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The mechanical behaviour of rockfill materials is strongly affected by particle breakage, which causes a continuous variation of the grain size distribution (GSD) until a stationary condition. Although the evolution of grain crushing caused among others by the initial grading, the relative density and stress level has been extensively studied, the relationship describing the influence of the current GSD on other soil properties such as the critical state line is not uniquely defined. In this study, a series of triaxial compression tests with various stress paths under monotonic loading were performed on a rockfill to examine the effect of particle breakage on the position of the critical state lines (CSLs) in the compression plane. Specimens were prepared with the same initial grading and relative density to investigate the evolution of the GSD as a result of grain breakage determined by different stress paths applied in a large triaxial apparatus. In addition, a recently proposed simplified procedure is employed to capture the evolution of the CSLs of the tested crushable rockfill as a function of a breakage parameter related to the breakage index Bg. Experimental results obtained for the tested rockfill demonstrate that the abovementioned procedure is capable to predict the position of the CSL linked to the GSD reached at the end of the triaxial test, also when the critical state condition, defined as the ultimate condition in which shearing could continue indefinitely without changes in volume or effective stresses, is not reached.

Earthen river embankments are typically in unsaturated conditions during their lifetime and the degree of saturation within their bodies may vary significantly throughout the year, due to seasonalfluctuations of the river stage, as well as infiltrations of meteoric precipitation and evapotranspiration phenomena. Given the significant effects of partial saturation on the hydro-mechanical behaviour of soils, realistic assumptions on the actual water content distribution inside the embankments are essential forproperly modelling their response to hydraulic loadings. In this framework, centrifuge modelling is a useful tool to get insights into the evolution of saturation conditions of a water retaining structure during flood events. It allows for the direct observation of the groundwater flow process, which is hardly detectable at the prototype scale, enabling, at the same time, the validation and calibration of predictive numerical tools.In this paper, the results of a centrifuge test carried out on small-scale physical model of a compacted silty clayey sand embankment subjected to a simulated high-water event, at the enhanced gravity of 50-g, are presented and discussed. The physical model was carefully instrumented with potentiometers, miniaturized pore pressure transducers and tensiometers. Pore pressures and suctions measured during the experiment showed that the stationary flow conditions were reached only after an unrealistic hydrometric peak persistence. It therefore emerges that, for the design and/or the assessment of the safety conditions of a river embankment similar to the one tested, the simplified hypothesis of a steady-state seepage, in equilibrium with the maximum river stage expected could result, in many cases, an excessively conservative assumption.

The study of the hydraulic behaviour of compacted soils in partially saturated conditions is essential for understanding the engineering performance of geotechnical structures such as river embankments. The paper presents the results of an experimental study focusing on the effects of the initial water content and dry density on soil water retention curve (SWRC) and volume change of a compacted soil mixture under hydraulic loading. For this purpose, soil specimens compacted at different water contents(dry, wet and optimum water content), chosen on the basis of standard Proctor compaction test, were used. Specimens of a mixture composed of 70% Ticino sand (TS) and 30% Pontida silt (PON) have been tested. This is a heterogeneous mixture of sand and silt, that usually constitute the embankments of tributaries of river Po (Italy). The SWRCs along drying paths were performed by means of evaporation tests starting from the saturated conditions gained in permeameter tests. For the investigation of the change in the void index during the evaporation test, the volume variation of the tested specimens was estimated by means of a calliper and photographic comparison. Changes in the SWRCs are consistent with changes in specimen initial condition while the soil volume change exhibited at the end of evaporation test is always negligible.

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Rockfill dams have become more and more recognized for their safety, economy and adaptability to widely varying site conditions. As a contribution to the understanding of the main factors affecting the rockfill behaviour, the paper reports and discusses experimental data on several aspects relevant to the interpretation and analysis of their in-situ response. The experimental programme involved three series of oedometric tests on specimens of two different gravels having the same grading, reconstituted at the same initial relative density. Experimental observations on rockfills compressibility are presented and discussed: attention is paid to the role of degree of saturation (Sr) through the analysis of “driest”, “fully saturated” conditions, and the transition from one to the other. Grain crushing tests on dry and saturated soil particles are also reported. Grain size distributions of the specimens, both after compaction and after the oedometer tests, are compared in the paper. The results show that the effect of Sr cannot be overlooked in the mechanical characterization of the material, especially in rockfill/stress conditions prone to crushing

As well known, rockfill behaviour is strongly influenced by both intrinsic (mineralogy and size of particles, grain shapes, soil grading etc.) and state parameters (relative density, stress state, relative humidity). To investigate their mechanical response to stresses and relative humidity (RH) loadings, a large size triaxial device (H = 410 mm, D = 200 mm) has been developed at the University of Naples Federico II (Italy), including modifications required to impose partially saturated conditions in the specimen by means of the vapour equilibrium technique. In order to evaluate local axial and radial strains and global volumetric strains in partially saturated conditions, a magnetic shape detector device has been designed and installed. The accuracy of this system has been evaluated in some isotropic compression triaxial tests on compacted sandy-gravel specimens. The experimental data clearly show the effectiveness of the magnetic system in the measurement of axial displacements while the measurement in radial direction appear to be strongly affected by the non-linearity of the complex magnetic field generated during the test and requires further checking tests.

To investigate the hydraulic behaviour of the fine-grained embankments along the mid-course of the Po River, research was carried out on a full-scale physical model, built on the floodplain along the existing embankment and forming a pond. The pond was filled to reproduce historical floods. The prototype was built according to recommendations formulated by the Po River Management Authority. The engineering properties of the foundation soils were investigated by in situ tests and complemented by some suction-controlled laboratory tests. Pore-water pressure was measured in the embankment and in its foundation before, during, and after the experimental reproduction of two floods that occurred in 1976 and 2000. Atmospheric variables were monitored at the prototype site. Monitoring data refer to 6 months of experimental activities. Pore-water pressure measurements were first presented and subsequently interpreted through an isothermal two-dimensional flow approach where boundary flow rates express the evolution of atmospheric variables. The distribution of the pore water provided by this interpretation was used for stability analyses of the prototype. Results from the experimental activities and their interpretation indicate that the river embankment remains extensively unsaturated during floods. Typical suction trends within the embankment, suction- associated soil strength, and the resulting slope stability safety factors are also shown. Key words: embankments, partially saturated soil, in situ measurements, numerical analysis, hydraulic conductivity. Un projet de recherche a ete realise afin d'etudier le comportement hydraulique de berges de materiaux fins placees a mi-chemin de la riviere Po, grace a un modele physique a l'echelle reelle construit sur la plaine inondable le long d'une berge existante et formant un etang. L'etang a ete rempli pour reproduire des inondations historiques. Le prototype a ete construit selon les recommandations formulees par l'Autorite de gestion de la riviere Po. Les proprietes d'ingenierie des sols de fondation ont ete evaluees par des essais sur le terrain et completes par quelques essais de controle de succion en laboratoire. Les pressions interstitielles dans la berge et dans sa fondation ont ete mesurees avant, pendant, et apres les reproductions experimentales de deux inondations survenues en 1976 et 2000. Les variables atmospheriques ont ete mesurees sur le site du prototype. Les donnees de suivi recueillies couvrent 6 mois d'activites experimentales. Les mesures de pression interstitielle sont d'abord presentees et ensuite interpretees a l'aide d'une approche d'ecoulement isotherme en 2D dans laquelle les conditions frontieres de taux d'ecoulement expriment revolution des variables atmospheriques. La distribution des pressions interstitielles obtenue par cette interpretation est utilisee pour des analyses de stabilite du prototype. Les resultats des activites experimentales et leur interpretation indiquent que les berges de la riviere demeurent fortement non saturees durant les inondations. Les tendances typiques de succion a l'interieur de la berge, la resistance du sol associee a la succion, et les facteurs de securite de stabilite de pente sont aussi presentes. [Traduit par la Redaction] Mots-cles: berges, sols partiellement satures, mesures in situ, analyse numerique, conductivite hydraulique., Introduction The Po River, which crosses northern Italy from west to east (Fig. 1), is Italy's main water course in terms of length and capacity. Past flooding of the main [...]

An experimental study has been carried out to investigate the effects of isotropic compression, wetting, and drying on the initial shear stiffness of Zenoz kaolin, an unsaturated lean clay, both in normally consolidated and overconsolidated conditions. The proposed study was conducted using fixed-free resonant column--torsional shear (RCTS). Specimens were compacted using the undercompaction technique. Initial shear stiffness was measured almost continuously along complex stress paths including (i) an initial equalization stage to a suction value of 0, 50, 150, and 300 kPa; (ii) an isotropic compression stage at constant suction, up to a net stress high enough to move the loading collapse line; (iii) an isotropic unloading stage at constant suction; (iv) a wetting and (or) drying path. The mentioned stress path allowed elimination or determination of the overconsolidation effect on the initial shear stiffness measured. The behavior observed is qualitatively similar to that of saturated soil, while wetting data clearly indicate that [G.sub.0] depends significantly on volumetric behavior. In normally consolidated samples where wetting is accompanied by collapse, reduction in suction has no remarkable effect on G0. Conversely, in overconsolidated samples [G.sub.0] reduces significantly as suction decreases. Key words: unsaturated kaolin, small-strain behavior, volumetric behavior, stress history, isotropic compression and wetting. Une etude experimentale a ete realisee pour etudier les effets de la compression isotrope, du mouillage et du sechage sur la rigidite en cisaillement initiale d'un kaolin Zenoz, une argile maigre non saturee, autant en conditions de consolidation normale et de surconsolidation. L'etude proposee a ete realisee avec une colonne de resonance-isaillement en torsion (CRCT) fixe-libre. Les echantillons ont ete compactes a l' aide de la technique de sous-compaction. La rigidite au cisaillement initiale a ete mesuree presque en continu le long de cheminements des contraintes complexes incluant : (i) une etape initiale d'egalisation a une valeur de succion de zero, 50, 150 et 300 kPa; (ii) une etape de compression isotrope a succion constante, jusqu' a une contrainte nette suffisante pour deplacer la ligne rupture en chargement; (iii) une etape de dechargement isotrope a succion constante; (iv) un cheminement de mouillage et (ou) de drainage. Le cheminement des contraintes mentionne permet d' eliminer ou de determiner l' effet de la surconsolidation sur la rigidite en cisaillement initiale mesuree. Le comportement observe est similaire qualitativement a celui d'un sol sature, tandis que les donne es de mouillage indiquent clairement que [G.sub.0] depend de facon significative du comportement volumetrique. Dans le cas d'echantillons normalement consolides pour lesquels le mouillage s'accompagne d'une rupture, la reduction de la succion n'a pas d'effet marque sur [G.sub.0].Al'inverse, dans le cas d'echantillons surconsolides, [G.sub.0] diminue significativement lorsque la succion diminue. Mots-cles : kaolin non sature, comportement a faible deformation, comportement volumetrique, historique des contraintes, compression et mouillage isotrope. [Traduit par la Redaction], Introduction The initial shear modulus, [G.sub.0], is a key parameter for predicting the dynamic response of soils, for the design and the analysis of earthquake-resistant foundations and vibrating machine foundations, [...]

Abstract: This is the follow-up paper to Vassallo et al. (2007), which discussed the experimentally observed small-strain behaviour of an unsaturated compacted silt. The influence that suction and, more in [...]

Abstract: An experimental study was carried out to investigate the effects of the mean net stress and suction history on the initial shear stiffness, [G.sub.0], of a compacted clayey silt. [...]

A clayey soil has been tested in the laboratory in order to investigate the influence of the compaction procedure on the soil retention behaviour. In common engineering practice, data available for modelling are those of the soil compacted in the laboratory and soil behaviour during the earth structures lifecycle is predicted on that basis. This practice, however, seems to overlook the fact that construction procedures in the field might differ significantly from the compaction techniques used in the laboratory and this may induce considerable differences in material texture and therefore in the soil behaviour. The investigation shown in the present work aims to provide further insight into this aspect and to help endorsing or refuting the validity of such practice.

The paper presents and discusses some results of an experimental research aimed at analysing the influence of compaction variables (w and energy) and method on the resulting microstructure of a compacted silty soil. In particular, the experimental data here discussed allow to compare the microstructure induced by different dynamic compaction techniques, comparing that characterising specimens obtained by two laboratory methods (Proctor standard and Harvard) and that of samples compacted in-situ during the construction of an embankment built for river regimentation purposes. Both undisturbed and disturbed samples have been retrieved from the embankment, the latter one with the purpose of collecting the soil subsequently used for laboratory compaction. Microstructural analyses (SEM, MIP) performed on laboratory and in-situ compacted samples evidenced a substantial similarity of the texture induced by the various compaction techniques, highlighting that laboratory compaction is suitable to provide soil samples representative of earth in-situ compacted soil.

Photographic objects in ethnological and anthropological collections are systematically called into question in current debates on the nature and functions of the museum vis à vis the legacy of colonialism and imperialism, systemic racism, and the persistence of Eurocentric and patriarcal ideologies. The aim of this dossier is to offer a first opportunity to confront these issues by sharing the experiences of three of the most important institutions of this kind in Italy and their daily work on the conservation, valorization, and communication of the cultural heritage. [ABSTRACT FROM AUTHOR]