1,721,012 research outputs found
Geophysical characterization of an unstable rock mass
Full text linkA pre-requisite in rock mass stability analysis is to obtain the internal structure and the mechanical
properties of the investigated rock mass with a reasonable degree of uncertainty. In this respect, geophysical
methods can be profitably used as an imaging and characterization tool. Seismic methods are often more suitable
because the measurements depend on the mechanical properties of the rock mass. The present paper presents
the use of cross-hole seismic tomography in a site (Madonna del Sasso – NW Italy) affected by a rock instability
phenomenon, highlighted by episodes of slow deformation recorded by standard measurement devices.
Geophysical tests have been fundamental in imaging the fracturing state and the relative variation of seismic
velocities between intact an altered rock and in defining the seismic velocity field of the rock mass, a basic
prerequisite for the future planned microseismic monitoring step
Detecting Near-Surface Cavities and Shallow Heterogeneities through Surface Wave Attributes: Methods and Applications
No full textDetecting cavities, fault zones, and low-velocity anomalies is a primary objective for geotechnical characterization and urban planning, as well as for geohazard studies and mineral exploration. Surface wave attributes based on energy and attenuation of the raw seismic data can provide a major contribution in the identification and location of these near-surface heterogeneities. The attribute computation is fast and straightforward, making them ideal tools for automatic site screening in near real time. Their effectiveness has been tested on a wide variety of numerical models and real data
Continuous vertical electrical soundings (CVES) for the geological investigation of underwater deposits beneath the lake of Candia (Turin NW Italy)
No full textWe discuss below the results of a survey conducted with the CVES method on the Lake of Candia, near the city of Turin, in north-western Italy. The main objective of the study was the characterization of the sediments of the basin, in order to define the nature, the composition, the geometry and the spatial relationships of detected geological bodies. Another aim of the survey was to try to understand the hydrogeological dynamics that govern the lake basin, in order to determine, at least qualitatively, the presence of interconnecting paths with groundwater and to locate areas in which recharge or seepage flows are concentrated. Using a Laterally Constrained Inversion (LCI) approach for the data inversion, we managed to obtain fifteen resistivity sections that cover almost the entire area of the lake. By joining and interpolating the profiles it was possible to produce a three-dimensional model of the electrical resistivity distribution below the water basin. Thanks to the study, we found the presence of coarse glacial deposits, with high resistivity values, along the southern shore of the lake. These coarse deposits, primarily consisting of gravel and pebbles mixed with a sandy matrix, could be considered as the main hydrogeological window connecting surface and underground wate
Machine Learning-Based Event Classification of Passive Seismic Data for the Early Warning of Landslides
No full textAmbient seismic noise and microseismicity monitoring of a prone-to-fall quartzite tower (Ormea, NW Italy)
Full text linkRemote sensing techniques are leading methodologies for landslide characterization and monitoring. However, they may be limited in highly vegetated areas and do not allow for continuously tracking the evolution to failure in an early warning perspective. Alternative or complementary methods should be designed for potentially unstable sites in these environments. The results of a six-month passive seismic monitoring experiment on a prone-to-fall quartzite tower are here pre-sented. Ambient seismic noise and microseismicity analyses were carried out on the continuously recorded seismic traces to characterize site stability and monitor its possible irreversible and reversible modifications driven by meteorological factors, in comparison with displacement measured on site. No irreversible modifications in the measured seismic parameters (i.e., natural resonance fre-quencies of the tower, seismic velocity changes, rupture-related microseismic signals) were detected in the monitored period, and no permanent displacement was observed at the tower top. Results highlighted, however, a strong temperature control on these parameters and unusual preferential vibration directions with respect to the literature case studies on nearly 2D rock columns, likely due the tower geometric constraints, as confirmed by 3D numerical modeling. A clear correlation with the tower displacement rate was found in the results, supporting the suitability of passive seismic monitoring systems for site characterization and early waning purposes
Special Issue “Remote Sensing in Applied Geophysics”
Full text linkThe Special Issue "Remote Sensing in Applied Geophysics" is focused on recent and upcoming advances in the combined application of remote sensing and applied geophysics techniques, sharing the advantages of being non-invasive research methods, suitable for surface and near-surface high-resolution investigations of even wide and remote areas. Applied geophysics analyzes the distribution of physical properties in the subsurface for a wide range of geological, engineering and environmental applications at different scales. Geophysical surveys are usually carried out deploying or moving the appropriate instrumentation directly on the ground surface. However, recent technological advances have brought to the development of innovative acquisition systems more typical of the remote sensing community (e.g., airborne surveys and unmanned aerial vehicle systems). At the same time, while applied geophysics mainly focuses on the subsurface, typical remote sensing techniques have the ability to accurately image the Earth's surface with high-resolution investigations carried out by means of terrestrial, airborne, or satellite-based platforms. The integration of surface and subsurface information is often crucial for several purposes, including the georeferencing and processing of geophysical data, the characterization and time-lapse monitoring of surface and near-surface targets, and the reconstruction of highly detailed and comprehensive 3D models of the investigated areas. Contributions to the issue showing the added value of surface reconstruction and/or monitoring in the processing and interpretation of geophysical data, integration and cross-comparison of geophysical and remote sensing techniques were required to the research community. Contributions discussing the results of pioneering geophysical acquisitions by means of innovative remote systems were also addressed as interesting topics. The Special Issue received great attention in the combined community of applied geophysicists and remote sensing researchers. A total of 15 papers are included in the Special Issue, covering a wide range of applications. This is one of the highest number of papers among the Remote Sensing Special Issues, showing great interest in the proposed topic. The relevant number of contributions also highlights the relevance and increasing need for integration between remote sensing and ground-based geophysical exploration or monitoring methods. In particular, one of the main fields of research showing the potential integration of the geophysical and remote sensing techniques is archaeological exploration
Waterborne and on-land electrical surveys to suggest the geological evolution of a glacial lake in NW Italy
Full text linkGeophysical surveys on and around the Candia Lake, located NE of Turin (NW Italy), in the internal depression of the Ivrea Morainic Amphitheatre (IMA) right frontal sector, are reported in this paper. The surveys were intended to obtain a geophysical characterization of the lakebed, to investigate the interconnection paths between surface water and groundwater and to be used as a first general survey for suggesting the geological processes which lead to the actual morphology. An extensive waterborne Continuous Vertical Electrical Soundings (CVES) survey consisting of 15 profiles, with a total length of about 19 km of acquisition, was carried out on the lake surface. The processing of the acquired profiles with a Laterally Constrained Inversion (LCI) approach lead to the reconstruction of the lakebed sediments distribution, down to 10 meters depth. Self Potential (SP) data recorded on the lake surface have also been analyzed. Moreover, to verify the areal distribution of the deposits, three Electrical Resistivity Tomographies (ERT) were carried out on land near the northern and southern shore of the lake. The combination of the geophysical surveys results with hydrogeological information and geological observations and interpretations allowed the characterization of the submerged deposits, the probable identification of the main areas of groundwater recharge and the preliminary reconstruction of the lake genesis
Detecting Slow Deformation Signals Preceding Dynamic Failure: A New Strategy For The Mitigation Of Natural Hazards (SAFER)
Full text linkFirst results from microseismic monitoring of a rockslide at Madonna del Sasso (Verbania, Italy)
Full text linkUltrasonic equipment aimed to detect grouting homogeneity in geothermal heat exchangers
Full text linkThe purpose of this study is to assess homogeneity and
integrity of cementing grout in vertical borehole heat
exchangers used for geothermal heat pumps using an
ultrasonic non-destructive test. The used testing
equipment, TUC (Ultrasonic Test to certificate
grouting Continuity), is based on an ultrasonic system
able to generate and record wave propagation from the
inside of heat exchangers to the surrounding
(cementation and soil, possibly). Differences in signal
characteristics of the recorded waves along the pipe
can indirectly provide useful information to evaluate
the successful realization of the well cementation in
terms of vertical homogeneity and continuity. Both
laboratory and field tests have been evaluated and are
hereafter presented to verify tests effectiveness and
discuss eventual limitation of the proposed approach
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