In this work, the thermo-mechanical stress–strain history of an Alpine slope is analyzed, with particular focus on the historical Cimaganda large landslide (Sondrio Province, Italy), which mobilized ...an estimated volume of 7.5 mm
3
of rock material. Accurate geomorphological and geomechanical characterization involving field surveys and laboratory testing was carried out, leading to the development of a conceptual model of the slope. A thermo-mechanical semi-coupled approach was developed, considering both glacial debuttressing and thermo-mechanical effects due to gradual exposure of the slope to atmospheric conditions and paleo-temperature redistribution resulting from the Last Glacial Maximum deglaciation. A 2D distinct-element numerical approach was adopted, supported by a 2D finite-element analysis to simulate heat diffusion over the Valley cross-section. Modelling results allow to simulate the general evolution of the Cimaganda rock-slope and to highlight the significance of thermal processes in preparing rock-slope instabilities. While the mechanical effect of ice thickness reduction alone brings about moderate rock mass damage, the introduction of temperature couplings results in a substantial increase of damage, representing a significant factor controlling the stress–strain evolution of the slope. Simulated displacement and the development of a deep region of shear strain localization at a depth roughly corresponding to that of the detected Cimaganda sliding surface, allow to highlight the significance of temperature influence in preparing the rock-slope to instability.
Highlights
The effects of surface temperature variations on the stress-strain evolution of an Alpine rock-slope are examined through numerical simulation.
This study contributes to the understanding of Thermo-Mechanical processes driving damage in rock masses.
Results showed how Thermo-Mechanical stresses induced by temperature variations at both long- and short-term timescales, can represent a significant preparatory factor to rock slope instability.
The factors introduced in the analysis allowed to simulate the general evolution of the Cimaganda rock-slope, which is corroborated by field survey data.
This study exploited the historical rockfall inventory and the meteorological stations database of Mont Cervin and Mont Emilius Mountain Communities (Aosta Valley, northern Italy) to decipher ...relationships between climate processes, typical of mountain environments and rockfall phenomena. The period from 1990 to 2018 was selected as reference to perform the analysis. Climate processes were translated into four climate indices, namely short-term rainfall (STR), effective water inputs (EWI, including both rainfall and snow melting), wet and dry episodes (WD) and freeze-thaw cycles (FT). The comparison between climate indices values at each rockfall occurrence and the statistical distributions describing the whole indices dataset allowed to define not ordinary climatic conditions for each index and their influence on rockfall occurrence. Most of the events analysed (>95% out of 136) occurred in correspondence of the defined not ordinary climatic conditions for one or for a combination of the indices. The relationships between rockfalls and climate showed a seasonality. In spring, most of the events resulted to be connected to FT (70%) while in autumn to EWI (49%). The relative seasonal importance of WD reached its maximum in summer with 23% of the events related to this index alone. Based on these results, different strategies to define empirical critical thresholds for each climate index were explored, in order to make them valid for the whole study area. A preliminary exploratory analysis of the influence of high temperatures and temperature gradients was carried out for some summertime rockfalls, not correlated to the other investigated indices. The presented approach is exportable in neighbouring regions, given the availability of a dated rockfall dataset, and could be adapted to include different processes.
The Piuro 1618 landslide represents a well-known case history of a large Alpine landslide. It destroyed the ancient village of Piuro (Italian Bregaglia Valley), renowned as an important trading ...center between the Mediterranean region and Northern Europe. The event had a significant impact among communities of all Alpine regions and was well documented by chronicles and paintings during subsequent decades. However, some aspects, such as the geometry reconstruction of the landslide body, the location of the landslide scarp, and its dynamics, remained undefined in previous studies, and a geomechanical characterization of the failure area is completely missing. Using field and laboratory analysis followed by stress–strain numerical modelling, this work develops a 3D conceptual geomechanical model of the slope considering its complex geological framework. The aim is to back-analyze the 1618 event, defining predisposing and triggering factors of the sliding event, and providing verifications on the geometry and location of the failure scar, as well as on the landslide dynamics. A coupled hydro-mechanical analysis with a 3D numerical approach is presented, assuming a rainfall scenario as a possible triggering factor. Simulated displacement and the development of a deep region of shear strain localization at a depth roughly corresponding to that of the detected Piuro sliding surface, allow us to highlight the mechanical role of geological elements outcropping along the slope and to validate the proposed scenario as a likely triggering factor for the 1618 event.
The Piuro 1618 landslide is renowned as one of the most catastrophic historical events of the Central Alps. The landscape of the Bregaglia Valley has been successively modified to such an extent to ...make it difficult to ascertain the source of the landslide, the extent of its deposits and the setting of the ancient village. This study focuses on the identification of the source area of the landslide, its dynamics, the extent of its deposits and the estimation of the involved volumes. The geological map here proposed permitted to reconstruct the relationships between the pre-1618 setting, the 1618 restructuration of the landscape and the post-event changes that occurred owing to erosion by the trunk river, deposition of debris flow fans and slope dynamics. The paper shows how geological mapping may help to unravel landscape evolution of an Alpine valley even at the high-resolution required by historical and archaeological studies.
AMALPI Trek is a cross-border geotouristic trail that, from the Maloja Pass to the Gotthard region, leads along ancient and new routes, with their natural and anthropic peculiarities (waterfalls, ...villages), historical-archaeological (such as the excavations in Piuro) and gastronomic (such as foods prepared in soapstone pots, “lavecc”), to discover the processes that drastically change the Alpine territory: the great landslides of the past, present and future. The guidebook allows anyone to enjoy in another way the beauty of the crossed valleys, perhaps walking only short distances, or reaching them by other transportation means (preferably public or zero emissions), relying on interpretations provided by scholars, to understand the landscape evolution and the history of landslides. The hope is to help in promoting a new curiosity towards mountains and what animates them, landslides, increasing the risk awareness in the Alpine environment.
The
IGCP 714 project “3GEO – Geoclimbing & Geotrekking in Geoparks
” is financed by the International Geoscience Programme (IGCP) and supported by the International Union of Geological Sciences ...(IUGS). In this paper, we report on the results of the first phase of the project focused on the criteria to be adopted to select geodiversity sites equipped for climbing or trekking. The selection of geoclimbing sites and geotrekking routes is aimed at combining multimedia tools and outdoor activities for Geosciences promotion and conservation in UNESCO Global Geoparks, aspiring geoparks or geoparks project, and also in protected areas featuring geoheritage sites. Indeed, both outdoor activities and multimedia tools favour the pursuing of many of the United Nations Sustainable Development Goals (e.g., 3, 4, 8, 11). An international consortium of geoscientists from 12 different countries selected, through the proposed procedure, 22 geoclimbing sites, and then they also detected 30 geotrekking routes mirroring Earth geodiversity. At some test sites (geoclimbing and geotrekking) multimedia tools and digital outcrop models have been developed through different methodological approaches (e.g., Structure from Motion and Multi-View Stereo photogrammetry), to open the way to the second part of the project still in progress. These sites and the relative virtual models are herein also shown. The final aim of the IGCP 714 project is indeed to create an open data repository (digital outcrop models, videos, virtual tours, photos, scientific information, and interpretations) to upload data of the selected sites to mirror Earth geodiversity for different users including tourists and school groups.
Settlements of ground subjected to foundation load are often due to both natural and/or anthropogenic causes, such as differential consolidation, seepage, periods of drought alternating with heavy ...rainfalls, growth of tree roots, sewer leaks, vibrations induced by vehicle traffic, excavations, or construction defects. Techniques of soil consolidation and stabilization by means of injection of polyurethane expanding resins have been efficiently used to mitigate or even solve this issue. The efficiency of the resin injection treatment has been well documented also thanks to the develop of a procedure of planning and monitoring which combines traditional geotechnical tests with the application of electrical resistivity tomography, which is strongly sensitive to the presence of water or voids. The combination of these survey methodologies allows to recognize the effect of injection in terms of soil compaction and water migration, a key factor for understanding the phenomenon and planning of resolutive interventions. The present study follows a previous work aimed at evaluating the increase in the geotechnical performance of cohesive soils treated by injection of expanding resins (same soil, resin, at the same site) and integrates it by focusing on the quantification of the effects of consolidation treatments, by means of expanding resins injection, on hydrologic properties of cohesive soils, focusing on saturated hydraulic conductivity measurements. Laboratory permeability test, performed in triaxial cell at different stress conditions and hydraulic gradients, were performed on undisturbed samples collected on “natural (non-treated)” and “treated soils”, before and after the injection of resin (MAXIMA ® by GEOSEC ® ) in a full-scale test site characterized by the presence of continuous and homogeneous cohesive soils, (clay and silts). The investigated soil is classified as CH or CL soil, very firm and apparently overconsolidated. The study shows how the treatment is able to modify the characteristics of hydraulic conductivity of the soil. The injected resins partly follow pre-existing weaknesses and partly impregnate homogeneous and continuous masses of soil in a capillary way, giving it, in addition to the already documented greater mechanical strength, a lower hydraulic conductivity. The electrical resistivity investigations allow to appreciate the volumes affected by the treatment to which the variations of the measured properties can be attributed.
The urban area of Como (Italy) is particularly susceptible to subsidence. The reason is the particular structure of the subsoil, combined with the anthropic modification of the lakeshore lands linked ...to the historical evolution of the area. Moreover, this phenomenon exposes the lakefront areas to an increasing risk of flooding. The primary purpose of this study was to develop an effective methodology for the assessment of subsidence in urban areas, to be used as a support in groundwater management. The development of a coupled hydrogeological-geotechnical numerical model for the period 2004–2011 allowed recognizing the shoreline results as most susceptible areas to the phenomenon. Model results were critically evaluated through comparison with time series of PSInSAR and high precision levelling data available in the area. The anthropic perturbations of groundwater flow linked to the construction of lake flooding defenses in 2008–2009, enhanced the subsidence phenomenon in a localized area, pointing out the strong inter-dependence of groundwater circulation, lake level oscillations and geotechnical behavior of soils. Thus, the model revealed the most critical zones and geotechnical units, demonstrating to be a potential powerful tool to predict subsidence scenarios (e.g. the future completion of the floods defense works in the shoreline area).
•A coupled hydro-geotechnical numerical model for Como urban area was developed.•Numerical model was integrated with satellite and levelling monitoring data.•Reworked anthropic soils are critical in governing subsidence along the shoreline.•Anthropic perturbations of groundwater flow enhance subsidence up to 6–7 cm per year.•Future completion of Lake's floods defense system could develop new critical areas.
Stromboli island has a complex geological history with repeated changes in the volcanic activity alternating with destructive events, caldera collapses and flank landslides. The last activity ...resulted in the creation of the Sciara del Fuoco depression which was modified by the recent 2002-2003 landslide. The variation in lithology, degree of tectonization and disturbance has resulted in the presence of a wide spectrum of geotechnical materials. This paper summarises the physical and mechanical properties of Stromboli's intact rocks, rock masses and loose deposits, based on field surveys and laboratory tests. A new classification of the rock succession is introduced and four lithotechnical units defined: Lava, Lava-Breccia, Breccia and Pyroclastic deposit. The range of variability in bulk volume, porosity, intact rock compressivestrength and geological strength index is presented. The Hoek and Brown's failure criterion was appliedfor each lithotechnical unit and the rock mass friction angle,apparent cohesion,tensile and compressivestrength, global strength and modulus of deformation calculated in a specified stress range.
Natural and anthropogenic mountain landscapes coevolve responding on different temporal scales to climate changes and geodynamics by a series of increments that cause the dynamic association of ...morphological stabilization surfaces, stratigraphic units and landforms. Understanding the incremental history of palimpsest landscapes helps to recognize and forecast the effects of climate change on the sensitive mountain environments, contributes to archaeological and historical reconstruction and supports management strategies for natural risks prevention and mitigation. The Italian Bregaglia Valley provides an excellent site to unravel the recent/historical increments of evolution of landforms and human settlement, permitting to map the paleo‐digital terrain models (DTMs) corresponding to the relevant landscape turning points. After the last de‐glaciation, two large‐scale landslides reshaped the valley floor, both predisposed by deep‐seated gravitational slope deformations and one surely triggered by intense rainfalls. The most recent and impacting event buried in 1618 the rich border town of Piuro, the ancient one occurred in the same area at least 1.5 ka before. Combining stratigraphic, geomorphological, topographic, archaeological and historical data, we drew the paleo‐DTMs of the pre‐ and post‐1618 settings of Piuro, sketching the landscape evolution. Since two millennia, human settlements took advantage of the decadal to secular most stable surfaces, represented by the inactive lobes of debris‐flow fans, the highest trunk river terraces and the top of humps formed by the ancient landslide body in the valley centre. Stratigraphic relationships, archaeological findings and age determinations show that both landslides diverted the trunk river and covered the existing fan lobes. On a secular timescale, fan progradation and trunk river terracing buried and reworked both the landslide bodies. The paleo‐DTMs show their original areal extent and permit to compute their volume and to sketch the setting of the buried Piuro settlements, drawing the changes of the Mera trunk river course and the chronology of activity of the lateral debris‐flow fan lobes.
Considering the catastrophic 1618 landslide as a morphological turning point, the understanding of the progressive evolution of the palimpsest landscape of Piuro made it possible to draw two DTMs depicting the pre‐ and post‐1618 morphology of the valley bottom, useful for archaeological reconstructions and quantitative analyses.
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