Ground Penetrating Radar Method Research Articles

Application of Ground-Penetrating Radar for Specifications of Blasting Rocks

Proposed a method for optimizing the parameters of drilling and blasting operations, considering the physical and technical properties of rocks within the blasted block, in order to improve the quality of the blasting quarries with a complex geological structure. Described the ground-penetrating radar method is with the application of the "Oko-2" series of the development of the group of companies "LOGIS-GEOTECH" with antenna blocks AB-90 with a depth of sounding up to 16 m. and a resolution of 0.5 m. in depth and AB-150 with a sounding depth of 12 m. and resolving ability of 0.35 m. in depth. The results of laboratory experiments carried out on blasting blocks with various strength properties are presented, confirming the improvement in the quality of crushing of rock samples by explosion of charges with variable decelerations and location, depending on the strength properties of the samples, relative to charge explosions with unchanged parameters. This will ensure a better crushing of the blasted rock mass.

Degradation of architectural precast concrete elements on the facade of St. Michael the Archangel church in Warsaw

The paper presents the case study of the degradation of architectural precast concrete elements on the facade of St. Michael the Archangel church in Warsaw. The background of the contemporary precast non-standard prefabrication was presented with the examples of polish recent applications. The GPR (ground penetrating radar) method was used in determining the location of reinforcement in the precast elements in the degraded façade. The conceptions of repair were analyzed and the reasons of the destructions of the precast elements.

Determination of unstable tectonic zones in C–North deposit, Sangan, NE Iran using GPR method: importance of structural geology

Ground Penetrating Radar (GPR) is an effective and practical geophysical imaging tool, with a wide set of applications in geological mapping of subsurface information. This research study aims at determination of the geophysical parameter differences in the subsurface geological structures and construction of a 3D fracture model. GPR and resistivity methods were applied to detect the unstable tectonic zones in the C-North deposit. Structural geology investigations were, first, surveyed to detect the faults and fractures in the study area. Based on the structural features, the survey was conducted over an area of 1 km2 with a total of 30 profiles and low-resistivity zones in the C-North deposit which is a great help in reducing their impacts in slope stability studies. GPR sections were, then, obtained from low and high frequency antennas (10 and 50 MHz) to detect fractures and water content zones. The obtained data results demonstrated that the major structural trends in the study area were W–E, NE–SW, and NW–SE while fault zones that can create pathways for groundwater inflow into the deposit in the future. Information obtained from geological and GPR studies were also integrated with drill hole data. The geological information from structures are in good agreement with the actual geological situation. Method and results of this study could be useful in solving problems related to subsurface structures in mining engineering.

Application Research of Ground-Penetrating Radar in the Quality Inspection of Concrete Anti-seepage Panels

If the sand-free cushion of concrete anti-seepage panels of reservoir is void, it will cause local instability or even crack and collapse of the panel, which will lead to large leakage of reservoir and affect the safe operation of the project. In this paper, the ground-penetrating radar (GPR) method is used to scan the concrete panel. The results show that the quality of the panel is good overall, the distribution of rebar is uniform, and the contact between the panel and the sand-free cushion is dense. Some panels have internal voids and the contact between the cushion and the rock foundation is not dense, while no obvious hollowing is found in the sand-free cushion.

Magnetometry and ground penetrating radar in application to mapping of polygonal wedge ice of yedoma complex

Paper is dedicated to geophysical mapping of polygonal wedge ice. Magnetometric and ground penetrating radar surveys were implemented on a small area of Yedoma ice complex on Kurungnakh island in Lena river delta. Such deposits are widely spread on a huge areas of Siberia and Alaska. The study was conducted near the thermoerosional gully, which propagates along the most thick ice wedges. Polygonal pattern is observable on high-resolution aerial imagery and digital elevation model - this data was used during the interpreting of obtained results. Study area (40×50 m) was covered with highresolution magnetic survey at the elevation of 2 m with 2×2 m step and with ground penetrating radar survey along profiles with 1 m distance between the profiles. Map of total magnetic field anomalies allow to determine the ice wedges of Yedoma ice complex distinctly. Difference between maximum positive (polygons centers) and negative (ice wedges) anomalies reaches 6 nT (error of the survey is 0,3 nT). Beyond that smaller ice wedges which penetrate the ice wedges of Yedoma complex are also observable in magnetic field. Basing on ground penetrating radar data an amplitude slice of at 3,5 m depth was built. Yedoma ice wedges are observable at depth of 3–4 m. Ground penetrating radar data is quite noisy due to surface inhomogeneity (puddles, knolls, etc.). Results of the surveys were compared in the light of practical application of the methods for above mentioned goal. Magnetometric method appears as more efficient than ground penetrating radar survey: it does not require a contact with the surface and more rapid, it is more sensitive as the case stands. Ground penetrating radar method may have advantages in the case of natural (magnetic storm, high-magnetized overlaying deposits) and anthropogenic (metal constructions — pipelines, ETL) noise.

Determination of Grave Locations with High Resolution Ground-penetrating Radar (GPR) in War Cemeteries: Sample Study of Biga (Çanakkale) War Graves

The most important turning point in Turkish history of the Çanakkale War, known in English as the Dardanelles Campaign, the Battle of Gallipoli, or the Battle of Çanakkale, involves many omissions in terms of historical records due to the situation facing the country at the time and the threats from both internal and external enemies. Though there is very valuable information like notes and maps left by officers in the Ottoman army (Col. Şevki Paşa etc.), due to the intense severity of the war much important information has not been transferred directly to the present day. Most probably, one of the areas with greatest omissions is the location of war grave sites (martyr’s cemeteries). The main reason for this is considered to be the excessive number of fallen soldiers or martyrs and the extreme loss of life in a very short period. In spite of these negative aspects, the locations of many war grave sites have been determined by detailed research by historians and the use of maps drawn during wartime. However, in these cemetery areas, approximate locations were defined for war graves and in line with this, areas were fenced off as war cemeteries. Using the same logic, an area close to the location used as Biga War hospital during the Çanakkale War was renovated and opened to visitors as Biga War Cemetery with gravestones in certain locations. The high-resolution, non-destructive shallow geophysical method of ground-penetrating radar (GPR) has long been used with the aim of identifying structural elements that are buried (graves, tunnels, archeological remains, etc.). In line with this, its use to research war grave sites in areas known as war cemeteries will illuminate the past and contribute to reorganizing war cemeteries according to war grave locations and providing the necessary importance and respect that war cemeteries deserve.

Use of GPR method for prediction of sinkholes formation along the Dead Sea Shores, Israel

It seems the highly saline conditions of the Dead Sea (DS) coast line are not favorable for the use of Ground Penetrating Radar (GPR) method for detection of underground caverns before sinkhole formation (short-time prediction). The location of the formed caverns within the salt layer (significantly more than the penetration depth of the electromagnetic waves) combined with the saline DS brine (groundwater) covering the salt layer from above, characterized by low electrical resistivity, makes the application of electromagnetic waves (EW) impossible. However, our experience has shown that GPR technique in its 2D and 3D modifications can be a very efficient tool to predict sinkhole susceptibility. Case histories of GPR studies in the Mineral Beach and Nahal David sites are presented. The GPR study has shown that the method is effective in both urban sites and at most of sites of human activities of the Dead Sea coast (dwellings, routes, agricultural areas etc.), but it fails in areas composed of saline mud in the subsurface (some areas lower than −400 m elevation). The fan areas are composed of sandy-gravel sediments and the penetrating depth of the electromagnetic waves varies but is usually limited to the first meters up to 8–10 m (maximum to 13–15 m), but in any case not deeper than the water table (depending on the dielectric constant, which as a rule is 4–25). In areas covered by Dead Sea mud, penetration depth is limited to the first meter due to the low electrical resistivity of the sediments. Models of sinkhole formation and principles of cavity detection in the DS area are discussed to understand the fundamentals of GPR use for the prediction of sinkhole susceptibility.

Detection of ground ice using ground penetrating radar method

Detection of ground ice using ground penetrating radar method

Experimental Assessment of Rebar Corrosion in Concrete Slab Using Ground Penetrating Radar (GPR)

Corrosion of steel reinforcement is a major cause of structural damage that requires repair or replacement. Early detection of steel corrosion can limit the extent of necessary repairs or replacements and costs associated with the rehabilitation works. The ground penetrating radar (GPR) method has been found to be a useful method for evaluating reinforcement corrosion in existing concrete structures. In this paper, GPR was utilized to assess corrosion of steel reinforcement in a concrete slab. A technique for accelerating reinforcement bar corrosion using direct current (DC) power supply with 5% sodium chloride (NaCl) solution was used to induce corrosion to embedded reinforcement bars (rebars) in this concrete slab. A 2 GHz GPR was used to assess the corrosion of the rebars. The analysis of the results of the GPR data obtained shows that corrosion of the rebars could be effectively localized and assessed.

Detecting and Measuring Internal Anomalies in Tree Trunks Using Radar Data for Layer Identification

Radar detection has proven to be an effective, nondestructive test for the determination of the quality of wood-based materials, especially in the wooden structures of ancient buildings and trees. However, the results are usually inaccurate, and it is difficult to interpret internal anomalies due to the moisture content of wood, individual differences, and other factors. In this paper, a new measurement method is proposed based on the use of ground-penetrating radar (GPR) for abnormality localization and imaging. Firstly, the time delay of the reflected signal in the inner trees is analyzed with matched filter and Hilbert detections. Secondly, the two approaches are compared with the use of a forward model, and the Hilbert algorithm is found to be more accurate. Thirdly, a laser scanner is used to collect contour data and determine the location and characteristics of internal tree anomalies. Lastly, the proposed method is tested on ancient willows at the Summer Palace. The results show that the error in the depth and area estimates of the anomalies was within 10% and 5%, respectively. Consequently, the GPR method for locating the anomalies in trees is feasible, and a laser scanner combined with contour data can present the size of the abnormal regions within the trees.

Velocity analysis of CMP gathers acquired by an array GPR system ‘Yakumo’: results from field application to tsunami deposits

This paper examines the capability of a multi-static ground penetrating radar (GPR) system ‘Yakumo’ to estimate a vertical profile of dielectric constants of stratified geological layers. Yakumo is equipped with eight transmitting and eight receiving antennas. By using Yakumo, we propose to obtain an eight-channel common mid-point (CMP) gather from the 64-channel multi-static radar dataset acquired at each point on the survey line. From each CMP gather, a vertical profile of interval velocities can be estimated by velocity spectrum analysis. By a laboratory sandbox experiment, we validate that the thickness of an 83 cm sand layer is estimated with an error of less than 4%. A field survey carried out on tsunami deposits demonstrates that our GPR method can provide the spatial distribution of layer velocities of the sedimentary structure and that the results are comparable with the geological logs at three points and a conventional common-offset GPR profile.

Simultaneous Estimation of Rebar Diameter and Cover Thickness by a GPR-EMI Dual Sensor.

Precise characterization of reinforcing bars (rebars) in a concrete structure is of significant importance for construction quality control and post-disaster safety evaluation. This paper integrates ground-penetrating radar (GPR) and electromagnetic induction (EMI) methods for simultaneous estimation of rebar diameter and cover thickness. A prototype of GPR-EMI dual sensor is developed, and a calibration experiment is conducted to collect a standard EMI dataset corresponding to various rebar diameters and cover thicknesses. The handheld testing cart can synchronously collect both GPR and EMI data when moving on the concrete surface, from which a data processing algorithm is proposed to simultaneously estimate the rebar diameter and cover thickness. Firstly, by extracting the apex of the hyperbolic reflection from the rebar in the preprocessed GPR profile, the rebar position is determined and further used to extract the effective EMI curve. Then, the rebar diameter and cover thickness are simultaneously estimated from the minimum mean square error between the measured and calibrated EMI data under the constraint of the GPR-estimated cover thickness. A laboratory experiment is performed using four casted concrete specimens with 11 embedded steel rebars. The results show that the diameters of 10 rebars are correctly estimated out of the 11 rebars, and the maximum estimation error for the cover thickness is 6.7%. A field trial is carried out in a newly-constructed building, and the diameters of four tested rebars are all accurately estimated while the estimation errors of the cover thickness are less than 5%. It is concluded that the developed GPR-EMI dual sensor and the proposed algorithm can estimate the rebar diameter and cover thickness accurately by a single scan.

Diagnostics of pillars in St. Mary’s Church (Gdańsk, Poland) using the GPR method

ABSTRACTThe main goal of this study was non-destructive evaluation of pillars in the St. Mary’s Church (Gdańsk, Poland) using the ground penetrating radar (GPR) technique. The GPR inspection was conducted on four brick masonry pillars and five pillars strengthened by reinforced concrete jacketing. Data were acquired with a 2 GHz antenna along longitudinal and transverse profiles. The study involved the estimation of the electromagnetic wave velocity in both brick and concrete, the inspection of the internal structure of the pillars, and the precise identification of reinforcement bars. To determine the wave velocity in bricks, a novel mathematical model was developed. Finite-difference time-domain (FDTD) simulations were used to verify and assess the feasibility of the proposed model. Finally, GPR maps were processed using the hyperbolic summation method to visualize the reinforcement distribution in the concrete jacket.

Monitoring water transfers in limestone building materials with water retention curve and Ground Penetrating Radar: A comparative study

The rehabilitation of older buildings is necessary to achieve both a reduction in energy consumption and the preservation of cultural heritage. To ensure a successful building rehabilitation project, an efficient diagnosis makes it possible to determine the various existing pathologies and their causes. In this study, we focus on the “Tuffeau”, which is a kind of limestone widely found in older buildings of the Loire Valley region in France. The durability is strongly affected by the water content for such kind of material. However, very few studies can be found in this field. Moisture condition measurements are currently carried out using punctual sensors placed into the walls. These sensors record highly localized measurements through structural alteration (coring). This paper proposes two non-destructive testing (NDT) methods with the application of Ground Penetrating Radar (GPR) in order to compare the ability of the two methods to analyze the water transfer in limestone blocks. A modified water retention curve model is proposed here to characterize the water gradients in limestone blocks: the limestone - water characteristic (LWC) model. The analysis of the results shows good agreement between the two GPR methods, which shows good capability of monitoring water ingress linking to the results of LWC model.

Ground Penetrating Radar digital imaging and modeling of microbialites from the Salitre Formation, Northeast Brazil

Thanks to the discovery of new giant oil fields in the South Hemisphere in the last decades, named Pre-salt, there has been a considerable interest in the geometrical and sedimentological characterization of microbial deposits, coquinas, and collapsed caves, which represent a considerable part of these reservoirs. It is known that exposures analogous to oil reservoirs are an important source of information at the sub-seismic scale, as this information is helpful in parametrizing and modeling reservoirs, especially microbial reservoirs. This scenario is more favorable when the Ground Penetrating Radar (GPR) method is used in analogous exposures located in arid regions with scarce or no soil, such as the Fazenda Arrecife, in the Chapada Diamantina (Salitre Formation), Northeastern Brazil. Although rarely mentioned in the literature on microbialite geophysical imaging, GPR has been used in microbial deposits associated with the Neoproterozoic storm deposits of the Salitre Formation. The results of 3D imaging of a microbial colony, using the 200 MHz antenna, with both conventional processing and processing using geophysical attributes, are presented in this study. The conventional processing produced a 3D digital model that allowed the geometrical characterization and parametrization of the imaged microbial colony. The use of four geophysical attributes yielded good results, establishing the contact between the microbial colony and tempestite deposits, and determining the internal geometry of microbial deposits. The processing with “instantaneous amplitude” and “Hilbert trace with energy” highlighted the contact between the microbialite colony (low amplitude) and tempestite deposits (high amplitude), whereas the processing with the “energy” attribute provided a better visualization of the internal lamination of columnar microbialites, result similar to that obtained in the processing with “Hilbert trace with similarity”. GPR obtained images of up to 10 m in depth, with excellent resolution for microbial deposits and tempestites associated with them. The processing using geophysical attributes achieved considerably better results when compared to conventional processing, allowing a better visualization of the internal and external geometry of the imaged colony.

Investigation on Reinforcement and Lapping Effect of Fracture Grouting in Yellow River Embankment

Fracture grouting has been a mitigation measure widely used against seepage in the Yellow River Embankment. However, there is currently a lack of systematic investigations studying the anti-seepage effect of the fracture grouting employed in this longest river embankment in China. Therefore, in this work, laboratory and in situ experiments are carried out to investigate the reinforcement effect of fracture grouting in the Jinan section of the Yellow River Embankment. In particular, laboratory tests concentrate on studying the optimum strength improvement for cement–silicate grout by varying the content of backfilled fly ash and bentonite as admixtures. Mechanical strength and Scanning Electron Microscope photographs are investigated for assessing the strength and compactness improvement. Subsequently, based on the obtained optimum admixtures content, in situ grouting tests are carried out in the Jinan section of the Yellow River Embankment to evaluate the reinforcement and lapping effect of fracture grouting veins, where geophysical prospecting and pit prospecting methods are employed. Laboratory results show that, compared with pure cement–silicate grouts, the gelation time of the improved slurry is longer and gelation time increases as fly ash content increases. The optimum mixing proportion of the compound cement–silicate grout is 70% cement, 25% fly ash, and 5% bentonite, and the best volume ratio is 2 for the investigated cases. Geophysical prospecting including the ground penetrating radar and high-density resistivity method can reflect the lapping effect of fracture grouting veins on site. It shows that the grouting material mainly flows along the axial direction of the embankment. The treatment used to generate directional fracture is proved to be effective. The injection hole interval distance is suggested to be 1.2 m, where the lapping effect of the grouting veins is relatively significant. For the investigated cases, the average thickness of the grouting veins is approximately 6.0 cm and the corresponding permeability coefficient is averagely 1.6 × 10−6 cm/s, which meets the anti-seepage criterion in practice.

Railway Subgrade Defect Automatic Recognition Method Based on Improved Faster R-CNN

Railway subgrade defect is the serious threat to train safety. Vehicle-borne GPR method has become the main railway subgrade detection technology with its advantages of rapidness and nondestructiveness. However, due to the large amount of detection data and the variety in defect shape and size, defect recognition is a challenging task. In this work, the method based on deep learning is proposed to recognize defects from the ground penetrating radar (GPR) profile of subgrade detection data. Based on the Faster R-CNN framework, the improvement strategies of feature cascade, adversarial spatial dropout network (ASDN), Soft-NMS, and data augmentation have been integrated to improve recognition accuracy, according to the characteristics of subgrade defects. The experimental results indicates that compared with traditional SVM+HOG method and the baseline Faster R-CNN, the improved model can achieve better performance. The model robustness is demonstrated by a further comparison experiment of various defect types. In addition, the improvements to model performance of each improvement strategy are verified by an ablation experiment of improvement strategies. This paper tries to explore the new thinking for the application of deep learning method in the field of railway subgrade defect recognition.

Significant improvement of detection of underground rectilinear objects based on anisotropy measurements

Orthogonal scanning is a ground penetrating radar (GPR) method recently developed for underground inspection. Orthogonal scanning GPR is based on measuring the anisotropy of soil layers. When applied to detection of underground narrow rectilinear objects, this method allows for improving the signal-to-noise ratio (SNR) and selectivity of GPRs. (Noise refers to signals reflected from large voids, debris of construction materials, etc.).In this work, we further develop the orthogonal scanning method and show that this method can increase the SNR also when the reflected signal is very small, and also significantly improve the horizontal resolution. We show that the SNR improving factor can reach several tens of dB. To improve selectivity we have developed a method of dual orthogonal scanning (the so-called differential method) which can significantly improve the selectivity in the horizontal plane. It is shown that for an object depth of 20 m, it is possible to achieve a selectivity of 0.55 m, which is much smaller than that of commercial GPR (5 m).

The application of non-destructive methods in the diagnostics of the approach pavement at the bridges

The article presents the possibility of using non-destructive methods of road pavement diagnostics as an alternative to traditional means to assess the reasons for premature cracks adjacent to bridge objects. Two scanning methods were used: laser scanning to measure geometric surface deformation and ground penetrating radar (GPR) inspection to assess the road pavement condition. With the use of a laser scanner, an effective tool for road deformation assessment several approach pavement surfaces next to the bridges were scanned. As the result, a point cloud was obtained including spatial information about the pavement deformation. The data accuracy was about 3 mm, the deformations were presented in the form of deviation maps between the reference surface and the actual surface. Moreover characteristic pavement surface cross-sections were presented. The in situ measurements of the GPR method were performed and analysed in order to detect non-homogeneity in the density of structural layers of the pavement. Due to the analysis of the permittivity of individual layers, it was possible to detect non-homogeneity areas. The performed GPR measurements were verified by standard invasive tests carried out by drilling boreholes and taking cores from the pavement and testing the compaction and air voids content in asphalt layers. As a result of the measurements made by both methods significant differences in layer compacting factor values were diagnosed. The factor was much smaller in the area directly next to the bridgehead and much larger in the zone located a few meters away. The research showed the occurrence of both design and erection errors as well as those related to the maintenance of engineering structures.

Application of Ground Penetrating Radar Supported by Mineralogical-Geochemical Methods for Mapping Unroofed Cave Sediments

Ground penetrating radar (GPR) using a special unshielded 50 MHz Rough Terrain Antenna (RTA) in combination with a shielded 250 MHz antenna was used to study the capability of this geophysical method for detecting cave sediments. Allochthonous cave sediments found in the study area of Lanski vrh (W Slovenia) are now exposed on the karst surface in the so-called “unroofed caves” due to a general lowering of the surface (denudation of carbonate rocks) and can provide valuable evidence of the karst development. In the first phase, GPR profiles were measured at three test locations, where cave sediments are clearly evident on the surface and appear with flowstone. It turned out that cave sediments are clearly visible on GPR radargrams as areas of strong signal attenuation. Based on this finding, GPR profiling was used in several other places where direct indicators of unroofed caves or other indicators for speleogenesis are not present due to strong surface reshaping. The influence of various field conditions, especially water content, on GPR measurements was also analysed by comparing radargrams measured in various field conditions. Further mineralogical-geochemical analyses were conducted to better understand the factors that influence the attenuation in the area of cave sediments. Samples of cave sediments and soils on carbonate rocks (rendzina) were taken for X-ray diffraction (XRD) and X-ray fluorescence (XRF) analyses to compare the mineral and geochemical compositions of both sediments. Results show that cave sediments contain higher amounts of clay minerals and iron/aluminium oxides/hydroxides which, in addition to the thickness of cave sediments, can play an important role in the depth of penetration. Differences in the mineral composition also lead to water retention in cave sediments even through dry periods which additionally contribute to increased attenuation with respect to surrounding soils. The GPR method has proven to be reliable for locating areas of cave sediments at the surface and to determine their spatial extent, which is very important in delineating the geometry of unroofed cave systems. GPR thus proved to be a very valuable method in supporting geological and geomorphological mapping for a more comprehensive recognition of unroofed cave systems. These are important for understanding karstification and speleogenetic processes that influenced the formation of former underground caves and can help us reconstruct the direction of former underground water flows.