Abstract
As the rise in pore water pressure is one of the main factors in triggering landslides, the understanding of groundwater processes taking place at the hillslope scale is a crucial issue in slope stability analysis. However, identifying flow-paths travelled by water molecules from their infiltration is still a complex task. Hydrochemistry is recognized as a powerful tool that can help to gain useful hydrogeological information and has gradually become increasingly used in addition to conventional study methods. This manuscript presents a comprehensive geochemical investigation consisting of leaching tests and quantitative mineralogical analyses on soil samples, chemical analyses on groundwater samples and modelling. Our results highlighted the usefulness of coupling, even in hydrogeological studies focusing on landslides, geochemical surveys on both water and the soil matrix to constrain the interactions between host-rocks and groundwater. Moreover, it demonstrated that kinetic-based geochemical models, if properly calibrated on leaching tests, can provide valuable information on groundwater dynamics, allowing us to elucidate water-mixing processes beneath the soil surface.
Highlights
The chemical composition of groundwater represents a signature of the hydrogeological processes taking place beneath the soil surface
The same authors took the examples of several cases from the French Alps, in which hydrogeochemical features provided evidence of external recharge areas (Super Sauze landslide, [4]), water reservoir characteristics (La Clapiere landslide, [5]), chemical changes related to mechanical stresses (Le Séchilienne landslide, [6] and La Clapiere landslide, [7])
Modelling efforts are focused to simulate the interaction between meteoric recharge and solid matrix that usually takes place in late summer-early autumn, when meteoric water infiltrates towards the main soil slip surface through open cracks and fissures, inducing quick rises in pore pressures and subsequent potential reactivation of landslides [12,13,14]
Summary
The chemical composition of groundwater represents a signature of the hydrogeological processes taking place beneath the soil surface Within the slopes, it is the result of the interaction between infiltrating water and subsurface soil (vadose zone) and subsequently groundwater and host soils and rocks (saturated zone). Modelling efforts are focused to simulate the interaction between meteoric recharge and solid matrix (made up of both disrupted rocks and weathered soils) that usually takes place in late summer-early autumn (i.e., the end of the low-flow period in the northern Italian Apennines), when meteoric water infiltrates towards the main soil slip surface through open cracks and fissures, inducing quick rises in pore pressures and subsequent potential reactivation of landslides [12,13,14]
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