Search Results (10)

Monitoring surface displacements of landslides is essential for evaluating their evolution and the effectiveness of mitigation works. Traditional methods like robotic total stations (RTSs) and GNSS provide high-accuracy measurements but are limited to discrete points, potentially missing the broader landslide’s behavior. On the contrary, laser scanner surveys offer accurate 3D representations of slopes and the possibility of inferring their movements, but they are often limited to infrequent, high-cost surveys. Monitoring techniques based on ground-based digital photogrammetry may represent a new, robust, and cost-effective alternative. This study demonstrates the use of multi-temporal images from fixed and calibrated cameras to achieve the 3D reconstruction of landslide displacements. The method presented offers the important benefit of obtaining spatially dense displacement data across the entire camera view and quasi-continuous temporal measurement. This paper outlines the framework for this prototyping technique, along with a description of the necessary hardware and procedural steps. Furthermore, strengths and weaknesses are discussed based on the activities carried out in a landslide case study in northeastern Italy. The results from the photo-monitoring are reported, discussed, and compared with traditional topographical data, validating the reliability of this new approach in monitoring the time evolution of surface displacements across the entire landslide area. Full article

The challenge of maintaining ride quality and serviceability in flexible pavements built over expansive soil deposits remains a critical concern for transportation agencies. These expansive subgrades exhibit swell-shrink behavior in response to moisture fluctuations, leading to differential heaving and subsequent costly maintenance. This paper explores the effectiveness of a Hybrid Geosynthetic Reinforcement System (HGRS)—a composite of geocell and geogrid—as a targeted mitigation strategy for differential heaving induced by expansive soils. A large-scale box test was designed to simulate a flexible pavement section, consisting solely of a base course layer and the underlying expansive subgrade. Four test conditions were investigated: an unreinforced control, a geocell-reinforced section, a geogrid-reinforced section, and an HGRS-reinforced section. Vertical displacements on the surface of the base course layer were longitudinally monitored and compared against the control. The results reveal that the use of geosynthetic reinforcements, and HGRS in particular, significantly mitigates both maximum surficial heave and differential swelling. Among the systems tested, flexible pavements featuring HGRS demonstrated the most effective performance in alleviating the challenges posed by expansive soil deposits. Full article

In the second half of the 20th century, the western Antarctic Peninsula recorded the highest mean annual air temperature rise in the Antarctic. The South Shetland Islands are located about 100 km northwest of the Antarctic Peninsula. The mean annual air temperature at sea level in this Maritime Antarctic region is close to −2 °C and, therefore, very sensitive to permafrost degradation following atmospheric warming. Among geomorphological indicators of permafrost are rock glaciers found below steep slopes as a consequence of permafrost creep, but with surficial movement also generated by solifluction and shallow landslides of rock debris and finer sediments. Rock glacier surface velocity is a new essential climate variable parameter by the Global Climate Observing System, and its historical analysis allows insight into past permafrost behavior. Recovery of 1950s aerial image stereo-pairs and structure-from-motion processing, together with the analysis of QuickBird 2007 and Pleiades 2019 high-resolution satellite imagery, allowed inferring displacements of the Hurd rock glacier using compression ridge-and-furrow morphology analysis over 60 years. Displacements measured on the rock glacier surface from 1956 until 2019 were from 7.5 m to 22.5 m and surface velocity of 12 cm/year to 36 cm/year, measured on orthographic images, with combined deviation root-mean-square of 2.5 m and 2.4 m in easting and northing. The inferred surface velocity also provides a baseline reference to assess today’s displacements. The results show patterns of the Hurd rock glacier displacement velocity, which are analogous to those reported within the last decade, without being possible to assess any displacement acceleration. Full article

Mountain territories affected by natural hazards are vulnerable areas for settlements and inhabitants. Additionally, those areas are characterized by socio-economic marginality, further favoring their abandonment. The study area is located in Liguria (Italy), and a large, slow-moving phenomenon endangers the settlements in the region. Monitoring such phenomena requires the use of instruments capable of detecting yearly, millimetric displacements and, due to their size, the use of remote techniques which can provide deformation measurement of the entire extent of the phenomenon. The methodology proposed here couples long-term interferometric remote sensing data analysis with intensive in situ monitoring (inclinometer, piezometers and global navigation satellite systems). Furthermore, the inclinometric measurements were carried out with an experimental, robotized inclinometer. The aim is to frame the overall context of ground deformation, assure information for inhabitants, stakeholders and land-planners, and secure coexistence with the phenomenon. Remote sensing provided a time series of 28 years of deformation measurements while in situ instrumentations allowed, in the last years, a better understanding of the surficial and deep behavior of the phenomenon, confirming the satellite data. Additionally, the high-frequency monitoring allowed us to record acceleration after precipitation peaks. The proposed approach, including the experimental instruments, proved its viability and can be replicated in similar mountain contexts. Full article

The interferometric synthetic aperture radar (InSAR) technique was used in this study to derive the temporal and spatial information of ground deformation and explore its temporal correlation with groundwater dynamics. The random forest (RF) machine learning method was used to model the spatial variability of the temporal correlation and understand its influential contributors. The results showed that groundwater dynamics appeared to be an important factor in InSAR deformation at some bores where strong and positive correlations were observed. The RF model could explain up to 72% of spatial variances between InSAR deformation and groundwater dynamics. The spatial and temporal InSAR coherence (a proxy for the noise in InSAR results that is strongly related to vegetation) and soil moisture (difference, trend, and amplitude) were the most important factors explaining the spatial pattern of the temporal correlation between InSAR displacements and groundwater levels. This result confirms that noise sources (including deformation model fitting errors and radar signal decorrelation) and perturbation of the InSAR signal related to vegetation and surficial soils (clay content, moisture changes) should be accounted for when interpreting InSAR to support groundwater-related risk assessments and in groundwater resource management activities. Full article

Reinforced drapery meshes, both secured and pinned, constitute a compelling solution for rockfall risk mitigation on rock slopes facing structures and infrastructures. They consist of steel wire mesh panels combined with a systematic anchoring pattern. In secured drapery systems, the anchors are connected to each other and to the net through ropes. The system prevents both global instability of the surficial part of the slope thanks to the anchors and local instability by confining small detached fragments in delimited mesh sections. The mesh is generally designed with mechanical resistance derived from the puncturing force–displacement behavior observed during a standardized laboratory test. Despite the fact that a codified design method has not yet been defined, the mesh is generally verified without considering the presence of the ropes. In the present work, an enhanced design method is introduced that accounts for retaining ropes, with the aim of achieving a confining effect similar to the constraints adopted in laboratory tests. In addition, the rope pattern enables the consideration of portions of mesh smaller than pinned drapery systems. In the proposed method, rope elongation is limited such that failure of the mesh near the anchor plate is prevented. The proposed design assessment reveals that the presence of ropes provides possible cost reductions in the choice of the mesh type. Full article

The present research focuses on the investigation of an in situ hydrogen charging effect during Crack Tip Opening Displacement testing (CTOD) on the fracture toughness properties of X65 pipeline steel. This grade of steel belongs to the broader category of High Strength Low Alloy Steels (HSLA), and its microstructure consists of equiaxed ferritic and bainitic grains with a low volume fraction of degenerated pearlite islands. The studied X65 steel specimens were extracted from pipes with 19.15 mm wall thickness. The fracture toughness parameters were determined after imposing the fatigue pre-cracked specimens on air, on a specific electrolytic cell under a slow strain rate bending loading (according to ASTM G147-98, BS7448, and ISO12135 standards). Concerning the results of this study, in the first phase the hydrogen cations’ penetration depth, the diffusion coefficient of molecular and atomic hydrogen, and the surficial density of blisters were determined. Next, the characteristic parameters related to fracture toughness (such as J, KQ, CTOD_el, CTOD_pl) were calculated by the aid of the Force-Crack Mouth Open Displacement curves and the relevant analytical equations. Full article

The main aim of this paper is to test the use of multi-temporal differential interferometric synthetic aperture radar (DInSAR) techniques as a tool for geological and geomorphological surveys in urban areas, where anthropogenic features often completely obliterate landforms and surficial deposits. In the last two decades, multi-temporal DInSAR techniques have been extensively applied to many topics of Geosciences, especially in geohazard analysis and risks assessment, but few attempts have been made in using differential subsidence for geological and geomorphological mapping. With this aim, interferometric data of an urbanized sector of the Venetian-Friulian Plain were considered. The data derive by permanent scatterers InSAR processing of synthetic aperture radar (SAR) images acquired by ERS 1/2, ENVISAT, COSMO SKY-Med and Sentinel-1 missions from 1992 to 2017. The obtained velocity maps identify, with high accuracy, the border of a fluvial incised valley formed after the last glacial maximum (LGM) and filled by unconsolidated Holocene deposits. These consist of lagoon and fluvial sediments that are affected by a much higher subsidence than the surrounding LGM deposits forming the external plain. Displacement time-series of localized sectors inside the post-LGM incision allowed the causes of vertical movements to be explored, which consist of the consolidation of recent deposits, due to the loading of new structures and infrastructures, and the exploitation of the shallow phreatic aquifer. Full article

We investigated the contribution of earthquake-induced surface movements to the ground displacements detected through Interferometric Synthetic Aperture Radar (InSAR) data, after the M_w 3.9 Ischia earthquake on 21 August 2017. A permanent displacement approach, based on the limit equilibrium method, allowed estimation of the spatial extent of the earthquake-induced landslides and the associated probability of failure. The proposed procedure identified critical areas potentially affected by slope movements partially overlapping the coseismic ground displacement retrieved by InSAR data. Therefore, the observed ground displacement field is the combination of both fault slip and surficial sliding caused by the seismic shaking. These findings highlight the need to perform preliminary calculations to account for the non-tectonic contributions to ground displacements before any estimation of the earthquake source geometry and kinematics. Such information is fundamental to avoid both the incorrect definition of the source geometry and the possible overestimation of the coseismic slip over the causative fault. Moreover, knowledge of the areas potentially affected by slope movements could contribute to better management of a seismic emergency, especially in areas exposed to high seismic and hydrogeological risks. Full article

In this work, we map surficial ground deformations that occurred during the years 2004–2010 in the Crati Valley (Southern Italy). The valley is in one of the most seismically active regions of the Italian peninsula, and presents slope instability and widespread landslide phenomena. We measured ground deformations by applying the small baseline subset (SBAS) technique, a multi-temporal synthetic aperture radar interferometry (InSAR) methodology that is used to process datasets of synthetic aperture radar (SAR) images. Ground displacements are only partially visible with the InSAR technique. Visibility depends on the geometry of the acquisition layout, such as the radar acquisition angle view, and the land use. These two factors determine the backscattering of the reflected signal. Most of the ground deformation detected by InSAR can be attributed to the gravitational mass movements of the hillslopes (i.e., landslides), and the subsidence of the quaternary deposits filling the valley. The movements observed along the valley slopes were compared with the available landslide catalog. We also identified another cause of movement in this area, i.e., ground subsidence due to the compaction of the quaternary deposits filling the valley. This compaction can be ascribed to various sources, such as urban population growth and sprawl, industrial water withdrawal, and tectonic activity. Full article