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An extensive experimental program of constant-volume (undrained) cyclic simple shear tests was undertaken on Ticino, Italy, sand with different contents of nonplastic fines, ranging from 0%...

Sustainable development principles aim to re-utilize wastes to reduce their impact on the environment. In this context, the present contribution shows preliminary results on the preparation of innovative synthetic lightweight aggregates, starting from biomass-derived fly ash and high-density polyethylene (HDPE), to be used in geotechnical applications. The present work focuses on the manufacturing process of aggregate blends (including the selection of the right proportions of the two components) as well as on the relative determination of (i) physical&ndash, chemical properties (i.e., chemical composition, morphological analysis, mineral leachability, water absorption, specific gravity, grain size distribution), (ii) permeability features and (iii) mechanical properties (one-dimensional compression and shear strength behavior). The results, gathered from the new synthetic lightweight aggregates and compared with the corresponding ones obtained in a previous study conducted on natural and synthetic lightweight aggregates, appear promising for a potential utilization in geotechnical engineering.

Low plasticity sand-silt mixtures are very common in Italy either in natural depositional environment or in man-made earth-fill, hence the knowledge of their behavior is a crucial aspect in many practical applications. Due to higher compressibility features, significant strains and strength loss may be triggered by earthquakes. The results of a laboratory-based investigation undertaken on undisturbed samples of low plasticity silty-sandy soils recovered from a bank stretch after the 2012 Emilia Romagna earthquake in Italy, when serious damages and widespread liquefaction events were observed, are herein presented. Special emphasis was given to susceptibility to liquefaction and pore water pressure response in presence of an initial static shear stress. As part of the present work, the results of undrained cyclic simple shear (CSS) tests carried out on reconstituted specimens of sand-fines mixtures, covering a range of non plastic fines contents from 0% to 40%, were used for predicting undrained cyclic resistance through the concept of equivalent granular void ratio, e* . The conceptual framework based on e* appears appropriate for streamlining the effect of fines on cyclic liquefaction resistance of these intermediate soils, provided that fines content is less than a limiting value. Since an important stage in the assessment of liquefaction potential is to predict excess pore water pressure during cyclic loading, the results of CSS tests were also utilized for analysing pore water pressure generation models of silty sands over a wide range of fines contents.

This paper describes the results of a laboratory investigation performed on clean sand and low-plasticity silty sands, recovered at different locations of the bank stretch at Scortichino, which was affected by serious damages following the 2012 Emilia Romagna earthquake in Italy. A comprehensive cyclic simple shear (CSS) testing program was undertaken to evaluate the liquefaction potential and pore pressure response of silty sand layers, which form the subsoil at the site. A series of undrained CSS tests were carried out on undisturbed samples by applying an initial static driving shear stress before cyclic loading (nonsymmetrical tests), with the aim of gaining a better understanding of the role played by a static preshearing on the observed liquefaction phenomena. The results obtained prove that, in nonsymmetrical cyclic loading tests, low-plasticity silty sands tend to be more susceptible to liquefaction than in symmetrical cyclic loading tests. The onset of liquefaction occurs by large shear s...

The paper deals with an experimental study of the undrained cyclic behavior of a natural coarse sand and gravel deposit located in Gioia Tauro, a town situated on the continental side of the Messina Strait in Italy. The study was conducted through cyclic undrained triaxial tests carried out on both undisturbed and reconstituted samples. Undisturbed samples were recovered by an in situ freezing technique and the sample quality was carefully assessed. Reconstituted samples were prepared by using two different reconstitution methods, namely air pluviation (AP) and water sedimentation (WS), and tested under the same in situ initial relative density and effective overburden stress. Tests were carried out on both isotropically and anisotropically consolidated specimens. The results obtained from this study provide direct evidence that cyclic liquefaction resistance obtained from water sedimented samples closely approximates that exhibited by undisturbed samples in both isotropically and anisotropically consolidated tests. Conversely, AP leads to a marked underestimation. Since the investigated deposit is considered to have been formed by the marine water environment, these results can be regarded as proof that WS closely replicates the in situ fabric of the investigated deposit allowing the substitution of the expensive undisturbed samples with their reconstituted counterparts. Anisotropically consolidated specimens respectively exhibit "cyclic liquefaction" or "cyclic mobility" depending on whether or not they are loaded under the shear stress reversal mode.

An unprecedented transformation in the design, deployment, and application of short-range wireless devices and services is in progress today. This trend is in line with the imminent transition from third- to fourth-generation radio systems, where heterogeneous environments are expected to prevail eventually. A key driver in this transition is the steep growth in both demand and deployment of WLANs/WPANs based on the wireless standards within the IEEE 802 suite. Today, these short-range devices and networks operate mainly standalone in indoor home and office environments or large enclosed public areas, while their integration into the wireless wide-area infrastructure is still nearly nonexistent and far from trivial. This status quo in the short-range wireless application space is about to be disrupted by novel devices and systems based on the emerging UWB radio technology with the potential to provide solutions for many of today's problems in the areas of spectrum management and radio system engineering. The approach employed by UWB radio devices is based on sharing already occupied spectrum resources by means of the overlay principle, rather than looking for still available but possibly unsuitable new bands. This novel radio technology has received legal adoption by the regulatory authorities in the United States, and efforts to achieve this status in Europe and Asia are underway. This article discusses both the application potential and technical challenges presented by UWB radio as an unconventional but promising new wireless technology.

The paper will offer insights regarding the effects of cyclic prestrain history on the undrained behaviour of an uncemented carbonate sand (Quiou sand) through a modified NGI simple shear (SS) apparatus. Tests were carried out on specimens reconstituted at two void ratios (loose and dense) by using the water sedimentation method. The influence of cyclic undrained pre-shearing was investigated by applying both small and large limiting shear strains; after reconsolidation, the specimens were again subjected to the same cyclic phase as before, until the sample liquefied. The pattern of post-cyclic behaviour of the tested sand showed the relevant role assumed by the phase transformation line obtained from monotonic tests on virgin specimens. For both loose and dense specimens a threshold value of cyclically induced pre-shear strain was found at which the positive effect of previous cyclic loading history on liquefaction resistance disappears or starts to reverse. A normalising criterion, capable of providing ...

The paper presents a study of the undrained behaviour of an uncemented carbonate sand (Quiou sand) under simple shear loading conditions. The experimental study was conducted through cyclic and monotonic undrained/constant volume simple shear tests carried out on reconstituted specimens prepared by using the sedimentation in water (WS) method. Tests were carried out on specimens reconstituted at two void ratios (i.e. loose and dense) and different effective consolidation stresses. Furthermore, to account for the effect of non-zero mean shear stress level, cyclic simple shear tests were performed under both symmetrical and non-symmetrical cyclic loading. Two types of failure modes have been observed in cyclic tests, that is ‘cyclic liquefaction’ or ‘cyclic mobility’, depending on whether or not they were conducted under shear stress reversal conditions. A unified framework seems to exist whereby undrained monotonic and cyclic response can be comparatively analysed. In particular, normalising the cyclic liquefaction resistances obtained from symmetrical tests by phase transformation strengths determined in corresponding monotonic tests, provides a cyclic liquefaction resistance curve which was found to be unique, irrespective of initial void ratio and vertical effective stress. Undrained cyclic shear strength of the tested sand appears to be affected by the presence of a non-zero mean shear stress, following a pattern of behaviour, which is similar for both loose and dense specimens. Furthermore, the normalised stress–strain curves of the cyclic tests show back-bone curves that are practically coincident with the equivalent monotonic curves.

La sequenza sismica che ha colpito la pianura padana emiliana nel 2012, con scosse principali il 20 e 29 maggio, ha prodotto diffusi ed estesi dissesti in alcuni rilevati arginali che, in qualche caso, hanno determinato l’inagibilità di edifici e la chiusura di strade. Uno degli argini maggiormente colpiti è quello del canale diversivo in località Scortichino, frazione del Comune di Bondeno, sede di oltre 400 tra unità abitative e produttive, molte delle quali classificate inagibili proprio a causa dei dissesti verificatisi nell’argine. La Regione Emilia-Romagna, su richiesta dell’Amministrazione Comunale, ha costituito un Gruppo di Lavoro in cui l’Associazione Geotecnica Italiana, con diversi gruppi di ricerca già coinvolti nella rete di laboratori ReLuis, ha affiancato i tecnici della Regione con l’obiettivo di analizzare la risposta sismica dell’argine durante la sequenza sismica del 2012, comprendere le cause dei dissesti osservati e suggerire le necessarie azioni di mitigazione ed eventuali interventi di messa in sicurezza nei confronti di terremoti futuri. A questo scopo è stata condotta un’ampia campagna sperimentale di indagini in sito, sia geofisiche che geotecniche, e di prove di laboratorio, finalizzate alla ricostruzione di un accurato modello geotecnico per la valutazione delle condizioni di stabilità dell’argine in condizioni sismiche, portando in conto anche l’eventuale insorgenza di fenomeni di liquefazione nei terreni sabbiosi superficiali costituenti la fondazione del corpo arginale. La presente memoria intende dare conto delle attività del Gruppo di Lavoro e sintetizzare i principali risultati conseguiti.