation Characteristics of Geomaterials, January, 267-274. https://doi.org/10.3233/978-1-61499-601-9-267.
  43. Rasool, A.M., Kuwano, J. and Tachibana, S. (2020), "Experimental Study on the response of unsaturated silt due to change in drainage conditions during the triaxial test process", Geotech. Geolog. Eng., 38(2), 1707-1719. https://doi.org/10.1007/s10706-019-01125-3.
  44. Song, Y.S. and Hong, S. (2020), "Infiltration characteristics and hydraulic conductivity of weathered unsaturated soils", Geomech. Eng., 22(2), 153-163. https://doi.org/10.12989/gae.2020.22.2.153.
  45. Sun, W.C. (2013), "A unified method to predict diffuse and localized instabilities in sands", Geomech. Geoeng., 8(2), 65-75. https://doi.org/10.1080/17486025.2012.695403.
  46. Thu, T.M., Rahardjo, H. and Leong, E.C. (2006), "Shear Strength and Pore-water pressure characteristics during constant water content triaxial tests", J. Geotech. Geoenviron. Eng., 132(3), 411-419. https://doi.org/10.1061/(asce)1090-0241(2006)132:3(411).
  47. Yang, S.R., Lin, H.D. and Huang, W.H. (2012), "Variation of initial soil suction with compaction conditions for clayey soils", J. Mech., 28(3), 431-437. https://doi.org/10.1017/jmech.2012.52.
  48. Zhao, H.F. and Zhang, L.M. (2014), "Instability of saturated and unsaturated coarse granular soils", J. Geotech. Geoenviron. Eng., 140(1), 25-35. https://doi.org/10.1061/(ASCE)GT.1943-5606.0000976.
  49. Zhou, A., Huang, R. and Sheng, D. (2016), "Capillary water retention curve and shear strength of unsaturated soils", Can. Geotech. J., 53(6), 974-987. https://doi.org/10.1139/cgj-2015-0322.