1,721,014 research outputs found
Deep Movements in Clayey Slopes Relating to Climate: Modeling for Early Warning System Design
No full textThe current landslide activity in the southern Italian Apennines has been found often prompted by the slope-vegetation-atmosphere interaction, as recognized through both phenomenological and numerical diagnoses in literature. In the very top soil layers this interaction causes transient seepage, resulting in significant variations of pore water pressures with time at both very shallow depths, and at larger depths, below the water table. As consequence, the slope-vegetation-atmosphere interaction often represents the triggering factor of the activity of shallow failure mechanisms, as well as the acceleration of deep slow landslide bodies. In particular, the latter is the case of either structurally complex clayey slopes or slopes location of pre-existing landslide bodies. With reference to the geo-hydro-mechanical context characterizing the south-eastern Italian Apennines, this contribution reports about the numerical investigation of both the pore water pressure and safety factor variations with time across the Pisciolo hill-slope, a representative slope, in relation to the real weather conditions from the 2001 to the 2016. The numerical investigation is aimed at designing an early warning system for the mitigation of the risk related to deep landsliding
EFFETTI DEL GRADO DI SATURAZIONE SUL COMPORTAMENTO MECCANICO DEL LIMO
Get PDFFrancesco Silvestri, Federica Cotecchia, Cristina Jomm
COMPORTAMENTO DI GRANDI FRANE IN ARGILLE
No full textFrancesco Silvestri, Federica Cotecchia, Cristina Jomm
Bearing Capacity of Foundations Under Highly Eccentric Loads
No full textIn the case of wind turbines the eccentricity of the loads at foundation level is generally very high and very often the application point of the vertical load falls outside the core of the foundation. In the paper, two types of foundation of a tall wind turbine under highly eccentric loads are considered and designed: A shallow foundation and a pile group foundation. The design of the shallow foundation is based on the requirement of bearing capacity and on the allowable rotation for a safe operation. On the contrary, for pile groups the main design requirement is to avoid a bearing capacity failure, since the rotation limitation at foundation level is usually ensured by the high rotational stiffness of the group. Widespread practice for pile groups design is to consider the achievement of the axial capacity (in compression or in uplift) on the outermost pile as the ultimate limit state of the pile group. This approach neglects the ductility of the foundation system and therefore is uselessly conservative. A recently proposed and more efficient approach for the evaluation of ultimate moment-axial force interaction diagrams for a pile group is applied, and comparison with the design of a shallow foundation is presented
The influence of meso-structure on the mechanical behaviour of marly clays from low to high strains.
No full textOn the 31st of October 2002, a ML=5.5 earthquake struck the Molise region in Southern Italy. The earthquake was followed by a comparable aftershock (ML=5.4) nearby on the day after, and by a series of seismic events of lower energy in the following month (Fig. 1).
In the town of San Giuliano di Puglia, the distribution of the damage consequent to the mainshocks was strongly non-uniform: the old part, which was less damaged, lies on outcropping rock, while the most severe damages were surprisingly concentrated in the new part of the town, lying on fine-grained soils. This evidence suggested that differential site amplification significantly affected the seismic response in the town. This hypothesis has been confirmed by aftershock records logged by two temporary accelerometric stations, located both in the ancient and in the new portions of the town (Puglia, 2005).
In order to develop a seismic microzonation of the area (Baranello et al., 2003), the Department of Civil Protection of the Italian Government committed a comprehensive investigation on the subsoil properties. The experimental programme included: boreholes, in situ piezometric measurements, CPT, cross-hole and down-hole tests and laboratory investigations on undisturbed samples, namely oedometer, triaxial and cyclic/dynamic torsional shear tests.
The geotechnical laboratories of both the University of Naples and the Technical University of Bari were entrusted by the Department of Civil Protection with the laboratory investigations, aiming at the characterisation of the mechanical behaviour of the fine-grained soils.
The present paper discusses the main experimental results of such laboratory investigations, as well as a comparison with seismic in-situ tests, giving evidence to the dependency of both the soil strength properties and stress-strain behaviour on the soil structural features
Hydrological Characterization of Silty Volcanic Slopes and Physically-Based Early Warning Systems
No full textThe paper analyses how rainfall-induced landslide risks may be mitigated by implementing early warning systems in sloping silty volcanic covers. Their answer to rainfall and other atmospheric variables seems to contain features and factors such to provide generality to the topic. The work firstly investigates the factors influencing the hydrological response of a silty volcanic cover referring to results provided by two physical models. Experimental results evidence the importance of accounting for evaporation (or evapotranspiration) and a realistic lowermost boundary condition when the evolution of the hydrological behaviour has to be predicted for early warning purposes. All findings are used to develop a physically-based model suitable for early warning prediction and provide an example of application. © Springer Nature Switzerland AG 2020
Assessing Future Variations in Landslide Occurrence Due to Climate Changes: Insights from an Italian Test Case
No full textThe paper compares the findings provided by empirical and physically-based models in estimating future evolutions in landslide occurrence as a consequence of the ongoing Climate Change. As test case, the phenomena affecting pyroclastic covers on Lattari Mts. (Campania Region) are considered. Simulation chains developed for both the approaches, pros and cons are carefully displayed pointing out the uncertainties currently associated to projections and the main gaps to bridge. Whatever the approach, an increase is expected but the relative magnitude and the evolution is deeply influenced by impact tools beyond the selected climate projections and concentration scenario
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Hydro-Mechanical Behaviour of a Sand-Bentonite Mixture for the Confinement of Nuclear Wastes
No full textThe established concept for the protection of the biosphere from high-level nuclear wastes consists in the use of multi-barrier systems in deep geological repository, for which clayey geomaterials are key elements. Bentonite-based materials are selected as buffer and backfilling materials. Once in place, the barriers will be subjected to a series of severe loadings, including strong variations of suction (i.e. wetting and drying cycles). The paper presents selected results from a large ongoing research work to investigate the behaviour of bentonite-based materials in the context of nuclear waste disposal. In particular, the paper focuses on the response of a Sand/Bentonite mixture under different hydro-chemo-mechanical loadings. Performed experiments include free and confined swelling tests and controlled-suction confined swelling tests, along with an assessment of the fabric evolution during those loadings. Different dry densities and waters of different salinity were considered in the experiments. The obtained data combined with results from other studies allowed to define a trend for the calculation of the swelling pressure as a function of the relative dry density of the bentonite in the mixture
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