An insight into the water retention properties of compacted clayey soils

TLDR

Experimental data from different testing methodologies on compacted clayey soils with a dominant bimodal pore size distribution are presented and analysed to provide a comprehensive picture of aggregated fabric evolution along hydraulic and mechanical paths. The study investigates how aggregated fabric evolution affects the water retention properties of compacted soils and proposes a new model that links intra‑aggregate pore volume to water content. Fabric changes are examined via mercury intrusion porosimetry and environmental scanning electron microscopy, and the model incorporates air entry and occlusion values that depend on aggregate swelling, shrinking, and void ratio. The model accurately tracks hydraulic state evolution across soils and reveals coupling between intra‑aggregate and inter‑aggregate pores in water retention.

Abstract

Experimental data from different testing methodologies on different compacted clayey soils, with dominant bimodal pore size distribution, are presented and analysed, to provide a comprehensive picture of the evolution of the aggregated fabric along hydraulic and mechanical paths. Fabric changes are analysed both from the porous network viewpoint, by means of careful mercury intrusion porosimetry investigation, and from the soil skeleton viewpoint, by quantifying swelling and shrinkage of the aggregates in an environmental scanning electron microscopy study. The consequences of the aggregated fabric evolution on the water retention properties of compacted soils are analysed and discussed. A new model for water retention domain is proposed, which introduces a dependence of the intra-aggregate pore volume on water content. The model succeeds in tracking correctly the evolution of the hydraulic state of the different soils investigated along generalised hydromechanical paths. The proposed approach brings to light coupling between intra-aggregate and inter-aggregate pores in the retention properties of compacted clayey soils. Dependence of the air entry and the air occlusion values on swelling and shrinking of aggregates, besides void ratio, is introduced and discussed.