The durability of the mechanical improvements brought by lime once the involved earth structures are exposed to long-term hydraulic conditions (long-term water contact and water circulation) is still under discussion. This paper aims at assessing i) the impact of such hydraulic conditions on the mechanical shear strength of a lime-treated silty soil, and ii) the effect of initial conditions (lime content and compaction conditions) on the lime treatment durability. The results showed that water contact leads to a significant decrease in shear strength. The results also indicated that the mechanical performance of soils exposed to water circulation is highly related to the quantity of water passing through the soil specimens and hence to the permeability of the soils: the lower the permeability, the better the durability. Futhermore, it has been observed that a lime content higher than the lime modification optimum (LMO) enables a better homogeneity of the treatment, giving rise to a longer resistance to water circulation.