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This paper investigates the effects of indigenous vegetation on the shear strength of loose pyroclastic soils of the Campania region (southern Italy); these soils are frequently affected by shallow landslides 1–2 m deep that experience static liquefaction during the post-failure stage. Perennial graminae grasses were seeded in a one-dimensional column 2 m high and filled by pyroclastic soils, allowing the root to grow under atmospheric conditions. A noninvasive sampling procedure was adopted to take the vegetated soil samples, in which the roots were in their natural geometrical distribution. For each rooted sample, the root biomass, RM, was measured and the root volume density, RVD, was calculated. Isotropic consolidated triaxial tests in both drained and undrained conditions were performed on the rooted specimens, as well as on bare specimens as a control. The obtained results showed that the roots generally provided an increment to the soil strength. In drained conditions a reduction in the volumetric deformation was observed, which, under undrained conditions, was reflected in a general reduction of the excess pore-water pressures with a possible inhibition of the static liquefaction occurrence. This study highlights the potential role of grass roots as bio-engineering practice for stabilizing shallow covers of pyroclastic soils. [ABSTRACT FROM AUTHOR]

This paper reports the main results of an extensive piezocone testing campaign performed over the last years at the Treporti test site (Venice, Italy) within a long-lasting and comprehensive research project aimed at developing a reliable geotechnical model of the heterogeneous and highly stratified Venetian lagoon basin. The project included the construction of a full-scale vertical-walled cylindrical test bank, together with a detailed monitoring system of surface settlements, pore-water pressures, subsoil strains, and stresses beneath the loaded area. The analysis of the large amount of data thus available, referring to different phases of the loading history, confirms the great potential of piezocone as an in situ testing technique, especially for stratigraphic profiling of the predominantly silty subsoil of the Venetian lagoon, but at the same time reveals some limitations of widely used empirical correlations for the relevant soil characterization, with special reference to compressibility and consolidation properties of such intermediate sediments. Indeed, partial drainage effects during cone penetration, as well as potentially dilative behaviour of these soils, should be taken into careful consideration to derive reliable soil parameters from in situ measurements. More suitable site-specific correlations have been introduced, according to the recent findings on piezocone data interpretation. [ABSTRACT FROM AUTHOR]

This paper presents and discusses the results of investigations carried out by the authors on two castles that are considered as case histories within a project financed by the European Commission (project EVK4-2001-00091 ONSITEFORMASONRY), coordinated by C. Maierhofer of Bundesanstalt für Materialforschung und prüfung (BAM), Germany. An extensive investigation programme (including sonic, radar, flat-jack, coring, boroscopy, etc.) was planned to support the preservation and restoration actions of two ancient castles. The experience from this investigation shows the importance of the diagnosis project in selecting the most relevant strategies and tests for each specific problem. Cet article présente et discute des résultats des examens effectués par les auteurs sur deux châteaux, considérés comme des études de cas dans le cadre d’un projet financé par la communauté européenne (projet EVK4-2001-00091 ONSITEFORMASONRY), coordonné par C. Maierhofer de BAM (Bundesanstalt für Materialforschung und Prüfung, Allemagne). Un programme d’examen détaillé (incluant sonar, radar, vérin plat, carottage, inspection endoscopique, etc.) a été planifié afin de soutenir les mesures de préservation et de restauration des deux anciens châteaux. L’expérience montre l’importance, pour le projet de diagnostic, de sélectionner les stratégies et les tests les plus adéquats pour chaque problème spécifique. [ABSTRACT FROM AUTHOR]

In situ, seasonal changes expose soils to frequent wetting–drying–freezing–thawing cycles. Such processes can favour and trigger shallow instabilities controlled by the weathering process. This paper presents an experimental study carried out to investigate the effects of the weathering process, caused by the wetting–drying–freezing–thawing cycles, on the compressibility and shear strength of a natural clay. Several specimens were trimmed from block samples of overconsolidated clays taken from a slope in south Calabria, Italy. Specimens were subjected to wetting–drying–freezing–thawing cycles of different durations and then tested with standard equipment (oedometer and direct shear). Test results show that the wetting–drying–freezing–thawing cycles caused a change in the initial microstructure that produced a decrease in the compression index and an increase in the swelling index. Moreover, the direct shear test results show a decrease in the peak shear strength and demonstrate that a larger reduction occurs in the first month of weathering cycles. The intense cycles performed in the laboratory produced a decay of compressibility and a shear strength approaching reconstituted values. The conclusions are important when choosing the shear strength parameters required when studying shallow landsliding in clay slopes. [ABSTRACT FROM AUTHOR]

Stromboli volcano is well known for its continuous strombolian activity. Moreover, the volcano occasionally shows effusive phases, the latest in 1985–1986. On 28 December 2002 Stromboli entered a new effusive phase, accompanied by different paroxysmal events that led to considerable hazards for inhabitants and tourists on the island of Stromboli. On 30 December 2002 a major sector collapse affected the Sciara del Fuoco slope and initiated a tsunami. On 5 April 2003 a powerful explosion, which can be compared in size with the most recent explosion in 1930, covered a large part of the normally tourist accessible summit area with bombs. As this explosion was not forecasted, although the island was by then effectively monitored by a dense deployment of instruments, in this paper, we tackle the problem of highlighting the time scale of preparation of this event and conduct a search for possible precursors. For this purpose, we analyze the seismic data preceding the paroxysm with spectral and dynamical methods, highlighting that this paroxysmal event can be seen as the final result of a dynamical phase that started at least 2.5 h before the event. Therefore, this is the time scale during which the search can and should be made for possible precursors. Moreover, the application of the "material failure forecast" method suggests that this final dynamical phase may be just the final acceleration of a process that was building up for at least several days prior to the event. [ABSTRACT FROM AUTHOR]