Civil engineering applications of Ground Penetrating Radar: research perspectives in COST Action TU1208

Ground Penetrating Radar (GPR) is a safe, non-destructive and non-invasive imaging technique that can be effectively used for advanced inspection of composite structures and for diagnostics affecting the whole life-cycle of civil engineering works. GPR provides high resolution images of structures and subsurface through wide-band electromagnetic waves. It can be employed for the surveying of roads, pavements, bridges, tunnels, for detecting underground cavities and voids, for utility sensing, for the inspection of buildings, reinforced concrete and pre-cast concrete structures, for geotechnical investigation, in foundation design, as well as for several other purposes. Penetration and resolution of GPR depend primarily on the transmitting frequency of the equipment, the antenna characteristics, the electrical properties of the ground or of the surveyed material, and the contrasting electrical properties of the targets with respect to the surrounding medium. Generally there is a direct relationship between the transmitter frequency and the resolution that can be obtained; conversely there is an inverse relationship between frequency and penetration depth. GPR works best in dry ground environments, but can also give good results in wet, saturated materials; it does not work well in saline conditions, in high-conductivity media and through dense clays which limit signal penetration. Different approaches can be employed in the processing of collected GPR data. Once data have been processed, they still have to be analysed. This is a challenging problem, since interpretation of GPR radargrams is typically non-intuitive and considerable expertise is needed. In the presence of a complex scenario, an accurate electromagnetic forward solver is a fundamental tool for the validation of data interpretation. It can be employed for the characterization of scenarios, as a preliminary step that precedes a survey, or to gain a posteriori a better understanding of measured data. It can be used by GPR operators to identify the signatures generated by uncommon targets or by composite structures. Repeated evaluations of the electromagnetic field scattered by known targets can be performed by a forward solver, in order to estimate – through comparison with measured data – the physics and geometry of the region investigated by the GPR. It is possible to identify three main areas, in the GPR field, that have to be addressed in order to promote the use of this technology in the civil engineering. These are: a) increase of the system sensitivity to enable the usability in a wider range of conditions; b) research novel data processing algorithms/analysis tools for the interpretation of GPR results; c) contribute to the development of new standards and guidelines and to training of end users, that will also help to increase the awareness of operators. In this framework, the COST Action TU1208 "Civil Engineering Applications of Ground Penetrating Radar", proposed by Lara Pajewski, "Roma Tre" University, Rome, Italy, has been approved in November 2012 and is going to start in April 2013. It is a 4-years ambitious project already involving 17 European Countries (AT, BE, CH, CZ, DE, EL, ES, FI, FR, HR, IT, NL, NO, PL, PT, TR, UK), as well as Australia and U.S.A. The project will be developed within the frame of a unique approach based on the integrated contribution of University researchers, software developers, geophysics experts, Non-Destructive Testing equipment designers and producers, end users from private companies and public agencies. The main objective of the COST Action TU1208 is to exchange and increase scientific-technical knowledge and experience of GPR techniques in civil engineering, whilst promoting the effective use of this safe and nondestructive technique in the monitoring of systems. In this interdisciplinary Action, advantages and limitations of GPR will be highlighted, leading to the identification of gaps in knowledge and technology. Protocols and guidelines for European Standards will be developed, for an effective application of GPR in civil engineering. A novel GPR will be designed and realized: a multi-static system, with dedicated software and calibration procedures, able to construct real-time lane three-dimensional high resolution images of investigated areas. Advanced electromagnetic-scattering and data-processing techniques will be developed. The understanding of relationships between geophysical parameters and civil-engineering needs will be improved. Freeware software will be released, for inspection and monitoring of structures and infrastructures, buried-object localization, shape reconstruction and estimation of useful parameters. A high level training program will be organized. Mobility of early career researchers will be encouraged. The scientific work-plan of the Action is open, to ensure that experts all over the world, who did not participate in the preparation of the proposal but are interested in the project, may join the Action and participate in its activities. More information about the project can be found at http://www.cost.eu/domains_actions/tud/Actions/TU1208

COST Action TU1208 civil engineering applications of Ground Penetrating Radar: first-year activities and results

This work aims at presenting the first-year activities and results of COST (European COoperation in Science and Technology) Action TU1208 “Civil Engineering Applications of Ground Penetrating Radar”. This Action was launched in April 2013 and will last four years. The principal aim of COST Action TU1208 is to exchange and increase scientific-technical knowledge and experience of GPR techniques in civil engineering, whilst simultaneously promoting throughout Europe the effective use of this safe and non-destructive technique in the monitoring of infrastructures and structures. Moreover, the Action is oriented to the following specific objectives and expected deliverables: (i) coordinating European scientists to highlight problems, merits and limits of current GPR systems; (ii) developing innovative protocols and guidelines, which will be published in a handbook and constitute a basis for European standards, for an effective GPR application in civil- engineering tasks; safety, economic and financial criteria will be integrated within the protocols; (iii) integrating competences for the improvement and merging of electromagnetic scattering techniques and of data- processing techniques; this will lead to a novel freeware tool for the localization of buried objects, shape-reconstruction and estimation of geophysical parameters useful for civil engineering needs; (iv) networking for the design, realization and optimization of innovative GPR equipment; (v) comparing GPR with different NDT techniques, such as ultrasonic, radiographic, liquid-penetrant, magnetic-particle, acoustic-emission and eddy-current testing; (vi) comparing GPR technology and methodology used in civil engineering with those used in other fields; (vii) promotion of a more widespread, advanced and efficient use of GPR in civil engineering; and (viii) organization of a high-level modular training program for GPR European users. Four Working Groups (WGs) carry out the research activities. The first WG focuses on the design of innovative GPR equipment, on the building of prototypes and on the testing and optimisation of new systems. The second WG focuses on the GPR surveying of pavement, bridges, tunnels and buildings, as well as on the sensing of underground utilities and voids. The third WG deals with the development of electromagnetic forward and inverse scattering methods, for the characterization of GPR scenarios, as well as with data- processing algorithms for the elaboration of the data collected during GPR surveys. The fourth WG works on the use of GPR in fields different from the civil engineering, as well as on the integration of GPR with other non-destructive testing techniques. Each WG includes several Projects. COST Action TU1208 is active through a range of networking tools: meetings, workshops, conferences, training schools, short-term scientific missions, dissemination activities. During the first year of activities, a First General Meeting was organized in Rome, in July 2013, a second meeting took place in Nantes, in February 2014, and the Second General Meeting is being held jointly with the 2014 EGU General Assembly. A training school on "Microwave Imaging and Diagnostics: Theory, Techniques, and Applications", held in March 2014, was co-organised with the European School of Antennas. Four Short-Term Scientific Missions were funded, allowing young researchers to spend a period of time in an institution abroad, in order to carry out a research project contributing to the scientific objectives of the Action. The Action’s activities were disseminated in international conferences [1]-[4], as well as in further workshops and meetings. Two volumes were published [5]-[6], and several scientific papers on peer-reviewed journals. A Springer book presenting the state of the art on civil engineering applications of Ground Penetrating Radar is being prepared and is going to be published in summer 2014. A COST Action is a wide bottom-up interdisciplinary science and technology network, open to researchers from universities, public and private research institutions, as well as to NGOs, industry and SMEs. At present, About 100 Institutions from 24 COST Member Countries (Austria, Belgium, Croatia, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Italy, Latvia, Malta, Macedonia, The Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Switzerland, Turkey, United Kingdom) have already joined the Action, together with an Institution from Armenia (Near Neighbour Country, NNC). Beyond European borders, six Institutions from U.S.A., one from Rwanda and one from Australia have joined the Action. Further applications from two NNCs (Egypt and Ukraine) and International Partner Countries (Hong Kong and Japan) are under examination. COST Action TU1208 is still open to the participation of new parties and it is possible to include, in the scientific work plan, new perspectives and activities. Scientists and scientific institutions willing to join COST Action TU1208 are encouraged to contact the Chair of the Action and to follow the procedure described at http://www.cost.eu/participate/join_action. For more information on COST Action TU1208, please visit www.GPRadar.eu. —————————– Acknowledgement The Authors thanks COST for funding COST Action TU1208

Estimating reservoir permeability with borehole radar

We would like to express our gratitude to C. Warren at Northumbria University for the valuable help in gprMax modeling and W. Filinger at The University of Edinburgh and J. Liu at the Delft University of Technology for their assistance in the high-performance computing. We acknowledge the Sinopec Petroleum E&P Institute for the permission to use the oil field logging and coring data. The research was funded by the National Natural Science Foundation of China (41674138, 41811530749, 41974165), the NWO Cooperation and Exchange Fund (040.22.011/7048), and the China Scholarship Council grant (201806415048). The work has been performed under the Project HPC-EUROPA3 (INFRAIA-2016-1-730897), with the support of the EC Research Innovation Action under the H2020 program, and used the Cirrus UK National Tier-2 HPC Service at EPCC (http://www.cirrus.ac.uk) funded by the University of Edinburgh and EPSRC (EP/P020267/1). DATA AND MATERIALS AVAILABILITY Data associated with this research are available and can be obtained by contacting the corresponding author.Peer reviewedPostprin

Probing the solution space of an EM inversion problem with a genetic algorithm

SUMMARY In an inversion for the subsurface conductivity distribution using frequency-domain Controlled-Source Electromagnetic data, various amounts of horizontal components may be included. We investigate which combination of components are best suited to invert for a vertical transverse isotropic (VTI) subsurface. We do this by probing the solutionspace using a genetic algorithm. We found, by studying a simple horizontally layered medium, that if only electric data are used, either the horizontal or the vertical conductivity of a layer can be estimated properly, but not both. Including the crossline electric field does not add additional information. In contrast, including the two horizontal magnetic components along with the two horizontal electric components allows to retrieve a better estimate of some of the VTI parameters. For an isotropic subsurface, the electric field is sufficient to invert for the subsurface conductivity

Data-driven retrieval of primary plane-wave responses

Seismic images provided by reverse time migration can be contaminated by artefacts associated with the migration of multiples. Multiples can corrupt seismic images, producing both false positives, i.e. by focusing energy at unphysical interfaces, and false negatives, i.e. by destructively interfering with primaries. Multiple prediction / primary synthesis methods are usually designed to operate on point source gathers, and can therefore be computationally demanding when large problems are considered. A computationally attractive scheme that operates on plane-wave datasets is derived by adapting a data-driven point source gathers method, based on convolutions and cross-correlations of the reflection response with itself, to include plane-wave concepts. As a result, the presented algorithm allows fully data-driven synthesis of primary reflections associated with plane-wave source responses. Once primary plane-wave responses are estimated, they are used for multiple-free imaging via plane-wave reverse time migration. Numerical tests of increasing complexity demonstrate the potential of the proposed algorithm to produce multiple-free images from only a small number of plane-wave datasets.Comment: 20 pages, 8 figur