Abstract
The modelling of the triggering mechanism of rainfall-induced landslides in slopes covered by pyroclastic soil (as the area surrounding Mount Vesuvius in Campania, Italy) requires the hydraulic characterization of soil in unsaturated conditions in order to analyse the slope response to rainfalls. In previous studies carried out on Campanian pyroclastic soils, the volumetric soil changes due to suction changes have been disregarded, being them negligible in soils characterized by low plasticity and low clay contents. However, a more accurate determination of the water retention curve (WRC) in terms of volumetric water content requires a correct estimation of the total soil volume, which is affected by the soil stress-state. The proper approach would require the estimation of both WRC in terms of gravimetric water content and the shrinkage curve (SC). In the present study, a relation between void ratio and suction was determined for a pyroclastic soil sampled at Mount Faito in Southern Italy. Therefore, a correction of the volumetric water content was carried out resulting in updated water retention curves. Here, the matric suction was the only factor affecting the stress-state of the soil.
Highlights
In the Campania region (Southern Italy), shallow landslides triggered by intense rainfall occur in sloping pyroclastic deposits generated by explosive eruptions of Mount Vesuvius [1]
A more accurate determination of the water retention curve (WRC) in terms of volumetric water content requires a correct estimation of the total soil volume, which is affected by the soil stress-state
The WRCs in terms of gravimetric water content measured on these specimens by the ku-pf are presented in Figure 1, i.e. mean values of matric suction measured by the two tensiometers and respective gravimetric water content derived from recorded weight variations of the sample
Summary
In the Campania region (Southern Italy), shallow landslides triggered by intense rainfall occur in sloping pyroclastic deposits generated by explosive eruptions of Mount Vesuvius [1]. Previous studies on the Campanian pyroclastic soil assumed that the volume changes due to drying and wetting are negligible, as usually occurs when contents of fines and plasticity are low [2-7]. Picarelli et al [8] present the only study on the volume change effect on the water retention curve (WRC) of the Neapolitan pozzolana. Water content variations in the soil are linked to variations of matric suction which in turn changes the effective stress-state of the soil. The suction increase leads to a decrease of the soil volume [9, 10] that must be taken into account in the estimation of the water content, especially when it is defined in terms of volume of water per unit volume of soil, i.e. the volumetric water content
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