GPR clutter amplitude processing to detect shallow geological targets

The analysis of clutter in A-scans produced by energy randomly scattered in some specific geological structures, provides information about changes in the shallow sedimentary geology. The A-scans are composed by the coherent energy received from reflections on electromagnetic discontinuities and the incoherent waves from the scattering in small heterogeneities. The reflected waves are attenuated as consequence of absorption, geometrical spreading and losses due to reflections and scattering. Therefore, the amplitude of those waves diminishes and at certain two-way travel times becomes on the same magnitude as the background noise in the radargram, mainly produced by the scattering. The amplitude of the mean background noise is higher when the dispersion of the energy increases. Then, the mean amplitude measured in a properly selected time window is a measurement of the amount of the scattered energy and, therefore, a measurement of the increase of scatterers in the ground. This paper presents a simple processing that allows determining the Mean Amplitude of Incoherent Energy (MAEI) for each A-scan, which is represented in front of the position of the trace. This procedure is tested in a field study, in a city built on a sedimentary basin. The basin is crossed by a large number of hidden subterranean streams and paleochannels. The sedimentary structures due to alluvial deposits produce an amount of the random backscattering of the energy that is measured in a time window. The results are compared along the entire radar line, allowing the location of streams and paleochannels. Numerical models were also used in order to compare the synthetic traces with the field radargrams and to test the proposed processing methodology. The results underscore the amount of the MAEI over the streams and also the existence of a surrounding zone where the amplitude is increasing from the average value to the maximum obtained over the structure. Simulations show that this zone does not correspond to any particular geological change but is consequence of the path of the antenna that receives the scattered energy before arriving to the alluvial depositsPeer ReviewedPostprint (published version

Resolution in evaluation of structural elements by using ground-penetrating radar

Ground-penetrating radar (GPR) is a non-invasive geophysical technique widely used in civil engineering, archaeology and shallow geology. Radar images of the inner media provides information about inner.Postprint (published version

Ground penetrating radar assessment of historical buildings: the study of the roofs, columns and ground of Santa Maria del Mar, in Barcelona / GPR assessment of the basilica Santa Maria del Mar

Santa Maria del Mar is a magnificent gothic church built between 1329 and 1383 in a neighbourhood outside the city walls, over the remains of a more ancient church. The inhabitants of this district (merchants, downloaders of the port, ship-owners artisans and craftsmen) contributed and took part in the construction of this building. Nowadays it is one of the most representative gothic buildings of Barcelona. The structure was completely studied with GPR in order to obtain useful information for a further restoration. Some of the most interesting results were obtained during the evaluation of the vaults and roofs of the building. Radar images demonstrate that the inner structure was designed in order to diminish the load on the arches and walls. Hollow elements were used to support partly the roof in some areas. Moreover, walls, floors and columns were also assessed, and also the ground outside the building. A large number of graves were located under the church floor, but also some of the radar images suggest the existence of large underground walls. The GPR study of the columns and walls was completed with a seismic survey that demonstrates the existence of zones of non-consolidated materials and defined the joints of the ashlars.Postprint (author's final draft

Characterization of non-intentional emissions from distributed energy resources up to 500 kHz: A case study in Spain

Narrow Band Power Line Communications (NB-PLC) systems are currently used for smart metering and power quality monitoring as a part of the Smart Grid (SG) concept. However, non-intentional emissions generated by the devices connected to the grid may sometimes disturb the communications and isolate metering equipment. Though some research works have been recently developed to characterize these emissions, most of them have been limited to frequencies below 150 kHz and they are mainly focused on in-house electronic appliances and lightning devices. As NB-PLC can also be allocated in higher frequencies up to 500 kHz, there is still a lack of analysis in this frequency range, especially for emissions from Distributed Energy Resources (DERs). The identification and characterization of the emissions is essential to develop solutions that avoid a negative impact on the proper performance of NB-PLC. In this work, the non-intentional emissions of different types of DERs composing a representative microgrid have been measured in the 35–500 kHz frequency range and analyzed both in time and frequency domains. Different working conditions and coupling and commutation procedures to mains are considered in the analysis. Results are then compared to the limits recommended by regulatory bodies for spurious emissions from communication systems in this frequency band, as no specific limits for DERs have been established. Field measurements show clear differences in the characteristics of non-intentional emissions for different devices, working conditions and coupling procedures and for frequencies below and above 150 kHz. Results of this study demonstrate that a further characterization of the potential emissions from the different types of DERs connected to the grid is required in order to guarantee current and future applications based on NB-PLC.This work has been financially supported in part by the Basque Government (Elkartek program)

Project 4.4: application of GPR in association with other non-destructive testing methods in buildings and assessment and in geological/geotechnical tasks. State of the art and open issues

Postprint (published version

COST Action TU1208 - Civil Engineering Application of Ground Penetrating Radar: Una acción coordinada a nivel europeo: Objetivos, organización y trabajos

Fundada en 1971 a partir de acuerdos intergubernamentales de 35 paises, la red European Cooperation in Science and Technology (COST) es la primera organización creada para la coordinación de actividades de investigación financiadas de los países de Europa. El objetivo principal de esta red es disminuir la fragmentación de la inversión en investigación europea, facilitando el desarrollo científico y reforzando la capacidad investigadora y de innovación. Dentro de estos objetivos generales se pueden considerar cuatro vertientes principales: - La mejora de la capacidad investigadora gracias a la conexión entre comunidades científicas de gran calidad, europeas y del resto del mundo. - El aumento y desarrollo de oportunidades para investigadores jóvenes. - El impulso del impacto de la investigación desarrollada entre los cuerpos legislativos y reguladores centrados en la toma de decisiones. - La difusión y promoción de la investigación en el sector privado.Peer Reviewe

Lab non destructive test to analyze the effect of corrosion on ground penetrating radar scans

Corrosion is a significant damage in many reinforced concrete structures, mainly in coastal areas. The oxidation of embedded iron or steel elements degrades rebar, producing a porous layer not adhered to the metallic surface. This process could completely destroy rebar. In addition, the concrete around the metallic targets is also damaged, and a dense grid of fissures appears around the oxidized elements. The evaluation of corrosion is difficult in early stages, because damage is usually hidden. Non-destructive testing measurements, based on non-destructive testing (NDT) electric and magnetic surveys, could detect damage as consequence of corrosion. The work presented in this paper is based in several laboratory tests, which are centered in defining the effect of different corrosion stage on ground penetrating radar (GPR) signals. The analysis focuses on the evaluation of the reflected wave amplitude and its behavior. The results indicated that an accurate analysis of amplitude decay and intensity could most likely reveal an approach to the state of degradation of the embedded metallic targets because GPR images exhibit characteristics that depend on the effects of the oxidized rebar and the damaged concrete. These characteristics could be detected and measured in some cases. One important feature is referred to as the reflected wave amplitude. In the case of corroded targets, this amplitude is lower than in the case of reflection on non-oxidized surfaces. Additionally, in some cases, a blurred image appears related to high corrosion. The results of the tests highlight the higher amplitude decay of the cases of specimens with corroded elements.Peer ReviewedPostprint (published version

Upgrading Urban Services Through BPL: Practical Applications for Smart Cities

Current initiatives related to smart cities in LATAM reveal an increasing interest in the improvement of cities and the wellbeing of their citizens. In addition, specific working groups have been created for this purpose. In this sense, the communication technologies set the basis for gathering, transporting, and managing the large amount of data generated in cities to provide a wide range of services. Within the many alternatives available, BPL positions as a promising technology, since smart cities can greatly benefit of its higher data rates and low latency. In addition, since the medium is already deployed and most of the assets and sensors are connected to the same medium, the cost of the communication systems will be reduced in price and simplicity. The work presents four practical applications: smart buildings, urban lighting, energy assets management and broadband access, in which the possibilities and advantages of BPL are further addressed. Finally, some conclusions and key aspects relating BPL to the success of smart cities are identified.Eusko Jaurlaritza IT-1234-19, KK-202