The hysteretic response of a shallow pyroclastic deposit

In the last decades, in Campania (southern Italy), steep slopes mantled by loose air-fall pyroclastic soils have been the seat of shallow, fast, rainfall-induced landslides. The occurrence of such events has been the result of the combination of critical rainstorms and of unfavourable initial conditions determined by antecedent infiltration, evaporation, and drainage processes. In order to understand the nature of the phenomena at hand and to clarify the role of all influencing factors, an automatic monitoring station has been installed in an area already subject to a recent killer flowslide (December, 1999). The paper reports data collected in 2011 about volumetric water content and suction (used to investigate the soil water retention features) and rainfall depth and temperature (providing the boundary conditions). In particular, the installation at the same depths of tensiometers and time domain reflectometry (TDR) sensors allowed us to recognise the hysteretic nature of the wetting and drying soil response to weather forcing and its influence on the slope stability conditions. The data reported in the paper are freely available at https://doi.org/10.5281/zenodo.4281166 (Comegna et al., 2020)

Conceptual hydrological modeling of the soil-bedrock interface at the bottom of the pyroclastic cover of Cervinara (Italy)

On the basis of the data collected by a monitoring station, a simplified mathematical model of the hydrological behavior of the layered pyroclastic cover of the slope of Cervinara (southern Apennines) has been developed. The model considers a single homogeneous soil layer, for which effective hydraulic characteristic curves have been defined. The top boundary condition accounts for the effects of evapotranspiration. The bottom boundary condition conceptually simulates, by means of a linear reservoir model, the hypothesized effects, on the soil water potential at the soil-bedrock interface, of the fluctuations of the water table of an ephemeral aquifer stored in the underlying fractured limestone. Despite its simplifying assumptions, the model satisfactorily reproduces the observed soil water potential at all the monitored depths. The obtained results indicate that even the highest rainfall intensity can pass through the highly conductive unsaturated soil cover, and leak through the fractured bedrock. Only when the water level in the underlying aquifer is high, as it happens after long lasting periods of rainfall, the establishment of the vertical water potential gradients, needed for the leakage of high infiltration peaks, leads to soil saturation at the bottom of the cover. Such a picture provides a possible interpretation of the triggering mechanism of the landside occurred in 1999 along the slope

Analisi del meccanismo di rottura in un rilevato autostradale fondato su un versante marnoso

La pavimentazione di un tratto di rilevato autostradale dell’A24 ricadente nel comune di Roviano (RM), fondato su un pendio marnoso-arenaceo, è stata interessata dal 1988 da continui fenomeni di avvallamento. I dati inclinometrici a disposizione hanno evidenziato che tale spostamento è il risultato di movimenti lenti sviluppatisi lungo superfici di rottura interne sia al rilevato sia ai terreni di fondazione. La nota descrive i principali caratteri cinematici del fenomeno evidenziati dal monitoraggio ed i risultati di alcune analisi finalizzate alla comprensione del meccanismo di rottura osservato

Riflessioni sulla cinematica di una grande colata attiva della valle del Basento

La nota riporta alcune considerazioni sul meccanismo di spostamento di una grande e lenta colata attiva della valle del fiume Basento, in Basilicata. Le principali caratteristiche cinematiche sono: uniformità di spostamento nelle sezioni trasversali del canale, velocità sensibilmente decrescente da monte verso valle, modeste variazioni stagionali di velocità. Tra le potenziali cause di spostamento, qui si esamina il possibile ruolo dell’erosione al piede esercitata dal corso d’acqua con l’ausilio di analisi numeriche 2D basate su metodi dell’equilibrio limite e agli elementi finiti

Analisi dei cinematismi post rottura meteo-indotti in un rilevato stradale fondato su un versante marnoso

Un tratto di rilevato dell’Autostrada A24 Roma-L’Aquila-Teramo, realizzato lungo una porzione della dorsale appenninica laziale posta tra i comuni di Roviano (RM) ed Arsoli (RM), è stato interessato a partire dalla fine degli anni ‘80 da continui fenomeni di avvallamento. I dati inclinometrici a disposizione hanno evidenziato che tali dissesti sono il risultato di un meccanismo di rottura che ha interessato non solo il rilevato ma anche il versante marnoso-arenaceo su cui esso è fondato. Avendo il monitoraggio messo in luce una variabilità stagionale delle velocità di spostamento, è stato sviluppato un modello semplificato finalizzato a ricostruire la cinematica meteo-indotta del fenomeno portando in conto le forzanti atmosferiche che regolano il processo. La nota descrive i principali risultati di tali analisi

Gut Microbiota Features in Young Children With Autism Spectrum Disorders

Proliferation and/or depletion of clusters of specific bacteria regulate intestinal functions and may interfere with neuro-immune communication and behavior in patients with autism spectrum disorder (ASD). Consistently, qualitative and quantitative alteration of bacterial metabolites may functionally affect ASD pathophysiology. Up to date, age-restricted cohort studies, that may potentially help to identify specific microbial signatures in ASD, are lacking. We investigated the gut microbiota (GM) structure and fecal short chain fatty acids (SCFAs) levels in a cohort of young children (2–4 years of age) with ASD, with respect to age-matched neurotypical healthy controls. Strong increase of Bacteroidetes and Proteobacteria and decrease of Actinobacteria was observed in these patients. Among the 91 OTUs whose relative abundance was altered in ASD patients, we observed a striking depletion of Bifidobacterium longum, one of the dominant bacteria in infant GM and, conversely, an increase of Faecalibacterium prausnitzii, a late colonizer of healthy human gut and a major butyrate producer. High levels of F. prausnitzii were associated to increase of fecal butyrate levels within normal range, and over representation of KEGG functions related to butyrate production in ASD patients. Here we report unbalance of GM structure with a shift in colonization by gut beneficial bacterial species in ASD patients as off early childhood