ALBERT

Description: The use of Non-Destructive Testing (NDT) applied to construction materials allows to highlight and characterize their features, especially in the case of old buildings. The multi-technique high resolution 3D modelling described here is aimed to investigate the conservation state of the central column of a colonnade in the ancient church of Saints Lorenzo and Pancratio, dating to about the second half of the thirteenth century and located in the old town of Cagliari (Italy). This column was considered of interest because its longitudinal axis deviates from its ideal position and it appears the most deteriorated. In this work we describe the integrated application of 3D diagnostic methods, i.e. Terrestrial Laser Scanner (TLS), close range photogrammetry (CRP) and ultrasonic tomography supported by petrographic investigations. They were used to improve the diagnostic process of the conservation state of the investigated column. The TLS technique was supported by CRP to obtain a natural colour texturized 3D model of the column. The geometrical anomaly maps derived from the data of the TLS-CRP survey show the presence of some anomalies worthy of attention. Starting from the 3D reconstruction with previous techniques we planned and implemented a 3D ultrasonic tomography. Ultrasonic tomography proved to be a successful tool in identifying internal defects, as well as the presence of voids and flaws within the materials through the analysis of the propagation of ultrasonic waves. The integration of the three non-invasive techniques supported by petrographical analyses demonstrates its potential in reducing ambiguities since each technique brings its clue to the overall diagnostic process.

Description: This study presents the integrated application of a few non-destructive techniques, i.e., Close Range Photogrammetry (CRP), and low frequency (24 kHz) ultrasonic tomography complemented by petrographical analysis. The aim here is to assess the conservation state of a Carrara marble column in the Basilica of San Saturnino, which is part of a V-VI century Palaeo Christian complex in the city of Cagliari (Italy). The high resolution 3D modelling of the studied artifact was computed starting from the integration of proximal sensing techniques, such as CRP based on the Structure from Motion (SfM) technique, which provided information on the geometrical anomalies and reflectivity of the investigated marble column surface. The inner parts of the studied body were inspected successfully in a non-invasive way by computing the velocity pattern of the ultrasonic signal through the investigated materials, using 3D ultrasonic tomography. The latter was optimally designed based on the 3D CRP analysis and the locations of the source and receiver points were detected as accurately as possible. The integrated application of in situ CRP and ultrasonic techniques provided a full 3D high resolution model of the investigated artifact, which made it possible to evaluate the material characteristics and its degradation state, affecting mainly the shallower parts of the column. The 3D visualisation improves the efficiency, accuracy, and completeness of the interpretative process of data of a different nature in quite easily understood displays, as well as the communication between different technicians.

Description: The use of Non-Destructive Testing (NDT) applied to construction materials allows to highlight and characterize their features, especially in the case of old buildings. The multi-technique high resolution 3D modelling described here is aimed to investigate the conservation state of the central column of a colonnade in the ancient church of Saints Lorenzo and Pancratio, dating to about the second half of the thirteenth century and located in the old town of Cagliari (Italy). This column was considered of interest because its longitudinal axis deviates from its ideal position and it appears the most deteriorated. In this work we describe the integrated application of 3D diagnostic methods, i.e. Terrestrial Laser Scanner (TLS), close range photogrammetry (CRP) and ultrasonic tomography supported by petrographic investigations. They were used to improve the diagnostic process of the conservation state of the investigated column. The TLS technique was supported by CRP to obtain a natural colour texturized 3D model of the column. The geometrical anomaly maps derived from the data of the TLS-CRP survey show the presence of some anomalies worthy of attention. Starting from the 3D reconstruction with previous techniques we planned and implemented a 3D ultrasonic tomography. Ultrasonic tomography proved to be a successful tool in identifying internal defects, as well as the presence of voids and flaws within the materials through the analysis of the propagation of ultrasonic waves. The integration of the three non-invasive techniques supported by petrographical analyses demonstrates its potential in reducing ambiguities since each technique brings its clue to the overall diagnostic process.

Description: Published

Description: 119-127

Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica

Description: JCR Journal

Description: The diagnosis of the conservation state of monumental structures from constraints to the spatial distribution of their physical properties on shallow and inner materials represents one of the key objectives in the application of non-invasive techniques. In situ, CRP and 3D ultrasonic tomography can provide an effective coverage of stone materials in space and time. The intrinsic characteristics of the materials that make up a monumental structure and affect the two properties (i.e., reflectivity, longitudinal velocity) through the above methods substantially differ. Consequently, the content of their information is mainly complementary rather than redundant. In this study we present the integrated application of different non-destructive techniques i.e., Close Range Photogrammetry (CRP), and low frequency (24 KHz) ultrasonic tomography complemented by petrographycal analysis based essentially on Optical Microscopy (OM). This integrated methodology has been applied to a Carrara marble column of the Basilica of San Saturnino, in Byzantine-Proto-Romanesque style, which is part of the Paleo Christian complex of the V-VI century. This complex also includes the adjacent Christian necropolis in the square of San Cosimo in the city of Cagliari, Sardinia, Italy. The column under study is made of bare material dating back probably to the first century A.D., it was subjected to various traumas due to disassembly and transport to the site, including damage caused by the close blast of a WWII fragmentation bomb. High resolution 3D modelling of the studied artifact was computed starting from the integration of proximal sensing techniques such as CRP based on Structure from Motion (SfM), with which information about the geometrical anomalies and reflectivity of the investigated marble column surface was obtained. On the other hand, the inner parts of the studied body were successfully inspected in a non-invasive way by computing the velocity pattern of the ultrasonic signal through the investigated materials using 3D ultrasonic tomography. This technique gives information on the elastic properties of the material related with mechanical properties and a number of factors, such as presence of fractures, voids, and flaws. Extracting information on such factors from the elastic wave velocity using 3D tomography provides a non-invasive approach to analyse the property changes of the inner material of the ancient column. The integrated application of in situ CRP and ultrasonic techniques provides a full 3D high resolution model of the investigated artifact. This model enhanced by the knowledge of the petrographic characteristics of the materials, improves the diagnostic process and affords reliable information on the state of conservation of the materials used in the construction processes of the studied monumental structure. The integrated use of the non-destructive techniques described above also provides suitable data for a possible restoration and future preservation.

Description: Copernicus

Description: Published

Description: On line

Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica

Description: A new methodology is presented consisting of a multi-step procedure based on the integrated application of different diagnostic techniques aimed at recognizing altered and unaltered parts of architectural elements of ancient buildings and at identifying zones where structural damage has occurred on their surface. The methodology was tested on a historical building of the monumental compound in Piazza Palazzo in the historical center of the town of Cagliari (Italy). Three types of carbonate building materials have been used historically to construct ancient monuments in the historical center of Cagliari, which in order of increasing hardness are: Pietra Cantone, Tramezzario and Pietra Forte. Our methodology begins with an accurate microscopic examination of petrographic thin sections and scanning electron microscope (SEM) analysis of the above carbonate materials in order to identify their textural characteristics and especially the nature and distribution of their porosity. Other rock properties such as wet and dry bulk density were calculated from saturated and dry mass and volume respectively. In a second step we used a Leica HDS-6200 terrestrial laser scanner (TLS) to 3D model some building of the studied monumental compound (Piazza Palazzo). Surface geometrical anomalies have been modeled for the most interesting architectural elements, such as a Pietra Cantone portal in Late Gothic style inside the Antico Palazzo di Città, a historical building that hosts the civic museum bearing the same name. Since TLS technology is characterized by high productivity but is unable to investigate the inner parts of the studied materials, a third step of our procedure was complemented by several ultrasonic in situ and laboratory tests in the 54kHz - 82kHz range. The ultrasonic parameters, especially longitudinal and transversal velocities, can be measured very accurately and correlated with various material properties with reasonable confidence. This task has two objectives: one is to compare the petrographical and petrophysical rock properties with the elastic-dynamic ones, while the other is to compare TLS geometrical anomalies with the anomalies of the velocity field detected with ultrasonic methodology, which is very effective in detecting altered and/or damaged zones both on the surface and inside the building materials of architectural elements. Analogies between TLS surface geometrical anomalies and the ultrasonic velocity field are evident at the surface and in shallow parts of the investigated architectural elements, as in the mentioned Pietra Cantone ancient portal. This study illustrates how the integrated application of TLS technology and the ultrasonic method contributes in overcoming ambiguities in the interpretation of the individual dataset. Therefore the methodology proposed in this study has proved to be effective in giving useful indications aimed at formulating a recovery and preservation plan for a monumental structure and to monitor its conservation status in time.

Description: Copernicus Meetings

Description: Published

Description: Vienna | Austria | 17–22 April 2016

Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica

Description: The selection of a CO2 geologic storage site requires the choice of a study site suitable for the characterization in order to create a robust experimental database especially regarding the spatial petrophysical heterogeneities and elasto-mechanical properties of the rocks that make up a potential caprock-reservoir system. In our study the petrophysical and elasto-mechanical characterization began in a previously well drilled area in the northern part of the Sulcis coal basin (Nuraxi Figus area - SW Sardinia - Italy) where crucial geologic data were recovered from high-quality samples from stratigraphic wells and from mining galleries. The basin represents one of the most important Italian carbon reserves characterized by a great mining potential. In the study area, the Middle Eocene - Lower Oligocene Cixerri Fm. made up of terrigeneous continental rocks and the Upper Thanetian - Lower Ypresian Miliolitico Carbonate Complex in the Sulcis coal basin have been identified respectively as potential caprock and reservoir for CO2 storage. Petrophysical and geophysical investigations were carried out by a great number of laboratory tests on the core samples and in situ measurements on a mining gallery in order to characterize the potential caprock-reservoir system and to substantially reduce geologic uncertainty in the storage site characterization and in the geological and numerical modelling for the evaluation of CO2 storage capacity. In order to better define the spatial distribution of the petrophysical heterogeneity, the seismic responses from the caprock-reservoir system formations were also analysed and correlated with the petrophysical and elasto-mechanical properties In a second step of this work, we also analysed the tectonic stability of the study area by the integrated application of remote-sensing monitoring spatial geodetic techniques. In particular, the global positioning system (GPS) and interferometric synthetic aperture radar (inSAR) were considered useful tools to test the tectonic stability of the storage site. We computed the crustal strain rate of the Sulcis basin starting from the horizontal and vertical velocities detected by applying the two above remote sensing techniques. At the beginning we calculated the Eurasian intra-plate velocity and position time series of some good quality permanent GPS sites present in the study area. We then compared the computed GPS height variation of these sites with the line of sight (LOS) component of InSAR permanent scatters time series detected with the aid of the small baseline (SBAS) method and located closer to the GPS stations. The horizontal components show insignificant residual intra-plate velocities ranging between 0-1 mm/y, while the vertical velocities are comprised between 0 to 2 mm/y, testifying to the stability of the area. The same remote techniques mentioned above can be used during and after the injection of the CO2 to monitor the storage site. This remote monitoring option can be effective, cheap and repeatable.

Description: Copernicus Meetings

Description: Published

Description: Vienna | Austria | 17–22 April 2016

Description: 7A. Geofisica per il monitoraggio ambientale

Description: The need to integrate different non invasive geophysical datasets for an effective diagnostic process of the stone materials of cultural heritage buildings is due to the complexity of the intrinsic characteristics of the different types of stones and of their degradation process. Consequently integration between different geophysical techniques is required for the characterization of stone building materials. In order to perform the diagnostic process by different non-invasive techniques thus interpreting in a realistic way the different geophysical parameters, it is necessary to link the petrophysical characteristics of stones with the geophysical ones. In this study the complementary application of three different non invasive techniques (terrestrial laser scanner (TLS), infrared thermography and ultrasonic surface and tomography measurements) was carried out to analyse the conservation state and quality of the carbonate building materials of three inner columns of the old precious church of San Lorenzo in the historical city center of Cagliari (Sardinia). In previous works (Casula et al., 2009; Fais et al., 2015), especially the integrated application of TLS and ultrasonic techniques has been demonstrated to represent a powerful tool in evaluating the quality of the stone building materials by solving or limiting the uncertainties typical of all indirect methods. Thanks to the terrestrial laser scanner (TLS) technique it was possible to 3D model the investigated columns and their surface geometrical anomalies. The TLS measurements were complemented by several ultrasonic in situ and laboratory tests in the 24kHz - 54kHz range. The ultrasonic parameters, especially longitudinal and transversal velocities, allow to recover information on materials related with mechanical properties. A good correlation between TLS surface geometrical anomalies and the ultrasonic velocity ones is evident at the surface and in shallow parts of the investigated architectural elements. To calibrate the geophysical results and provide reliable data for the interpretation, the petrophysical properties (porosity, density, water absorption) and petrographical characteristics (especially texture) of the carbonate building materials under study were examined. By combining petrographical, petrophysical, terrestrial laser scanner and ultrasonic techniques, a consistent diagnostic process of the carbonate building materials can be achieved to detect the presence of defects, fissures, fractures, weathering process or compositional variations. The above diagnostic process is very useful also to evaluate the behavior of the carbonate building materials, facilitating the planning of urgent and long-term conservation programs and in time monitoring.

Description: Copernicus Meetings

Description: Published

Description: Vienna | Austria | 23–28 April 2017

Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica

Description: Both assessment and mitigation of seismic vulnerability connected to cultural heritages monitoring are non-trivial issues, based on the knowledge of structural and environmental factors potential impacting the cultural heritage. A holistic approach could be suitable to provide an effective monitoring of cultural heritages within their surroundings at different spatial and temporal scales. On the one hand, the analysis about geometrical and structural properties of monuments is important to assess their state of conservation, their response to external stresses as well as anomalies related to natural and/or anthropogenic phenomena (e.g. the aging of materials, seismic stresses, vibrational modes). On the other hand, the investigation of the surrounding area is relevant to assess environmental properties and natural phenomena (e.g. landslides, earthquakes, subsidence, seismic response) as well as their related impacts on the monuments. Within such a framework, a multi-disciplinary system has been developed and here presented for the monitoring of cultural heritages for seismic vulnerability assessment and mitigation purposes*. It merges geophysical investigations and modeling, in situ measurements and multi-platforms remote sensing sensors for the non-destructive and non-invasive multi-scales monitoring of historic buildings in a seismic-prone area. In detail, the system provides: a) the long-term and the regional-scale analysis of buildings’ environment through the integration of seismogenic analysis, airborne magnetic surveys, space-borne Synthetic Aperture Radar (SAR) and multi-spectral sensors. They allow describing the sub-surface fault systems, the surface deformation processes and the land use mapping of the regional-scale area on an annual temporal span; b) the short-term and the basin-scale analysis of building’s neighborhood through geological setting and geotechnical surveys, airborne Light Detection And Radar (LiDAR) and ground-based SAR sensors. They enable assessing the site seismic effects, the built-up structural features and the surface deformation processes of the local-scale area on a monthly temporal span; c) the real- to near-real-time and building scale analysis of the heritage through proximal remotely sensing tools (e.g. terrestrial laser scanning, infrared thermal cameras and real aperture radar), combined with ambient vibration tests. They allow analyzing geometric, structural and material properties / anomalies of buildings as well as the state of conservation of structures on a real-time temporal span. The proposed approach is: Specific (it targets the cultural heritages monitoring for seismic mitigation purposes); Measurable (it provides synthetic descriptors or maps able to quantify structural and the environmental properties / anomalies / trends); Action-oriented (it provides information to plan consolidation and restoration actions for prevention activity); Relevant (it allows achieving consolidated results for cultural heritage monitoring); Time-related (it specifies when the results can be achieved). Meaningful results, obtained for the Saint Augustine Complex (XVI century) located in the historic center of the Calabrian chief town of Cosenza, are presented in terms of a web-based Geographic Information System (GIS) platform and a 3-dimensional (3D) visual software for the monitoring of environmental/urban landscapes and buildings. These tools represent the added-value products of the proposed SMART system, which allow integrating and combining multi-sensors analyses in order to support end-users involved into a cultural heritage monitoring.

Description: Copernicus Meetings

Description: Published

Description: Vienna | Austria | 17–22 April 2016

Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica

Description: The acquisition of 3D data by means of different methodologies on architectural monumental structures when combined can highlight with efficiency the characteristics of the stone building materials. The result is a threedimensional imaging of different physical properties that can be analyzed and interpreted more objectively and accurately than the conventional two-dimensional ones. We have applied various three-dimensional non-destructive techniques to produce data that can better visualize and detect defects in the shallow and inner parts of the architectural elements built with stone materials. The 3D data volume of a different nature provides a less ambiguous image of the materials and contributes in efficiency by increasing both fidelity and resolution in the diagnostic process. In this paper, we combined high resolution Digital Color Images (DCI) and Terrestrial Laser Scanner (TLS) data for a dense 3D reconstruction of an ancient pillar in a monument of the town of Cagliari, Italy. The TLS technique was supported by a digital photogrammetry survey in order to obtain a natural color texturized 3D model of the study pillar. The 3D model was built with a specific software aligning and combining a set of 2D high resolution color images captured all around the investigated architectural element from multiple viewpoints using a normal handheld 2D digital reflex camera. Final high resolution natural color 3D model reproduces a faithful metrically –correct-scale copy of the analyzed structure and therefore can be effectively compared with the surface geometric anomalies and reflectivity values obtained by the TLS. During the TLS survey we operated a Leica HDS-6200 long-range phase shift terrestrial laser scanner in order to compute an aggregated 3D cloud representing the pillar surface texturized with its reflectivity and the position of the pixels in an intrinsic reference system. Geometrical anomaly maps showing interesting analogies were computed either from the 3D model derived from the TLS application or from the high resolution 3D model detected with the photogrammetry. Starting from the 3D reconstruction from previous techniques an acoustic tomography in an sector of prior interest of the investigated architectural element was carried out. Travel time of longitudinal elastic waves were measured along a great number of measurement paths between stations located on the perimeter of the investigated sections. Each station was alternatively used as transmitter and receiver and measurements of paths crossing the section in a large number of different directions were carried out. Each ray between stations divided in small segments, each corresponding to a pixel element. Inversion techniques were used to obtain a map of the distribution of the longitudinal wave velocity across the sections, thanks to specific software exploiting appropriate reconstruction algorithms. The ultrasonic tomography proved to be an effective tool for detecting internal decay or defects, locating the position of the anomalies and estimating their sizes, shapes, and characteristics in terms of elastic-mechanical properties. Finally, the combination of geophysical and petrographical data sets represents a powerful method for understanding the quality of the building stone materials in the shallow and inner part of the investigated architectural structures.

Description: Copernicus Meetings

Description: Published

Description: Vienna | Austria | 8–13 April 2018

Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica

Description: This paper presents an integrated seismic and aeromagnetic approach applied in the geological complex area of the Cagliari Gulf in the southern Sardinian margin (Western Mediterranean). The investigated area represents the southern extreme part of the main branch of the Sardinian Rift (SR) (Western Mediterranean) that is made up here of a sub-basin bounded by approximately NW faults. The study was also integrated by complementary information deduced from the GNSS network in southern Sardinia. The aim of this study was to give a contribution on the knowledge of the tectonic evolution and volcanism of the investigated area. For this purpose we used an integrated interpretation of two-dimensional reflection seismic sections and aeromagnetic data. In the same area a well drilled for oil prospection was used for calibrating the seismic interpretation up to approximately 1.8 sec.. It is worth noting that the interpretation of the seismic data can be problematic in structurally complex areas where volcanic formations occur, but it can be assisted effectively by magnetic interpretation. An interesting magnetic pattern represented by a strong, well-localized positive magnetic anomaly extending N-S for approximately 35 km is present in the western part of the Gulf. Its width in the W-E direction is of almost 20 km. The anomaly seems to be linked with the magnetic anomalies that characterize the southern Sardinian Rift in correspondence to the Campidano Graben. In fact, a set of localized high-gradient anomalies generally corresponding to the Oligo-Miocene andesitic calc-alkaline complexes is present in this Graben. The aeromagnetic interpretation was carried out to explain the origin of the above strong elongated magnetic anomaly that has never been quantitatively interpreted. In this work, this anomaly has been interpreted by means of Euler deconvolution, the analytical signal and by a delineation technique based on the maxima of the radial horizontal derivative of the total magnetic field. The geological knowledge of the area by means of earlier studies also on land contributed to give a petrographic meaning to the magnetic sources, while by the magnetic and seismic integrated interpretation it was possible to carry out a spatial reconstruction of the volcanic source body and to give an useful contribution to the knowledge on the volcano-tectonic evolution of the area. Recently the area of the Gulf of Cagliari was affected in its western sector by a weak earthquake with hypocenter at around 10 km of depth, localized by Istituto Nazionale di Geofisica e Vulcanologia (INGV). The results of this study also provided new elements of knowledge which have contributed to understand this seismic event.

Description: Copernicus Meetings

Description: Published

Description: Online | 4–8 May 2020

Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica