Pore water pressure measuring and modeling in stiff clays and clayey flysch deposits: A challenging problem

A set of materials covering a wide class comprised between soils and fractured rocks displays a variable and complex hydraulic/mechanical response to external inputs that make both the measurement of properties and the modeling of material behaviour quite complicated. In fact, weak interparticle bonding and a network of irregular and often interconnected discontinuities can strongly and unevenly affect permeability, stiffness and shear strength, making difficult the interpretation of natural events, such as landslides, and uncertain the analysis and design of engineered slopes and man-made works. This paper reports some examples taken from the Authors' experience and from the literature, which illustrate the difficulty to correctly understand or analyze the behaviour of such complex materials through the classical approaches of Soil or of Rock Mechanics, highlighting at the same time the complex role that discontinuities play in groundwater flow and pore water pressure regime.