GPR Scanning Research Articles

Utilizing of 500 MHz Ground Penetrating Radar Antenna Coupling at Different Interval Heights Clearance

Understanding the characteristics of the GPR antenna for underground utility detection purposes is critical to ensuring that buried pipes and cables can be accurately located. Considering the ground coupling antenna is the most effective way to carry out the GPR scan, most of the operators applied this setup to ensure the maximum amount of the electromagnetic wave could be penetrated into the ground. However, the contact between the GPR and the ground surface causes the bottom of the antenna enclosure to become scratched and worn out. Due to the cost and time involved in transportation to replace the antenna protector, a few GPR operators changed the protector to the cheapest one, which affects the characteristics of the antenna and could alter the depth of the underground utilities. A 500 MHz GPR antenna are tested to identify the optimum antenna coupling based on the accuracy assessment at various interval clearance heights in order to reduce damage and preserve the antenna. An experiment was carried out at Department of Survey and Mapping Malaysia (JUPEM) Kuala Lumpur’s Underground Utility Test Base. Based on the result of the signal strength, the higher the antenna is lifted, the higher the rate of the signal becomes weak or lost. For the depth accuracy test, the high differences in depth when the antenna is lifted up at 4cm to 6cm based on the result of comparison with the standard values provided by the JUPEM. On the other hand, the accuracy of each antenna height is compared and validated based on the Residual Mean Square Error (RMSE). Overall, this study could lead to the conclusion that the result of the assessment is within the acceptable RMSE tolerance, which is below 0.1m. The objective of the research is successfully achieved when the antenna at a 3cm to 6cm interval height setup provides the best clearance based on the criteria of signal strength, depth comparison, and accuracy assessment. Finally, the issue of contact between the antenna and the ground surface, which causes the antenna to become scratched and worn out, could be reduced and preserved as a result of the findings.

Below Victory

Recent advances in Ground Penetrating Radar have caused the imaging technology to pivot from a simple construction engineering tool to a valuable new option for archaeology. Newfound abilities to model sound echoes resonating through stone have revealed archeological discoveries where excavation is not possible. Working with a transdisciplinary team, the artist secured a GPR scan of 2,000-year-old Gallo-Roman temple ruins below the plaza of a gothic cathedral in France. The technology's sounding image of the hidden site became a visual language that was explored in a 2-year series of artworks based on the discovery. The art + science research project resulted in data visualizations across many creative media including site-specific public trompe l'oeil, augmented reality, and hundreds of design experiments. Using the GPR dataset as a foundational resource in art-making, the project expanded the interpretation of Digital Heritage. Collectively, the works reinforced the understanding of a site hidden since Antiquity but also considered public non-sites in pandemic times. The advances in this scanning technology proved to be a powerful creative tool to highlight themes of how we protect and understand heritage, how we create public experiences in socially distanced times, and our responsibility to continually reconsider complex history.

Highway Tunnel Defect Detection Based on Mobile GPR Scanning

In order to overcome the difficulty in rapid detection for expressway tunnels, the coherence calculation of dual-frequency radar signal in the time domain is proposed to suppress the interference. A dual-frequency (400 MHz and 900 MHz) GPR and a manipulator are developed. In the horizontal direction, it has a −90°~90° range, a vertical rotation range from 0 to 90°, a length range from 5~9.5 m, and an antenna rotation between −40°~40°. The mobile scanning has been realized in the expressway tunnel, taking the vehicle as the mobile carrier. The research shows that: This equipment realizes the rapid detection of the tunnel without affecting the expressway’s opening. The imaging algorithm recognizes the structural thickness, reinforcement distribution characteristics, and structural diseases. According to the detection carried out in Zhejiang, China, the spacing between reinforcement in the second lining is 4 cm, and the thickness of the structure is about 0.55 m. However, the reinforcement has deformed badly, and the defects are also discerned in the structure. Compared with the traditional handheld radar detection, the equipment dramatically reduces the labor demand, time, and cost and can meet engineering needs. With the proposed method, the detection time is reduced to 12 min/km from 0.5 d/km, and the cost is reduced by more than two times. Furthermore, during the detection, the traffic can be maintained normally.

ADDRESSING THE ELEPHANT IN THE UNDERGROUND: AN ARGUMENT FOR THE INTEGRATION OF HETEROGENEOUS DATA SOURCES FOR RECONCILIATION OF SUBSURFACE UTILITY DATA

Abstract. In this paper we address the issue of unreliable subsurface utility information. Data on subsurface utilities are often positionally inaccurate, not up to date, and incomplete, leading to increased uncertainty, costs, and delays incurred in underground-related projects. Despite opportunities for improvement, the quality of legacy data remains unaddressed. We address the legacy data issue by making an argument for an approach towards subsurface utility data reconciliation that relies on the integration of heterogeneous data sources. These data sources can be collected at opportunities that occur throughout the life cycle of subsurface utilities and include as-built GIS records, GPR scans, and open excavation 3D scans. By integrating legacy data with newly captured data sources, it is possible to verify, (re)classify and update the data and improve it for future use. To demonstrate the potential of an integration-driven data reconciliation approach, we present real-world use cases from Denmark and Singapore. From these cases, challenges towards implementation of the approach were identified that include a lack of technological readiness, a lack of incentive to capture and share the data, increased cost, and data sharing concerns. Future research should investigate in detail how various data sources lead to improved data quality, develop a data model that brings together all necessary data sources for integration, and a framework for governance and master data management to ensure roles and responsibilities can be feasibly enacted.

Investigation of structural problems on the ground and walls of Diyarbakir Historical Behram Pasha Mosque by the georadar (GPR) method

Behram Pasha Mosque is one of the historical mosques, which is the work of Mimar Sinan [1], located in the southwest of Diyarbakır’s Suriçi Region. Georadar (GPR) method is one of the geophysical applications in which possible gaps, fractures, collapses, etc. damages are determined non-destructively on the walls and floors of historical buildings. Therefore, in one of the historic mosques in Diyarbakir Behram Pasha Mosque, expert geophysical engineers carried out the GPR scanning of the grounds and walls without damaging the mosque’s physical structure. In GPR surveys, the depth of investigation (penetration) was chosen as 20 m on the ground and 4 m on the wall. It is aimed to show the anomaly structures in the study area and its immediate surroundings due to the determination of the underground void structures and the continuity of the surface fractures at the research depth. In GPR studies, it has been determined that there are cracks and fractures on the walls of the mosque, of which the smallest was 12 cm and the largest was 40 cm, water leakage on the ground, deterioration due to corrosion, and partial collapses. The regions with the detected deformations are marked on the radar sections. The study was completed with the thought that the determined structural problems will contribute to the restoration and strengthening works to be done in the future in the mosque as an up-to-date guide.

Enhanced GPR data interpretation to estimate in situ water saturation in a landfill

Research was completed to show that using the complex refractive index model (CRIM) to interpret GPR data can improve the estimation of in situ water content of the waste in the landfill. Literature shows that the Topp equation is normally used to analyse GPR data, despite the fact it fails to consider porosity and other properties of the landfill material or soil that can affect the electromagnetic properties of the material. The application of (CRIM) overcomes these limitations and more. Previously measured field GPR data were reanalyzed with CRIM and supported by synthetic GPR data to show that CRIM provides a better prediction of the water content of the landfill material.Further enhancement of GPR data interpretation was implemented by optimizing the frequency of the GPR scan and determining the ideal offset separation distance between the transmitter and the receiver using sensitivity tests. The sensitivity tests were based on synthetic 2D surface based-reflection GPR data sets generated by MATLAB®. The sensitivity results showed that the optimum frequency was 1 GHz, with an ideal offset distance of 0.75 m. After using the optimized values, it was possible to obtain a percentage of error of 1% between modelled water saturation and GPR measured water saturation.

The use of ground Penetrating Radar to distinguish between seismic and non-seismic hazards in hard rock mining

Rock related fatalities and injuries are still reported at an alarming rate in South Africa’s deep to ultra-deep level (1500 m to 4500 m from earth surface) hard rock mining/tunneling. Most of these events are associated with seismic hazards (rockburst) or intersecting hazardous features (old tunnels, seismic active geological features, etc). As a result, researchers have been called upon to provide solutions to the problem, given that, most solutions were in the form of numerical approximation of the rock behavior, requesting critical skills given to young rock engineers and seismologists. Nonetheless, the solutions provided appears to be inadequate in reducing the re-occurrence of rock-related fatalities and injuries within the mines. In this study, a modified Ground Penetrating Radar was used to distinguish between seismic and non-seismic hazards that were not identified using conventional and numerical approaches in hard rock mining/tunneling. The instrument was used in several case studies; firstly, to validate the effectiveness of preconditioning practice, secondly, to monitor the performance of the in-stope pillar, thirdly, to identify unknown seismic and non-seismic active geological features ahead of the tunnel faces and lastly to identifying old tunnels excavations ahead, above or below the excavation and monitor the quality backfill support installation. The GPR signal model, its shortcomings and suggestions are also described. Nevertheless, the instrument was found to provide reasonable results. The study proposed that the GPR scanner should have specific forward numerical software that incorporates inputs parameters of different material and it is also proposed that the GPR scan should always be calibrated by the borehole periscope. The study maintained that the instrument has the potential of reducing rock-related injuries, fatalities and also improve the mining/ tunnel designs; by predicting the hazardous features and the fracture frequency ahead of the mining/ tunnel faces as well within the rock pillar.

Long-term monitoring of spillway using various NDT techniques-case studies

The erosion under a spillway can be a long-term issue that threatens the structural integrity of a water reservoir. The heavy rainfall associated with storms or typhoons could cause a serious flood if the spillways do not function properly. The spillway under investigation was suspected to be defective after they had been commissioned in 1987. Potholes and subsurface cavities were confirmed in the safety assessment using various NDT techniques including ground penetrating radar and impact echo. The engineering team applied the repair project that aimed to remedy the deteriorating concrete structure. The GPR inspection was able to differentiate the repaired region from the cavities under concrete slabs. The results were verified against other measurement data obtained independently. Hence, the GPR technique is effective for quality check of grouting repair of spillways. Repetitive GPR scans were also carried out after the rehabilitation of spillways. Not only the quality of repair can be evaluated, but the scans were also provided as the baseline record for long-term condition assessment of the spillway-reservoir system in the future.

PRACTICAL USE OF MODERN INVESTIGATION AND MONITORING METHODS IN POLISH LANDSLIDE REMEDIATION PROJECTS

This paper discusses exemplary landslide investigations in natural Carpathian and man-made opencast mine slopes. Research methods included mapping, core drilling, laboratory testing, GPR scanning, on-line inclinometer, piezometer, and pore pressure monitoring and also numerical modelling. Landslide triggers were complex and diverse. On flysch slopes movements were activated by heavy rainfalls and in opencast mines, by exploiting the parameters of clayey soils. Precise prediction of landslide activation is impossible. Identification of landslide triggers for mitigation measures requires a multiple analysis of integrated external and internal variables.

Measurement of iron mass in concrete wall using ultra‐wide band radar

Here, it is aimed to measure and detect the iron mass of a concrete solid wall, column, floor by using of ultra-wide band radar. Electromagnetic waves boundary conditions, reflection, and refraction of waves that radiate in solid material are analysed. GPR imaging methodology and scanning types such as A, B, and C are analysed. Ultra-wide band radar imaging is used for detecting measuring the diameter of the iron material.

Sensitivity of the inverse problem solution related to detection of rebars buried in concrete by using GPR scanning

Ground Penetrating Radar is a device which is nowadays largely used in civil engineering applications. Considering a rebar buried in a concrete medium, this work addresses sensitivity of the inverse problem solution associated to identification of the object radius and its depth from B-scan data acquired by the GPR. The approach uses a closed form parameterisation of the hyperbola trace emerging in the radargram as function of the hyperbola apex coordinate along the direction of B-scan, the cover depth, the radius of the object and the relative permittivity of the medium. Estimation of the wave velocity, the hyperbola apex coordinates and the rebar radius was performed through solution of an appropriate nonlinear least mean squares problem. Perturbation analysis was then conducted by assuming that the hyperbola points coordinates, extracted from raw data of radargram, are randomly distributed according to Gaussian densities of probabilities. The effect of the amount of data was also analyzed. The method was implemented in Matlab environment. The obtained results have shown that identification process is extremely sensitive to noise affecting the B-scan raw data, but not to the number of points used in identification.

Point coordinates extraction from localized hyperbolic reflections in GPR data

In this paper, we propose an automated detection algorithm for the localization of apexes and points on the prongs of hyperbolic reflection incurred as a result of GPR scanning technology. The objects of interest encompass cylindrical underground utilities that have a distinctive form of hyperbolic reflection in radargram.Algorithm involves application of trained neural network to analyze radargram in the form of raster image, resulting with extracted segments of interest that contain hyperbolic reflections. This significantly reduces the amount of data for further analysis. Extracted segments represent the zone for localization of apices. This is followed by extraction of points on prongs of hyperbolic reflections which is carried out until stopping criterion is satisfied, regardless the borders of segment of interest. In final step a classification of false hyperbolic reflections caused by the constructive interference and their removal is done. The algorithm is implemented in MATLAB environment.There are several advantages of the proposed algorithm. It can successfully recognize true hyperbolic reflections in radargram images and extracts coordinates, with very low rate of false detections and without prior knowledge about the number of hyperbolic reflections or buried utilities. It can be applied to radargrams containing single and multiple hyperbolic reflections, intersected, distorted, as well as incomplete (asymmetric) hyperbolic reflections, all in the presence of higher level of noise. Special feature of algorithm is developed procedure for analysis and removal of false hyperbolic reflections generated by the constructive interference from reflectors associated with the utilities.Algorithm was tested on a number of synthetic and radargram acquired in the field survey. To illustrate the performances of the proposed algorithm, we present the characteristics of the algorithm through five representative radargrams obtained in real conditions. In these examples we present different acquisition scenarios by varying the number of buried objects, their disposition, size, and level of noise. Example with highest complexity was tested also as a synthetic radargram generated by gprMax. Processing time in examples with one or two hyperbolic reflections is from 0.1 to 0.3s, while for the most complex examples it is from 2.2 to 4.9s.In general, the obtained experimental results show that the proposed algorithm exhibits promising performances both in terms of utility detection and processing speed of the algorithm.

Determination of concrete rebars characteristics by enhanced post-processing of GPR scan raw data

A method for the estimation of rebar radius by post-processing the raw data acquired by the ground penetrating radar as a B-scan radargram is proposed. Considering the hyperbola trace and the diffracted amplitudes an inverse problem consisting of two steps was stated. Using at first hyperbola fitting, the wave velocity and the coordinates of the hyperbola apex are identified. Then the rebar radius is retrieved as solution of a further optimization problem for which the cost function measures the misfit between the actual value of the maximum diffracted amplitudes and their theoretical predictions. The procedure was implemented in Matlab and tested in realistic situations. The obtained results showed improved accuracy.

Research using GPR into the cause of cracks and depressions in the floor of the gallery of Hagia Sophia Museum

Hagia Sophia Museum is one of Istanbul's most important historical structures. Considering its location in Istanbul and the use of the building through history, visible damage is noted in the structure. To determine whether this damage noted on the exterior of the building is present in the interior, the gallery of Hagia Sophia Museum was scanned with ground penetrating radar. The GPR scanning of the floor of the gallery revealed the presence of weak zones in the floor and varying scales of deformation within the structure. Detailed study of the vaults showed that the geometrical symmetry of the curve of the vault dome was disrupted. The results obtained in this study show that necessary precautions should be urgently completed to prevent damage to Hagia Sophia, especially when the earthquake expected near Istanbul is considered.

DYNAMIC ERROR OF THE TEMPERATURE SENSORS WITH THE SOUNDING OF THE ATMOSPHERE

Radiosounding of the atmosphere is an essential component constituting the base for prognostic aviation authorities. GPR scanning data are the basis for the mapping of baric topography used in the development of aviation weather forecasts. Currently, numerical methods of weather forecast have become especially popular. This is quite justified, as these methods allow to increase the accuracy of weather forecasts and these techniques represent the future. However, the era of "numerical weather prediction" will not come soon. This is primarily due to imperfect numerical forecast models, which do not provide for timeliness and reliability of weather forecasting required for aviation. However, the quality of meteorological support of aircraft flights is largely determined by the timeliness and predictability of the aviation weather forecasts. In this regard, the network of radiosounding functions require the presentation of the theoretical foundations and providing consumers with normalized metrological characteristics of the measuring system of radio sounding, methods of measurement and a reasonable assessment of the reliability of the results of sensing. A number of these problems have been resolved nowadays, however, so far the problem of estimating dynamic measurement errors in the sounding is not solved. The metrological characteristics and the dynamic error of measurement of temperature with the new temperature sensors of foreign production (NТС MFB-5000-3220), recently used in the Russian radiosondes still require the detailed studies. This article is devoted to one of the most important types of errors of radio sounding – the dynamic errors of measurement, to be precise, the dynamic error of the temperature measurement. In the article the problem of determining the value of dynamic errors of radiosondes is being solved alongside with the investigation of the role of this kind of errors when assessing the reliability of the results of the atmosphere radio sounding.

GPR abilities in investigation of the pavement transversal cracks

This paper describes the results of an investigation into the capabilities of the GPR technique within the field of pavement crack diagnostics. Initially, laboratory tests were performed on prototypes simulating idealized cracks. Next, long-term visual observation and repeated GPR scanning were performed, on three roads of semi-rigid construction, several hundreds of meters long and subjected to heavy traffic. Furthermore, a road of rigid construction was tested, having a more than 70-year history of use. In several cases the cracks were probed by drillings, in order to recognize structures responsible for signal generation, or to explain reasons of signal lacking. The main result of this work is a list of GPR indications of cracks, which can be noticed on echograms. It was created through a correlation of the visually-observed cracks with the corresponding echograms, with decimeter accuracy. Several types of GPR responses were classified and linked to possible categories of crack structures, or to processes associated with the presence of cracks (as crumbling, erosion, and lithological alterations). The poor visibility of cracks was also studied, due to small crack size, or to the blurred character of the damaged area, or else to masking effects related to coarse grains in the asphalt mixture. The efficiency of the proposed method for the identification and localization of cracks is higher when a long-term GPR observation is performed.

Coastal changes from open coast to present lagoon system in Histria region (Danube delta)

Preoteasa, L., Vespremeanu-Stroe, A., Hanganu, D, Katona, O.,Timar-Gabor, A., 2013. In: Conley, D.C., Masselink, G., Russell, P.E. and O’Hare, T.J. (eds.), Coastal changes from open coast to present lagoon system in Histria region (Danube delta). Proceedings 12 th International Coastal Symposium (Plymouth, England), Journal of Coastal Research, Special Issue No. 65, pp. 564-569, ISSN 0749-0208. Histria (Istros) is a Milesian colony founded on the Black Sea coast during the 7th c.BC. Nowadays, the remains of the ancient city are located 8 km inland form the Black Sea coast, on the continental edge of the Razelm-Sinoe lagoon system which forms the southern part of the Danube Delta. Significant environmental changes occurred during and after the ancient city’s lifetime, particularly related to dramatic shoreline displacement. The present study deals with the Late-Holocene coastal landscape transformation from the open-coast stage to the present-day lagoon system. Our research includes stratigraphic records by Ground Penetrating Radar scanning of the beach ridges, cores in lagoons and beach ridges and absolute age determination of the paleoshorelines. The study shows that the ancient city decoupling from the sea was due to the beach ridge plain development southward and eastward of the acropolis. The decline of the Histria city, documented during the 7th c. AD, temporally coincides with the decoupling of the city from the open coast as a consequence of the shoreline progradation. Discontinuous chronology and discordant stratigraphy obtained by OSL dating and GPR scanning of successive ridges document intense neotectonic movements which affected Saele-Chituc beach ridge plain. The seismic activity led to the recent drowning of its central part and the formation of the Sinoe lagoon; the same processes acted at the downdrift part of the Dunavat lobe and also in the areas presently occupied by Histria and Nuntasi Lakes. Several areas containing archeological remains are currently below sea-level due to local neotectonics.

Characterization of historical lime plasters by combined non-destructive and destructive tests: The case of the sgraffito in Bożnów (SW Poland)

Mortars used in the two-color sgraffito, dated back to 17th century, have been investigated in order to fully characterize the material and to evaluate the state of its preservation. The non-destructive tests carried out “in situ”, comprising thermal imaging and ground penetrating radar, revealed the inner structure of the decoration, which was exfoliated from the wall in ca. 90%. The obtained thermograms and the GPR scans allowed to choose sampling areas for subsequent destructive-tests, performed by means of optical microscopy, chemical analysis, granulometric analysis, X-ray diffractometry, scanning electron microscopy, infrared spectroscopy and differential thermal/thermogravimetric analysis. The results reveal the decoration is composed of two separate coats of lime plasters: (1) the primer plaster and (2) the sgraffito plaster. Both the coats appeared to be a mixture of lime binder (aerial lime) and fine- to medium-grained sand, with addition of small amounts of brick chunks and charcoal. The latter is abundant in the sgraffito plaster, serving as a coloring agent. For elimination of plasters exfoliation, a calcareous PLM-A product of C.T.S. Italy was applied by injection. The non-destructive studies performed after this conservation demonstrates that the rehabilitation work has reestablished homogeneous structure of the sgraffito decoration.Our study indicates that full characterization and proper reconstruction of ancient mortars could be attained by complementary employment of destructive and non-destructive test methods. Moreover, repetition of the non-destructive tests after the rehabilitation works provide valuable insights into their effectiveness.