Effects of repeated hydraulic loads on microstructure and hydraulic behaviour of a compacted clayey silt

Arash Azizi*, Guido Musso, Cristina Jommi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Soils used in earth construction projects are mostly unsaturated, and they undergo frequent drying–wetting cycles (repeated hydraulic loads) due to changes in climatic conditions or variations of the ground water level, particularly at shallow depths. After compaction, changes in water content can significantly influence the hydromechanical response of the construction material, which therefore must be assessed for repeated hydraulic loads. This research investigates the effect of such loads on the microstructure and hydraulic behaviour of a silty soil, typically used in the construction of embankments and dykes, with the aim of providing a better understanding of the consequences of drying–wetting cycles on the response of the material over time. Experimental tests were performed to study the impact of drying–wetting cycles on the water retention, hydraulic conductivity, and fabric of compacted specimens. Fabric changes are documented to take place even without significant volumetric strains, promoting an irreversible increase in the hydraulic conductivity and a reduction in the capacity to retain water compared to the as-compacted soil. The fabric changes are interpreted and quantified by means of a hydromechanical model, which accounts for the evolving pore-size distribution at different structural levels. The proposed model reproduces quite well the microstructural observations, together with the evolution of the water retention behaviour and hydraulic conductivity.

Original languageEnglish
Pages (from-to)100-114
Number of pages15
JournalCanadian Geotechnical Journal
Issue number1
Early online date25 Mar 2019
Publication statusPublished - 1 Jan 2020


  • Compacted silt
  • Drying-wetting cycle
  • Hydraulic conductivity
  • Hydromechanical model
  • Microstructure
  • Water retention


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