Ground Penetrating Radar Applications Research Articles

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.

Frequency 3D slice image visualization for GPR applications

Ground Penetrating Radar (GPR) is an efficient tool for the detection of the underground utilities. However, most data collected by GPR are in the spatial/time domain, the information in frequency domain is sometimes neglected. Joint Time-frequency Analysis (JTFA) methods are widely used to deal with the problem. In this paper, we propose a further application based on JTFA method to re-construct the frequency 3D slice image visualization (frequency C-scan) to represent the distributions of the main frequency components of the surveying area. The experiments are conducted in our sandbox with a PVC pipe buried in. After employing the proposed signal processing flow, the frequency C-scan can be re-constructed. By segmenting the frequency C-scan, frequency distribution over a surface at particular radar time/depth can be obtained. The results exhibit the capability of the proposed method to show the spatial and frequency signatures of the buried objects at certain depth.

Compact Dual-Polarized Vivaldi Antenna with High Gain and High Polarization Purity for GPR Applications

A compact ultra-wideband dual-polarized Vivaldi antenna is proposed for full polarimetric ground-penetrating radar (GPR) applications. A shared-aperture configuration comprising four Vivaldi elements for orthogonal polarizations is designed to reduce the low-end operating frequency and improve the port isolation with a compact antenna size. The directivity of the antenna is enhanced by the oblique position of the radiators and the implementation of a square loop reflector. Experimental results demonstrate that the antenna has very good impedance matching, port isolation, and dual-polarized radiation performance, with low dispersion characteristics across band of interest from 0.4 GHz to 3.0 GHz. GPR measurements with the designed antenna show that the antenna maintains good detection capability even for objects buried in a highly conductive soil.

Application of ground penetrating radar for estimating the water content of road structure

Due to the influence of construction quality, material aging, uneven settlement of foundation and other factors, cracks and water accumulation often occur in the road structure layer. The accumulated water will directly affect the overall quality, service life and normal functions of roads, and adversely affect the integrity, stability and driving safety of pavement structures. In this paper, based on the characteristics of high efficiency and nondestructive detection by ground penetrating radar, and relying on an actual road project in Anyuan County, Ganzhou City, and based on theoretical analysis, it is proposed to use ground penetrating radar to obtain measured data to estimate the water content of road structure. The application and research status of ground penetrating radar detection technology at home and abroad were analyzed. Based on Maxwell basic equation, the basic principle and field detection technology of ground penetrating radar were analyzed. Based on the actual road engineering, the water content of road structure layer was estimated theoretically and verified by core drilling. The results show that it is feasible to estimate the water content of road structure layer by using ground penetrating radar, which can provide relevant reference for nondestructive testing of road structure.

Application of ground penetrating radar in concrete defect detection of sluice floor

The defect investigation of sluice floor is an important measure to ensure the safe operation of the sluice. due to the traditional drilling methods will cause damage to the sluice floor, and the appearance inspection and compressive strength test can not evaluate the internal defects of reinforced concrete in the sluice floor. In this paper, we apply the ground penetrating radar(GPR) to the concrete quality inspection of a sluice gate in a seawall. And we describe the layout, detection principle and data processing flow of GPR. Then we simulate the propagation characteristics of radar electromagnetic wave in the presence of twodimensional electrical anomaly bodies by finite difference method. Through analyzing the amplitude, frequency and event characteristics of reflection wave shown in the gray map of GPR profiles, we determine the dividing line between concrete and muddy silty clay, finding out the density of steel in concrete, framing the location of construction joints and suspected water-filled gaps.

Scattering by Perfectly Conducting Cylindrical Targets Hidden Below a Multilayered Medium

An approach to solve the scattered field by perfectly conducting cylinders with circular cross-section, placed below a multilayered medium, under illumination by a line source, is presented. In principle, the interaction of the field scattered by the targets with the multilayer above leads to an infinite number of scattered fields, excited as multiple reflections in each layer by the interfaces. Nevertheless, the developed theoretical formulation is a very compact one, as only two scattered-field contributions are used in each layer, a down-propagating term, described as scattered-reflected field, and an up-propagating one relevant to the scattered-transmitted field. Suitable basis functions, i.e., cylindrical waves expressed through plane-wave spectra, are employed, which are defined through reflection and transmission coefficients of a multilayered medium. As shown in the numerical implementation, the method can be applied to the modeling of several radar problems of targets in complex environments. For example, the technique can be employed to model buried cylinders in geophysical scenarios, in Ground Penetrating Radar applications. The modeling of scattered field by hidden targets in Through-the-Wall radar surveys is another possible field of use. The multilayer may, indeed, model a stratified masonry, but also a room hiding a target in a buildings’ interior.

Experimental detection of the volume of the drip irrigation soil wetted body using Ground Penetrating Radar

The accurate detection of the volume of the soil wetted body (SWB) is the theoretical basis for the optimal design of a drip irrigation system. In view of the shortcomings of traditional detection methods, such as low efficiency, high cost, and poor in situ detection, this paper explores the rapid, in situ, and nondestructive estimation techniques of SWB volume using Ground Penetrating Radar (GPR). Through drip irrigation of different water volumes and geotechnical experiments, the SWBs with different sizes were formed in air-dried soil and natural soil, respectively. The GPR scan lines on the ground were arranged to obtain the SWB radargram, and the profile shape of the wetted body was restored by the F-K transformation process (frequency-wave domain migration algorithm) that can transform the wave equation in the time-space domain into the frequency-wavenumber domain to achieve offset homing. On this basis, the SWB volume estimation model was constructed by three methods: regression analysis, geometric calculation, and profile triple integration (profile area accumulation). Additionally, the accuracies of the models were verified by the measured data of the SWB excavation. For each of these methodologies, we illustrate the quality of the output with the measured data and discuss the possibilities and limitations. The results show that the profile triple integration model is not accurate. The regression analysis model has the greatest accuracy. However, owing to the difference in soil characteristics, the model input parameters must be changed. Relatively, the geometric calculation model is the best model to detect the SWB volume. From the results, we can draw a conclusion that the method combining F-K transformation process and the geometric calculation model can accurately measure the volume of SWB, and it has better adaptability in different soils. We demonstrate the GPR as a rapid geophysical tool that can be used successfully to explore the volume of the SWB formed under drip irrigation. This study expands the agricultural application of GPR and provides a new method for in situ nondestructive rapid detections of the SWB volume.

Sharp Triple-Notched Ultra Wideband Antenna with Gain Augmentation Using FSS for Ground Penetrating Radar

A printed ultra-wideband antenna that provides wide bandwidth of 2.6–10.58 GHz, with sharp triple notches at 3.3–3.92, 5.1–5.4 and 5.68–6.02 GHz to eliminate the WiMAX and WLAN interferences, is proposed. Triple notches are implemented by embedding split ring shaped slot and unique circular split ring resonator pairs in the antenna. The antenna provides monopole like radiation patterns with gain variation of 2.5–5 dBi and average radiation efficiency of 86% in its pass band. Wide bandwidth of the antenna makes it well suited in low depth subsurface scanning ground penetrating radar (GPR) applications where better lateral resolution is desired. To improve the depth resolution, the antenna is integrated with reflective type frequency selective surfaces. Overall gain augmentation of 3 dBi with maximum gain increment of nearly 6 dBi at 5.5 GHz is achieved by adding the FSS. The antenna-FSS composite structure provides impedance band of 2.52–10.66 GHz with triple notches at 3.26–3.84, 5.1–5.38 and 5.66–5.95 GHz. Performance of the composite structure is evaluated in close proximity of sandy soil test bed by keeping thin aluminium sheet at the bottom of sand. Adequate VSWR, transfer function and group delay responses ensure the eligibility of proposed antenna to work for GPR.