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The defense of the city of Venice and of the lagoonal ecosystem: an ongoing challenge for geotechnical engineering|La difesa della città di Venezia e dell’ecosistema lagunare: una sfida continua per l’ingegneria geotecnica
No full textThe worldwide-known historic city of Venice continues to preserve a rather precarious equilibrium with the surrounding lagoon, although the margin of security is being eroded at increasing rate. The rate of environmental deterioration is being accelerated by the increasing frequency of the flooding of the historic city and surrounding lagoon caused by the natural eustatic rise of the sea level, by natural subsidence and by a regional man-induced subsidence, the latter particularly important in the last century. The paper, based on the Croce Conference given in Rome on the 16 December 2021, emphasizes the relevant role of geotechnical engineering, and especially site and laboratory investigations, monitoring, data analysis and interpretation and modelling of fundamental geotechnical issues for the preservation of city and surrounding lagoon
Geotechnics of Venice and Its Lagoon
No full textWithout any protective intervention, the historic city of Venice and its surrounding islands would suffer rapid deterioration due to the increased frequency of tidal flooding, as the gap between land surface and sea levels has reduced due to a coupled effect of climate change-induced sea-level rise and natural and anthropic subsidence. Geotechnics of Venice and Its Lagoon provides a clear and comprehensive illustration of the extensive geotechnical aspects of not only the various environmental problems such as land subsidence and wetland surface reduction, but also solutions such as the design of the tilting gate foundations against high tides and the restoration and improvement of the drainage system of the renowned Piazza San Marco, which have been necessary for the preservation of the extraordinary cultural heritage of Venice. Readers will gain a better understanding of the complex phenomena occurring in the sensitive Venice silts, whose hydro-mechanical behavior has required compre..
Rilevati e argini
No full textLa progettazione e costruzione di rilevati stradali, ferroviari ed arginali, e più in generale delle opere in materiali sciolti, già oggetto di interventi normativi di carattere nazionale, è trattata dettagliatamente nell’ Eurocodice 7 - Parte 1 e, per gli aspetti sismici, nell’Eurocodice 8 - Parte 5. Dopo un breve riepilogo delle problematiche attinenti a tali manufatti, la presente nota analizza e commenta gli argomenti trattati nell’EC7 e nell’EC8 relativamente agli argini ed ai rilevati, proponendo anche un confronto con le disposizioni della Normativa Italiana
Investigation and monitoring to model the interaction between the Scrovegni’s Chapel in Padova (Italy) and the underlying foundation soil
Full text linkIn Padova's historic centre lies the renowned Scrovegni’s Chapel, painted by Giotto in 1303. The local subsoil primarily consists of silty sand with some layers of silt. The crypt beneath acts as a buffer against soil moisture, preventing damage to the frescoes. However, during heavy rain, groundwater rises flowing across the floor and lateral walls, therefore flooding the pavement. A pumping system is eventually activated to mitigate the pavement inundation. Several investigations including geophysical surveys, piezocone tests, and boreholes with soil sampling have been conducted to provide the subsoil geotechnical model and understand the local hydrogeological behaviour. Monitoring systems, such as piezometers, deep extensometers and optical fiber cables, track groundwater levels and long-term soil displacements.
The paper aims to characterize the subsoil's stratigraphy, mechanical properties and permeabilities to model how the environmental conditions affect the ancient Chapel and ensure its long-term stability
Applicability of CPTU to characterize diatomaceous fine-grained soils: a case study in Euganean Hills (Italy)
Full text linkDiatomaceous soils, composed of diatom fossils and clay minerals typically formed in volcanic environments, exhibit characteristics such as low unit weight, high plasticity and liquid limit, significant compressibility, and high friction angles. Despite their presence in various locations globally, knowledge about their geotechnical behavior is limited and primarily based on laboratory tests conducted on artificial samples. This paper presents data obtained from undisturbed samples of natural diatomaceous soils and discusses the interpretation of Cone Penetration Test with Pore Pressure (CPTU) data to classify these complex non-textbook soils and estimate their mechanical properties.
The study area is situated in the Po Plain near the thermal anomaly region of the Euganean Hills in Northeast Italy. Three CPTUs and one borehole with the collection of four Osterberg undisturbed samples were conducted. Laboratory tests on the undisturbed samples provided values for Atterberg Limits, soil unit weight, in-situ void ratio, compressibility, and permeability, which were compared with estimations derived from CPTU data analysis. Moreover, Scanning Electron Microscope images provided insight into the distinctive microstructure of diatom microfossils embedded in a clayey matrix.
Based on these comparisons, CPTU proves to be effective in estimating relevant parameters of diatomaceous soils, particularly the Soil Behavior Type (SBT) and consolidation coefficient from dissipation tests. However, the agreement in estimating the oedometric modulus is less satisfactory. Therefore, for a precise definition of the geotechnical model, it is recommended to conduct additional laboratory tests, particularly those focused on defining compressibility parameters, given the unique behavior of natural diatomaceous soils
Monitoring and Modeling Tidally Induced Pore-Pressure Oscillations in the Soil of St. Mark's Square in Venice, Italy
Full text linkSea level rise and high tide events are threatening many coastal cities, which require adequate and sustainable protection measures. The historic city centre of Venice (Italy) is often flooded during very high tide events, especially the area of St. Mark's Island, which is at the lowest elevation among all the islands forming the city. To design cost-effective protection interventions to safeguard the historical heritage, a deep understanding of flooding mechanisms and the relationship between groundwater pressure and tidal oscillations is necessary. Geotechnical survey and analyses play an important role in this process. This paper presents the results of a recent monitoring campaign carried out in St. Mark's Island. A simplified one-dimensional analytical model was derived for saturated conditions to understand the key parameters that govern tidal induced pressure oscillations in soil (material properties, geometrical features, and wave properties). Additional features, such as partially saturated soil conditions and two-dimensional effects, were investigated numerically. Results showed that significant pressure oscillations occur in the subsoil, which should not be neglected when considering the stability of horizontal architectural structures, such as the historical mosaics and paving. However, seepage flow rate is small, and thus its impact on the drainage system is limited in terms of water discharge
Microstructural Analyses of a Stabilized Sand by a Deep-Mixing Method
No full textThe deep-mixing method (DMM) involves the mechanical mixing of in-situ soil with various stabilizing binders, which chemically react with the soil or the groundwater. Microstructural analyses are valuable tools to support ordinary geotechnical laboratory tests to assess the effectiveness of ground improvement works. This paper presents the results of microstructural analyses on in-situ retrieved samples and laboratory mixed specimens related to an actual deep mixing job site. Mercury porosimetry and X-ray computed Microtomography were used to determine the total porosity and to characterize the pore network of both types of samples. The results of the analyses allowed a qualitative understanding of the degree of mixing of the soil with the binder suspension under laboratory and field conditions. Additionally, an original correlation between total porosity and unconfined compressive strength was obtained based on the experimental data for cement-treated sandy soils at long curing time
Alcune osservazioni sull'impiego della prova di taglio semplice nella caratterizzazione meccanica di terreni coinvolti in movimenti franosi
No full textCharacterization of geotechnical spatial variability in river embankments from spatially adjacent SCPT
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