A numerical inspection on the squeezing test in active clays

Squeezing tests are performed to obtain liquid samples from soil to characterise the chemical composition of the aqueous saline solution in its pores. However, the representativeness of the extract obtained from active clays has been debated, as a mixture of macrostructural and microstructural solutions is likely to be obtained. To analyse this question, given the complexity and the strong hydro-chemo-mechanical coupling of the processes that occur during a squeezing test, it is of interest to simulate the test using a conceptual model that is able to characterise the processes involved in active clays. This type of simulation is performed in the study, showing that the chemo-mechanical interaction between macrostructure and microstructure is unavoidable. However, in saturated soils with low dry densities, most of the extracted water is directly obtained from the macrostructure, and the extract can be considered representative of the macrostructural solution. With increasing dry density, the mixing increases, and the representativeness of the extract may be compromised. In unsaturated soil with a low water content and high dry density, an important mass exchange occurs between the macrostructure and microstructure. If the test is viable (i.e. sufficient solution volume can be obtained), the representativeness of the extract must be carefully evaluated.