Ground Penetrating Radar Applications Research Articles

Radiation Pattern Performance of Bow Tie Patch Antenna for Ground Penetrating Radar (GPR) Applications

This paper presents a directional bow tie patch antenna for ground penetrating radar (GPR) applications. There are four proposed designs for this paper. Three of the antenna is designed by introducing Sierpinski gasket fractal concept on bow tie patch antenna. There is some modification on this design in order to create a new different fractal design that is applicable for GPR applications. The bow tie antenna performance is studied across 1 GHz to 4 GHz. The best return loss obtained for this paper is at 3.7 GHz where all four designs have its best performance. The comparison at 3.7 GHz of these four antenna designs presented in this paper.

Review of Applications of Ground Penetrating Radar as an NDT Tool

Ground-penetrating radar (also referred to as GPR, ground probing radar, or georadar) is a near-surface geophysical tool with a wide range of applications. Over the past 30 years, GPR has been used successfully to aid in constraining problems in diverse fields such as archaeology, environmental site characterization, glaciology, hydrology, land mine/unexploded ordinance detection, sedimentology, and structural geology. In many cases, however, GPR surveys have been planned or executed with little or no understanding of the physical basis by which GPR operates and is constrained. As a result, many unsuccessful GPR studies have also been presented or published over the past 30 years. The objectives of this primer are to (1) provide an introduction to the important variables pertinent to GPR and (2) explain the relevant aspects of these variables in GPR acquisition, in an attempt to provide fundamental knowledge for improving GPR usage in the future.

An Application of Ground-Penetrating Radar at a Greater Yellowstone Area Ice Patch

Ice patches are an irreplaceable archive of past events. With atypical melting now occurring around the world, it is important to be able to quantify and interpret the potential of what remains in areas of archaeological interest. A ground-penetrating radar (GPR) survey was conducted at an archaeologically productive ice patch in the Greater Yellowstone Area to identify sediment layers in which archaeological materials may be present. Numerous reflective surfaces were observed and interpreted as being organic-rich layers called lags. GPR did not reveal all lag surfaces that were easily identifiable in an ice core that was collected concurrently at the same ice patch. 400 MHz and 900 MHz antennas were used in the survey, but neither fully revealed the basal profile of the ice patch. This is likely the result of the short time-window in which the data were collected, as opposed to attenuation of the radar waves deep in the ice. Future applications of the technology are explored.

Interactions between soil properties and the rhizome-root distribution in a 12-year Moso bamboo reforested region: Combining ground-penetrating radar and soil coring in the field

Moso bamboo (Phyllostachys pubescens) plays an important role in mitigating climate change and ameliorating soil degradation because of its high carbon sequestration capacity and erosion resistance. Its strong underground rhizome-root systems form the basic framework of the aboveground system of Moso bamboo forest and define the basic ecological characteristics. However, studies on the relationship between the spatial distribution of roots and soil resources have often been neglected due to methodological limitations. The objective of this study was to test the detectability of rhizomes in the field by ground-penetrating radar (GPR) and to understand the interactions between rhizome-root systems and soil characteristics. The rhizome-root system distribution was investigated using GPR; and the soil texture, soil organic carbon and soil nutrients were investigated using a soil coring method to prepare 50-cm soil profiles. A few key findings were emphasized. First, the rhizome-root system was mainly distributed over a soil depth of 0–30 cm; and the rhizomes were larger in diameter (often greater than 1.0 cm). Therefore, GPR can accurately detect rhizomes in the field, making the non-invasive and long-term estimation of rhizome biomass and monitoring of changes in rhizome dynamics possible under field conditions. Second, the spatial heterogeneity of the soil moisture content, alkaline hydrolysed nitrogen and available phosphorus had a greater effect on the rhizomes spatial distribution than did the spatial heterogeneity of other soil characteristics. The rhizomes clonal growth led to increases in soil organic carbon, which promoted the amelioration of degraded soil. Third, the results provide insights for bamboo forest management, such as the application of GPR to prevent bamboo invasion and to determine the appropriate fertilizer level for a rhizome system. More field tests are needed to validate the application of GPR to rhizome systems and enhance the detection and quantification of rhizome systems in bamboo forest ecosystems.

Ground penetrating radar (GPR) applications in concrete pavements

ABSTRACT This article aims to outline the established Ground Penetrating Radar (GPR) applications for concrete pavements that are currently under development or not yet commonly applied. GPR is a non-destructive method that detects variations in the electromagnetic properties of materials, primarily the permittivity. The principles of GPR systems operation, including signal processing and data interpretation practices, are summarized in this study to review current and future uses of GPR in concrete pavement detail analysis. The use of different approaches besides GPR, makes pavement evaluation more efficient and provides more details of the material properties. In concrete pavement structure investigations, GPR technology has been utilized to detect layer thickness and rebar properties, and it also determines subsurface defects and assesses base layer conditions. In quality control studies, GPR technology is implemented for thickness and air void content measurements. Future research may include investigating GPR technique in supporting pavement designs and repair strategies. Regardless of the benefits, several limitations are reported that prevent using this technique for pavement investigation on a broader scale. The problems associated with this procedure, such as the accuracy of the method and the difficulties in interpreting recorded signals, are discussed.

Preliminary Application of Ground-Penetrating Radar for Reconstruction of Root System Architecture in Moso Bamboo

Root system architecture (RSA) refers to the geometric features and topology of the root system. Ground-penetrating radar (GPR) is a possible method of RSA reconstruction. However, because the topology of the root system is not directly accessible by GPR, GPR-based reconstruction must be complemented by manual connection of root points, resulting in limited accuracy. In this study, we used both GPR and direct excavation to obtain 3D coordinates (XYZ coordinates) and diameters of moso bamboo rhizomes on an orthogonal grid. A score function for selecting the best-connected root points was developed using rhizome diameter, depth, extension angle, and measured line spacing, which was then used to recover the topology of discrete root points. Based on the recovered topology, the 3D RSA of the rhizomes was reconstructed using a smoothing function. Based on the excavation data, the reconstructed RSA was generally consistent with the measured RSA, with 78.13% of root points correctly connected. The reconstructed RSA based on GPR data thus provided a rough approximation of the measured RSA, with errors arising due to missing root points and rhizome displacement. The proposed algorithm for reconstructing 3D RSA further enriches the application of ground-penetrating radar to root detection.

Performance investigation of patch and bow-tie antennas for ground penetrating radar applications

Performance investigation of patch and bow-tie antennas for ground penetrating radar applications

Detection of soil physical properties of reclaimed land in open-pit mining area: feasibility of application of ground penetrating radar.

In order to obtain the typical soil physical properties of reclaimed land more quickly and accurately, the South Dump of the China Coal's Antaibao Open-Pit Mine in Pingshuo was focussed on in this paper, and ground penetrating radar (GPR) technology was utilized to detect the soil physical properties of reclaimed land in the mining area. The soil profile sampling and GPR detection methods were used to acquire the data. The gravel content of surface soil was analyzed by counting the number of isolated gravel signals in GPR images. The change of effective soil thickness was analyzed by establishing the fitting relationship between calibration depth and GPR image depth. The Topp's model was validated by comparing its inversion with the measured soil volumetric water content. And the Topp's model was further validated by the soil volumetric water content obtained from the Topp's model and which obtained from the wave velocity inversion. The results are as follows: (1) Based on the number of isolated gravel signals in GPR images, we could qualitatively analyze the gravel content of surface soil reclaimed in the mining area. As the number of isolated gravel signals was greater, the gravel content of the surface soil was higher. (2) Using the known relative permittivity, electromagnetic wave velocity, and soil volumetric water content, the calibration depth and the reflection depth of the target (calibrator) of the GPR images were segmented, and the correlation between them is high. The fitting relationship (R2) of each segment was higher than 0.940, and the average value of the five-segment R2 was 0.966, which indicated more accurate detection of the effective soil thickness of the reclaimed land in the mining area. (3) GPR could be used to detect the soil volumetric water content of reclaimed land in mining area, and Topp's model was used for calculation of soil volumetric water content. The average deviation rate between the values from Topp's model and the measured values was 12%, and the average absolute value of the difference was 2%. In summary, the benefits of using GPR to detect soil physical properties of reclaimed land in mining area are as follows: (1) GPR can be used to detect soil layer thickness and surface gravel content faster and more accurately. (2) Topp model can also be used to calculate the soil moisture content of non-natural deposits such as reclaimed land in mining area.

The Effect Ricker Wavelet of Duty Cycle Adjustment on GPR Detection Result

Ground Penetrating Radar (GPR) employs an ultra-wideband (UWB) signal for detecting objects under the ground surface. In a certain GPR application, a proper UWB signal is needed to obtain a good detection result. Ricker wavelet is one type of UWB signal that can be used in GPR operation. The effect of adjusting the Ricker wavelet duty cycle on the B-scan result was investigated and the result is discussed in this paper. Laboratory experiments were performed by modelling the GPR system using Vector Network Analyzer (VNA). The result shows that selecting a Ricker wavelet’s duty cycle is successful to show the target clearly.

A Study of the Application and the Limitations of GPR Investigation on Underground Survey of the Korean Expressways

In this study, the applications and the limitations of the Ground-penetrating radar (GPR) investigation have been addressed with the main objective of improving the efficient GPR application of subsurface surveys on Korean expressways. The depth of investigation and detection performance of anomalous objects have been studied using two different types of multichannel GPR on the Korean Expressway Corporation’s nondestructive testing testbed for subsurface detection. Based on the field survey, it was found that utilizing the plane view by depth, cross-sectional and longitudinal profile data of the multichannel GPR simultaneously, analysis and evaluation of the GPR signals are more efficient and practical. Although there was a difference in the frequency of use, the precision difference between two GPR is almost similar in the investigation depth and detection performance of the pavement subsurface anomaly. Under an asphalt concrete standard pavement section, the effective depth of cavity detection is 1–1.5 m, while detection under concrete pavement is less than 1.0 m. In addition, there is still a need to calibrate depths using field cores when constructing a 3D underground facility map.

Research on application of Ground Penetrating Radar in road Inspection

Traditional road quality inspection is time-consuming, laborious and not highly accurate. As a new type of non-destructive detection tool, Ground Penetrating Radar (GPR) has the advantages of fast, efficient, continuous, simple and accurate operation, and is widely used. This research uses GPR to conduct non-destructive testing of cement road in a cold storage base to detect quality problems such as road diseases. Through detection, it was found that the cold storage base had no obvious cavities within 10m depth in the detection area, but there was a phenomenon of incompact and loose water accumulation. The foundation should be strengthened during construction. The thickness of the cement road was uniform, and its construction quality was good. Through on-the-spot detection, it provides reference for the ground-penetrating radar non-destructive detection of concrete roads and disaster warning.

An Automatic Processing Framework for In Situ Determination of Ecohydrological Root Water Content by Ground-Penetrating Radar

Root water content (RWC) is a vital component in water flux in soil–plant–atmosphere continuum. Knowledge of RWC helps to better understand the root function and the soil–root interaction and improves water cycle modeling. However, due to the lack of appropriate methods, field monitoring of RWC is seriously constrained. In this study, we used ground-penetrating radar (GPR), a common geophysical technique, to characterize RWC of coarse roots noninvasively. An automatic GPR data processing framework was proposed to (1) identify hyperbolic root reflections and locate roots in GPR images and (2) extract waveform parameters from the reflected wave of identified roots. These waveform parameters were then used to establish an empirical model and a semiempirical model to determine RWC. We validated the developed models using GPR root data at three antenna center frequencies (500 MHz, 900 MHz, and 2 GHz) that were produced from simulation experiments (with RWC ranging from 70% to 150%) and field experiments in sandy soils (with RWC ranging from 66% to 144%). Our results show that both the empirical and the semiempirical models achieved a good performance in estimating RWC with similar accuracy, i.e., the prediction error [root-mean-square error (RMSE)] was less than 8% for the simulation data and 12% for the field data. For both models, the accuracy of RWC estimation was the highest when applied to 2-GHz data. This study renders a new opportunity to determine RWC under field conditions that enhances the application of GPR for root study and the understanding and modeling of ecohydrology in the rhizosphere.

An Ultra-Wideband Antenna With Low Dispersion for Ground Penetrating Radar System

An Ultra-wideband Antenna with funnel-shaped slots and rectangle copper sheets loaded was proposed for ground penetrating radar applications covering the frequency range from 250 MHz to 780 MHz. The performances of the proposed antenna were modeled and optimized by using finite difference time domain methods and measured in both time and frequency domains. The proposed antenna had a bandwidth of 102.9% with voltage standing-wave ratio (VSWR) < 2 and a pick gain over 3 dBi, even when the antenna was bent according to the shape of antenna carrier. In addition, a reconfiguration antenna array with switching matrix, which could be loaded up to 12 antennas, was proposed, where the scanning strategy could be programmed according to the requirements. On this basis, the VSWR of antenna array with and without switching matrix were compared, and the performances of bent and non-bent antenna were also compared in the far-field region. For the radiation pattern, the back-lobe level of bent antennas in E-plane was much lower than non-bent antennas, and the main-lobe of bent antennas in H-plane were rotated. For the peak realized gain, although the antenna gain decreases with increasing frequency, the rate of decline of bent antenna gain is significantly less than that of non-bent antenna gain. Finally, the fabricated antennas could be loaded on a SFCW-GPR system for detecting the depth of cable wells under the road.

Stochastic Processes Approach in GPR Applications

In this article, we present a postprocessing tool to gain powered information for the interpretation of the raw data collected in ground-penetrating radar (GPR) scans by simulations. The method can be extended to measurements raw data and various applications. The proposed approach is based on space ensemble and time ensemble correlation functions applied to GPR B-scan raw data and yields higher detailed information for tracking buried objects. The gprMax simulation results for soil and concrete models confirm the high resolution of the proposed method for sites’ allocation and time stamp of underground objects. The method can be further extended by the introduction of stochastic collocations ensembles in computations.

Application of Ground Penetrating Radar in Reservoir Leakage Detection in Complex Geological Areas

As a typical nondestructive testing method, ground penetrating radar (GPR) has been widely applied in geological detections of highways and coalmines, but rarely in leakage detection of reservoirs. Taking Taohe Reservoir as an example, this paper deploys multiple GPR detection lines on site, and carries out intensive detection in the upstream/downstream of the reservoir, as well as on the left/right abutments of the dam. In this way, leaks were detected on the left and right dam abutments. The detection results provide a reference for subsequent analysis and treatment of reservoir leakage.

Application of Ground-Penetrating Radar for Living Trees Detection

In order to evaluate the potential hazards, researchers are working on revealing the inner structural of a living trunk using different diagnostic techniques. Nondestructive techniques (NDTs), such as stress wave method and ultrasonic wave method, have become increasingly convenient and economical in trees detection. To improve forest management and to prevent collapses of trees, it is necessary to investigate the internal part of tree trunks. In order to do it non-invasively, ground-penetrating radar (GPR) appears as a promising inspection device. Each of these NDTs has its pros and cons. Among all, the GPR is capable of multiple measurements with hardly any damage to the body of a tree, perfect for investigations on roots and trunks of living trees. 15 camphor trees are selected and subject to GPR testing for the study. The results of inductive method and GPR wave signals indicate that the GPR image shows “wavy” features when an eccentric void is found inside a tree, meaning that the travel time is the shortest for the return signals when the antenna is closest to the void. However, GPR wave signals appear to be discontinuous and fluctuate when there are irregular cavities. The signal time is defined by using the metal plate to generate strong reflection in the case of on-site monitoring. The internal condition of tree trunk is usually tested based on detecting 2D image of tree trunk by the stress wave method, as to confirm that the application of GPR is feasible to detect the trunk of camphor tree. The method proposed in this paper can realize the accurate localization and imaging distribution of the internal defects of the trees by the radar wave scanning images.

Design and simulation of a rectangular microstrip patch antenna with single stub for GPR applications at 500 MHz

GPR (ground penetrating radar) is an equipment that makes it possible to detect objects below the ground surface. The antenna is one of the components needed in GPR. In this paper, the microstrip antenna design was discussed and proposed for GPR applications that work at a frequency of 500 MHz. This antenna design has a size of 29 × 22 cm2 using the FR4 substrate with a thickness of 1.6 mm. The optimal design was carried out by using a single stub. Based on the simulation results, the minimum VSWR was achieved at 1.009 with a bandwidth of 12 MHz (493.2 - 505.2 MHz). The minimum return loss value obtained is -47.21 dB and 5.695 dB of the gain.

Non-Destructive Corrosion Inspection of Reinforced Concrete Using Ground-Penetrating Radar: A Review.

Reduced maintenance costs of concrete structures can be ensured by efficient and comprehensive condition assessment. Ground-penetrating radar (GPR) has been widely used in the condition assessment of reinforced concrete structures and it provides completely non-destructive results in real-time. It is mainly used for locating reinforcement and determining concrete cover thickness. More recently, research has focused on the possibility of using GPR for reinforcement corrosion assessment. In this paper, an overview of the application of GPR in corrosion assessment of concrete is presented. A literature search and study selection methodology were used to identify the relevant studies. First, the laboratory studies are shown. After that, the studies for the application on real structures are presented. The results have shown that the laboratory studies have not fully illuminated the influence of the corrosion process on the GPR signal. Also, no clear relationship was reported between the results of the laboratory studies and the on-site inspection. Although the GPR has a long history in the condition assessment of structures, it needs more laboratory investigations to clarify the influence of the corrosion process on the GPR signal.

Optimising the Complex Refractive Index Model for Estimating the Permittivity of Heterogeneous Concrete Models

Estimating the permittivity of heterogeneous mixtures based on the permittivity of their components is of high importance with many applications in ground penetrating radar (GPR) and in electrodynamics-based sensing in general. Complex Refractive Index Model (CRIM) is the most mainstream approach for estimating the bulk permittivity of heterogeneous materials and has been widely applied for GPR applications. The popularity of CRIM is primarily based on its simplicity while its accuracy has never been rigorously tested. In the current study, an optimised shape factor is derived that is fine-tuned for modelling the dielectric properties of concrete. The bulk permittivity of concrete is expressed with respect to its components i.e., aggregate particles, cement particles, air-voids and volumetric water fraction. Different combinations of the above materials are accurately modelled using the Finite-Difference Time-Domain (FDTD) method. The numerically estimated bulk permittivity is then used to fine-tune the shape factor of the CRIM model. Then, using laboratory measurements it is shown that the revised CRIM model over-performs the default shape factor and provides with more accurate estimations of the bulk permittivity of concrete.

A Review of GPR Application on Transport Infrastructures: Troubleshooting and Best Practices

The non-destructive testing and diagnosis of transport infrastructures is essential because of the need to protect these facilities for mobility, and for economic and social development. The effective and timely assessment of structural health conditions becomes crucial in order to assure the safety of the transportation system and time saver protocols, as well as to reduce excessive repair and maintenance costs. Ground penetrating radar (GPR) is one of the most recommended non-destructive methods for routine subsurface inspections. This paper focuses on the on-site use of GPR applied to transport infrastructures, namely pavements, railways, retaining walls, bridges and tunnels. The methodologies, advantages and disadvantages, along with up-to-date research results on GPR in infrastructure inspection are presented herein. Hence, through the review of the published literature, the potential of using GPR is demonstrated, while the main limitations of the method are discussed and some practical recommendations are made.