Emilia Damiano

An Instrumented Flume to Investigate the Mechanics of Rainfall-Induced Landslides in Unsaturated Granular Soils

The mechanics of rainfall-induced flowslides in pyroclastic soils have yet to be completely clarified. The complexity of phenomena (rainfall-induced failure in initially unsaturated granular deposits, post-failure transition to flow-like landslide) requires the use of a well-equipped small-scale flume. To this aim, flume experiments at the Second University of Naples were performed to analyze the fundamental aspects of such phenomena. A new experimental program is now being carried out to assess the performance of a time domain reflectometry device and optical fibers as indicators of impending failure. The paper describes the instrumented flume and the procedures adopted for monitoring the major aspects of slope behavior. Our first experimental results are very promising in this respect.

Potential Effects of Climate Change on Slope Stability in Unsaturated Pyroclastic Soils

Landslides are one of the most dangerous natural hazards since they degrade the productivity of soils, harm people, and damage property. Slope failures are caused by a combination of several factors; in unsaturated granular deposits which are often susceptible to rapid catastrophic landslides induced by rainwater infiltration, climatic conditions play a fundamental role. Therefore, global warming due to the greenhouse effect and changes in precipitation and evaporation patterns might affect future landslide hazard.

Performance of Slope Behavior Indicators in Unsaturated Pyroclastic Soils

Landslide risk is increasing in many parts of the world due to growth of population and infrastructures. Therefore, an effort has to be made in developing new and cheap sensors for areas susceptible of landslides to continuously control the slope behaviour, until approaching failure conditions. The paper reported experimental data from small-scale physical models about the performance of Time Domain Reflectometry (TDR) and optical fibres, which act as the indicators of the incoming failure of slopes covered by unsaturated granular soils. Obtained results appear encouraging, since both sensors provide continuous information about the state of the slope, in terms of water content profiles and ongoing deformations, induced by rainwater infiltration, even immediately before the triggering of a fast landslide.

A Laboratory Study on the Use of Optical Fibers for Early Detection of Pre-Failure Slope Movements in Shallow Granular Soil Deposits

Although landsliding is the macroscopic effect of slope failure, it is only the final stage of an often time-consuming process of soil deformation. In many cases, slope movement remains extremely slow and undetected for a long time; in other cases, failure is abrupt, preceded by small deformations and followed by rapid, destructive movements. This is the case of slope failure in granular soils of pyroclastic nature, which involve an extensive mountainous area surrounding Mt. Vesuvius in southern Italy. Given that the area around Vesuvius is highly urbanized and densely populated, the detection and interpretation of pre-failure slope deformations are of great importance for risk mitigation. To this aim, Brillouin optical time-domain analysis (BOTDA), a distributed fiber optic sensing technique, may represent an efficient new tool. This paper illustrated the results of laboratory experiments on small-scale slopes instrumented with optical fiber sensors, showing the main features of this technique for early detection of slope failure.

Short Term Weather Forecasting for Shallow Landslide Prediction

The paper describes the activities developed within the work package 4.1 of the UE/FP7 SAFELAND Project. The first scope of this research activity is to define and to implement a warning system for shallow landslide prediction, at large and slope scale, based on the forecast precipitation. The warning system is based on different numerical tools and simulation models: stability analysis model at slope and regional scale and numerical weather prediction models (global and regional) and downscaling algorithms.

Investigation on the Hydraulic Parameters Affecting Shallow Landslide Triggering in a Pyroclastic Slope

Large mountainous areas surrounding the city of Naples (southern Italy) are characterized by the presence of steep slopes covered with few meters of loose pyroclastic materials in unsaturated conditions, lying upon a fractured limestone bedrock, the stability of which is ensured by the contribution to shear strength due to suction. Wetting of the soil cover during rainfall infiltration may cause the triggering of shallow landslides, sometimes developing in form of fast and destructive flows. In this preliminary study, a sensitivity analysis is carried out, aiming at quantifying the effects on the hydrological response of a slope to precipitations, of some factors, related either to the hydraulic properties of the soil cover or to the permeability of the soil-bedrock interface. In particular, the sensitivity analysis refers to the slope of Cervinara, around 40 km northeast of Naples (Italy), covered by a pyroclastic deposit with an average thickness around 2.0 m, and characterized by an average slope angle of 40°. For the sake of simplicity, the analysis is carried out by means of a one-dimensional infiltration model, based on the Richards’ equation written for a single homogeneous soil layer. The obtained results highlight that the equilibrium of the slope during rainfall infiltration is affected not only by the hydraulic characteristics of the soil cover, but a major role is played by the permeability of the soil-bedrock interface.

Suction Fluctuations in Unsaturated Slopes: Evidences from Two Test Sites in Southern Italy

Slope failures in partially saturated pyroclastic slopes are often induced by rainwater infiltration. Monitoring pore pressure in the subsoil makes it possible to identify the most critical period for slope stability and to determine whether current site conditions are critical for slope failure (according to a Civil Protection approach). This paper deals with the behaviour observed from 2002 to 2011 in two test sites in southern Italy. Using the data obtained, typical aspects of groundwater regime are described. The effect of single rainfall events is recognized only in the shallowest layers, with a relatively small perturbation in the suction trend compared to the amplitude of seasonal fluctuations (that reach 80 kPa). Minimum suction values occur during winter in all layers. Therefore, we can conclude that the critical period for landslide triggering is between January and April.