A water retention model for compacted clays subjected to salinization and desalinization processes

Giulia Scelsi,Guido Musso,Gabriele Della Vecchia,R Cardoso,C Jommi,E Romero

doi:10.1051/e3sconf/202019502011

Giulia Scelsi, Guido Musso + Show 4 more

Open Access

https://doi.org/10.1051/e3sconf/202019502011

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Abstract

Environmental actions are known to induce relevant effects on the fabric of compacted active clays, which are successfully described by adopting a double porosity framework. In particular, the role of aggregate deformation has been recognized as fundamental to interpret the water retention behavior and the transport properties. These aspects are particularly relevant in the context of clay liners, being the material cast in place in unsaturated conditions and subjected to wetting process by pore fluids characterized by a chemical composition that is different from the one of compaction. Experimental data evidence that the water retention properties of active clays evolve as a function of pore water chemistry, since for a given matric suction the mass of stored water changes with water salinity. In this paper, a double porosity water retention model is proposed, capable of reproducing the variation of matric suction with water content accounting for the salinity of pore fluid. The role of salinity changes is accounted for by a suitable evolution law for aggregate deformation, which in turn affects the inter-aggregate porosity and thus the storage properties of the material.

Highlights

Pore fluid composition strongly influences the hydromechanical behaviour of compacted active clays and its appropriate modelling is crucial for geo-environmental applications, such as waste containment barriers and cutoff walls
The interaction between particles of active clays is substantially ruled by environmental variables such as the water content and the chemical composition of the pore water
The fabric of these soils is by no means a fixed soil property, as testified by the experimental evidences about its evolution with water content, and with the salinity and the dielectric constant of pore fluid

Summary

Introduction

Pore fluid composition strongly influences the hydromechanical behaviour of compacted active clays and its appropriate modelling is crucial for geo-environmental applications, such as waste containment barriers and cutoff walls. Compacted clays are characterized by a structure composed of aggregates, and two pore categories do exist: micropores within the clay aggregates and macropores between the aggregates This doublestructure arrangement evolves upon chemical changes, as testified by several experimental observations [1,2,3]. Being the role of microfabric variations well recognized in terms of water retention behaviour [4,5,6], a relevant role of pore fluid composition on storage properties of clays is anticipated. The model stems from the proposal of [6], which considers the evolution of the retention properties related to changes in intra and inter-aggregate void ratio. The original model, limited to distilled water as saturating fluid, is here enhanced introducing a suitable law capable of describing the evolution of the intra-aggregate void ratio with osmotic suction. The evolution law relies on the microstructural evidences discussed in [1]

The retention model for active clays permeated with distilled water

Modelling the effects of pore water salinity on the water retention curve

Karnataka clay

MX-80 bentonite

Findings

Conclusions and discussion