SANICLAY-T: simple thermodynamic-based anisotropic plasticity model for clays

In this work the anisotropic model for clays SANICLAY proposed by Dafalias and Taiebat (2013) is reformulated within the framework of hyper-elastoplasticity. The model, called SANICLAY-T, is fully defined by two scalar potential functions, the free energy and the rate of dissipation. It is first presented in the triaxial space and then generalised in the multiaxial one. The model reproduces exactly the original one for the case of associate flow rule, while leads to a different outcome for non-associated flow. When compared to existing hyperplastic models accounting for rotational hardening, the proposed one proves to be more versatile, as characterised by less restrictive constraints on the hardening and asymptotic behaviour of the soil. The predictive capability of the model is illustrated with reference to experimental data on natural and reconstituted clays, highlighting its merits and limitations

Sedimentary facies characterization through CPTU profiles: An effective tool for subsurface investigation of modern alluvial and coastal plains

Cone penetration tests, a method that is typically used to determine the engineering properties of soils, can be used as an effective tool for refined subsurface stratigraphic investigations of alluvial and coastal plains, aside from the geographic location. High-resolution calibration of piezocone penetration tests (CPTU) with 20 sediment cores enabled the detailed characterization of alluvial, deltaic and coastal depositional systems of the Po Plain. Twelve cored facies associations, typical of alluvial and coastal plain environments, were characterized based on four distinct CPTU profiles: basic cone resistance (Qc), sleeve friction (Fs), water pore pressure (U) and friction ratio (FR). Sandy facies associations (fluvial/distributary channel, bay-head delta, transgressive barrier, delta-front/beach-ridge) typically have high (>4 MPa) Qc, low-to-negative U and low (<2%) FR. Muddy deposits (well-drained/poorly-drained floodplain, swamp, lagoon and prodelta) exhibit opposite trends. Heterolithic facies associations (crevasse-levee, offshore/delta-front transition) display characteristic seesaw profiles. Plotting of late Quaternary deposits onto the latest version of the cone penetration test typical soil behaviour chart (Robertson, 2010) enables the identification of distinctive facies associations reflecting distinctive grain size. CPTU interpretation leads to sedimentary facies recognition well beyond the simple lithological differentiation and, in particular, allows the refined characterization of clay-rich and silt-rich depositional units (swamp clays and peats, central-inner and outer lagoon, proximal/distal prodelta deposits) that exhibit only subtle differences in lithology. CPTU data can also serve for the accurate detection of key stratigraphic surfaces with potential engineering applications, such as the Pleistocene-Holocene boundary. This latter, a common feature of several alluvial and coastal plain successions, is commonly marked by an abrupt upward decrease of basic cone resistance and sleeve friction from Late Pleistocene, pedogenized, stiff strata to overlying Holocene, organic-rich, soft deposits. This study offers an updated CPTU-facies characterization method that could be suitable for subsurface investigations of modern alluvial and coastal plains worldwide

Interaction Between Tunnel Excavations and Historical Structures in Rome: A Fully Coupled Structural and Geotechnical Approach

In this paper we propose a 3D Finite Element (FE) approach to model the excavation of twin tunnels, accounting for the strongly non-linear soil behaviour, interacting with monumental masonry structures, carefully modelling their geometry and non-linear anisotropic mechanical behaviour. The work focuses on a specific case-study related to the ongoing construction of the line C of Rome underground

Post-LGM valley fills from the northern coast of Tuscany: depositional facies and stratigraphic architecture

The stratigraphic architecture of three adjacent valley bodies of post-LGM age buried beneath the northern coast of Tuscany is illustrated in detail. Above a gravel fluvial deposit, the valley fills exhibit a distinctive succession of coastal plain to estuarine facies, punctuated by an aggradational stacking pattern of millennial-scale depositional cycles with distinctive climatic signature. Radiocarbon dates document that the three valleys were active simultaneously and that rapidly created accommodation during transgression was filled under conditions of very high sediment supply

Закон України «Про позашкільну освіту» (витяг)

All around the world, paleovalley systems have trapped great amounts of deposits and hold a quite complete Late Quaternary record. Uniquely, these records directly interlink the shelf marine with the hinterland fluvial realms. In the vicinity of ice sheets, in similar ways, paleovalleys interlink the glacial record with the non-glacial domain. Considerable advances have been made in their study over the past decades, and many case well-dated and well-mapped case studies are now available. The means for comparison of records from older glacials and interglacials with that of the youngest ones have also improved. To further improve our understanding of the paleovalley systems, it is timely to start to intercompare the many cases at the new obtained resolutions. This is a correlation exercise in which we can make use of our established chronologies, sea-level histories, sedimentary evolution, human impact history and what is more. This is not just needed for the paleovalley system research itself, but also to unlock the records from the lower reaches of rivers and of deltas, estuaries and shelf areas for global research questions (climate responses and feedbacks, sediment fluxes, chronostratigraphy). This session introduction will give a quick tour around a series of events holding large correlation potential, via downstream and via upstream controls. E.g. the recording of transgression and high stand in the Last Interglacial and the Holocene, of regressions and low stands in the Last Glacial and earlier, of sustained climatic amelioration and deterioration at Milanković-scales, of shorter-lived events. Some of these correlation targets will work better than others, and case-to-case differences in performance are expected, as the presentations and discussions in the further session hopefully will sho

Landslide Hazard Affecting Historical Buildings: Santa Scolastica Monastery in Subiaco

Every year landslides occur as a consequence of ground conditions, geomorphological, physical or man-made processes, often triggered by heavy rainfalls or earthquakes. They affect buildings and infrastructures, causing economic and life losses. On the Italian territory, more than 14,000 heritage sites interact with potentially unstable slopes. This work investigates the effects of a landslide, occurred on the 26th of November 2018, on the Monastry of Santa Scolastica in Subiaco (Rome), one of the most ancient and well-preserved examples of medieval architecture in Central Italy. The geometry of the slope was reconstructed based on aerial photographic survey and point-cloud processing, obtaining meshed surfaces and extracting relevant sections. The mechanical parameters and the specific hydraulic conditions triggering the failure mechanism were first recognised by traditional limit equilibrium back-analyses and then implemented in a 3D non-linear finite element (FE) model, which included both the slope and the interacting portion of the ancient structure. Elastic-perfectly plastic constitutive assumptions were adopted for the soil, while the structure was modelled by a three-dimensional anisotropic elastic-perfectly plastic constitutive model, specifically conceived for masonry, accounting for block dimensions and staggering joints effects. Finite element approach proves to be very effective in the analysis of such a coupled interaction problem, leading to a realistic representation of the interplay between the soil displacements and their deformative effects within the structure. The numerical results have been interpreted to highlight the structural response in terms of crack pattern and stress distribution as induced by the interaction with the deforming slope, leading to a quantitative evaluation of the landslide-induced damage. Several scenarios were simulated: first, the pre landslide existing crack pattern was reproduced, then the event was modelled as it occurred, evaluating its consequences on the structure

Provenance and sediment dispersal in the Po-Adriatic source-to-sink system unraveled by bulk-sediment geochemistry and its linkage to catchment geology

The Po-Adriatic region offers an excellent case for reconstructing sediment provenance and transport pathways of a multi-sourced sediment-routing system. Through a comprehensive set of ~1,400 geochemical data, a model for provenance and sediment flux was built based on distinct compositional fingerprints of 53 fluvial systems and their comparison to coastal, shelf and deep-marine sediments. Geochemically unique catchment lithologies (mafic/ultramafic rocks, limestones and dolostones) were used as end-members to assess exclusive source-rock signatures. Following calibration with sedimentary facies, selected key elements and element ratios poorly sensitive to particle size (Ni/Cr, MgO, Ni/Al2O3, Cr/V, Ca/Al2O3 and Ce/V) were adopted as provenance indicators. The high-Ni and high-Cr source-rock signature of mafic/ultramafic rocks widely exposed in the Po River watershed and along the Albanian Dinarides contrasts markedly with the high-Ca (and locally high-Mg) geochemical composition of Eastern Alpine, Apennine, and Eastern Adriatic (Montenegro, Croatia, Slovenia) river catchments, which are, instead, carbonate-rich and virtually ophiolite-free. Relatively high Ce values from Apulian river samples serve as a key marker for a minor, but very distinct sediment provenance from southern Apennine alkaline volcanic rocks. Despite along-shore mixing and dilution with sediment sourced from other river catchments, the geochemical signature of Adriatic shelf muds primarily reflects composition of sediment eroded from the contiguous continental areas. Chromium-rich and nickel-rich detritus generated in mafic and ultramafic complexes of the Western Alps and conveyed through the Po River into the Adriatic Sea records a geochemical signal that can be traced downstream as long as 1000 km, from the Alpine zone of sediment production to the area of final deposition, offshore Apulia. While longitudinal dispersion linked to the general cyclonic, counter-clockwise Adriatic circulation is prevailing along the Western Adriatic Sea, conspicuous detrital input from transversal pathways to the deep sea is revealed across the Eastern Adriatic shelf using heavy metals as provenance tracers. Estimates of fluvial sediment loads and compositional fingerprinting of fluvial, coastal and shelf sediments indicate that previously neglected ophiolite-rich successions of Albania represent a major sediment-conveyor to the offshore sinks (Southern Adriatic Deep and Mid-Adriatic Deep) through significant cross-shore and NNW-directed sediment transport in the Eastern Adriatic Sea. A cut-off value of the Ni/Cr ratio targeted around 0.8 represents an effective tool for the differentiation in marine sediments of Ni-rich (serpentine-rich) ophiolite detritus of Albanian origin from mafic/ultramafic sources of Alpine affinity. High trace-metal contents found within the Adriatic deep basin are mostly of natural origin and only minimally reflect metal contamination