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Morphological transitions for pore water and pore air during drying and wetting processes in partially saturated sand


Water retention characteristics are important for modeling the mechanical and hydraulic behavior of partially saturated sand. It is well known that the soil water characteristic curve shows hysteresis during drying and wetting processes. For a better understanding of the water retention characteristics of partially saturated soil, a microscopic investigation of the morphological transitions for the pore water phase and the pore air phase, such as volume distribution, spatial distribution and continuity during drying and wetting processes, is crucial. In the present study, different water retention states of a partially saturated sand were visualized during water retention tests using microfocus X-ray computed tomography (CT). The CT images obtained from the tests were segmented into the soil particle phase, the pore water phase and the pore air phase. Then, a series of image processing, erosion, dilation and cluster labeling was applied to the images in this order to quantify the cluster volume distributions, the number of clusters and the continuity of both the pore water phase and the pore air phase. The morphological transitions for the pore air phase and the pore water phase, subjected to decreasing and increasing degrees of saturation, were revealed using the results of the image processing, and then, the water retention states were characterized based on the morphologies for the two phases. The influence of the morphologies on the hysteresis was discussed.

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  1. 1.

    Andò E, Hall SA, Viggiani G, Desrues J, Bé-suelle P (2012) Grain-scale experimental investigation of localised deformation in sand: a discrete particle tracking approach. Acta Geotech 7(1):1–13

    Article  Google Scholar 

  2. 2.

    Bear J (1979) Hydraulics of groundwater. McGraw-Hill, New York, pp 190–224

    Google Scholar 

  3. 3.

    Blake TD, Haynes IM (1973) Contact-angle hysteresis. Prog Surf Membr Sci 6:125–138

    Article  Google Scholar 

  4. 4.

    Bruchon JF, Pereira JM, Vandamme M, Lenoir N, Delage P, Bornert M (2013) Full 3D investigation and characterization of capillary collapse of a loose partially saturated sand using X-ray CT. Granul Matter 15(6):783–800

    Article  Google Scholar 

  5. 5.

    Chiu DF, Ni XW, Zhang LS (2014) Effect of hydraulic hysteresis on shear strength of partially saturated clay and its prediction using a water retention surface. Eng Geol 173:66–73

    Article  Google Scholar 

  6. 6.

    De Souza EJ, Gap L, McCarthy TJ, Arzt E, Crosby AJ (2008) Effect of contact angle hysteresis on the measurement of capillary forces. Langmuir 24(4):1391–1396

    Article  Google Scholar 

  7. 7.

    Desrues J, Chambon R, Mokni M, Mazerolle F (1996) Void ratio evolution inside shear bands in triaxial sand specimens studied by computed tomography. Géotechnique 46(3):539–546

    Article  Google Scholar 

  8. 8.

    Feia S, Ghabezloo S, Bruchon JF, Sulem J, Canou J, Dupla JC (2014) Experimental evaluation of the pore-access size distribution of sands. Geotech Test J 37(4):613–620

    Article  Google Scholar 

  9. 9.

    Fredlund DG, Xing A, Fredlund MD, Barbour SL (1995) The relationship of the partially saturated soil shear strength to the soil–water characteristic curve. Can Geotech J 33(3):440–448

    Article  Google Scholar 

  10. 10.

    Gallage CPK, Uchimura T (2010) Effects of dry density and grain size distribution on soil-water characteristic curves of sandy soils. Soils Found 50(1):161–172

    Article  Google Scholar 

  11. 11.

    Gallipoli D, Wheeler S, Karstunen M (2003) Modelling the variation of degree of saturation in a deformable partially saturated soil. Géotechnique 53(1):105–112

    Article  Google Scholar 

  12. 12.

    Gvirtzman H, Magaritz M, Klein E, Nadler A (1983) A scanning electron microscopy study of water in soil. Transp Porous Media 2:83–93

    Google Scholar 

  13. 13.

    Haines WB (1930) Studies in the physical properties of soil—V: the hysteresis effect in capillary properties and the modes of water distribution associated therewith. J Agric Sci 20(1):97–116

    Article  Google Scholar 

  14. 14.

    Hamamoto S, Moldrup P, Kawamoto K, Sakaki T, Nishimura T, Komatsu T (2016) Pore network structure linked by X-ray CT to particle characteristics and transport parameters. Soils Found 56(4):676–690

    Article  Google Scholar 

  15. 15.

    Haralick RM, Sternberg SR, Zhuang X (1987) Image analysis using mathematical morphology. IEEE Trans Pattern Anal Mach Intell 9(4):532–550

    Article  Google Scholar 

  16. 16.

    Hashemi MA, Khaddour G, François B, Massart TJ, Salager S (2014) A tomographic imagery segmentation methodology for three phase geomaterials based on simultaneous region growing. Acta Geotech 9(5):831–846

    Article  Google Scholar 

  17. 17.

    Higo Y, Oka F, Kimoto S, Sanagawa T, Matsushima Y (2011) Study of strain localization and microstructural changes in partially saturated sand during triaxial tests using microfocus X-ray CT. Soils Found 51(1):95–111

    Article  Google Scholar 

  18. 18.

    Higo Y, Oka F, Sato T, Matsushima Y, Kimoto S (2013) Investigation of localized deformation in partially saturated sand under triaxial compression by microfocus X-ray CT with digital image correlation. Soils Found 53(2):181–198

    Article  Google Scholar 

  19. 19.

    Higo Y, Oka F, Morishita R, Matsushima Y, Yoshida T (2014) Trinarization of μX-ray CT images of partially saturated sand at different water retention states using a region growing method. Nucl Instrum Methods Phys Res B 324:63–69

    Article  Google Scholar 

  20. 20.

    Higo Y, Morishita R, Kido R, Khaddour G, Salager S (2015) Local water retention behavior of sand during drying and wetting process observed by micro X-ray tomography with trinarization. The 15th Asian regional conference on soil mechanics and geotechnical engineering. Jpn Geotech Soc Spec Publ 2(16):635–638

    Google Scholar 

  21. 21.

    Higo Y, Oka F, Morishita R, Matsushima Y (2015) Quantitative observation of strain localisation in a partially saturated triaxial specimen using microfocus X-ray CT with image analysis. In: Proceedings of the 10th international workshop on bifurcation and degradation in geomaterials, pp 325–330

  22. 22.

    Higo Y, Kido R, Takamura F, Fukushima Y (2018) Pore-scale investigations of partially water-saturated granular soil. Mech Res Commun 94:1–7

    Article  Google Scholar 

  23. 23.

    Khaddour G, Salager S, Higo Y, Andò E, Desrues J (2015) Discrete analysis of water phase evolution within unsaturated soil. In: Proceedings of the 2nd international conference on tomography of materials and structures, 30th June–3rd July 2015, Quebec, Canada

  24. 24.

    Khaddour G, Riedel I, Ando E, Charrier P, Besuelle P, Desrues J, Viggiani G, Salager S (2018) Grain-scale characterization of water retention behaviour of sand using X-ray CT. Acta Geotech 13:497–512

    Article  Google Scholar 

  25. 25.

    Kido R, Higo Y (2017) Evaluation of distribution of void ratio and degree of saturation in partially saturated triaxial sand specimen using micro X-ray tomography. Jpn Geotech Soc Spec Publ 5(2):22–27

    Google Scholar 

  26. 26.

    Kido R, Higo Y, Salager S (2017) Microscopic investigation of progressive changes of pore water distribution in shear band of unsaturated sand under triaxial compression. In: Proceedings of the 19th international conference on soil mechanics and geotechnical engineering, pp 1171–1174

  27. 27.

    Kido R, Higo Y (2019) Distribution changes of grain contacts and menisci in shear band during triaxial compression test for unsaturated sand. Jpn Geotech Soc Spec Publ 7(2):627–635

    Google Scholar 

  28. 28.

    Kim FH, Penumadu D, Hussey DS (2012) Water distribution variation in partially saturated granular materials using neutron imaging. J Geotech Geoenviron Eng 138(2):147–154

    Article  Google Scholar 

  29. 29.

    Kim FH, Penumadu D, Gregor J, Kardjilov N, Manke L (2013) High-resolution neutron and X-ray imaging of granular materials. J Geotech Geoenviron Eng 139(5):715–723

    Article  Google Scholar 

  30. 30.

    Kohgo Y, Nakano M, Miyazaki T (1993) Theoretical aspects of constitutive modelling for partially saturated soils. Soils Found 33(4):49–63

    Article  Google Scholar 

  31. 31.

    Lai Z, Chen Q (2019) Reconstructing granular particles from X-ray computed tomography using the TWS machine learning tool and the level set method. Acta Geotech 14:1–18

    Article  Google Scholar 

  32. 32.

    Manahiloh KN, Meehan CL (2017) Determining the soil water characteristic curve and interfacial contact angle from microstructural analysis of X-ray CT images. J Geotech Geoenviron Eng 143(8):1–11

    Article  Google Scholar 

  33. 33.

    Mašín D (2010) Predicting the dependency of a degree of saturation on void ratio and suction using effective stress principle for partially saturated soils. Int J Numer Anal Methods Geomech 34(1):73–90

    MATH  Google Scholar 

  34. 34.

    Moro F, Böhni H (2002) Ink-bottle effect in mercury intrusion porosimetry of cement-base materials. J Colloid Interface Sci 246:135–149

    Article  Google Scholar 

  35. 35.

    Mukunoki T, Miyata Y, Mikami K, Shiota E (2016) X-ray CT analysis of pore structure in sand. Solid Earth 7(3):929–942

    Article  Google Scholar 

  36. 36.

    Nguyen CD, Benahmed N, Andò E, Sibille L, Philippe P (2019) Experimental investigation of microstructural changes in soils eroded by suffusion using X-ray tomography. Acta Geotech 14:749–765

    Article  Google Scholar 

  37. 37.

    Oda M, Takemura T, Takahashi M (2004) Microstructure in shear band observed by microfocus X-ray computed tomography. Géotechnique 54(8):539–542

    Article  Google Scholar 

  38. 38.

    Prapaharan S, Altschaeffl AG, Dempsey BJ (1985) Moisture curve of a compacted clay: mercury intrusion method. J Geotech Eng 111(9):1139–1143

    Article  Google Scholar 

  39. 39.

    Romero E, Gens A, Lloret A (1999) Water permeability, water retention and microstructure of unsaturated compacted Boom clay. Eng Geol 54(1–2):117–127

    Article  Google Scholar 

  40. 40.

    Romero E, Simms PH (2008) Microstructure investigation in unsaturated soils: a review with special attention to contribution of mercury intrusion porosimetry and environmental scanning electron microscopy. Geotech Geol Eng 26(6):705–727

    Article  Google Scholar 

  41. 41.

    Scheel M, Seemann R, Brinkmann M, Di Michiel M, Sheppard A, Breidenbach B, Herminghaus S (2008) Morphological clues to wet granular pile stability. Nat Mater 7:189–193

    Article  Google Scholar 

  42. 42.

    Sun D, Sun W, Xiang L (2010) Effect of degree of saturation on mechanical behaviour of unsaturated soils and its elastoplastic simulation. Comput Geotech 37:678–688

    Article  Google Scholar 

  43. 43.

    Vachaud G, Thony JL (1971) Hysteresis during infiltration and redistribution in a soil column at different initial water contents. Water Resour Res 7(1):111–127

    Article  Google Scholar 

  44. 44.

    Van Genuchten MT (1980) A closed-form equation for predicting the hydraulic conductivity of partially saturated soil. Soil Sci Soc Am J 44(5):892–898

    Article  Google Scholar 

  45. 45.

    Vanapalli SK, Nicotera MV, Sharma RS (2008) Axis translation and negative water column techniques for suction control. Geotech Geol Eng 26:645–660

    Article  Google Scholar 

  46. 46.

    Wang JP, Lambert P, De Kock T, Cnudde V, François B (2019) Investigation of the effect of specific interfacial area on strength of unsaturated granular materials by X-ray tomography. Acta Geotech 14:1545–1559

    Article  Google Scholar 

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This research was partly supported by grants given by Tec 21, the Obayashi Foundation, SPIRITS project of Kyoto University and the Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for JSPS Fellows [Subject No. 17J06250]. The authors gratefully acknowledge the support of Mr. Takanobu Ishimura (Maxnet Co., Ltd., Japan) who assisted us in performing the image analysis by using 3D image analysis software Avizo9.4.0 (FEI) in the present study.

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Correspondence to Yosuke Higo.

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Kido, R., Higo, Y., Takamura, F. et al. Morphological transitions for pore water and pore air during drying and wetting processes in partially saturated sand. Acta Geotech. 15, 1745–1761 (2020).

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  • Image processing
  • Microfocus X-ray CT
  • Morphology
  • Partially saturated sand
  • Water retention state
  • Water retention test