11th IAEG Asian Regional Conference (ARC-11)

Clay-rich soils are widespread throughout the globe. Their mechanical properties can be deeply affected by the chemical composition of the pore fluid. As an example, Fig. 1a shows the residual friction angle evaluated on specimens of an illitic soil of marine origin, in equilibrium with the natural pore fluid, with distilled water or with two different salt solutions at different concentrations. In loessic soils too, which can contain up to 30% of clay (mainly illite), the magnitude of the chemomechanical effects has been shown to be noticeable (Fig. 1b). Several Authors (Scaringi, 2016) hypothesized connections between changes in pore fluid chemistry and activity of some types of landslides in clay soils. In a slow earthflow in a marine clay formation, Di Maio et al. (2015) showed that the pore ion concentration can decrease significantly from the depth towards the ground surface (Fig. 1c). Thus, different parts of the landslide shear zone may exhibit different values of shear strength parameters. Natural and anthropic processes (e.g. exposure to rain water, irrigation water, freshwater from confining aquifers) can cause the concentration to decrease further over time, leading to further weakening which can produce shear displacements (Di Maio and Scaringi, 2016). On the other hand, an increase of pore solution concentration, e.g. through ion diffusion from salt piles (Di Maio et al., 2016; 2017) can produce strength increase (as in Fig. 1a). The role of chemo-mechanical coupling in the initiation and movement of landslides in clay soils should be evaluated explicitly, as it can be fundamental for a correct assessment and management of the landslide risk. Furthermore, applications of the chemomechanical concepts can lead to innovative and environmentfriendly solutions of landslide stabilization, based, for instance, on engineered modifications of the clay behavior driven through the pore fluid chemistry.