Instability mechanisms and collapse range prediction of steep high slopes during the open-pit to underground transition: A case study

The aim of the PhD thesis was to look for a relationship between the landslide-induced damage recorded on structures and facilities based on the results of several field campaigns and kinematic parameters quantitatively estimated by remote sensing techniques. Investigations were developed on two test sites: a deep-seated landslide in Colle Lapponi-Piano Ovetta in municipality of Agnone (Molise region, southern Italy) and the landslides affecting the southwestern sector of Volterra (Tuscany region, central Italy). First of all, a re-enactment of the evolution of both landslides were conducted, by means of 3D reconstructions based on historical aerial series of images and the analysis of Persistent Scatterers of ERS1/2, ENVISAT and COSMO-SkyMed satellites. The 3D Points Clouds and models were developed on several sets of aerial historical images dating from different years starting from 1945 and 1954 for Agnone and Volterra, respectively. To better understand the morpho-evolutionary stages, a qualitative assessment of changes of volume were made combining the oldest and the latest 3D reconstructed Points Clouds. This interpretation, even if qualitative and not quantitative, can be helpful for understanding possible effects of future reactivations and as a support to realize mitigation plans, susceptibility maps and other useful for the local administrators. The Persistent Scatterers were used to monitor the evolution in recent years, up to 2015. Then, for both case studies, the damage was revealed on structures and facilities by several field surveys and classified by means of five literature damage categorizations. During their application, some drawbacks and benefits of the methodologies were carried out and a new approach to improve the categorization of the damage on structures, facilities and ground surfaces was developed. This was conceived in two subsequent phases: i) a classification to use during the field campaign to quantify the severity of cracks and fractures on structures, facilities and ground surfaces; ii) an a posteriori ranking to apply on the entire structure, involving the extension of damage classes, performed by a cell-grid matrix. Furthermore, a damage recording scheme, useful for the recognition of cracks and fractures during the field surveys, was proposed. A critical comparison between the results obtained applying the different classification approaches, then followed. Buildings and facilities, for both sites, were categorized using also kinematic parameters such as velocity and maximum displacement measured along the Line Of Sight, derived by A-DInSAR, and their absolute values re-projected along the steepest local slope. Once characterized and categorized all structures and facilities of both sites of interest, a correlation between the surveyed damage classes and the deriving parameters by satellite were looked for. The investigation was carried to understand the behaviour of entire structures, subject to displacements. The first analysis was conducted on the Agnone test site where for several constructions an upper regression line between damage categories and velocity reprojected along the slope was recognized. Some outlayers were identified, mainly for low damage levels, then singularly investigated. To assess the reliability of all the structures, a matrix involving damage and velocity along the slope parameter acquired by ENVISAT and COSMO-SkyMed sensors was developed in order to obtain a classification. To validate the correlation and the reliability matrix the same procedure was applied to the Volterra site. Once asserted the validity of the relation between the velocity reprojected along the steepest slope and the classes of damage also for this area, the reliability matrix was applied on the constructions of the Volterra site. In this way, the relation between the displacement occurred during the period covered by ENVISAT and COSMO-SkyMed shows how the surveyed damage construction are related to the displacement. Some areas where damage occurred in the 2000 shows high reliability with ENVISAT recorded velocity, while others structures exhibits high reliability with COSMO-SkyMed data. The results were interesting because they highlight the fact that for some construction there is correlation between velocity of displacement of the entire structure and affecting damage; for others, instead, the high damage is related to the differential settlement and not necessarily to a high rate of displacement velocity.

The Triassic platforms of the Dolomite Alps of northern Italy are famous for their well-preserved platform flanks. We report on the discovery of extensive automicrite on these platform slopes. Automicrite stands for autochthonous micritic carbonate, formed by in-situ precipitation that was mediated by organisms. The automicrite occurs on the 400 m high, 25°–35° dipping slopes of the Sella platform that were pervasively dolomitized. Textures include peloidal aggregates (thrombolitic microfabric), irregular spar-filled cavities as well as biodetritus and are in many samples clearly visible despite the dolomitization. The peloids may occur as loose particles floating in lighter-colored cement or form a loosely connected framework. The preservation of automicrite textures along with the nearly unaltered slope geometry of the platform lead to several conclusions on the development of automicrite on such steep and high platform slopes. 1) Automicrite formed patches and layers from the platform top down to over 200 m on the flank and constitutes about 25% of the volume of slope sediment. 2) Automicrite alternates with layers of skeletal and lithoclastic rubble and sand. 3) Despite the extensive occurrence of automicrite, no mud mounds developed on the steep slopes. The autochthonous carbonate only forms layers and cushions that do not significantly alter the planar clinoforms. 4) On the slope, layers of automicrite slid, became fragmented and turned into breccias that dominate the lower slope. The undolomitized, distal ends of these breccias contain the Cipit boulders extensively described in the past.

Most accessible mineral deposits are nearly exhausted. Consequently, some resources that were previously abandoned are now being considered for remining. This paper describes a case study that aims at revealing the instability mechanism and selecting the optimal control countermeasures for a cataclastic roadway regenerated roof (CRRR) during the extraction of the remaining mineral resources. Based on the structural model of a cataclastic regenerated roof (CRR) of a remaining lower slice, a modified natural arch mechanical model for a CRRR was established by considering the lateral pressure and stress concentration coefficient of the bearing arch, through which the modified bearing arch curve equation and arch rise expression were deduced. The relationship between the modified arch rise and the lateral stress was obtained through a practical case. Next, a numerical model of a CRRR, which accounted for the cataclastic features, was built in the Universal Distinct Element Code (UDEC). The development of subsidence and fractures in the roadway roof was determined through modeling under various roof support scenarios, namely no support, rock bolt (RB) support, rock bolt and cable (RBC) support and a combined support of the rock bolt, cable and steel beam (RBCS). The theoretical analysis, numerical simulation and monitoring results of the RB and RBC stress all indicated that a bearing arch existed in the CRRR and that the arch rise underwent changes during the roof hanging time and with different support scenarios. The support structure should exceed the bearing arch rise in height and should be leak proof to avoid roof leakage. After a comparative analysis of the numerical and field support effects provided by various supporting scenarios, the RBCS support scenario was shown to be the optimal roof support choice, providing a good controlling effect for a CRRR and meeting the production requirements.

The load margin is an important index used in power system operation centers to assess how far the system is from an instability mechanism. Usually, this load margin is calculated considering the Voltage Stability requirements through static models. However, as the load level increases in one direction, low-dampened low-frequency oscillation modes can arise and they compromise the angular stability of the system. Thus, it is important to consider the dynamic model of the system and determine the load margin by meeting the requirements of Voltage and Small-Signal Stability. This article proposes a method based on Particle Swarm Optimization to determine the load margin of power systems meeting the requirements of the Voltage Stability (voltage collapse) and Small-Signal Stability (eigenvalues with low damping). Case studies on the IEEE 39-bus system are presented and discussed.

Accurate determination of the physico-mechanical parameters of rock and soil masses is fundamental to the quantitative stability analysis and engineering mitigation of open-pit mine slopes. However, existing studies often rely on generalized parameters and lack systematic empirical data based on full-hole in situ core sampling to quantitatively verify the link between microscopic mineralogy and macroscopic instability. To address this gap, this study investigates the mineral composition, microstructure, and hydro-mechanical behavior of geotechnical materials, using the XG Open-pit Coal Mine in Inner Mongolia as a case study. Field drilling and sampling with a cumulative depth of 1500.7 m were conducted, combined with systematic laboratory tests. The results reveal significant lithological heterogeneity within the mining area. Specifically, hard rocks (e.g., fine sandstone) constitute the stable framework of the slope, whereas mudstones rich in hydrophilic clay minerals, along with low-strength coal seams, form potential weak sliding interfaces. Quantitative X-ray Diffraction (XRD) analysis reveals that the weak mudstone layers contain up to 32.4% hydrophilic expansive minerals (montmorillonite and illite/smectite). Scanning Electron Microscopy (SEM) and slake durability tests demonstrate that the mudstone is characterized by well-developed micropores (1–2 μm) and loose cementation. Theoretical analysis indicates that upon saturation, the strength of these weak layers is reduced by over 40%, causing the factor of safety (FoS) to drop from a stable 1.48 to a critical 0.89. Based on these findings, the slope instability mechanism driven by “Stiffness Mismatch and Hydro-Weakening” is elucidated. Consequently, targeted reinforcement and drainage measures are proposed to provide a scientific basis for safe mining operations.

A case study of the temporal behavior of ionospheric scintillations and their frequency spectra in the cusp/cleft and polar cap regions is presented. These measurements were made at Søndrestrom and Thule, Greenland, using the 243‐MHz transmissions from quasi‐stationary satellites during a coupling energetic and dynamics of atmospheric regions (CEDAR) high‐latitude plasma structure (HLPS)/solar terrestrial energy program (STEP) global aspects of plasma structures (GAPS) campaign. During this campaign, the incoherent scatter radar (ISR) observations were also performed at Søndrestrom, which defined the dynamic ionospheric environment in the cusp/cleft region. The availability of the radar results has enhanced this case study. It is found that scintillations at Søndrestrom are abruptly enhanced about an hour before magnetic noon when the propagation path to the satellite entered the cusp/cleft region. Subsequently, a series of enhanced and reduced scintillation activity was detected. The enhanced scintillation structures were found to be asymmetric, with sharp leading edges and diffuse trailing edges. Spaced‐antenna scintillation measurements at Søndrestrom detected considerable velocity shear, and the frequency spectra showed flat low‐frequency portions, implying the presence of turbulent plasma flows. A comparison with the ISR observations indicates that the temporal variation of scintillation was caused by the poleward convection of alternate regions with high‐ and low‐ionization density, the density depletions being caused by channels of high zonal flows associated with velocity shear. The level of scintillation observed in the low‐density regions imply the presence of small‐scale irregularities with considerable irregularity amplitude. In contrast to the above behavior, the polar cap scintillations exhibit deep minima between the transit of successive “patches” of ionization, and their frequency spectra imply the absence of turbulent plasma flows. It is postulated that in the cusp/cleft and polar cap regions, the gradient‐drift instability mechanism generates the observed small‐scale irregularities associated with discrete density enhancements, whereas a shear‐driven instability, such as the nonlinear collisional Kelvin‐Helmholtz (K‐H) instability mechanism, may generate the irregularities in the intervening low‐density regions.

Engineering practice shows that the deformation of the slide‐resistant pile may be transferred to the adjacent bridge foundation on an inclined slope, which can compromise the safety of the entire bridge. However, this phenomenon has rarely been considered in the past. To reveal the deformation transfer mechanism between the slide‐resistant pile and the adjacent structures, a full‐scale field test was performed on a high and steep slope located in a section of a certain railway. A numerical analysis model was constructed to simulate the field test and validate its parameters. Moreover, parametric analysis was also conducted to examine the influence of the pile length, pile diameter, and arrangement of the pile foundation. The results show that the bridge pile foundation is simultaneously affected by the “load transfer effect” caused by the slide‐resistant pile and “traction effect” of the sliding slope. With the distance between the pile foundation and the slide‐resistant pile increasing, the dominant factor affecting the deformation mode of the pile body is switched from the “load transfer effect” to the “traction effect.” Furthermore, a critical embedment depth exists for the bridge pile foundation built on a high and steep slope, which varies at different locations along the inclined stratum. In addition, using a pile arrangement with a larger pile diameter and lower number of piles is more beneficial for controlling the horizontal displacement of the bridge foundation. The results of the research provide a reference for the safety control of the engineering on the high and steep slope.

Land-use changes affecting Mediterranean mountains represent the intensification of use in valley bottoms, accompanied by land-use conflicts, and a generalized abandonment of the hillslopes, which in the past were perfectly integrated in the system of land management. Farmland abandonment, reforestation, diminution of the livestock pressure and substitution of cereal crops by meadows are the most outstanding features of the recent land-use changes. The question is whether the new spatial organisation is in accordance with a longterm policy of sustainable development in mountain areas. The results obtained confirm that farmland abandonment on steep slopes — and the resulting colonization of old fields by a dense shrub cover — and afforestation contribute to control both soil erosion and surface runoff. As a result some of the most important rivers and alluvial fans have recently stabilized their sedimentary structures.

A combined retaining structure (CRS) that consists of numerous piles, a concrete platform, and a gravity retaining wall was built to support a high embankment constructed on a steep slope....

New prospects on high on-current and steep subthreshold slope for innovative Tunnel FET architectures

Landslide is a common natural hazard that usually occurs in mountainous areas. Rapid urban development and high traffic intensity movements have been hampered to a great extent by phenomenon of landslides. In Ghat section, vertical cuttings and steep slopes are induced slope failures. An assessment of landslide hazards is therefore a prerequisite for sustainable development of the hilly region. In the present study, Macro Landslide Hazard Zonation was carried out in the Bodi – Bodimettu ghats section, Western Ghats, Theni district. The slope spreads over an area of about 10.09 sq km encompassing Puliuttu Ar. sub-watershed. The study was made with help of different types of data including Survey of India topographic map, geology map, important inherent factors like lithology, structure, slope morphometry, relative relief, land use/land cover and hydrogeological conditions using Bureau of Indian Standard (BSI 14496 (Part 2):1998) and related thematic maps. Based on the thematic layers, landslide hazard evaluation factor (LHEF) and total estimated hazard (TEHD) were calculated and the macro hazard zonation map was prepared. Landslide Hazard Zonation (LHZ) of the terrain shows that out of 17 facets, facets 1 to 5 and 8 falls under Moderate Hazard zone category and facets 6, 7 and 9 to 17 under the High Hazard zone category. The field study with further analysis for hazard concluded that about 68% of the total area falls in the high hazard zone.

<p>The case study is located in the municipality of Les Fréaux, France. The site consists of Cambrian-Ordovician of amphibolite and gneiss rock with complex structural geology that formed in mountainous and large valley with steep slopes and even overhanging rock walls. In this site, rockfall is a major hazard for access roads and houses.</p><p>To assess rockfall hazard in the vicinity of the elements at risk, LiDAR data have been analysed and field work done on site from 2020 to 2021.  Rockfall source areas were identified directly on 3D point clouds (PC) based on two criteria, which are large slope angles and kinematic analysis from structural identification of fault, folds and joints. Based on these source areas, several 3D point cloud trajectory models were processed using the freeware stnParabel, for various block diameters (d1, d2, d3) in order to determine the propagation and the probability of reaching the settlements or roads.</p><p>Preliminary simulation of trajectories based on several method of simulations results showed some potential directions are reaching the road and also leading to settlements.</p>

The impacts caused by flood waves due to dam ruptures usually cause irreversible damages to the resident population, and, the loss of body equilibrium in floods contributes to aggravate this scenario. In this context, this work aimed to analyse the influence of consideration of physical mechanisms that cause instability in the human body on the definition of hazard zones. Therefore, it was developed simulation of the propagation of the flood wave due to the hypothetical rupture of Santa Helena Dam in Bahia, using the hydrodynamic model HEC-RAS. The results of flow velocities and heights were related and compared to different criteria of hazard zonings and mechanisms that cause body instability. It was verified that the consideration of instability mechanisms of the human body can contribute to hazard management, through the knowledge of areas in which different individuals may topple or slide. It was confirmed that in supercritical flow regimes is more likely for the individual to slide and that in subcritical regimes the individual will topple. Moreover, the consideration of parameters such as buoyancy force and the angle related to the human body's adaptive ability in a flooding influence on the definition of zones.

The mechanism of wave-induced instability in a permeable seabed have been studied for more than two decades. The distinction between shear failure and liquefaction, however, has not been clearly defined. This paper presents a fundamental study on the differences in two failure modes for a fully saturated seabed of both finite and infinite thickness. The wave-induced effective stresses and pore pressure, obtained from an analytical solution of Biot’s pore-elastic consolidation theory, were employed to examine the failure modes under a two-dimensional plane strain condition. A case study is presented to examine the failure modes with respect to several parameters, such as excess pore pressure, seepage flow, seepage force, failure areas and stress path in the seabed. The conclusions obtained from this study were as follows; (1) the thickness of a permeable seabed affects the pore pressure and effective stress response to ocean waves and the failure mode of the seabed, (2) either a liquefaction or shear failure, or both, occur in the seabed, even in the saturated seabed, (3) the Mohr-Coulomb’s failure criterion, when combined with elastic stresses, can not be employed to estimate the liquefaction failure in the seabed, (4) the liquefaction can be evaluated by a criterion in terms of the excess pore pressure, (5) The liquefied zone in the seabed is significantly different from the shear failure zone. The shape beneath the seabed surface for the former is almost identical to the contour where the upward seepage flow is concentrated.

A framework for an IoT-based local landslide early warning system (Lo-LEWS) has been proposed in Piciullo et al., 2022. The framework is composed by four main components: monitoring, modelling, forecasting and warning. The first two phases have been applied to capture the hydrological behavior and compute the slope stability of a natural unsaturated slope located adjacent to a railway track in Eastern Norway. The steep slope (about 45° in the upper part) is instrumented with several sensors since 2016 (Heyerdahl et al., 2018). Volumetric water content (VWC) and pore-water pressure (PWP) sensors were installed in late spring of 2016. In 2022 a weather station has been added to the monitoring network for measuring climate variables. These data are collected in real-time and are accessible on internet, while the PWP from the electric piezometers are collected manually.GeoStudio software was used to create a slope model able to replicate the in-situ monitored conditions. SEEP module was used to back calculate the observed VWC and PWP. Simulations were carried out by changing the initial and boundary climate conditions of the slope. Two main simulation sets were conducted considering: an initial calibration of VWC profile (C), no calibration (NC). For each one, three different surface boundary conditions were applied: i) only precipitation, ii) precipitation and atmospheric conditions, iii) precipitation, atmospheric conditions and vegetation, considering the Penman-Monteith equation for evapotranspiration. The simulations have been validated using Taylor diagrams that graphically summarize how closely a pattern, or a set of patterns, matches observations. The results show that including an initial calibration, climate variables and vegetation, is crucial to best model the response of the unsaturated slope in Eidsvoll.A sensitivity analysis on the hydraulic conductivity and the permeability anisotropy contributed to better define the input data and to improve the fitting model-observations. The effectiveness of the best simulation, in back-calculating VWC, was tested for 3 different time periods: 6-month, 1-year, 1.25-year. The results show that the hydrological model can adequately represent the real monitored conditions up to a 1-year period, a recalibration is needed afterward. In addition, a slope stability analysis with GeoStudio SLOPE module, for the 1-year period, was coupled to the SEEP module (Piciullo et al., 2022) to compute the factor of safety (FS). A supervised, regression machine learning analysis has been carried out using a random forest machine learning model. The analysis has highlighted the importance of the monitored VWC in forecasting the FS. The VWC values are the variables measured in real time on the slope. For this reason, the possibility to predict the FS from VWC is relevant for the implementation of a real-time slope stability analysis as a Lo-LEWS.  Heyerdahl H., Hoydal O. A., Kvistedal Y., Gisnas K. G., Carotenuto P. (2018). Slope instrumentation and unsaturated stability evaluation for steep natural slope close to railway line. In UNSAT 2018: The 7th International Conference on Unsaturated Soils.Piciullo, L., Capobianco, V. & Heyerdahl, H. (2022) A monitored unsaturated slope in Norway: Eidsvoll case study. Klima 2050 Report;35 https://hdl.handle.net/11250/3000249