The role of infiltration processes in steep slope stability of pyroclastic granular soils: laboratory and numerical investigation

Abstract

Rainfall-induced landslides on steep slopes are a common feature in much of Italy's mountain areas covered by shallow-pyroclastic deposits. Generally, these deposits are unsaturated and have a slope angle higher than 40°-50°; hence their stability is due to the positive effect of matric suction on soil shear strength. During rainfall, rainwater infiltration causes a decrease in suction, which in turn causes changes in soil mechanical and hydraulic properties, leading towards an instability process. However, the response of pyroclastic soil slopes to rainwater infiltration is not fully understood. The aim of this study is to link slope instability to the infiltration process on the basis of advanced geotechnical characterization, in situ monitoring and numerical analysis calibrated through a backanalysis of well-instrumented flume tests.

A "simulation chain" to define a Multidisciplinary Decision Support System for landslide risk management in pyroclastic soils

“…Moreover, they took into account some predisposing factors, which are sometimes undervalued, such as stratigraphic details (Picarelli et al, 2004 (Guadagno et al, 2003), springs and morphological cuts (Cascini et al, 2010(Cascini et al, , 2011. Only recently, Damiano and Olivares (2010) added information intended to aid the authorities involved in land management in the southern Apennines to detect cases in which rainfall-induced slope failure may turn into flowslides. They stressed the mechanisms of how landslides evolve into flowslides (Olivares and Damiano, 2007), stressing the role played in failure by hydrological and geotechnical variables such as water content, degree of saturation and suction.…”

Natural Hazard Risk Management: a Multidisciplinary Approach to Define a Decision Support System for Shallow Rainfall-Induced Landslides

“…Therefore, quantitative prediction of the evolution of hydrological and geotechnical variables such as water content, degree of saturation and suction, corresponding to forecasted rainfall is of paramount importance, for the authorities in charge of land management, to detect cases in which rainfallinduced slope failure may evolve into flowslides. In fact, such information allows excluding the cases of landslides that will not evolve into catastrophic flowslides, with a reduction of the false alarms [13,19].…”

“…The infiltration process was numerically simulated assuming the hypothesis of homogeneous deposit and applying either the average daily rainfall intensity observed during rainy days (pluviometric measurements), or the evaporation flux during dry days (estimated from Cervinara suction measurements [13,20]), as top soil surface boundary condition. For the lateral and bottom boundary conditions, free flow was assumed.…”

“…(4 and 5) show the upper boundary condition in terms of applied daily rainfall, cumulative rainfall height, IN-OUT water daily flux, and cumulative IN-OUT water flux height [13,20].…”

“…Suction values higher than 70 kPa were observed only a few times. As in Damiano and Olivares [13], in the same figure also the water retention curve used for numerical simulations is plotted, along which three ranges of suction may be distinguished [25]:…”