From Sliding to Flowing: Integrating Geotechnical, Mineralogical, and Rheological Controls on Earthflow Mobility

Earthflows are flow-like landslides involving fine-grained, clay-rich materials that exhibit complex kinematics, long-term activity, and alternating phases of slow movement and sudden acceleration. Although their flow-like behaviour is commonly attributed to distributed internal deformation and plastic rheology, the mechanisms governing the transition from solid-like sliding to fluid-like flowing remain poorly understood, particularly with respect to boundary conditions and material properties. This transition is critical, as it may lead to surging events associated with high mobility and significant hazard.
This study investigates the role of mineralogical, geotechnical, rheological, and geomorphological factors in controlling earthflow mobility and material fluidization. A set of representative earthflows located in the southern Apennines was selected, covering a wide range of geological settings and morphological characteristics. Laboratory analyses were conducted on samples collected from different sectors of the landslides, including grain size distribution, Atterberg limits, mechanical behaviour, quantitative mineralogical composition. Moreover, rheometrical analysis of the fine fractions under controlled shear conditions were also performed. These data were integrated with long-term geomorphological analyses based on satellite imagery and morphometric reconstructions of landslide geometry.
Earthflow behaviour was analysed using a one-dimensional framework based on a Herschel–Bulkley viscoplastic rheological model, aimed at reproducing internal kinematic compartmentalisation in relation to variable water content.
The influence of water content variations, as a function of rainfall-induced infiltration conditions, on rheological parameters and mechanical response was investigated. The results highlight strong correlations between plasticity, occurrence of expandable clay minerals, rheology, and mobility, emphasizing the key role of fine-grained materials in promoting solid–fluid transitions. 
By integrating multi disciplinary datasets, this work advances the understanding and prediction of earthflow fluidization and mobility-processes for which current forecasting capabilities remain notably limited.