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One of the largest concentrations of giant landslides (≥108 m3) in Patagonia is in the eastern part of Lago Cochrane/Pueyrredón (LP) valley in Argentina. In addition to minor earthflows and rock slides, this landslide cluster is dominated by rock and debris avalanches that affect the northern slope of Meseta Belgrano, the largest of which have volumes >1 km3 and a runout of >10 km. To determine the chronology of these large landslides and their relationship to the geological setting and the glacial history related to the Last Glacial Maximum (LGM) ∼20–18 ka ago, we combined geomorphological mapping with absolute dating (luminescence and radiocarbon dating) and numerical modelling of slope stability. Dating and cross-cutting relationships with glaciolacustrine deposits suggest that some of the largest rock avalanches collapsed directly into a glacial lake between ∼17 and ∼12 ka, soon after deglaciation, but some were pre-glacial and landslide activity continued until today, posing a potential hazard to the area. In agreement with these data, numerical modelling suggests that slope stability was only marginally affected by ice retreat and glacial lake drainage, and landslides were most likely favoured by relatively low rock strength, related glacially-conditioned topography, and, possibly, seismic activity. A newly identified active fault at the base of the Meseta Belgrano, whose activity was likely enhanced by postglacial rebound, was probably the key factor that concentrated postglacial rock avalanches into the LP valley. We conclude that exceptionally large (km-scale) landslides can occur on slopes made of relatively weak rocks in a glacially-conditioned topographic setting even without a strong direct triggering effect of deglaciation, while fatigue due to long-term seismicity may promote collapse.

ndagini geofisiche e geomeccaniche hanno consentito di caratterizzare una Deformazione Gravitativa Profonda (DGPV) profonda 250 metri, che interessa circa 900 Mm3 di gneiss quasi completamente destrutturati per alterazione e metasedimenti (anidriti, gessi, marmi e dolomie) fortemente alterati e localmente ridotti a spessi livelli di sabbie dolomitiche. I log stratigrafici e geomeccanici di tre sondaggi profondi (300-400m) hanno consentito di tarare indagini geofisiche di superficie e di eseguire profili sismici verticali VSP, registrazioni FWS e BHTV. L’elaborazione delle indagini sismiche ha evidenziato inversioni di velocità associate a livelli di rocce particolarmente destrutturate, mentre la correlazione tra caratteristiche di fratturazione ed alterazione delle carote e logs sonici eseguiti nei sondaggi ha permesso la caratterizzazione delle proprietà fisico-meccaniche dei litotipi. La modellazione numerica suggerisce come l’innesco della DGPV sia da ricondurre alla strutturazione tettonostratigrafica della valle ed a intensi processi di alterazione, favoriti dalla decompressione dei versanti legata a deglaciazione e da un rilevante deflusso idrico sotterraneo.

The reliable in situ quantification of rock mass fracturing and engineering quality is critical for slope stability, surface mining and rock engineering applications, yet it remains difficult due to the heterogeneous nature of fracture networks. We propose a method to quantify and map the slope-scale geomechanical quality of fractured rock masses using infrared thermography (IRT). We use the Mt. Gorsa quarry (Trentino, Italy) as a field laboratory to upscale a physics-based approach, which was developed in the laboratory, to in situ conditions, including the effects of fracture heterogeneity, environmental conditions and IRT limitations. We reconstructed the slope in 3D using UAV photogrammetry, characterized the rock mass quality in the field at selected outcrops in terms of the Geological Strength Index (GSI) and measured their cooling behavior through 18h time-lapse IRT surveys. With ad hoc field experiments, we developed a novel procedure to correct IRT data in outdoor environments with complex topography. This allowed for a spatially distributed quantification of the rock mass surface cooling behavior in terms of a Curve Shape Parameter (CSP). Using non-linear regression, we established a quantitative CSP-GSI relationship, which allowed for the CSP to be translated into GSI maps. Our results demonstrate the possibility of applying infrared thermography to the slope-scale mapping of rock mass fracturing based on a physics-based experimental methodology.

The fracturing state of rocks is a fundamental control on their hydro-mechanical properties. It can be quantified in the laboratory by non-destructive geophysical techniques that are hardly applicable in situ, where biased mapping and statistical sampling strategies are usually exploited. We explore the suitabilty of infrared thermography (IRT) to develop a quantitative, physics-based approach to predict rock fracturing starting from laboratory scales and conditions. To this aim, we performed an experimental study on the cooling behaviour of pre-fractured gneiss and mica schist samples, whose 3D fracture networks were reconstructed using Micro-CT and quantified by unbiased fracture abundance measures. We carried out cooling experiments in both controlled (laboratory) and natural (outdoor) environmental conditions and monitored temperature with a thermal camera. We extracted multi-temporal thermograms to reconstruct the spatial patterns and time histories of temperature during cooling. Their synthetic description show statistically significant correlations with fracture abundance measures. More intensely fractured rocks cool at faster rates and outdoor experiments show that differences in thermal response can be detected even in natural environmental conditions. 3D FEM models reproducing laboratory experiments outline the fundamental control of fracture pattern and convective boundary conditions on cooling dynamics. Based on a lumped capacitance approach, we provided a synthetic description of cooling curves in terms of a Curve Shape Parameter, independent on absolute thermal boundary conditions and lithology. This provides a starting point toward the development of a quantitative methodology for the contactless in situ assessment of rock mass fracturing.

Kinematics is a key component of a landslide hazard because landslides moving at similar rates can affect structures or collapse differently depending on their mechanisms. While a complete definition of landslide kinematics requires integrating surface and subsurface site investigation data, its practical estimate is usually based on 2D profiles of surface slope displacements. These can be now measured accurately using Persistent Scatterer InSAR (PSI), which exploits open access satellite imagery. Although 2D profiles of kinematic quantities are easy to retrieve, the efficacy of possible descriptors and extraction strategies has not been systematically compared, especially for complex landslides. Large, slow rock slope deformations, characterized by low displacement rates (<50 mm/year) and spatial and temporal heterogeneities, are an excellent testing ground to explore the best approaches to exploit PSI data from Sentinel-1 for kinematic characterization. For three case studies, we extract profiles of different kinematic quantities using different strategies and evaluate them against field data and simplified numerical modelling. We suggest that C-band PSI data allow for an effective appraisal of complex landslide kinematics, provided that the interpretation is (a) based on decomposed velocity vector descriptors, (b) extracted along critical profiles using interpolation techniques respectful of landslide heterogeneity, and (c) constrained by suitable model-based templates and field data.

Glacial and paraglacial processes have a major influence on rock slope stability in alpine environments. Slope deglaciation causes debuttressing, stress and hydro-mechanical perturbations that promote progressive slope failure and the development of slow rock slope deformation possibly evolving until catastrophic failure. Paraglacial rock slope failures can develop soon after or thousands of years after deglaciation, and can creep slowly accelerating until catastrophic failure or nucleate sudden rockslides. The roles of topography, rock properties and deglaciation processes in promoting the different styles of paraglacial rock slope failure are still elusive. Nevertheless, their comprehensive understanding is crucial to manage future geohazards in modern paraglacial settings affected by ongoing climate change. We simulate the different modes and timing of paraglacial slope failures in an integrated numerical modelling approach that couples realistic deglaciation histories derived by modelling of ice dynamics to 2D time-dependent simulations of progressive failure processes. We performed a parametric study to assess the effects of initial ice thickness, deglaciation rate, rock-slope strength and valley shape on the mechanisms and timing of slope response to deglaciation. Our results allow constraining the range of conditions in which rapid failures or delayed slow deformations occur, which we compare to natural Alpine case studies. The melting of thicker glaciers is linked to shallower rockslides daylighting at higher elevation, with a shorter response time. More pronounced glacial morphologies influences slope lifecycle and favour the development of shallower, suspended rockslides. Weaker slopes and faster deglaciations produce to faster slope responses. In a risk-reduction perspective, we expect rockslide differentiation in valleys showing a strong glacial imprint, buried below thick ice sheets during glaciation.

This article provides an overview of deep-seated gravitational slope deformations (DSGSD). These large-scale mass movements are widespread in mountain belts in different geological and morpho-climatic settings, affect entire high-relief slopes and evolve over thousands of years under the effects of changing controls and triggers. Besides their spectacular geomorphological features, they pose significant risk to life and infrastructures, related to continuing slow movements and potential evolution towards catastrophic collapse. We review the definition, diagnostic features, activity, and mechanisms of DSGSD in the wider framework of progressive rock slope failure.

The interplay of tectonic and climatic forcing in the development of Alpine deep-seated gravitational slope deformations (DSGSD) is still poorly understood. We investigate a giant DSGSD affecting the Piz Dora slope (Val Müstair, Switzerland) by geological, structural and geomorphological analyses, spaceborne SAR interferometry and numerical modelling. The DSGSD affects Permian terrigenous and volcanoclastic successions folded into a kilometre-scale asymmetric anticline during the Alpine orogenesis. The area is characterized by active tectonic uplift and widespread shallow seismicity with dominant dip-slip fault mechanisms, experienced fast deglaciation after the Last Glacial Maximum and periglacial conditions between the Lateglacial and Holocene. The slope is affected by morpho-structural features testifying to the deep-seated gravitational sliding of 1.85 km3 of rock along a basal shear zone over 400 m deep. Analysis of rock glaciers and DInSAR data show that the DSGSD was active in Lateglacial times and is presently deforming at rates ö 15 mm/yr. Integrated kinematic analysis of field and radar data outlines a key control of the inherited fold structure on the DSGSD, with a transition from deep compound sliding to the West, controlled by massive conglomerates (Chazforà Formation), to shallower roto-translational sliding to the East, controlled by volcanoclastic foliated rocks (Ruina Formation). 2DFEM stress-strain numerical models, simulating the post-LGM slope evolution in static, pseudo-static and dynamic conditions allowed evaluating the contribution of long-term seismicity to DSGSD in a paraglacial setting. Dynamic modelling was performed starting from the characterization of a real earthquake, representative of the recent local seismotectonic activity, and scaled to obtain dynamic scenarios with different return periods. Results suggest that deglaciation-related perturbations promoted the inception of the DSGSD but not its complete development, that was li

The stability analysis of underground mine systems with complex 3D geometry is still a challenging task, especially when abandoned mines are planned for new uses with public access, that imply more restrictive safety requirements. This inherently multi-scale problem requires both the evaluation of the global mine stability and the assessment of local deformation and failure mechanisms of individual pillars or roof sectors in a robust 3D modeling framework. We integrated 3D remote survey techniques and FEM 3D modeling to perform a comprehensive stability analysis of an abandoned fluorite mine system in the central Southern Alps (Italy), including ten levels excavated in bedded limestones. We reconstructed the 3D geometry of three levels undergoing a reuse plan, combining a dynamic LiDAR system and close-range photogrammetry. We used point clouds in a workflow to generate solids, excavate the 3D analysis domain and generate a FEM 3D mesh for numerical modeling. We performed a series of continuum-based FEM 3D simulations of mine excavation and rock mass strength degradation. Our results allowed assessing the global stability of the abandoned mine and identifying critically stressed roof sectors and pillars to prioritize the local-scale analysis, remediation and monitoring of critical spots.

Large slow rock-slope deformations, including deepseated gravitational slope deformations and large landslides, are widespread in alpine environments. They develop over thousands of years by progressive failure, resulting in slow movements that impact infrastructures and can eventually evolve into catastrophic rockslides. A robust characterization of their style of activity is thus required in a risk management perspective. We combine an original inventory of slow rock-slope deformations with different PS-InSAR and SqueeSAR datasets to develop a novel, semiautomated approach to characterize and classify 208 slow rockslope deformations in Lombardia (Italian Central Alps) based on their displacement rate, kinematics, heterogeneity and morphometric expression. Through a peak analysis of displacement rate distributions, we characterize the segmentation of mapped landslides and highlight the occurrence of nested sectors with differential activity and displacement rates. Combining 2D decomposition of InSAR velocity vectors and machine learning classification, we develop an automatic approach to characterize the kinematics of each landslide. Then, we sequentially combine principal component and K-medoids cluster analyses to identify groups of slow rock-slope deformations with consistent styles of activity. Our methodology is readily applicable to different landslide datasets and provides an objective and cost-effective support to land planning and the prioritization of local-scale studies aimed at granting safety and infrastructure integrity.

Spaceborne radar interferometry is a powerful tool to characterize landslides at local and regional scales. However, its application to very slow rock slope deformations in alpine environments (displacement rates < 5 cm/year) remains challenging, mainly due to low signal to noise ratio, atmospheric disturbances, snow cover effects, and complexities resulting from heterogeneous displacement in space and time. Here we combine SqueeSARTM data, targeted multi-temporal baseline DInSAR, GPS data, and detailed field morpho-structural mapping, to unravel the kinematics, internal segmentation, and style of activity of the Mt. Mater deep-seated gravitational slope deformation (DSGSD) in Valle Spluga (Italy). We retrieve slope kinematics by performing 2D decomposition (2D InSAR) of SqueeSARTM products derived from Sentinel-1 data acquired in ascending and descending orbits. To achieve a spatially-distributed characterization of DSGSD displacement patterns and activity, we process Sentinel-1 A/B images (2016-2019) with increasing temporal baselines (ranging from 24-days to 1-year) and generate several multi-temporal interferograms. Unwrapped displacement maps are validated using ground-based GPS data. Interferograms derived with different temporal baselines reveal a strong kinematic and morpho-structural heterogeneity and outline nested rockslides and active sectors, that arise from the background displacement signal of the main DSGSD. Seasonal interferograms, supported by GPS displacement measurements, reveal non-linear displacement trends suggesting a complex response of different slope sectors to rainfall and snowmelt. Our analyses clearly outline a composite slope instability with different nested sectors possibly undergoing different evolutionary trends towards failure. The results herein outline the potential of a targeted use of DInSAR for the detailed investigation of very slow rock slope deformations in different geological and geomorphological settings.

Giant rockslides are widespread and sensitive to hydrological forcing, especially in climate change scenarios. They creep slowly for centuries and then can fail catastrophically posing major threats to society. However, the mechanisms regulating the slow-to-fast transition toward their catastrophic collapse remain elusive. We couple laboratory experiments on natural rockslide shear zone material and in situ observations to provide a scale-independent demonstration that short-term pore fluid pressure variations originate a full spectrum of creep styles, modulated by slip-induced undrained conditions. Shear zones respond to pore pressure increments by impulsive acceleration and dilatancy, causing spontaneous deceleration followed by sustained steady-rate creep. Increasing pore pressure results in high creep rates and eventual collapse. Laboratory experiments quantitatively capture the in situ behavior of giant rockslides and lay physically-based foundations to understand the collapse of giant rockslides.

Large-scale creeping landslides are widespread in alpine areas. Associated long-term, slow deformations threaten urban settlement, railways, main roads and hydropower facilities, on which our society is strictly dependent. Over the next decades, the continuous growing of the global population, the resulting increase in the urbanization (also closer to hazard-prone areas), and the climate change (e.g. melting of alpine glaciers) will increase these interactions and the related risk. Nevertheless, assessing the vulnerability of different types of elements at risk to this kind of hazard is not obvious, especially when hydropower structures (including dams, tunnels, penstocks, etc.) are involved. Large rockslides complexity often results in a variety of different evolutionary trends, making their forecasting and risk reduction a challenge. While catastrophic collapse can cause huge instantaneous damages, slow movements along long periods may lead to progressive damage of structures and infrastructures. In the alpine and pre-alpine areas of Lombardia (Central Italian Alps), slow rock-slope deformations affect an area of 750 km2, threatening more than 10 km2 of urban areas and about 100 km of penstocks or tunnels related to hydropower facilities. Here we focus on the Mt. Palino slope (Valmalenco, Italian Central Alps), that is affected by a complex, apparently long-lived DSGSD (Deep seated Gravitational Slope Deformation) with a relief exceeding 1000 m. The slope hosts hydropower facilities and a tourist resort. In order to recognize dominant processes and their possible evolution (internal deformation, low-rate steady activity, progressive behaviour, seasonal effects) for better risk assessment and mitigation, we investigated the volume and depth of displaced rock mass and the possible localization of deformations along a basal shear zone. Geomechanical and geomorphological surveys, seismic tomography, deep borehole logs and monitoring data (borehole instrumentation, pre

Deep-seated gravitational slope deformations (DSGSD) gains new attention in Taiwan due to their catastrophic impacts on lives and infrastructures during Typhoon Morakot in 2009. As the main Taiwan island is located on a complex convergent plate boundary, conventional observations and analyses suggest that the island’s strong tectonic activity has, along with its subtropical climate and intense human activity in mountain areas, contributed to the formation of deep-seated landslides. It is especially so for high-altitude areas featuring Miocene to Eocene meta-sandstone and slate successions, where reactivations of landslide terrains are observed from field observation and some GPS sites after specific events. Among them, Tienchih, located in Lalong River of Kaohsiung, and Yakou, few km east in Taitung County were assessed as highly landslide-prone area after the heavy precipitation of Typhoon Morakot (over 2700 mm of rainfall within only 5 days). In this areas, several deep-seated landslides were identified according to geomorphological features seen in the 1-m resolution LiDAR DEM and InSAR preliminary results. In Tienchih area, a catastrophic 240-mm displacement sized 6.7 ha was recorded by a continuous GPS site, TENC, in 2016 after a heavy rainfall occurred on June 2. The correlation in the temporal variation of continuous GPS displacement time series and rainfall suggests that the movement is possibly related to gravitational load overlying water-saturated sediments. In addition, the average annual displacement rate of this downslope movement was measured at 20-40 mm/yr using the recently developed temporarily coherence points InSAR (TCPInSAR) technique based on ALOS/PALSAR imagery collected between 2007 and 2011. Apart therefrom, the high-angle thrust with highly fractured metamorphosed sandstone on the hanging wall; and the river incision and lateral river bank erosion are considered as the triggering factor of this catastrophic landslide. Similar triggering fac

Slow rock slope deformations are widespread in alpine environments. They affect giant volumes and evolve over thousands of years by progressive failure, resulting in long-term slow movements threatening infrastructures and potential evolution into massive collapses. In the alpine sector of Lombardia (Italian Central Alps), 208 mapped slow rock slope deformations affect a total area exceeding 580 km2 and interact with a variety of elements at risk including settlements, hydroelectric facilities and lifelines characterized by different vulnerability to both slow and progressive deformations. In this context, a systematic, reliable and cost-effective approach is required to classify slow rock slope deformations on the regional scale for landplanning, prioritization and analysis of interactions with elements at risk, depending on their style of activity, including not only mean deformation rate, but also their kinematics and spatial complexity. In this work, we implemented a toolbox that integrates different approaches to classify a large dataset of slow rock slope deformations in discrete groups, according to the deformation style and morpho-structural expression of individuals, mapped on regional scale and characterized through remote sensing techniques. The landslide dataset used in this study was obtained by a “semi-detail” geomorphological and morpho-structural mapping on aerial imagery and DEM, performed on regional scale yet including local-scale information (e.g. tectonic lineaments, morpho-structures, landforms, nested deep-seated landslides) and a full set of geological and morphometric attributes. To characterize landslide activity, we use Persistent-Scatterer Interferometry (PSI) data, including PS-InSARTM and SqueeSARTM acquired by different sensors (ERS, Radarsat, Sentinel 1A/B) over different time periods from 1992 to 2017. Since Line-of-Sight velocity of point like data can hamper a correct evaluation of both landslide kinematics and deformation rates, f

We present a semi-automatic workflow aimed at extracting quantitative structural data from point clouds obtained with avionic and terrestrial laser scanners (Lidar and TLS). The workflow is characterized by a calibration phase followed by an automatic data-collection phase. The large datasets of “fractures” mapped in this way are analysed with statistical methods allowing to define representative parameters of the fracture network. In the first phase, the intervention of an expert interpreter with structural geology skills is fundamental to evaluate which features can be interpreted as fractures in the point clouds. In the second phase, an automatic segmentation and classification is performed, based on phase 1 calibration, that allows extracting very large fracture datasets. The main steps in phase 1 are: manual segmentation of facets representing fracture surfaces, orientation analysis and definition of fracture sets (possibly supported by kinematic analysis), definition of orientation parameters to be used for automatic segmentation. Phase 2 analysis proceeds with the automatic segmentation of subset point clouds that include just one fracture set. In these point clouds, facets representing fractures lying on different planes are well separated and disconnected, and this allows applying automatic vectorization techniques that extract individual facets representing single fractures on the outcrop surface. The datasets issued from this processing are analysed with automatic algorithms allowing to define fracture spacing and orientation statistics with a very large support, that would not have been allowed by other methodologies.

1 Introduction In order to consider the presence of cracks in an abandoned gypsum pillar in numerical simulations, a hybrid method FEM/DEM, which allows the transition from continuum to discontinuum, was assumed. By means of a specific numerical code (ELFEN), this approach has been calibrated involving both physical quantities introduced by fracture mechanics and numerical aspects in order to support this hybrid method. Furthermore, the approaches FEM and FEM/DEM have been compared, showing advantages and disadvantages through experimental tests carried out to characterize geomechanical response of the pillar. The interaction domain has been calculated thanks to the implementation of both methods. The meaning of determining this domain is related to the evaluation of failure limit when a coupled system of loads (normal and tangential force and momentum) is acting on pillars. An application to a case study of an abandoned gypsum mine interacting with building in San Lazzaro di Savena (Bologna) is shown. 2 Abandoned Gypsum Mine – specific pillar (P7) chosen The choice of this pillar is related to its complex and redundant joints’ system, its reduced section and its location. In fact, it was possible to obtain its topography by TLS to furnish a detailed geometrical for the simulation. In the following figure the mine system and the selected pillar is shown. 3 Laboratory tests (UCS, BT, Triax) A series of laboratory tests permitted to obtain failure parameters to be inserted both in constitutive model for the continuum approach (FEM) than for the crack propagation model for the discontinuum approach (FEM/DEM). 4 A numerical comparison between the two approaches A coupled system of loads acting on pillar P7 has been simulated. In particular, 3D numerical simulations have been run to calculate an interaction domain represented by normal and tangential force and momentum. Also for the 2D FEM/DEM approach an interaction domain has been built thanks to a simplified solution

Large slopes in alpine environments undergo a complex long-term evolution from glacial to postglacial conditions through a transient period of paraglacial readjustment. During and after this transition the interplay among rock strength, topographic relief and morpho-climatic drivers can promote different types of slope instability, from sudden failures to large, slow (yet potentially catastrophic) rockslides. Deep-seated rockslides are commonly characterised by time-dependent displacements with superposed “long-term creep” components, often considered as evidence of progressive (sub-critical) slope failure (Amitrano & Helmstetter 2006; Lacroix & Amitrano 2013), and “seasonal creep” components resulting from coupling between hydrological triggers and landslides (Cappa et al. 2014; Crosta et al. 2014). Modelling the progressive failure of large rock slopes is key to predict future displacements and potential catastrophic evolution for risk analysis and early warning. Failure forecast for “mature” rockslides with well-developed sliding shear zones and weakened, permeable landslide masses mostly relies on analytical, statistical or numerical models accounting for the hydromechanical response of landslides to rainfall or snowmelt (Guglielmi et al. 2005; Crosta & Agliardi 2003; Crosta et al. 2014). Nevertheless, the geometry, internal structure, strength and hydrology of rock slopes are usually poorly known and likely evolve throughout deglaciation and paraglacial adjustment. Understanding the long-term evolution and progressive failure of large rock slopes requires that we account for time-dependent effects of unloading during deglaciation, permeability and fluid pressure fluctuations, ongoing displacement, and fracture development (Riva 2017; Riva et al, in review). All these aspects are related to a convincing description of rock mass damage processes, from a subcritical (progressive) to a critical (catastrophic) stage. Nevertheless, time-dependent damage e

The Colima Volcanic Complex (CVC) is one of the most prominent volcanic edifices within the Tran-Mexican Volcanic Belt (TMVB). Its evolution has been characterized by complex interactions among regional tectonics, basement geometry and rheology, and successive volcanic edifices formed in several stages. In the first part of this review chapter, the state-of-the-art in the CVC structural and geological knowledge is summarized and discussed. Such knowledge is based on published structural, geological, geophysical, geodetic and petrological data and models, which allow identification of three main fault systems and definition of the general geometrical properties of the volcano plumbing system. The significance and supporting evidence for the Colima Rift faults, Tamazula Fault and volcano spreading structures, as well as their interactions with the CVC, are presented. In the second part of the paper, numerical models are performed to integrate previous knowledge and test the effects of different structural scenarios and different mechanical assumptions on the onset of gravitational spreading of the volcanic complex. Also, the state of activity of the three fault systems and their control on the magmatism and flank instability are discussed. Finally, the main findings on the CVC structural arrangement are summarized, and the most important requirements for improvement of our understanding of the interaction between regional tectonics, volcanic edifices and basement rheology are suggested. Future investigations are critical, as eruptions and sector failures represent potential high risks for more than 500,000 people.

The hydro-mechanical properties of rock masses in slopes vary in space and time alongside with progressive failure processes, modulating the mechanism, timing and collapse of large rock slope instabilities. A reliable assessment of initial properties in large rock slopes is elusive and further complicate by rock mass heterogeneity related to lithology, fracture network properties and discrete structures (e.g. fault zones). Thus, modelling tools able to properly account for the heterogeneity and damage dependence of rock properties are needed to obtain realistic simulations and predictions of rock slope evolution. In this perspective, we integrate the ability of stochastic Discrete Fracture Networks (DFN) to realistically represent the heterogeneity of rock mass permeability and deformability within a damage-based, time-dependent 2D FEM model. DaDyn-RS (Riva et al. 2018) simulates the long-term creep and collapse of rock slopes and is able to account for spatially and temporally variable fluid pressure distribution, based on damage-dependent dilatancy and fracture connectivity in a continuum simulation framework. Here we incorporate in DaDyn-RS initial hydro-mechanical properties of rock slopes derived by DFN fracture volumetric intensity (P32), through upscaling techniques. Starting from field or borehole fracture data (e.g. orientation, intensity, size) we generate DFN models. Then, through grid-based analyses, fracture network properties are upscaled to volumetric fracture intensity (P32) and extracted on representative 2D cross-sections for integration in DaDyn-RS. Depending on the model scale, small fractures are not explicitly represented by the DFN, yet they affect the geomechanical properties of “intact rock”. Thus, we account for the effect of fracture-related heterogeneity on rock mass strength and permeability in three different ways: a) small fractures, not represented in the DFN, are taken into account by assigning initial values of Geological Strength I

The Ligurian coast between Cinque Terre and Portovenere is a UNESCO cultural landscape site. Human settlement in this region over the past millennium have been developed by shaping a steep, uneven terrain, which is highly prone to landsliding. Rockfalls, shallow landslides, debris flows and deep-seated landslides have seriously affected the site during the last centuries, with serious damages and injuries to population. This site has been selected as a case study for the PROTHEGO (PROTection of European Cultural HEritage from GeO-hazards) research project. Two main processes have been analysed within the project: rockfalls along the well-known Via dell’Amore (Lover’s Lane), a 500 m long portion of the Cinque Terre coastal path between Manarola and Riomaggiore; and a deep-seated rockslide at Punta Persico, south of Campiglia. Since its construction in the 1920’s, the Via dell’Amore played an important role in the local history and more recently as a popular hotspot for tourists visiting the region. The walkway has been closed since 2012 when a rockfall severely injured 4 tourists on the path causing the local authorities to close the walkway since this event. Hazard and risk assessment along the closed portion of the path have been performed. Terrestrial Laser Scanning (TLS) was used to image the inaccessible rock faces and slopes, in order to characterize the discontinuities and perform kinematic feasibility analyses. The resulting susceptibility values were used, along with other inputs (i.e. DEM, block sizes, coefficients of restitution), to run rockfall simulations by 3D numerical modelling software Hy-Stone. The simulation results were used to attain a hazard zonation along the walkway. The individual risk of being killed by a rockfall while on the path on any given day is about one in every 200.000 people. The Punta Persico deep-seated landslide involves many houses inside the landslide, which can be subdivided in several sectors with different behavior. The la

Large alpine rock slopes undergo long-term evolution in paraglacial to postglacial environments. Rock mass weakening and increased permeability associated with the progressive failure of deglaciated slopes promote the development of potentially catastrophic rockslides. We captured the entire life cycle of alpine slopes in one damage-based, time-dependent 2-D model of brittle creep, including deglaciation, damage-dependent fluid occurrence, and rock mass property upscaling. We applied the model to the Spriana rock slope (Central Alps), affected by long-term instability after Last Glacial Maximum and representing an active threat. We simulated the evolution of the slope from glaciated conditions to present day and calibrated the model using site investigation data and available temporal constraints. The model tracks the entire progressive failure path of the slope from deglaciation to rockslide development, without a priori assumptions on shear zone geometry and hydraulic conditions. Complete rockslide differentiation occurs through the transition from dilatant damage to a compacting basal shear zone, accounting for observed hydraulic barrier effects and perched aquifer formation. Our model investigates the mechanical role of deglaciation and damage-controlled fluid distribution in the development of alpine rockslides. The absolute simulated timing of rock slope instability development supports a very long “paraglacial” period of subcritical rock mass damage. After initial damage localization during the Lateglacial, rockslide nucleation initiates soon after the onset of Holocene, whereas full mechanical and hydraulic rockslide differentiation occurs during Mid-Holocene, supporting a key role of long-term damage in the reported occurrence of widespread rockslide clusters of these ages.