Effect of freeze-thaw cycles on the hydraulic conductivity of a compacted clayey silt and influence of the compaction energy

Compacted clay layers are often used in impervious barrier systems to prevent the migration of water and pollutants. Environmental factors, acting during or after the clay deposition, may affect the layer integrity and induce a variation of hydraulic conductivity over time. The aim of the present research is to assess this variation when induced by freeze–thaw cycles. The paper summarizes some results of tests performed on a series of clayey silt samples, reconstituted at various levels of compaction energy and subjected to cyclic freezing according to a controlled and repeatable procedure, set to reproduce the natural environmental conditions. The hydraulic conductivity is evaluated directly from a flexible wall permeameter and indirectly from oedometric tests. The results show the consequences of cyclic freezing in relation to the compaction level and lead to insights into the development of fracture networks responsible for the increase in hydraulic conductivity

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

GFRP Pipe for Tunnel Face Reinforcement: The Laboratory Characterization

In tunnelling engineering the preliminary support of the tunnel face is often based on the soil nailing technique, considered as one of the most effective provisions for the control and reduction of the tunnel pre-convergence and face extrusion. The nails are mostly made of Glass Fibre Reinforced Polymer (GFRP), due to the advantages this material offers in this application. In the years, improvements have been introduced also in the theoretical and computational analysis of nailing systems, so that nowadays it is possible to take into account their mechanical action at the design stage. The nail performance being a key design parameter, an accurate investigation on the mechanical response of the GFRP pipe and on the pipe-soil interaction is therefore fundamental to support specific design assumptions. Moreover, the correct identification of the associated mechanical parameters, such as the pipe tensile strength and the pipe-soil bonding adherence, is required to limit the uncertainties in the values adopted in the design. In this paper the attention is focused on laboratory tests carried out for this characterization. The principal objective is to set up appropriate procedures to characterize GFRP pipes for soil nailing systems, that ensure reliability and repeatability of the tests. The result is a series of recommendations specifically addressed to adapt ordinary tensile and pull out tests to the treatment of GFRP pipes

MODELLAZIONE FISICA DEL FENOMENO DI EROSIONE INTERNA

Fra le cause di collasso di pendii e rilevati in terra soggetti a filtrazione vi è l’erosione interna di particelle, fenomeno evolutivo che può manifestarsi inizialmente in modo diffuso, per poi localizzarsi in canali di flusso, oppure innescarsi lungo discontinuità preesistenti. Questo contributo presenta lo sviluppo di un’attrezzatura di laboratorio per l’osservazione e la misura del fenomeno di erosione interna e formazione di canali di flusso alla piccola e media scala. Consente di analizzare l’influenza del percorso di flusso e di una pressione di confinamento, di condurre prove in regime di filtrazione confinata o non confinata, e di ricostruire modelli fisici in scala ridotta di pendii e rilevati, per strati di qualunque inclinazione

Systematic and statistical errors in homodyne measurements of the density matrix

We study both systematic and statistical errors in radiation density matrix measurements. First we estimate the minimum number of scanning phases needed to reduce systematic errors below a fixed threshold. Then, we calculate the statistical errors, intrinsic in the procedure that gives the density matrix. We present a detailed study of such errors versus the detectors quantum efficiency $\eta$ and the matrix indexes in the number representation, for different radiation states. For unit quantum efficiency, and for both coherent and squeezed states, the statistical errors of the diagonal matrix elements saturate for large n. On the contrary, off-diagonal errors increase with the distance from the diagonal. For non unit quantum efficiency the statistical errors along the diagonal do not saturate, and increase dramatically versus both $1-\eta$ and the matrix indexes

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

Robot-aided neurorehabilitation in sub-acute and chronic stroke: Does spontaneous recovery have a limited impact on outcome?

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Taking a Lesson From Patients' Recovery Strategies to Optimize Training During Robot-Aided Rehabilitation

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evaluation of upper limb sense of position in healthy individuals and patients after stroke

The aims of this study were to develop and evaluate reliability of a quantitative assessment tool for upper limb sense of position on the horizontal plane. We evaluated 15 healthy individuals (controls) and 9 stroke patients. A robotic device passively moved one arm of the blindfolded participant who had to actively move his/her opposite hand to the mirror location in the workspace. Upper-limb's position was evaluated by a digital camera. The position of the passive hand was compared with the active hand's 'mirror' position. Performance metrics were then computed to measure the mean absolute errors, error variability, spatial contraction/expansion, and systematic shifts. No significant differences were observed between dominant and non-dominant active arms of controls. All performance parameters of the post-stroke group differed significantly from those of controls. This tool can provide a quantitative measure of upper limb sense of position, therefore allowing detection of changes due to rehabilitation