The paper presents the phenomenological interpretation of the failure mechanism involving an active and complex landslide process within the Pisciolo hill-slope (Southern Apennines, Italy). The sliding process interacts with important infrastructures that in the last decade have undergone recurrent damage, prompting a comprehensive investigation and monitoring of the slope features and processes. Based on the study of all the investigation data, the interpretation of the failure mechanism has required the creation of the geological and the geotechnical model of the slope along with the reconstruction of the slope history. The case is representative of the slow evolution of landsliding typically occurring in chain areas where the outcropping clayey soils are extensively disturbed and fissured as result of intense long-lasting tectonics.

The diagnosis of landsliding at the slope scale resulted from synergic geohydromechanical analyses of the slope factors, which should represent the first step to assess landslide hazard. According to the methodological approach discussed in the paper, the landslide hazard analysis should start from a phenomenological interpretation of the slope behaviour, including the definition of the slope factors, getting then to a quantitative prediction of the slope evolution with time. This quantitative evaluation should result from limit equilibrium analyses and numerical modelling, both of them performed considering the outcomes of the phenomenological reconstruction. Therefore, the understanding of the slope factors and of the landslide mechanism at the slope scale should drive the landslide hazard assessment, through analyses performed for different levels of diagnosis (phenomenological, analytical and numerical). Some landslides, representative for chain slopes in the Italian peninsula, are discussed in the paper in order to show the maturity of the geohydromechanical diagnosis of landslide hazard and, hence, to properly design the mitigation actions. A methodology for intermediate to regional landslide hazard assessment, based on geomechanical interpretations, is finally proposed.

This lecture outlines a research approach, procedure and strategy aimed at the development of clay modeling in the context of natural clays of varying geological history. The aim is at providing evidence of the clay features causing given behavioral facets, at the micro to the meso-scale, in order to connect classes of behavior and corresponding models, to classes of clays. The approach to micro-macro is not that of deducing macro-behavior from modeling the micro-processes, not so feasible for clays, but to join systematically the knowledge of the micro to meso features and processes and the observations of macro-response. The procedure entails the development of analyses spanning from those generally carried out in clay science, at the micro-scale, to characterizations of the meso-scale, to analysis through element testing of the macro-behavior. Furthermore, the procedure includes studies of the geological history of the material. Examples of application of the research strategy to different case studies are presented, that document how it is possible to both identify the internal factors generating given clay behavioral facets and model clay behavior within a simple general framework. This framework represents an example of formalization of the variability of clay response with the micro to meso-features of the clay

This article presents the developments of an ongoing research aimed at modelling the influence of fissuring on the behaviour of clays. In particular, it recalls the main results of an extensive laboratory investigation on a fissured bentonite clay from the south of Italy and presents the data of a new investigation on the evolution with shearing of the strain fields developing within the clay, resulting from Digital Image Correlation (DIC). Element test results are analysed in the framework of continuum mechanics and linked to the clay fissuring features, once characterised using the Fissuring IDentity (F-ID) chart. This article compares the bentonite behaviour with that of other fissured clays of different F-IDs, highlighting the common behavioural features. Thereafter, the soil response at the macro level is related to the DIC-derived strain fields evolving within the clay with loading. For this purpose, DIC was successfully used to investigate the deformation processes active in the fissured clay and the sources of the localisation phenomena. DIC is shown to provide indications of the extent to which highly to medium fissured clays element test results can be of use to model the clay behaviour according to continuum mechanics. Copyright (c) 2012 John Wiley & Sons, Ltd.

The paper discusses the geological history, intrinsic properties, structural features and mechanical behaviour of three differently fissured clays outcropping within the Apennine chain in southern Italy. Based on a large experimental database, the mechanical behaviour of the clays is investigated in the light of their different fissuring features, which have been distinguished and characterised by means of a new chart. The study assumed the soil to be a continuum, despite the different fissuring features of the clay fabric. Therefore laboratory tests were carried out on both natural and reconstituted clay samples, and the results were compared with those recognised in the literature to be typical of unfissured sensitive clays. Based on these comparisons, a behavioural framework is proposed for clays possessing certain fissure structures. The results of the analysis show that the mini- to mesostructure of clays of fissuring intensity 15-16 can be modelled as part of the structure variable controlling the clay behaviour. Where the structure variable refers solely to the micro scale for unfissured homogeneous clays, for fissured clays 15-16 it spans from the micro to the meso scale. As for the microstructure of unfissured clays, this micro- to mesostructure influences the soil response as an internal state variable in addition to specific volume in controlling the mechanical response. In particular, it appears that for clays of fissuring intensity 15-16, structure is detrimental to strength, so that the material is even weaker than the reconstituted clay.

The paper presents the results of Digital Image Correlation (DIC) method applied to plane strain tests carried out on specimens of fissured clays from the south of Italy. Information about physical properties and Fissuring IDentity of the clays are reported together with an outline of the global behaviourial framework of the fissured clay Represententative Element Volume (REV). DIC has been used to explain some discrepancies found in the global shearing behaviour of some specimens which did not fit the framework. DIC revealed the sources of such discrepancies, which made these specimens much smaller than the REV.

This paper represents a further step in a longstanding research on the influence of fissuring on the mechanical behavior of natural clays. The results of an experimental investigation into the influence of fissure orientation on the evolution of strain localization in the intensely fissured scaly clay from Santa Croce di Magliano (south of Italy) are reported. The experimental program involved plane strain compression tests where the effects of the combination of different factors, such as the specimen size and the orientation of fissuring, were investigated. A key aspect to this work is that the standard global stress-strain measurements were augmented by full-field displacement and strain measurements through 2D digital image correlation. Access to incremental strain fields provided information about slight details or anomalies as well as the complexity of deformation processes, which is of crucial importance for proper interpretation of test results at the global, macroscopic level.

The paper reports the key features of the behaviour of different fissured clays whose fissuring features have been first related to specific classes within a characterization chart proposed by the Authors. For each of the clays under study, a Fissuring IDentity (F-ID) Chart has been created by selecting the most relevant fissuring features within the general chart. The approach used in the interpretation of the mechanical behaviour of the fissured clays has been that of continuum mechanics, through the development of element testing in the laboratory, analysis of the results in the framework of traditional Critical State Soil Mechanics and modelling following traditional elastic-plastic theory. Throughout the paper the mechanical effects of the different fissuring fea-tures of the clays have been evaluated accounting for their F-ID charts. The paper reports also the further requirements which elastic-plastic models of structured clays have to accomplish with in order to represent the behaviour of fissured clays.

This lecture outlines a research approach, procedure and strategy aimed at the development of clay modeling in the context of natural clays of varying geological history. The aim is at providing evidence of the clay features causing given behavioral facets, at the micro to the meso-scale, in order to connect classes of behavior and corresponding models, to classes of clays. The approach to micro-macro is not that of deducing macro-behavior from modeling the micro-processes, not so feasible for clays, but to join systematically the knowledge of the micro to meso features and processes and the observations of macro-response. The procedure entails the development of analyses spanning from those generally carried out in clay science, at the micro-scale, to characterizations of the meso-scale, to analysis through element testing of the macro-behavior. Furthermore, the procedure includes studies of the geological history of the material. Examples of application of the research strategy to different case studies are presented, that document how it is possible to both identify the internal factors generating given clay behavioral facets and model clay behavior within a simple general framework. This framework represents an example of formalization of the variability of clay response with the micro to meso-features of the clay.

Nella presente nota sono illustrati i risultati di una ricerca riguardante la modellazione fisica e numerica dello scavo di una galleria in condizioni di campo libero e in presenza di un elemento strutturale. Lo studio è finalizzato alla verifica dell’efficacia di strumenti di analisi numerica di tipo convenzionale per la simulazione dei risultati di prove su modello fisico in scala ridotta, eseguite nella centrifuga geotecnica del London Geotechnical Centrifuge Centre (LGCC) della City University di Londra.