The new challenge that the research in slopes instabilities phenomena is going to tackle is the effective integration and joint exploitation of remote sensing measurements with in situ data and observations to study and understand the sub-surface interactions, the triggering causes, and, in general, the long term behaviour of the investigated landslide phenomenon. In this context, a very promising approach is represented by Finite Element (FE) tech- niques, which allow us to consider the intrinsic complexity of the mass movement phenomena and to effectively benefit from multi source observations and data.In this context, we perform a three dimensional (3D) numerical model of the Ivancich (Assisi, Central Italy) instability phenomenon. In particular, we apply an inverse FE method based on a Genetic Algorithm optimization procedure, benefitting from advanced DInSAR measurements, retrieved through the full resolution Small Baseline Subset (SBAS) technique, and an inclinometric array distribution. To this purpose we consider the SAR images acquired from descending orbit by the COSMO-SkyMed (CSK) X-band radar constellation, from December 2009 to February 2012. Moreover the optimization input dataset is completed by an array of eleven inclinometer measurements, from 1999 to 2006, distributed along the unstable mass.The landslide body is formed of debris material sliding on a arenaceous marl substratum, with a thin shear band detected using borehole and inclinometric data, at depth ranging from 20 to 60 m. Specifically, we consider the active role of this shear band in the control of the landslide evolution process. A large field monitoring dataset of the landslide process, including at-depth piezometric and geological borehole observations, were available. The integration of these datasets allows us to develop a 3D structural geological model of the considered slope.To investigate the dynamic evolution of a landslide, various physical approaches can be considered according to the characteristics of the analyzed phenomenon. In present case, we focused on Newtonian approach by considering a creeping flow approximation, which are suitable to simulate the kinematical trend of the Ivancich landslide test site. This model is suitable to simulate soil material undergoing secondary creep (steady state creep), with the creep rate almost constant over time and depending on the current stress level of the soil.The experimental results are very promising and clearly show that this numerical approach is able to simulate the spatial distribution and temporal evolution of the landslide kinematic, highlighting that the translational movement of such a landslide portion results to be the reason for the long-term instability. We conclude that the developed three dimensional physical model, built up by the integration of dataset derived from geological information and different measure platforms, represents an innovative and effective approach to improve the comp

The landslide hazard assessment, when based on the deterministic diagnosis of the processes, can be pursued only through the interpretation and the geo-hydro-mechanical modelling of the slope equilibrium. In practice, though, landslide hazard assessment is still seldom dealt with slope modelling, in particular when it addresses vast areas, where either heuristic or statistical methods do not entail any geo-hydro-mechanical knowledge of slope features and stability. The Multiscalar Method for Landslide Mitigation (MMLM) is an original methodological approach for intermediate to regional landslide hazard assessment. It is based on the geo-hydro-mechanical knowledge achieved from the application of a stage-wise diagnostic methodology of the landslide mechanism at the slope scale. The paper discusses the main steps of the MMLM aiming at diagnoses of landslide hazard based on hydro-mechanics, for small scale hazard mapping (at the large area).

Soft highly porous carbonate rocks, such as calcarenites, and soluble sulphate rocks, such as gypsum, are very common in the Mediterranean region and, due to their microstructure and chemical composition, are prone to water induced weathering mechanisms. Cliffs, underground cavities and other morphological features in such formations are hence affected by intense erosion phenomena and weathering processes responsible for unexpected collapses and sinkholes. Just considering the Apulian region (Italy), 150 sinkholes have been recorded since 1925, with increasing frequency since 2000 (Fiore et al., 2018). The geosystem's failure is often the short or long-term result of a very complex hydro-chemo-mechanical process taking place at the micro-scale which can be detected and analysed by means of field and laboratory experimental test campaigns. Therefore, stability problems are often related to changes of the mechanical properties of the rock forming the cave caused byenvironmental weathering processes, despite the external boundary conditions are not changing with time. The paper deals with the assessment of hazard associated with the stability of abandoned underground caves, which is nowadays frequently required for land and urban planning activities. A methodological approach for hazard assessment based on a step-by-step procedure is proposed. This includes in-situ surveys, laboratory experimental studies, theoretical analyses and finally numerical investigations. The approach derives from the experience developed from several case studies analysed by the authors. In this work, two of these are presented. The first one concerns the stability of an anthropic cavity in a calcarenite formation which is affected by a water induced short-term and long-term debonding processes. The second one regards the stability of a three-level abandoned gypsum mine, the lowest level being partially flooded by water. The methodological procedure aims to evaluate the factors controlling the change of the mechanical properties of the rock so that efficient remediation measures can be designed in order to avoid any further decay of the rock mass stability with time.The proposed methodological approach, validated on real case studies, shows the convenience of performing advanced experimental, theoretical and numerical studies to properly assess the hazard in space and time and to better design the mitigation measures if they are required. The adoption of the proposed approach reduced the remediation costs of the second case study of one order of magnitude.

Natural and anthropogenic caves may represent a potential hazard for the built environment, due to the occurrence of instability within caves, that may propagate upward and eventually reach the ground surface, inducing the occurrence of sinkholes. In particular, when caves are at shallow depth, the effects at the ground surface may be extremely severe. Apulia region (southern Italy) hosts many sites where hazard associated with sinkholes is very serious due to presence of both natural karst caves and anthropogenic cavities, the latter being mostly represented by underground quarries. The Pliocene-Pleistocene calcarenite (a typical soft rock) was extensively quarried underground, by digging long and complex networks of tunnels. With time, these underground activities have progressively been abandoned and their memory lost, so that many Apulian towns are nowadays located just above the caves, due to urban expansion in the last decades. Therefore, a remarkable risk exists for society, which should not be left uninvestigated. The present contribution deals with the analysis of the most representative failure mechanisms observed in the field for such underground instability processes and the factors that seem to influence the processes, as for example those causing weathering of the rock and the consequent degradation of its physical and mechanical properties. Aimed at exploring the progression of instability of the cavities, numerical analyses have been developed by using both the finite element method for geological settings represented by continuous soft rock mass, and the distinct element method for jointed rock mass conditions. Both the effects of local instability processes occurring underground and the effects of the progressive enlargement of the caves on the overall stability of the rock mass have been investigated, along with the consequent failure mechanisms. In particular, degradation processes of the rock mass, as a consequence of wetting and weathering phenomena in the areas surrounding the caves, have been simulated. The results obtained from the numerical simulations have then been compared with what has been observed during field surveys and a satisfactory agreement between thenumerical simulations and the instability processes, as detected in situ, has been noticed.

The assessment of stability of man-made underground caves, excavated in the past and later on abandoned, represents a serious challenge for land and urban planning operations, especially for the areas of possible interaction of the caves with overlying structures and infrastructures. Several areas of Southern Italy are characterized by the presence of abandoned underground quarries for the extraction of soft calcarenite rocks, which now threatens the overlying environment due to the risk of collapse and the consequent generation of sinkholes. This work presents a back-analysis of a sinkhole occurred in 2011 in the town of Marsala, caused by the collapse of an underground quarry, as a representative case study of these phenomena. Based on the available geometrical and geological dataset as well as the field observations of the phenomenon, in this article the assumptions and the results about the genesis of the 2011 sinkhole, as derived from a three-dimensional finite element back-analysis aimed at reconstructing the stress-strain evolution that brought to the ground failure collapse, is discussed. In particular, the 3-D numerical analyses have been performed in order to identify the factors responsible of the genetic mechanism of the sinkhole. The finite element analysis has been carried out by accounting for the geotechnical characterization of the Marsala calcarenites derived from both specific laboratory tests performed on samples taken from the site and literature data available on the same rock material; the numerical results have been then validated by means of the comparison with field observations and also compared with those achieved through a 2-D model of the same case study.

Anthropogenic sinkholes have recently occurred in built-up areas of Sicily (southern Italy) and are generally associated with the presence of ancient underground quarries for the extraction of soft calcarenite rock, used as building material. These quarries were poorly excavated and then were abandoned in the following decades; urban expansion has recently enlarged to involve the areas affected by presence of the cavities, so that the likely collapse of the underground systems poses serious risks to people, buildings and infrastructures. The present work focuses on the case of the town of Marsala, where in 2003 a sinkhole opened at the outskirts of town, near peri-urban buildings. Field surveys, structural analysis of the joint networks in the rock mass and numerical modeling were carried out in order to investigate the most significant factors responsible of the instability processes of the underground quarry. In particular, a geotechnical three-dimensional model has been defined based on in-situ measurements and surveys.The FEM analyses have been performed with the code Plaxis-3D, by using initially the Mohr-Coulomb elasto-plastic model and then assessing the influence of the joint systems on the rock-mass stability with a jointed rock anisotropic model. Discrete planar bands have been also used to simulate the effect of specific joints, as an alternative to the jointed rock model. The results are in good agreement with the failure mechanism generated during the 2003 sinkhole event, and confirm that reliable analyses of these problems requires 3-D sophisticated tools.

In this paper, we propose an advanced methodology to perform three-dimensional (3D) Finite Element (FE) modeling to investigate the kinematical evolution of a slow landslide phenomenon. Our approach benefits from the effective integration of the available geological, geotechnical and satellite datasets to perform an accurate simulation of the landslide process. More specifically, we fully exploit the capability of the advanced Differential Synthetic Aperture Radar Interferometry (DInSAR) technique referred to as the Small BAseline Subset (SBAS) approach to provide spatially dense surface displacement information. Subsequently, we analyze the physical behavior characterizing the observed landslide phenomenon by means of an inverse analysis based on an optimization procedure. We focus on the Ivancich landslide phenomenon, which affects a residential area outside the historical center of the town of Assisi (Central Italy). Thanks to the large amount of available information, we have selected this area as a representative case study highlighting the capability of advanced 3D FE modeling to perform effective risk analyses of slow landslide processes and accurate urban development planning. In particular, the FE modeling is constrained by using the data from 7 litho-stratigraphic cross-sections and 62 stratigraphic boreholes; and the optimization procedure is carried out using the SBAS-DInSAR retrieved results by processing 39 SAR images collected by the Cosmo-SkyMed (CSK) constellation in the 2009-2012 time span. The achieved results allow us to explore the spatial and temporal evolution of the slow-moving phenomenon and via comparison with the geomorphological data, to derive a synoptic view of the kinematical activity of the urban area affected by the Ivancich landslide.

The present paper explores the combination of unmanned aerial vehicle (UAV) photogrammetry and three-dimensional geomechanical modeling in the investigation of instability processes of long sectors of coastal rocky cliffs. The need of a reliable and detailed reconstruction of the geometry of the cliff surfaces, beside the geomechanical characterization of the rock materials, could epresent a very challenging requirement for sub-vertical coastal cliffs overlooking the sea. Very often, no information could be acquired by alternative surveying methodologies, due to the absence of vantage points, and the fieldwork could pose a risk for personnel. The case study is represented by a 600 m long sea cliff located at Sant'Andrea (Melendugno, Apulia, Italy). The cliff is characterized by a very complex geometrical setting, with a suggestive alternation of 10 to 20 m high vertical walls, with frequent caves, arches and rock-stacks. Initially, the rocky cliff surface was reconstructed at very fine spatial resolution from the combination of nadir and oblique images acquired by unmanned aerial vehicles. Successively, a limited area has been selected for further investigation. In particular, data refinement/decimation procedure has been assessed to find a convenient three-dimensional model to be used in the finite element geomechanical modeling without loss of information on the surface complexity. Finally, to test integrated procedure, the potential modes of failure of such sector of the investigated cliff were achieved. Results indicate that the most likely failure mechanism along the sea cliff examined is represented by the possible propagationof shear fractures or tensile failures along concave cliff portions or over-hanging due to previous collapses or erosion of the underlying rock volumes. The proposed approach to the investigation of coastal cliff stability has proven to be a possible and flexible tool in the rapid and highly-automated investigation of hazards to slope failure in coastal areas.

La valutazione della stabilità di cave sotterranee artificiali, scavate nel passato ed oggi abbandonate, rappresenta una sfida importante per le attività di pianificazione territoriale e urbanistica, specie in zone di possibile interazione delle cave stesse con le strutture e le infrastrutture presenti. In molte aree dell'Italia meridionale sono diffuse cave sotterranee, realizzate per l'estrazione di rocce calcarenitiche tenere, che in taluni casi costituiscono una minaccia per l'ambiente sovrastante a causa del rischio di crolli e della conseguente formazione di "sinkholes". Il presente lavoro costituisce uno studio di back-analysis di un fenomeno di generazione di sinkhole verificatosi nel 2011 nella citta di Marsala, a seguito del collasso di una cava sotterranea, ben rappresentativo dei fenomeni descritti. Sulla base dei dati geometrici e geologici disponibili, nonché delle osservazioni in sito del fenomeno, nell'articolo sono discussi ipotesi e risultati relativi alla formazione della sinkhole del 2011, ottenuti da una analisi tridimensionale agli elementi finiti, mirata alla ricostruzione dell'evoluzione dello stato tenso-deformativo dell'ammasso roccioso che ha portato alla generazione dello sprofondamento. In particolare le analisi numeriche 3-D sono state svolte al fine di identificare i fattori responsabili del meccanismo di sinkhole. Le analisi agli elementi finiti sono state condotte tenendo in considerazione i dati di caratterizzazione geotecnica delle calcareniti di Marsala, ottenuti sia da prove di laboratorio svolte su campioni prelevati in sito, che dalla letteratura disponibile su materiali rocciosi simili; i risultati della modellazione sono stati validati attraverso il confronto con osservazioni in sito e comparati con i risultati ottenuti dalla modellazione 2-D dello stesso caso di studio.

The paper presents the analysis of the mechanism of reactivation of a deep landslide process which involves the western slope of Volturino in the Daunia Apennines (Southern Italy), where tectonized and fissured soils of poor mechanical properties outcrop. The reactivation, which is monitored by piezometers and inclinometers, takes place when the water table is approximately at the ground surface, i.e. during winter. Limit equilibrium back-analyses of the current landslide process, with a pore pressure distribution consistent with the field data, were performed to assess the in situ mobilised strengths and the depth of the sliding body. Drained finite element analyses were then carried out to simulate the reactivation mechanism by modelling the presence of a band of softened material within the slope along with the seasonal variation in seepage conditions. The results of the different analyses tend to confirm the higher instability of deep sliding bodies in the slope.

An intense reactivation of a large earthflow took place in Montaguto (Southern Apennines, Italy) between 2005 and 2006, with a 2/2.5 km long run-out distance and a landslide mass thickness approximately ranging between 5 m and 30 m. The average landslide displacement rate was estimated to range between 3 and 7 m/day and important transport infrastructures were affected by large debris volumes deposited at the toe of the slope. In this work an application of the Smoothed Particle Hydrodynamics method has been carried out in order to simulate both the main features of the earthflow propagation, that is the direction and the thickness of the flowing mass, as well as to investigate some factors of the soil mechanical behavior that might have controlled the earthflow mobility. In particular, two different assumptions concerning the soil rheology, i.e. Bingham visco-plasticity and frictional-consolidating soil model, have been made for comparison purposes. Based on the experiences gained from previous authors concerning the in-situ features of similar earthflow soil masses, these landslides are thought to behave more as a viscous fluid during the very first stages of propagation due to phase transition processes and, later on, to recover a soil-like behavior due to soil consolidation processes. The SPH numerical results of the Montaguto earthflow propagation seem to be in good agreement with the field observations in terms of both movement direction, run-out distance and thickness of the debris soil mass. The modelling results confirm that these landslide processes can be efficiently modelled by means of the SPH numerical technique, providing that a soil rheology capable of taking into account the main features of the soil behavior that control the earthflow mobility is used.

The assessment of hazards associated with active landslides and the related risk management takes advantage nowadays of using the integration of information arising from field monitoring data, including both displacement data, at ground surface and at depth, and pore pressure measurements well distributed throughout the landslide area, along with the results of numerical models. This paper provides an example of the application of this methodological approach to a case study represented by an active sector of the large Montaguto earthslide, located in the Italian Southern Apennines, which has shown in recent years a continuous slow movement, despite the draining interventions executed in 2011 and the general stability of the other portions of the earthslide. The near real-time topographic monitoring network installed in 2010 shows the presence of different kinematic sectors within the same landslide body, characterised by different velocities and evolution trends. After the proper emergency phase occurred in 2010, a specific area has still shown in 2011 and 2012 clear signs of activity, with acceleration stages generally recorded in the Spring. In order to explore the factors that presumably control the activity of this landslide sector, a two-dimensional finite element model has been developed by using PLAXIS-2D code. The numerical results are in good agreement with the displacement field measured throughout the landslide channel and confirm that numerical modelling can represent a reliable support for the interpretation of the landslide failure mechanism and the corresponding evolution, when calibrated against the in situ landslide behaviour reconstructed through a monitoring system.

On December 2013, the town of Montescaglioso (Basilicata, Southern Italy), located at the top of a prominent hill within a highly landslide-prone setting, was affected by reactivation of a large earth-slide along the south-western slope. The slope is formed of stiff clays, belonging to the Argille Subappennine formation, covered by sands and conglomerates, with these latter being chaotically dislocated into arenaceous blocks resulting from ancient gravitational processes. The sliding movement started rapidly, accordingly to eyewitness accounts, and in a time span lower than 1 hour destroyed more than 500 m of the main road connecting the town of Montescaglioso to the Province Road SP175, and involved a few warehouses, a supermarket, and private homes. Surface displacement analysis jointly with detailed field surveys, and with visual analysis of post-event terrestrial and helicopter-based photographs, carried out soon afterward the landslide activation, allowed to identify the main effects produced by the slope movement, and to compile a map of the landslide surface deformations, aimed at identifying the landslide zones characterized by different kinematical features. Both geomorphological evidences and post-event inclinometric measurements have indicated that the failure surface has presumably developed at high depths and specifically in the clay substratum. Laboratory tests have been carried out for the characterization of the mechanical behavior of the clays involved in the sliding process. Both a two-dimensional and a three-dimensional finite element analysis were carried out in order to investigate the overall failure mechanism, the factors that could have controlled the landslide triggering and the spatial directivity of the landslide movement. The modeling results are in very good agreement with the observed landslide process as regards the conditions leading to the slope reactivation and the displacement field occurred in situ and highlight the role of the slope saturation as the main triggering factor of the landslide process.

On 28 January 2009, a large debris slide was triggered by prolonged rainfalls at the southern suburbs of San Benedetto Ullano (Northern Calabria). The slope movement affected fractured and weathered migmatitic gneiss and biotitic schist, and included a pre-existing landslide. A detailed geomorphologic field survey, carried out during the whole phase of mobilization, allowed to recognize the evolution of the phenomenon. A set of datum points was located along the borders of the landslide and frequent hand-made measurements of surface displacements were performed. Since 11 February, a basic real-time monitoring system of meteoric parameters and of surface displacements, measured by means of high-precision extensometers, was also implemented.Based on the data gained through the monitoring system, and on field surveying, a basic support system for emergency management could be defined since the first phases of activation of the phenomenon. The evolution of the landslide was monitored during the following months: as a consequence, evidence of retrogressive distribution could be recognized, with initial activation in the middle sector of the slope, where new temporary springs were observed. During early May, the activity reduced to displacements of a few millimetres per month and the geo-hydrological crisis seemed to be concluded.Afterwards, the geological scheme of the slope was refined based on the data collected through a set of explorative bore-holes, equipped with inclinometers and piezometers: according to the stratigraphic and inclinometric data, the depth of the mobilized body resulted in varying between 15 and 35m along a longitudinal section. A parametric limit equilibrium analysis was carried out to explore the stability conditions of the slope affected by the landslide as well as to quantify the role of the water table in destabilizing the slope. The interpretation of the process based on field observations was confirmed by the limit equilibrium analysis: the first activation of the landslide was, in fact, to be expected in the middle portion of the slope, provided that the groundwater levels approximate the ground surface in the same sector.On 1 February 2010, another remarkable phase of landslide mobilization began, following a new period of exceptional and prolonged rainfalls. On 11 February, an abrupt stage of slope acceleration was observed, after further extraordinary rainfalls. The slope movement essentially replicated the phases of mobilization observed on 28 January 2009, thus confirming the results of the limit equilibrium analysis. Based on the outcomes of the parametric analysis, the support system for emergency management could then be tentatively refined on a more physical basis.

This paper concerns the landslide process occurring on a cut slope in stiff clays located at the north of the town of Lucera in southern Italy. This unstable slope lies between a hospital at the top and an abandoned quarry at the toe: the quarry was active until the end of the 1970s. Afirst landslide occurred around 1980, and was characterised by a subsequent retrogressive evolution. This paper presents an interpretation of the slope failure mechanism based on the results of geomorphological studies, field monitoring, laboratory testing, and both limit equilibrium and coupled numerical analyses, these latter carried out with FLAC2D. In particular, the numerical analyses have been performed in order to interpret the evolution of the slope movements with time, and to assess the influence of the quarrying-induced excess pore pressures on the development of the failure process. The numerical results show that during the excavation stages the negative excess pore water pressures due to undrained unloading allowed for a temporary stability of the slope. The analyses also indicate that the process of pore pressure equalisation triggered the 1980 failure, and initiated the retrogressive evolution of the landslide.

The paper presents a new methodology for the deterministic assessment of landslide hazard at the regional scale in geologically complex chain areas. The methodology entails site specific geo-mechanical studies, as background of any hazard prediction application, and the creation of a Regional Landslide Manual portraying the geo-mechanical knowledge about the slope conditions across the region. The search in the regional manual of the landslide mechanisms which may correspond to the combination of landslide factors recorded at the local scale results in the hazard prediction. The testing of the methodology in the Daunia Apennines is discussed.

The assessment of the slope failure mechanisms, along with the identification of the factors promoting the development of the landslide processes, represents the keystone for an effective design of landslide mitigation. The paper outlines some mitigation strategies for some slow-moving landslides, involving heterogeneous and tectonized soils, located in the outer sector of Southern Apennines. These mitigation designs result from a comprehensive analysis of the failure slope scenarios as resulted from field surveys and investigations, slope monitoring and laboratory testing.

The paper reports the results of a research aiming at the definition of innovative strategies to mitigate the risk generated by deep landsliding due to the slope-atmosphere interaction. The aim stems from the recognition of the connection between the accelerations of deep slow landslides and the seasonal fluctuations of the piezometric heads found to occur down to large depths in slopes, effect of seasonal cumulated rainfall infiltration, as verified in previous research studies for fissured clay slopes of the Italian southern Apennines. Given this slope behavior, the effects as stabilizing measure of systems of drainage trenches, from medium depth to deep, have been verified through the combination of finite element modeling of seepage and limit equilibrium analyses. The model results show that the trench system generates a 'group effect' on the piezometric heads at large depth, due to which the maximum drop in piezometric head occurs along the portion of maximum depth of spoon-shaped slip surfaces underlying the trench system. Hence, the reduction in piezometric head generated by the trench systemmakes such system an effective mitigation measure for deep landsliding. In the paper, the stabilizing effect of the trench system is also verified through its modeling for a deep landslide case history.

We extensively exploit advanced Differential SAR Interferometry (DInSAR) techniques for enhanced landslide investigations. We focus on the Ivancich area, Assisi, Central Italy, which is affected by a deep-seated landslide investigated through in-situ surveys. For this area, large data sets of SAR acquisitions were collected by the C-band ERS-1/2 and ENVISAT sensors (from April 1992 to November 2010), and by the X-band radars of the COSMO-SkyMed (CSK) constellation (from December 2009 to February 2012). We concentrate on the advanced DInSAR technique referred to as Small BAseline Subset (SBAS) approach, benefiting of its capability to generate deformation time series at full spatial resolution and from multi-sensor SAR data. This allows us to present one of thefirstexamples fora landslide area of ERS-1/2--ENVISAT deformation time series exceeding18years. The results allowed characterizing the long-term behaviour of the landslide, and identifying sectors of the unstable slope affected by different deformation dynamics. Analysis of the CSK data set, characterized by a reduced revisit time and improved spatial resolution, resulted in a 15-time larger point density with respect to the ERS-ENVISAT measurements, allowing to investigate nearly all the buildings (and, in many cases, portions of buildings) inthe landslide area. Lastly, we present an innovative modelling approach basedon the effective integration of the DInSAR measurements with traditional geological and geotechnical information, providing deeper insights on the kinematical evolution of the landslide. We consider our analysis a prototype example that can be extended to different geological and geotechnical conditions, providing significant advances in the understanding of ground deformations induced by active landslides.

Sinkholes are the main hazard related to underground voids of both natural and anthropogenic origin. Instabilities developing underground may propagate upwards in a dramatic manner and reach the surface in the form of a sinkhole. The Apulia region in southern Italy is an interesting case study due to the outcropping of soluble rocks throughout the region. These rocks are affected by karst processes and have a high number of anthropogenic cavities. The latter were excavated by humans at different times for a variety of purposes. The worrying recent increase in the number of sinkhole events registered in Apulia led us to collect information on natural and anthropogenic sinkholes in Apulia. We focused on anthropogenic cavities, mostly excavated in Plio-Pleistocene calcarenites, and characterized the rock masses before using two- and three-dimensional parametricnumerical analyses to model the instability processes, with the aim of exploring the failure mechanisms that lead to the occurrence of sinkholes. The parametric studies allowed us to carry out a preliminary evaluation of the stability conditions through simple charts designed for use in the field.

Indicator-based approaches are often used to monitor land degradation and desertification from the global to the very local scale. However, there is still little agreement on which indicators may best reflect both status and trends of these phenomena. In this study, various processes of land degradation and desertification have been analyzed in 17 study sites around the world using a wide set of biophysical and socioeconomic indicators. The database described earlier in this issue by Kosmas and others (Environ Manage, 2013) for defining desertification risk was further analyzed to define the most important indicators related to the following degradation processes: water erosion in various land uses, tillage erosion, soil salinization, water stress, forest fires, and overgrazing. A correlation analysis was applied to the selected indicators in order to identify the most important variables contributing to each land degradation process. The analysis indicates that the most important indicators are: (i) rain seasonality affecting water erosion, water stress, and forest fires, (ii) slope gradient affecting water erosion, tillage erosion and water stress, and (iii) water scarcity soil salinization, water stress, and forest fires. Implementation of existing regulations or policies concerned with resources development and environmental sustainability was identified as the most important indicator of land protection.

Soft and highly porous rocks such as calcarenites are very common in all Mediterranean region. Due to their porous calcareous structure these rocks are prone to water induced weathering mechanisms. Natural onshore and inland underground cavities are evidence of such phenomena. The collapse of cliffs and underground cavities is usually the long-term result of a complex hydro-chemo mechanical process taking place at the micro-scale. Experimental results mainly give evidence of: (a) a marked and instantaneous reduction in strength and stiffness for these porous rocks when macro-pores are filled with water, (b) a slow successive reduction in strength and stiffness occurring in the long-term due to dissolution processes; (c) a more pronounced weakening of the rock material as a consequence of wetting and drying cycles. In the present work a methodological path to cope with deterministic assessment of the stability of natural and anthropic caves will be presented. The following steps will be adopted: (i) experimental study: execution of an experimental campaign to identify the physics of the processes taking place at both the micro-scale and the macro-scale; (ii) theoretical study: extend the concept of strain hardening-non mechanical softening to the time evolution of c-fi reduction; (iii) numerical study: present the 3D numerical results of a real case-study showing the capability of the proposed methodology to cope with risk assessment in complex geomechanical situations concerning weathering, as for underground cavities.

The risk of failure of transportation embankments due to seepage induced by temporary and occasional impoundments taking place on the upstream side as a consequence of exceptional rainfalls is frequently underestimated. These failure events result from a combination of three main factors, i.e. the flooding event, the hydraulic weakness and the geotechnical weakness of the embankment. Based on the case study of a railway embankment in Southern Italy that collapsed in 2005 due to an upstream impoundment that occurred after few hours of a very intense rainfall, the paper describes a methodological approach aimed at assessing hazard of failure of transportation embankments induced by flooding and seepage. In particular, ccording to hydrological, hydraulic and geotechnical studies performed to define the factors affecting the process of the embankment failure, three subsequent activities are proposed: the historical analysis of flood damages at the watershed scale; and the assessment of the upstream peak impoundment based on hydrological analysis and the embankment stability analysis, these latter to be carried out at the site specific scale. The approach here proposed is planned to be further validated and improved by means of the application to other case studies, characterised by different contexts and embankment structures.

The stability of soft rock cliffs can be treated nowadays by using advanced calculation techniques, as the hybrid FDEM approach, which are capable of simulating rock fragmentation processes owing to post-failure material brittleness. In order to assess the stability of cliffs in soft rocks, modelling approach should take directly into account the processes of material detachment, shear sliding as well as crack opening and propagation. This work is aimed at highlighting the role of post-peak brittleness in sea cliff stability problems involving soft calcarenites by means of the application of a hybrid finite-discrete element method. In particular, the paper presents the simulations performed for an ideal vertical cliff formed of soft calcarenites outcropping in Southern Italy, with regard to a couple of factors, namely the influence of the depth of sea erosion at the toe of thecliff and the role of strength degradation of the calcarenite as an effect of the environmental weathering which is particularly intense along the coastal cliffs.

The stability of shallow, artificial underground cavities in soft rocks interacting with overlying structures and infrastructures representsa challenging problem to be faced. This paper discusses a methodology that can be useful for a preliminary stability assessment of underground cavities in soft calcarenites based upon the results of parametric two-dimensional (2D) and three-dimensional (3D) finite-element analyses of ideal underground cavities. The study aimed at exploring those relationships between the geometrical parameters of the cave system and the strength properties of the rock material to define charts that can be useful to evaluate the stability of the rock mass. Moreover, the influence of three-dimensionality was also accounted for based on 3D parametric analyses with variable cavity length and the comparison with the results of the corresponding 2D analyses.

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.

For soft rocks, brittle behavior occurring under low confinement stresses is generally underestimated or even neglected in the solution of boundary value problems, as for example those concerning the stability of rocky cliffs. In these cases, modelling approach should take directly into account processes as the material detachment as well as crack opening and propagation, following fracture mechanics and rock brittleness concepts. This work is aimed at highlighting the role of post-peak brittleness in cliff stability problems involvingsoft calcarenites by means of the application of a hybrid finite-discrete element method (FDEM), which allows for a proper simulation of the brittle rock behavior and the related mechanism of fracture propagation. In particular, the paper presents the simulations performed for an ideal vertical cliff formed of soft calcarenites belongingto the Calcarenite di Gravina Fm. (Upper Pliocene - Lower Pleistocene) - Apulia, Southern Italy. The numerical results highlight the impact of calcarenite brittleness in the stability assessment, the influence of the mesh dependency on the same results and the role of the combination of rock brittleness with joint sets to generate failure mechanisms in the cliff.

Il lavoro presenta i risultati di una integrazione di dati interferometrici e di osservazioni in sito ai fini di un'ottimizzazione dei risultati di un modello tridimensionale agli elementi finiti di una frana attiva a cinematica lenta.

In this work, we exploit the integration of an advanced synthetic aperture radar (SAR) interferometry technique and the application of the finite-element method for the assessment and the interpretation of a localized subsidence phenomenon that took place within a specific area of Lisbon, Portugal. SAR images over the Lisbon city, covering different time intervals in the period of 1995-2010, were acquired and processed by means of the persistent scatterers (PSs) technique. Results clearly reveals a localized subsidence, limited to an area 2 km × 1.5 km wide, which has been confirmed by the leveling performed in 1976, 1996, and 2010. A physical interpretation of the observed ground deformations is provided based on the results of a finite-element model using stratigraphic data, \textit{in situ} piezometric measurements, and geotechnical properties of the involved soils. The ground subsidence is interpreted as the consequence of a consolidation process affecting the central fine-grained soil layer, which in turn has been driven by water withdrawal from the existing aquifers. The change of the hydraulic boundary conditions was generated by the excavation works for the construction of underground lines and also by the reduction of rainfall water infiltration as an effect of the increase in ground surface impermeable areas due to urbanization. The consequent consolidation process of the compressible fine-grained soil layer is supposed to provide a reasonable explanation of the observed time series of ground displacement in the examined area.

Numerical modelling represents a powerful technique to develop a quantitative assessment of the stress-strain mechanisms leading to either first-time slope failures or evolution of slopes already failed in the past. In this perspective, a valid interpretation of the landslide behaviour and an adequate strategy of risk mitigation can be achieved from a numerical validation of both the causative factors and the evolution mechanism that have been previously assumed according to detailed phenomenological or simple analytical approaches. This paper presents two case histories of slow landslides in clay slopes, both located in Puglia (Southern Italy), for which detailed phenomenological studies have been firstly carried out to infer assumptions on the slope failure mechanisms that have been later on verified by means of numerical analyses accounting for soil mechanical behaviour and slope hydraulic processes. The first case study concerns the first-time failure of a stiff clay slope in Lucera, which has been induced by the slow dissipation of negative excess pore water pressures generated by previous quarry excavation at the slope toe. The second case history is represented by the analysis of the stress-strain evolution of the ancient Volturino landslide, which is observed to reactivate mainly in wet seasons.

Le frane, dopo i terremoti e le alluvioni, sono le calamità naturali che ancor oggi mettono più a repentaglio le popolazioni e ne condizionano lo sviluppo socio-economico. Questo avviene nonostante l'attenzione che oggi si rivolge al rilievo del rischio su area vasta, che però spesso non contempla un'adeguata caratterizzazione delle dinamiche di dissesto e delle cause e che, dunque, non è sempre base efficace di scelte di gestione del rischio. Nella nota si evidenzia come oggi la diagnosi dei processi franosi in termini geo-idro-meccanici, che consegue ad una sinergia di analisi del processo franoso secondo diversi approcci specialistici, può condurre ad una valutazione quantitativa del rischio da frana di base per una più consapevole gestione delle aree a rischio e scelta delle strategie di mitigazione. In quest'ottica, dopo aver evidenziato l'urgenza di una ricognizione dei processi che generano il rischio da frana sul territorio e le ripercussioni sulla crescita socio-economica che ne può conseguire, la nota inquadra il metodo di analisi geo-idro-meccanica dei meccanismi di frana e ne esemplifica l'applicazione attraverso alcuni casi di diagnosi di franosità, in cui si è adottata la metodologia a scala di pendio. Infine, si propone una metodologia per la valutazione della pericolosità da frana su area vasta, intesa ad adottare gli strumenti di diagnosi su base geo-idro-meccanica, invalsi a scala di pendio, per valutazioni a più piccola scala.

Landslide hazard maps are often defined as reliable a posteriori, in accordance with the real landslides occurring from the time of the map production. However, to be useful for planning, a reliability judgment concerning the hazard mapping should be a priori, based on data uncertainty characterization, and must be driven by the knowledge of the slope instability mechanisms. The landslide hazard assessment, when based on the deterministic diagnosis of the processes, may really lead to really providing clues about how and why the slope could fail (landslide susceptibility) and, possibly, when (landslide hazard). Such deterministic assessment can be pursued only through the interpretation and the geo-hydro-mechanical modelling of the slope equilibrium. In practice, though, the landslide hazard assessment is still seldom dealt with slope modelling, in particular when it addresses intermediate to regional zoning. The paper firstly offers an overview of the key steps of a methodology called the multiscalar method for landslide mitigation, MMLM, which that is a methodological approach for the intermediate to regional landslide hazard assessment using the hydro-mechanical diagnoses of landsliding. The validation of the MMLM to the geologically complex outer sectors of the Southern Apennines (Daunia-Lucanian mountains; Italy) is also delineated, together with a practical approach to incorporate a reliability judgment in the landslide susceptibility/hazard mapping.

The aim of this paper is to propose a methodology to perform inverse numerical modelling of slow landslides that combines the potentialities of both numerical approaches and well-known remote-sensing satellite techniques. In particular, through an optimization procedure based on a genetic algorithm, we minimize, with respect to a proper penalty function, the difference between the modelled displacement field and differential synthetic aperture radar interferometry (DInSAR) deformation time series. The proposed methodology allows us to automatically search for the physical parameters that characterize the landslide behaviour. To validate the presented approach, we focus our analysis on the slow Ivancich landslide (Assisi, central Italy). The kinematical evolution of the unstable slope is investigated via long-term DInSAR analysis, by exploiting about 20 years of ERS-1/2 and ENVISAT satellite acquisitions. The landslide is driven by the presence of a shear band, whose behaviour is simulated through a two-dimensional time-dependent finite element model, in two different physical scenarios, i.e. Newtonian viscous flow and a deviatoric creep model. Comparison between the model results and DInSAR measurements reveals that the deviatoric creep model is more suitable to describe the kinematical evolution of the landslide. This finding is also confirmed by comparing the model results with the available independent inclinometer measurements. Our analysis emphasizes that integration of different data, within inverse numerical models, allows deep investigation of the kinematical behaviour of slow active landslides and discrimination of the driving forces that govern their deformation processes.

With reference to landslides, Italy is exposed to the worst risk conditions among the industrialized countries (Guzzetti, 2000). In particular, the abundant and prolonged rains fallen in the 2008-2009 and 20092010 wet seasons triggered a great number of shallow and deep slope movements in Calabria (Southern Italy), mostly in the northernmost area. These geo-hydrological crises were so severe that the Italian government had to declare the “state of emergency” on both circumstances. Among the landslides activated in the mentioned wet periods, a largedebris slide threatened the southern suburbs of San Benedetto Ullano (SBU), a small village in the Cosenza province. In this paper, a brief description of the considered slope movement — that first mobilized on Jan. 28, 2009, and after a short period of inactivity, re-activated on Feb. 11, 2010 — is provided. In addition, the decision support system implemented following the first phases of activation is summarized. Based also on such system, the Authority of Civil Protection could effectively manage the geo-hydrological risk during the cited emergency phases.

modellazione numerica tridimensionale agli elementi fi- niti (FEM) applicata al caso di studio di una cava in sotterra- neo, scavata nelle calcareniti tenere della Formazione della Calcarenite di Gravina (Pliocene superiore - Pleistocene in- feriore), sita in località San Procopio (Barletta, Murge setten- trionali). Tale cava è stata recentemente interessata da un crollo parziale che ha determinato lo sprofondamento di un'area di circa 800 m^2. L'obiettivo dello studio è analizzare i fattori che hanno determinato lo sprofondamento e ricavare informazioni sullo "stato di salute" dei pilastri e delle volte non ancora interessati da dissesti, per poter pertanto valutare in via preliminare il relativo rischio residuo.Per il caso in esame si è fatto uso del software MIDAS GTS NX con cui sono state condotte analisi non lineari in- crementali al passo ("path-following"). Tali analisi si sono rese necessarie per ricostruire l'evoluzione dello stato tenso-de- formativo della struttura nelle fasi precedenti e successive al crollo. Per la definizione del modello numerico è stata utiliz- zata la geometria ricostruita dal rilievo speleologico fornito dalla Federazione Speleologica Pugliese, mentre per quanto riguarda i parametri meccanici delle calcareniti, si è fatto uso della letteratura disponibile.Questo studio evidenzia come la costruzione di un mo- dello numerico tridimensionale del sottosuolo sia un approc- cio imprescindibile per lo studio dei fenomeni di instabilità di cavità. I risultati permetteranno di fornire gli elementi di valutazione necessari per pianificare interventi di risana- mento strutturale delle cavità o per progettare interventi di bonifica laddove la situazione dovesse presentarsi compromessa.Il risultato più evidente della modellazione è stato quello di riconoscere il mutamento dello stato tenso-deformativo per i pilastri più prossimi alla zona del dissesto. Tali pilastri, nella fase precedente al collasso, si trovavano, data la regola- rità tra le spaziature delle gallerie, in condizioni di carico pres- soché centrato. Nella fase successiva alla rottura e al conseguente sprofondamento, a causa di una maggiore ec- centricità del carico venutasi a creare per lo squilibrio indotto dal crollo stesso, tali pilastri risultano sollecitati oltre che da sforzi normali anche da importanti componenti flessioni e di taglio. Tale incremento in alcuni casi potrebbe non essere trascurabile dato che un decadimento naturale delle caratte- ristiche meccaniche delle rocce, spesso accelerato da fattori legati all'uso del suolo, potrebbe determinare nel corso del tempo una eccessiva riduzione delle condizioni di sicurezza.

The behaviour of natural and artificial slopes is controlled by their thermo-hydro-mechanical conditions and by soil-vegetation-atmosphere interaction. Porewater pressure changes within a slope related to variable meteorological settings have been shown to be able to induce soil erosion, shrinkage-swelling and cracking, thus leading to an overall decrease of the available soil strength with depth and, ultimately, to a progressive slope collapse. In terms of numerical modelling, the stability analysis of partially saturated slopes is a complex problem and a wide range of approaches from simple limit equilibrium solutions to advanced numerical analyses have been proposed in the literature. The more advanced approaches, although more rigorous, require input data such as the soil water retention curve and the hydraulic conductivity function, which are difficult to obtain in some cases. The quantification of the effects of future climate scenarios represents an additional challenge in forecasting slope-atmosphere interaction processes. This paper presents a review of real and ideal case histories regarding the numerical analysis of natural and artificial slopes subjected to different types of climatic perturbations. The limits and benefits of the different numerical approaches adopted are discussed and some general modelling recommendations are addressed.

The strength decay that occurs in the post-peak stage, under low confinement stress, represents a key factor of the stress-strain behaviour of rocks. However, for soft rocks this issue is generally underestimated or even neglected in the solution of boundary value problems, as for example those concerning the stability of underground cavities or rocky cliffs. In these cases, the constitutive models frequently used in limit equilibrium analyses or more sophisticated numerical calculations are, respectively, rigid-plastic or elastic-perfectly plastic. In particular, most of commercial continuum-based numerical codes propose a variety of constitutive models, including elasticity, elasto-plasticity, strain-softening and elasto-viscoplasticity, which are not exhaustive in simulating the progressive failure mechanisms affecting brittle rock materials, these being characterized by material detachment and crack opening and propagation. As a consequence, a numerical coupling with mechanical joint propagation is needed to cope with fracture mechanics. Therefore, continuum-based applications that treat the simulation of the failure processes of intact rock masses at low stress levels may need the adoption of numerical techniques capable of implementing fracture mechanics and rock brittleness concepts, as it is shown in this paper. This work is aimed at highlighting, for some applications of rock mechanics, the essential role of post-peak brittleness of soft rocks by means of the application of a hybrid finite-discrete element method. This method allows for a proper simulation of the brittle rock behaviour and the related mechanism of fracture propagation. In particular, the paper presents two ideal problems, represented by a shallow underground cave and a vertical cliff, for which the evolution of the stability conditions is investigated by comparing the solutions obtained implementing different brittle material responses with those resulting from the assumption of perfectly plastic behaviour. To this purpose, a series of petrophysical and mechanical tests were conducted on samples of soft calcarenite belonging to the Calcarenite di Gravina Fm. (Apulia, Southern Italy), focusing specific attention on the post-peak behaviour of the material under three types of loading (compression, indirect tension and shear). Typical geometrical features representative of real rock engineering problems observed in Southern Italy were assumed in the problems examined. The numerical results indicate the impact of soft rock brittleness in the assessment of stability and highlight the need for the adoption of innovative numerical techniques to analyse these types of problems properly.

Apulia region, the foreland of the southern Italian Apennines, is made up of a 6-7 km-thick succession of Mesozoic shallow-water limestones and dolostones, locally covered by thin and discontinuous Tertiary and Quaternary carbonate and clastic deposits. Due to their long subaerial exposure, the Mesozoic carbonate bedrock recorded the development in the subsurface of a dense network of karst cavities, mostly controlled by tectonic discontinuities. As a result, a strong susceptibility to natural sinkholes has to be recorded in Apulia. In addition, the possibility of occurrence of other problems related to the high number of man-made cavities has to be added in the region. A great variety of different typologies of artificial cavities (mostly excavated in the Plio-Pleistocene soft calcarenites) is actually present, including underground quarries, worship sites, oil mills, civilian settlements, etc. Overall, 2200 natural and 1200 artificial cavities, respectively, have been so far surveyed in Apulia. Following the urban development in the last century in Apulia, many of these cavities lie nowadays below densely populated neighborhoods, roads or communication routes. These conditions are at the origin of the main geomorphological hazard for the human society in Apulia, which requires a careful evaluation, aimed at protecting and safeguarding the human life, and at providing the necessary information for a correct land use planning and management. The importance of the sinkhole hazard is further testified by the worrying increase in the number of events during the last 5-6 years. In response to these situations, joint research activities were started by the Institute of Research for Hydrological Protection of the National Research Council (CNR-IRPI) and the Basin Authority of Apulia, aimed at several goals, that include (but are not limited to) the collection of information on natural and anthropogenic sinkholes in Apulia, the implementation of numerical analyses for modelling the instability processes, and the development of charts for a preliminary evaluation of the stability of underground caves. Two distinct approaches were established to take into account the different petrographic, structural and geotechnical features of both the hard and soft carbonate rocks. The approach dealing with hard carbonate rocks (where natural karst caves develop) is based on speleological and geometrical surveys of the caves and on an integrated geological and geomechanical characterization of the carbonate rock mass, aimed at individuating the main critical aspects of the karst caves in terms of likely effects on the society. On the other hand, the approach to verify the stability of soft rocks where artificial cavities have been excavated is mostly dependent upon the peculiar petrographic and geomechanical characteristics of the calcarenite rock mass, typically massive and unaffected by tectonic discontinuities. As a consequence, the traditional analytical methods o

The paper presents the emblematic case of the Pianello slope, that is a complex landslide basin located in the town centre of Bovino, one of the most beautiful villages in Italy. The low gradient slope is formed of highly tectonised and heterogeneous clays and it is affected by very slow and deep landsliding. The failure mechanisms are representative of many others not only in the Daunia area in the south of Italy, but also in the slopes of the Italian Apennines. The analysis resulted from field surveys, investigations and monitoring data as well as from the laboratory test results of the geotechnical investigation. The phenomenological interpretation of the landslide mechanism, along with the identification of the predisposing and triggering factors has been validated by both limit equilibrium and numerical analyses.

The paper is concerned with the diffuse occurrence of movements in natural clay slopes that arefrom very slow to slow and that, at times, undergo accelerations bringing about significant damages of structuresand infrastructures in interaction with the slope. Four study cases are treated in the paper, showing bymeans of both in situ monitoring and mathematical modeling that such slope movements are effect of slidingprocesses along either pre-existing or newly developing shear bands, as part of progressive failure processesresulting from evolving equilibrium conditions. The evolving deformations are controlled by slow variationsof the effective stresses, largely associated to the hydro-mechanical coupling taking place in transient flowprocesses. Also, the lack of mitigation measures is shown to cause severe increase of the depth and extension ofthe landslide bodies, with a dramatic increase of the damaged structures and cost of final emergency measures.

Nel secolo scorso, l'attività estrattiva in sotterraneo in Puglia di calcareniti tenere, spesso utilizzate come materiale da costruzione, ha portato alla creazione di un numero elevato di cavità a geometria regolare, spesso rettangolare, o in alcuni casi secondo lo schema a "camere e pilastri". Dette cavità sono state progressivamente abbandonate e, in tempi recenti, si sono registrati nella stessa regione numerosi collassi delle stesse cavità, con coinvolgimento in alcuni casi delle strutture e delle infrastrutture ubicate a livello del piano campagna. Il presente lavoro, basato sui risultati di un'ampia casistica di analisi bidimensionali parametriche, svolte con il metodo degli elementi finiti, propone una metodologia utile a valutare, in forma preliminare, la stabilità di cavità sotterranee in calcareniti tenere. In particolare, con l'ausilio di analisi FEM bidimensionali condotte su casi ideali di cavità sotterranee a geometria regolare, sono state individuate possibili correlazioni tra le principali caratteristiche geometriche del problema (larghezza, altezza e profondità delle cavità) e le caratteristiche di resistenza dei materiali rocciosi interessati dalle cavità. Le analisi hanno previsto l'adozione sia di valori dei parametri geometrici osservati per un ampio numero di cavità sotterranee presenti in Puglia che di parametri di resistenza tipicamente misurati per le calcareniti tenere affioranti nella stessa regione. I risultati sono sintetizzati in abachi di stabilità utili a valutare, in forma preliminare e speditiva, le condizioni di stabilità di cavità con caratteristiche che ricadono nelle ipotesi del calcolo, eventualmente da verificare in fase successiva con analisi di maggiore dettaglio e livello di approfondimento.

Monitoring is essential to understand the mechanics of landslides, and predict their behavior in time and space. In this work we discuss the performance of multi-sensor monitoring techniques applied to measure the kinematics and the landslide hydrology of Portalet landslide complex, which is located in the SW-facing slopes of Petrasos peak at the border between Spain and France. In the summer 2004, the excavation of a parking lot at the foot of the slides triggered a secondary failure in the lower part of the slope, accelerating the dynamic of the landslide complex. The deployed hydro-meteorological network has been useful to understand that the greatest infiltration in the moving mass is produced in spring due to the combination of snow melt and seasonal rainfall. Landslide surface kinematics measured with differential GPS (D-GPS) were useful to measure the slower (<10 cm/year) and faster (20-30 cm/year) dynamic of the landslide complex. Advanced DInSAR was useful to monitor the slower ground displacements from long datasets of SAR images, providing a wider spatial coverage and measurement point density than the D-GPS. In addition, the NL-InSAR processing strategy was applied to monitor the faster motion using short datasets of TerraSAR-X images excluding the snow cover period.

The analysis of the displacement field due to a landslide process can be performed by means of either forward or inverse numerical models. Concerning the evolution of slow landslides, the Finite Element Method (FEM) represents a powerful tool to assess the relationships existing between the causative factors and the related effects, being the latter generally detected by field monitoring data. In this context, inverse models are useful to deduce the values of physical or mechanical parameters that control the landslide behavior over time. In this paper, we combined the potentiality of the FEM with Monte Carlo optimization procedures, based on a Genetic Algorithm (GA) technique, to back-analyze and interpret the kinematical evolution of very slow active landslides. In particular, we performed a two-dimensional time-dependent FE analysis by using a deviatoric creep model to simulate the evolution of the displacement field of the very slow Ivancich landslide (Assisi, Central Italy); an optimization procedure was performed by considering the Differential SAR Interferometry (DInSAR) data to derive the soil creep rate distribution, according to an inverse analysis approach. In particular the longterm Small BAseline Subset (SBAS) DInSAR analysis covering about 20 years was compared with the slope velocities calculated by the numerical model and the best-fit creep model was identified by considering the minimum Root Mean Square Error between field data and model results. Finally the model results in terms of slope displacements over time have been also compared with the available inclinometric measurements. .

Earthflow and mudflow processes represent a class of landslides that, owing to their typical long run-out, may generally induce huge damages to infrastructure lines, with negative economic impacts. Therefore, the analysis of the landslide propagation with time in such cases can provide useful information to mitigate landslide risk. The present paper discusses the case history of a huge earthflow developed in 2005-2006 in the area of Montaguto town (Southern Apennines, Italy), that produced significant damages to a national road and a national railway at the slope toe. The average displacement rate during the first critical stage of propagation was of some m/day. The aim of this contribution is the reconstruction of the propagation stage of this landslide during the first high-mobility stage. A detailed geomorphological analysis aimed at defining themain features of the insitu landslide propagation is firstly described. Later on, a back-analysis of the kinematical features of the same landslide process, based on a simple infinite-slope sliding-consolidation model, is presented to investigate the role of different factors in the process of landslide propagation. The application of this analytical solution suggests that the development of high excess pore water pressures due to undrained loading processes and the consequent consolidation process can represent a reasonable way to explain the earthflow mobility. The application of the analyticalmodel to the specific case study is also supported by the field evidence of the existence of excess porewater pressures in the landslide mass which have beenmeasured in situ during the recent monitoring campaign and the corresponding data are also discussed in the work.

An intense reactivation of a large earthflow (about 6 million m3 of soil debris) took place in Montaguto (Southern Apennines, Italy) between 2005 and 2006 as a consequence of the retrogression of a sliding process in the source area at the top of the slope. The earthflow run-out was approximately 2-2.5 km long, with the landslide mass thickness approximately ranging between 5 m and 30 m. Relevant damages were produced at the toe of the slope, since important infrastructures hereby located were covered by large volumes of landslide detritum. In the transition area, that is just downslope the source area, the landslide soil mass was channelized and transformed into a viscous soil flowing down through a natural depression channel, with an average displacement rate estimated to range between 3 and 7 m/day.In this work an application of the Smoothed Particle Hydrodynamics method has been carried out in order to simulate both the main features of the earthflow propagation, that is the direction and the thickness of the flowing mass, as well as to investigate some factors of the soil mechanical behavior that might have controlled the earthflow mobility. In particular, two different assumptions concerning the soil rheology, i.e. Bingham visco-plasticity and frictional-consolidating soil, the first complying more with the assumption of a flow-like behavior and the latter with a soil-like behavior of the landslide mass, have been made for comparison purposes. Based on the experiences gained from previous authors concerning the in-situ features of similar earthflow soil masses, these landslides are thought to behave more as a viscous fluid during the very first stages of propagation due to phase transition processes and, later on, to recover a soil-like behavior, therefore characterized by sliding mechanism, due to soil consolidation processes. Field evidences of consolidation processes have indeed been observed in situ in recent years based on pore water pressure monitoring.The SPH numerical results of the Montaguto earthflow propagation seem to be in good agreement with the field observations in terms of both movement direction, run-out distance and thickness of the debris soil mass. The modelling results confirm that these landslide processes can be efficiently modelled by means of the SPH numerical technique, providing that a soil rheology capable of taking into account the main features of the soil behavior that affect the earthflow mobility is used.

The work mainly discusses the use of the Ground-Based Synthetic Aperture Radar (GBSAR) interferometry technique to observe and control the behavior of earthfill or rockfill embankments for dam impoundments. This non-invasive technique provides overall displacements patterns measured with a sub-millimeter accuracy. The need of reliable monitoring of old embankment dams is rapidly increasing since a large number of these structures are still equipped with old monitoring devices, usually installed some decades ago, which can give only information on localized areas of the embankment. A case study regarding the monitoring of an earthfill dam embankment in Southern Italy by means of GBSAR interferometry is presented.

La valutazione del rischio da frana rappresenta un tema di crescente interesse a causa del condizionamento dei processi franosi sullo sviluppo socio-economico dei centri urbani e sulle possibilità di conservazione del patrimonio storico-culturale. Con riferimento alle frane a cinematica lenta, le valutazioni di rischio di tipo quantitativo riguardano aspetti prevalentemente connessi alla suscettibilità o, in alcuni casi, alla pericolosità, limitando invece gli studi sulla vulnerabilità strutturale ad analisi di natura pressoché qualitativa. Questo contributo indaga gli effetti dell'interazione tra una classe di frane a cinematica lenta ed il patrimonio costruito sovrastante. Si presentano i risultati dell'applicazione di una metodologia multilivello per l'analisi di vulnerabilità alla scala del centro urbano. L'area di applicazione corrisponde ad un territorio urbanizzato dell'Appennino Dauno ove affiorano successioni torbiditiche tettonizzate. I risultati delle analisi geomorfologiche, geotecniche e strutturali sono confluiti nella 'carta geotecnica del danneggiamento da frana', strumento di supporto per l'analisi di vulnerabilità in aree franose.