ANALISI TERMO-MECCANICHE DI DIAFRAMMI ENERGETICAMENTE ATTIVI

I diaframmi energeticamente attivi sono un particolare tipo di opera di sostegno all’interno dei quali è installato uno scambiatore di calore che sfrutta l’energia geotermica del terreno. Scopo di questo lavoro è stato individuare le condizioni termiche estive più gravose per un diaframma durante l’esercizio dell’impianto geotermico e, mediante analisi numeriche termo-meccaniche, studiare l’influenza dello scambio termico sul comportamento dell’opera di sostegno in termini di spostamenti, deformazioni e sforzi indotti nel diaframma

Structural and geotechnical effects of thermal loads in energy walls

Geotechnical structures embedded in the ground and equipped with heat exchangers permit to exploit the ground thermal energy. Their design should combine the prior structural function with the energetic function, and their response, under both thermal and mechanical loads, is still being investigated. Considering an energy diaphragm wall, the aim is to investigate, by sequentially coupled thermo-mechanical analyses, the heat transfer effects on the soil temperatures, the wall internal actions and the soilstructure interaction. The results show that the additional thermal loads are admissible, in terms of global stability and structural safety, though generally not negligible, since unusual internal actions, such as tensile axial stresses, may develop that should be taken into account in the design

Failure and deformation behavior of underground geo-structures: advances in geomechanics.

Underground geo-structures play a crucial role in various aspects of modern society for several reasons [...

Preliminary experimental investigation into the use of recycled fibres from textile waste for the improvement of embankments

Failures that occurred in the last few decades highlighted the need to raise awareness about the emergent risk related to the impact localised degradation phenomena have on embankments. Common interventions aimed to improve embankments, such as the reconstruction of the damaged area or the injection of low-pressure grouts to fill fractures and burrows, may cause the weakening of the structure due to discontinuities between natural and treated zones. Moreover, since such repair techniques require huge volumes of materials, more sustainable solutions are encouraged. At the same time, the textile and fashion industries are looking for sustainable waste management and disposal strategies to face environmental problems concerned with the voluminous textile waste dispatched to landfills or incinerators. The use of soil mixed with textile waste in embankment improvement has been investigated to identify an effective engineering practice and to provide a strategy for the circular economy of textiles. Preliminary laboratory tests have been conducted on soil specimens collected from the Secchia River embankment, Northern Italy, to define the appropriate mixture proportions and to compare physical properties and hydro-mechanical behaviour of natural and treated soils. The results show that an appropriate fibre content offers manageable and relatively homogeneous mixtures. The indluence on soil consistency is mainly due to the textile fibre hydrophilic nature. The addition of fibres reduces the maximum dry density and increases the optimum water content. At low stress levels, the compressibility and hydraulic conductivity appear higher, however macro voids produced during sample preparation may alter the findings

Compressibilità e resistenza di un terreno arginale rinforzato con fibre da scarti tessili

L'articolo propone un'indagine sperimentale sul miglioramento e il rinforzo di terreni arginali tramite l'utilizzo di fibre da scarti tessili. Attraverso prove di laboratorio su terreni a cui sono state aggiunte fibre di lino e viscosa, sono stati valutati gli effetti della presenza delle fibre sulla compattazione e sulla resistenza del terreno. I risultati mostrano che l’aggiunta di fibre modifica la risposta del terreno in termini di compattazione riducendo la massima densità secca e aumentando il contenuto d’acqua ottimo. Inoltre, la presenza delle fibre può aumentare significativamente la resistenza al taglio del terreno, in funzione della loro geometria (i.e. diametro e lunghezza) e della quantità considerata. Ulteriori analisi su campioni di dimensioni maggiori sono raccomandate per studiare il comportamento dei terreni rinforzati con fibre tessili, a diverse scale

Internal Erosion in Earthdams, Dikes and Levees

The volume contains the contributions to the 26th Annual Meeting of the European Working Group on Internal Erosion in Embankment Dams, Levees and Dikes, and their Foundations (EWG-IE), held at Politecnico di Milano, in Milano, Italy, from September 10 to 13, 2018. The European Working Group was set up in 1993 to focus on the vulnerability of dams to internal erosion. After an inaugural workshop on definitions and needs, the Group has regularly organized Annual Meetings to share knowledge and address emerging issues on soil internal erosion in water retaining structures. Over the years, the Meetings have seen the participation of university researchers, scientists and engineers from agencies, industries, and public bodies, from Europe and overseas. Following the last successful event in Delft in September 2017, the objective of the meeting in Milano was to serve as a fertile discussion platform, strengthening sound knowledge as well as introducing novel ideas, in the thematic areas in line with the traditional aims of EWG-IE. More than 100 authors, coming from academic institutions, private and public bodies, in European and overseas countries, contributed to the peer-reviewed papers included in the volume. These are grouped into four sections, namely • Laboratory techniques and findings; • From modeling to design criteria; • Prevention measures and field assessment; • Open issues for discussion and contribution. We gratefully acknowledge the careful reviewing work by the members of the Scientific Committee, the technical and administrative support by Federica Aggio and Silvia Spada of the Department of Civil and Environmental Engineering, the skills, patience and care of Marco Caruso who took charge of the editing process, and the support of Politecnico di Milano in providing the facilities for the organization of the meeting. Finally, we are very glad to have hosted the contributors in Milano, a city that was able to evolve and expand its horizons, from the Celtic origin to the twenty-first century, to become a center where dynamism and creativity still coexist with the quietness of old hidden corners. Cristina Jommi, Donatella Sterpi Chairpersons of 26th Annual Meetin

VP50.10: Predicting fetal and maternal complications with sFlt1/PlGF ratio in hypertensive disorders of pregnancy

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Numerical prediction of the drying-wetting process in a river levee and floodplain

One third of the economic losses due to natural disasters in the last century has been caused by floods. Today the flood hazard is increasing due to more frequent extreme hydrological events, caused by climate change, and to the land use change and urbanization, that reduce the water storage capacity of the subsoil and the floodplain areas. An appropriate planning of river levees and floodplains is required to protect inhabited areas and infrastructures. At the same time, an efficient management, assisted by effective monitoring and prediction tools, ensures the performance of the defence systems. In this context, a land reprofiling was designed for river Secchia in Northern Italy, to widen the natural floodplain. In the paper the response of the new system to flood events is assessed by finite element analyses able to describe the soil-water-atmosphere interaction. The reliability of the numerical prediction relies on a proper description of both the hydraulic behaviour of the unsaturated soil, i.e. the water retention curve and the permeability function, and the external load history, established from the hydraulic and atmospheric boundary conditions. Indirect methods for the estimation of the Soil Water Retention Curve may involve significant limits if not combined with a laboratory information on the soil nature and state. Moreover, the numerical results show that the drying-wetting process is highly dependent on the initial saturation conditions of the subsoil, thus making it essential to simulate a sufficiently long load history

Ground pressure and convergence for TBM driven tunnels in visco-plastic rocks

The time-dependent behaviour of rocks may be the cause of difficult tunneling conditions, especially for Tunnel Boring Machine (TBM) driven tunnels at great depth. In fact, the large deviatoric stresses associated with the excavation may induce squeezing conditions that, in the most severe cases, show up in a short time, during the tunnel excavation stages. In this case, the creep deformations lead to large tunnel convergence and consequent high pressures exerted on the permanent liner and on the TBM itself, in particular the cutter head and the shield. The possible occurrence of a TBM jamming should be predicted in advance, so that suitable countermeasures can be taken to prevent it. The increase of the ground pressure on shield and permanent liner during the tunnel face advance is discussed here on the basis of some results from a series of finite element analyses, carried out in axisymmetric regime and adopting an elasto-visco-plastic rheological model. Some comments are drawn on the relevance of some parameters, such as the tunnel advance rate and the tunnel section overboring, for the correct prediction of the ground pressure and of the risk of the machine jamming

Squeezing effects in the excavation of deep tunnels

Difficult conditions in mechanized tunnelling can be met when the rock mass behaviour is time dependent and the so called squeezing condition develops. In this case, large radial pressures on the tunnel boring machine and on the supports are expected in the short and long term. The results of some finite element analyses, in plane strain and axisymmetric regimes, are here discussed concerning the full face excavation of a deep circular tunnel. An elasto-visco-plastic constitutive model that accounts for tertiary creep has been adopted and calibrated on the basis of laboratory test data. Some comments are drawn on the effects of tertiary creep and on the influence of the tunnel face advance on the closure of the opening and on the stress redistribution around it