Study of the Evolution of Active Earthflows through Field Monitoring and Geophysical Investigations

Active earthflows commonly exhibit seasonal movements controlled by rainfall, snowmelt, and in some cases atmospheric tides. Earthflow response to rainfall or snowmelt is often delayed, and in several cases, long periods of cumulated precipitation are required to trigger activation. Movement and activity of the earthflows are controlled by the water content of the involved materials. Pore-pressure fluctuations, driven by rainfall and/or atmospheric tides, in combination with soil properties and shear-surface roughness, directly influence the rate of earthflow movement. Moreover, changes in pore-water pressure near the basal slip surface, induced by earthflow material deformation, may play a role in damping acceleration. The aim of this work is to study the evolution of active earthflows. At first, we focused our attention on the solid-to-fluid transition of the material involved in earthflows, and we analyzed this aspect through laboratory tests (rheometric tests as Standard Creep Tests and Oscillatory Creep Tests), field monitoring and geophysical investigations (ReMi-MASW surveys and continuous ReMi measurements) in order to define different rheological state of the material (“fluid state” and “plastic state”). On the second hand, we studied the distribution of surface structures to characterize the short-term behavior of an active earthflow in southern Italy, and we reconstructed the 3D geometry (using HVSR acquisitions and ReMi-MASW surveys) of the earthflow in order to compute sediment discharge at the transition of kinematic zones. Finally, we used similar geophysical approach also to improve the knowledge of the seismic liquefaction phenomena including the possibility to define a priori which soils were potentially subject to liquefaction.