Luciano Picarelli

The Varnes classification of landslide types, an update

The goal of this article is to revise several aspects of the well-known classification of landslides, developed by Varnes (1978). The primary recommendation is to modify the definition of landslide-forming materials, to provide compatibility with accepted geotechnical and geological terminology of rocks and soils. Other, less important modifications of the classification system are suggested, resulting from recent developments of the landslide science. The modified Varnes classification of landslides has 32 landslide types, each of which is backed by a formal definition. The definitions should facilitate backward compatibility of the system as well as possible translation to other languages. Complex landslides are not included as a separate category type, but composite types can be constructed by the user of the classification by combining two or more type names, if advantageous.

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.

Deterioration processes of hard clays and clay shales

Abstract Soil deterioration is one of the main causes of slope failure in hard clays and clay shales, but so far a clear general framework of the causes of deterioration is still missing. Based on laboratory data, field observations and speculation, this paper examines some processes of deterioration of stiff overconsolidated clays and clay shales with particular regard to their influence on the stability of slopes. In particular, deterioration localized within soil bands or involving large soil masses is described with reference to its mechanical or physico-chemical causes. Coupling between mechanical and physico-chemical processes is considered.

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.

The role of the lowermost boundary conditions in the hydrological response of shallow sloping covers

In many areas of the world, slopes covered by shallow unsaturated non-plastic soil layers experience rainfall-induced landslides causing heavy damage and casualties every year. Landslide occurrence depends on the amount of water infiltrated and stored. Among the contributing factors are the hydraulic conditions at the lowermost boundary, a feature that is often disregarded. The paper focuses on this topic, presenting the results of some laboratory and numerical experiments on ash-pumice interfaces. A strategy is then proposed for selecting the lowermost boundary condition, and some studies are carried out to compare the results obtained with the proposed solution and other more popular ones.

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.

Potential effects of climate changes on soil–atmosphere interaction and landslide hazard

In the recent years, the scientific community is involved in an intense debate around the effects of global warming. In fact, this could determine valuable changes in atmospheric forcing that govern the soil–atmosphere interaction and, in turn, water budget in the subsoil, with unpredictable consequences, inter alia, on geohydrological hazards. An early and proper assessment of the magnitude of such phenomena would be of great importance in establishing the priorities and timing in adaptation strategies. The paper reports some results obtained through a simulation chain which accounts for the potential climatic changes induced by two different socioeconomic concentration scenarios in atmospheric forcing and consequent changes in soil moisture and, then, slope response. The analyses concern a site located in Southern Italy, representative of Mediterranean area, deemed an “hot spot” for future climate changes. It is shown that, beyond the variations induced by climate changes, soil nature and land cover could play a major role.

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.

Fiber optic based inclinometer for remote monitoring of landslides: On site comparison with traditional inclinometers

Distributed optical fiber sensors, and in particular those based on stimulated Brillouin scattering, have in recent years been the object of a growing attention for structural and environmental monitoring of large areas because they allow to measure strain and temperature profiles up to tens of kilometers with a strain accuracy of ±10ue and a temperature accuracy of ±1°C. In this paper, we present the application of the above sensing principle to the realization and field testing of a novel inclinometer for the measurement of 3D deformation of soil.

A simulation chain for early prediction of rainfall-induced landslides

A new simulation chain for early prediction of rainfall-induced landslides in unsaturated soils is presented. It includes a special computational weather code for forecasting the evolution of the synoptic weather and its changes due to interaction with the Earth’s surface (rainfall pattern), and a hydro-mechanical code to analyse rainfall effects on slope stability by computing degree of saturation and pore pressure changes due to rainwater infiltration. The linkage between these two numerical codes is ensured by an interface with the aim of bringing the data provided by the first code, which operates at basin or slope scale. The simulation chain can work in computational times that may be considered suitable for civil protection operations.