An investigation of infiltration and deformation processes in layered small-scale slopes in pyroclastic soils

摘要

In recent years, a number of flowslides and debris flows triggered by rainfall affected a widernmountainous area surrounding the “Piana Campana” (southern Italy). The involved slopes are constituted byrnshallowunsaturated air-fall layered deposits of pyroclastic nature,which stability is guaranteed by the contributionrnof suction to shear strength.To understand the infiltration process and the soil suction distribution in such layeredrndeposits, strongly affecting slope stability, infiltration tests in small-scale layered slopes reconstituted in a wellinstrumentedrnflume have been carried out. The results highlight that the presence of a coarse-textured pumiceousrnlayer interbedded between two finer ashy layers, in unsaturated conditions, delays the wetting front advancement,rnthus initially confining the infiltration process within the uppermost finer layer. However, when high hydraulicrngradients establish across the pumices, water infiltration into the deepest layer starts. In sloping deposits, underrnhigh applied rainfall intensity, a seepage parallel to the slope seems to occur through the uppermost finerrnlayer when it approaches saturation. At the same time, water infiltrates through pumices. Thus, in presence ofrnlong lasting intense rainfall, the presence of a coarse-gained layer does not necessarily impede the progressivernsaturation of the lowest soil layer.