Ground Penetrating Radar Equipment Research Articles

Development of a Background Filtering Algorithm to Improve the Accuracy of Determining Underground Cavities Using Multi-Channel Ground-Penetrating Radar and Deep Learning

In the process of using multi-channel ground-penetrating radar (GPR) for underground cavity exploration, the acquired 3D data include reflection data from underground cavities or various underground objects (structures). Reflection data from unspecified structures can interfere with the identification process of underground cavities. This study aims to identify underground cavities using a C-GAN model with an applied ResBlock technique. This deep learning model demonstrates excellent performance in the image domain and can automatically classify the presence of cavities by analyzing 3D GPR data, including reflection waveforms (A-scan), cross-sectional views (B-scan), and plan views (C-scan) measured from the ground under roads. To maximize the performance of the C-GAN model, a background filtering algorithm (BFA) was developed and applied to enhance the visibility and clarity of underground cavities. To verify the performance of the developed BFA, 3D data collected from roads in Seoul, Republic of Korea, using 3D GPR equipment were transformed, and the C-GAN model was applied. As a result, it was confirmed that the recall, an indicator of cavity prediction, improved by approximately 1.15 times compared to when the BFA was not applied. This signifies the verification of the effectiveness of the BFA. This study developed a special algorithm to distinguish underground cavities. This means that in the future, not only the advancement of separate equipment and systems but also the development of specific algorithms can contribute to the cavity exploration process.

Application of ground-penetrating radar for shallow subsurface investigation at the coastal area of lhok village, lhoong, aceh besar regency, aceh

This research aims to identify subsurface layers in the coastal area of Lhok Village, Lhoong, Aceh Besar Regency, Aceh. Ground Penetrating Radar (GPR) was the primary method to extract information concerning concealed geological structures beneath the Earth's surface, including in coastal areas. GPR is a non-destructive geophysical technique that utilizes electromagnetic waves to explore and map subsurface layers. However, data collection involved field surveys utilizing GPR equipment directed at the ground's surface. During the survey, radar data was processed and analysed to pinpoint various subsurface level. The obtained information contributes to a deeper understanding of the region's geological characteristics and subsurface layers. Additionally, it aids in assessing geological risks, facilitating construction planning, and conserving natural resources in the area. Here, the outcomes of this study may also serve as a foundation for further research in geology and geophysics within the Aceh Coastal region.

Theoretical modeling on the temperature-dependent dielectric properties of concrete pavement materials

The variations of concrete pavement temperature will affect the dielectric properties of concrete, which have a substantial influence on the wireless power transfer efficiency of concrete electrified road and non-destructive accuracy of ground-penetrating radar (GPR). In order to elucidate and describe the variations in the dielectric properties of concrete with temperature, the dielectric properties of aggregates (limestone), six types of cement mortar (matrix) and concrete (two types of Portland Cement: P.O 32.5 and P.O 42.5; three W/C ratios: 0.4, 0.5 and 0.6) within the temperature of −30 ℃ to 60 ℃ were acquired via a network analyzer platform and an open-ended coaxial probe kit. The results show that the dielectric constants of limestone, cement mortar and concrete increase with varying degrees when temperature rises. Furthermore, strong linear agreement between the dielectric constants of limestone, cement mortar and concrete and temperature is identified, indicating that the variations in the dielectric properties of concrete with temperature should be taken into consideration. Meanwhile, a temperature-dependent dielectric model of concrete is established by introducing the dielectric-temperature coefficients so as to quantify the influence of temperature on the dielectric properties of concrete. Compared with the traditional models (Brown model, CRIM model, Looyenga model, and Rayleigh model), the proposed model has the highest precision and is less sensitive to temperature variations. Therefore, the proposed model is more suitable for predicting the dielectric properties of concrete at different temperatures, which is essential for the development of future electrified road and promoting non-destructive accuracy of GPR equipment.

USE OF GPR TECHNOLOGIES IN THE ROAD PAVEMENT SURVEY

The article contains information on the study of the possibilities of introducing GPR technologies into the practice of road surveying. The prospects for the development of this scientific direction are also analyzed. The tasks that can be solved with the use of ground-penetrating radar equipment during the non - rigid pavement. The main reasons preventing a more dynamic implementation of ground-penetrating radar technologies in the construction industry are considered in detail. The main reasons are: the difficulty of interpreting GPR data, the lack of an instrument base, the lack of a single complex of equipment and mathematical support for non - rigid pavement, which allows for guaranteed high-precision interpretation of the results of GPR surveys of non - rigid pavement and ground surfaces, and the absence of a regulatory framework that regulates the survey of highways with the use of ground-penetrating radars. Modeling of signal propagation in an environment with known electrophysical characteristics allows to determine the shape and amplitude of a complete signal, giving the possibility of correct interpretation of radargrams in order to determine the speed of signal propagation in the studied structures, electrophysical characteristics of structural materials of layers of non - rigid pavement, the interface of environments. To carry out experimental studies aimed at the development of methods of thickness measurement and defectoscopy of structural layers of non - rigid pavement, specialists of the Kharkiv national automobile and highway university use a set of geolocation equipment that uses ultra-broadband signals. A set of georadar equipment is used both for conducting experimental laboratory research of road clothing and for field surveys for the purpose of developing a road monitoring system using radar methods. For the verification and practical use of the proposed scheme for determining the time delay of signals, which allows to calculate the thickness of the structure under study, appropriate software was developed. A series of laboratory experiments were conducted using this software product. As shown by the experimental laboratory studies, the method allows to restore the thickness of the layer under investigation with a fairly high accuracy. Keywords: GPR diagnostics, highway, non - rigid pavement, ground surface, reliability, operational condition, research, electrophysical properties.

Testing of a GPR equipment to assess the integrity condition of a subway tunnel located under groundwater level

AbstractDetermining the condition of underground concrete tunnels is fundamental for ensuring continuity and safety of operations, as well as for deploying efficient maintenance plans. The increased traffic volumes in early infrastructures, which are characterized by outdated construction techniques and potential approximated realization, as well as rising groundwater levels due to variations in urban industrialization patterns, are among the main causes of current concerns regarding their performance. Such uncertainties and constraints push towards the use of non‐destructive techniques, rather than direct methods, to gather the required knowledge on the actual status of structures. This study presents the results of a ground penetrating radar (GPR) investigation carried out in a subway tunnel segment to characterize the thickness of its underlying concrete elements, namely the tunnel invert and the concrete filling, deemed necessary after relevant flooding events prompted the evaluation of its overall integrity condition. A preliminary step was performed to define the optimal frequency and polarimetric antenna configuration, given the resolution and penetration requirements and considering the high electromagnetic interference characterizing the site. The selected configuration was then assembled in a dedicated survey platform, and an entire 650 m long segment surveyed, producing a high resolution delineation of the concrete elements thickness. The accuracy of the estimation has been validated through nine core samples, demonstrating the reliability and consistency of the conceptualized GPR platform.

Ground-Penetrating Radar Method for Studying Water Drainage in Sand Layers

A ground-penetrating radar (GPR) technology was developed to study the process of water drainage in sand layers with an insignificant concentration of dusty and clayey particles when moistened from above. The technology includes a method of calibration of the GPR equipment, algorithms for processing the GPR information, and their software implementation. The technology was used to process the results of laboratory GPR measurements obtained during draining of water through sand layers from different quarries for 100 h. The absolute values and the changes in the refractive index and specific conductivity near the sand layer upper boundary and on average over the layer depth were calculated. The results show that the developed technology makes it possible to determine electrophysical properties with an accuracy of up to 10%. The developed method for calculating relative reflectivity and its derivative with respect to the depth of the layer made it possible to visualize the information contained in the radargrams on the distribution of water near the surface and deep in the sand layers. The application of the method makes it possible to quantitatively estimate the moisture content near the upper boundary of the layer and the depth of the location of the most moistened areas of the layer depending on the duration of water drainage.

On the Development and Application of Airborne GPR Solutions

Recent development of ground penetrating radar (GPR) technology, together with effective unmanned aerial vehicles (UAVs), have made it possible to carry out airborne GPR measurements across areas otherwise difficult to access and survey. The interest in airborne GPR studies has therefore been rising steadily in recent years and applications are many, including bathymetry, glaciology, archaeology, near-surface geology, ice- and snow thickness, road planning, peat, and wetland studies. However, airborne GPR measurements introduce several challenges that affect surface-based measurements to a lesser extent. Some of these challenges are regulatory, others of a more technical nature. In this article, we will discuss the effects an airborne antenna solution has on antenna footprint, unwanted signal input and signal loss. We will also describe a few scenarios where airborne GPR has been successfully used. Throughout the included studies, and depending on the application, different MALÅ GeoDrone antennas (developed and manufactured by Guideline Geo) have been used. At this point, it is also important to remind the reader the importance of adhering to local and regional regulations regarding the use of both UAV and GPR equipment.

Ballast fouling inspection and quantification with ground penetrating radar (GPR)

ABSTRACT Ground penetrating radar (GPR) has been applied for ballast layer inspection for two decades, mainly for the analysis of ballast layer fouling levels. However, some issues that affect the inspection quality remain unsolved, such as issues involving the GPR equipment quality (antenna) and the correlation between the GPR indicator and fouling index. With the aim of solving these two issues, in this paper, we investigated the difference between the results of two different antennas, the GPR data processing technique, indicators for the fouling level (by GPR signal processing) and the correlation between the indicators and fouling index (obtained by sieving). The results show that the antenna quality determines the inspection quality. The indicators can reflect the ballast layer fouling level, and they correlate the best with the fouling index (obtained by the percentage of particles passing through a 5 mm sieve size). This study is helpful for the future modification of railway ballast maintenance standards.

Joint Physics and Data Driven Full-Waveform Inversion for Underground Dielectric Targets Imaging

To better reconstruct underground targets based on ground-penetrating radar (GPR) data, this paper proposes a joint physics and data driven full-waveform inversion (PDD-FWI) scheme. This scheme combines a physics-based non-iterative approach and a data-driven deep neural network (DNN) to reconstruct target location, shape and permittivity accurately. Firstly, the normalized range migration algorithm (RMA) is introduced to extract the target contour and location information, which not only improves the robustness of the proposed scheme, but also ensures adaptability to different GPR equipment. Then, the GPR dielectric target reconstruction network (GPRDtrNet) is developed based on the improved U-net structure, including reducing network layers and adding multi-scale additive spatial attention gates and skip-connection structures. Compared with previous DNN-based reconstruction methods, GPRDtrNet has the advantages of small data requirement, high accuracy, strong generalization and noise tolerance. Finally, the simulated and real dataset containing kinds of targets is constructed to train and test GPRDtrNet. The results show that the proposed method can reconstruct underground dielectric targets accurately with high robustness and noise tolerance.

Reviewing methods for determination of Dielectric Constant required to Calibrate GPR Study for Asphalt Layers

Ground Penetrating Radar (GPR) is a non-invasive technique developed substantially in the recent years. Initially, GPR technology was applied to natural ground to explore the sub-surface conditions and identify the anomalies in it. Now it has become a well-accepted technique to investigate any kind of materials such as wood, ice, concrete, asphalt etc. The calibration of GPR equipment is most important prerequisite criteria before data collection for accurate investigation of pavement subsurface features. During calibration, the velocity of radar waves will be calibrated in contrast to subjected material as whole examination is governed on the basis of it. The basic dielectric properties required as a prerequisite while using GPR system are dielectric permittivity, electrical conductivity along with magnetic permeability. The dielectric constant affects the velocity of transmitting wave as inverse proportion i.e. velocity decreases with an increase in dielectric constant and vice-versa. Considering the principle, the detailed study of pavements requires understanding and estimation of ‘bulk’ dielectric constant. The heterogeneous conditions of pavement actually obscure the straightforwardness of analysis and therefore estimation of a ‘bulk’ dielectric constant value becomes essential. There are several methods to compute the dielectric constant of asphaltic layers, which are developed by different researchers, and these are discussed briefly in this paper. The paper tries to put forward the merits and demerits of these methods and to identify the most appropriate one suiting to Indian conditions.

Technique for Detecting Subsurface Cavities of Urban Road Using Multichannel Ground-penetrating Radar Equipment

Technique for Detecting Subsurface Cavities of Urban Road Using Multichannel Ground-penetrating Radar Equipment

Late Quarternary displacements along the Sarma segment of the Primorsky fault based on gpr survey data (Baikal rift)

Ground-penetrating radar (GPR) surveys were performed in the Sarma segment of the Primorsky fault between the settlements of Shida and Kurma. This segment belongs to one of the largest structures of the Baikal rift and was active in Late Quaternary (Early Holocene). The study aimed to reconstruct vertical displacement amplitudes and dip angles of fractures along the fault segment, clarify its kinematic type, and estimate a maximum magnitude of earthquakes that may occur in the study area. The GPR equipment set included an OKO-2 georadar and AB-250M and ABDL-Triton shielded antennas. The GPR surveys were supported by morphostructural and tectonophysical methods. Based on the interpretation of the geophysical survey data and satellite images, faults associated with the Sarma paleoseismic dislocation were mapped. Their total length amounts to 14 km. According to the GPR survey data, one-stage vertical displacements show normal faulting and vary from SW to NE from 4.4 to 7.7 m. Paleo-earthquake magnitudes calculated from the maximum displacement values (Mw=7.2, and Мs=7.4) suggest that potential earthquakes in the Primorsky fault zone may be stronger than previously assumed.

Development of Digital Subterranean Models for Real-Time Open Cut Horizon Control

A reliable coal seam sensing system is required to improve the productivity of selective mining in open-cut mining operations. A prototype system based upon commercial ground penetrating radar equipment, which measures coal thickness from the top of an exposed surface down to an underlying coal-interburden interface and generates digital subterranean models of the subsurface seam boundaries, was developed for this purpose. The models can be deployed to commercially available in-cab assistive guidance systems for bulldozers and other mining machinery in existing production processes, and can further contribute to the databases required for remote operation and control in a complete digital mine scenario. The system was evaluated at a production open cut coal mine in Queensland, Australia, with promising results. The benefits reported by operational personnel who evaluated the digital surface model in the mining environment provide strong motivation for ongoing technology development.

Application of Ground Penetrating Radar for Underground Utility Detection

The accurate location of underground utilities at a construction site can prevent any damage to the utilities during excavation works. The cost of fixing the damage utilities can be very costly and will reduced the expected profit of the construction works. Therefore underground utility detection using Ground Penetrating Radar (GPR) is important in providing accurate information of the utilities at a construction site. In this study TerraSIRch SIR-3000 GPR equipment have been used to detect underground utility, with a 400 MHz ability which can reach up to 3m depth. RADAN 7 software is used to interpret and analyze the GPR data. Based on the results obtained the GPR equipment is capable of detecting underground utilities such as pipe, cable, shaft, etc.. The detected utilities are then shown in the 2-D and 3-D drawing for better visualization and identification.

Ballistic Ground Penetrating Radar Equipment for Blast-Exposed Security Applications

Among all the forensic applications in which it has become an important exploration tool, ground penetrating radar (GPR) methodology is being increasingly adopted for buried landmine localisation, a framework in which it is expected to improve the operations efficiency, given the high resolution imaging capability and the possibility of detecting both metallic and non-metallic landmines. In this context, this study presents landmine detection equipment based on multi-polarisation: a ground coupled GPR platform, which ensures suitable penetration/resolution performance without affecting the safety of surveys, thanks to the inclusion of a flexible ballistic shielding for supporting eventual blasts. The experimental results have shown that not only can the blanket absorb blast-induced flying fragments impacts, but that it also allows for the acquisition of data with the accuracy required to generate a correct 3D reconstruction of the subsurface. The produced GPR volume is then processed through an automated learning scheme based on a Convolutional Neural Network (CNN) capable of detecting buried objects with a high degree of accuracy.

Evaluating the structure characteristics of epikarst at a typical peak cluster depression in Guizhou plateau area using ground penetrating radar attributes

Epikarst, defined as the “skin” of karst environment, is widely developed in southwest China, largely as a result of the subtropical monsoon climate. Typical SW China karst accommodates a dual hydrogeological structure, with surface and subsurface hydrological systems. The epikarst ecosystem of karst environments plays a key role in biogeochemical cycling and energy and material storage and transport. Due to low rates of soil-formation derived from carbonate rock weathering, the soil layer is shallow and scattered, presenting interlocked features within carbonate rock. Research on epikarst structure is primarily based on section field survey with semi-quantitative characterization, often lacking a fully quantitative description of soil-rock structural characteristics. We utilized ground penetrating radar (GPR) attributes to interpret the structure of epikarst at a peak cluster depression in the Guizhou karst plateau. Two typical types of epikarst slope profiles and one peak cluster depression in Maguan Town, Puding County were selected for study. We used MALA GPR equipment with 500 MHz and 50 MHz antennas to acquire data. GPR data was processed conventionally and then average energy attributes, average amplitude attributes and coherence attributes were extracted to interpret the structure of the two epikarst profiles and the soil depth of the depression. The results show that: (i) energy and coherence attributes can highlight the soil-rock structure of the epikarst profiles with relative ease; (ii) compared to the original returned image, the energy attributes visualise the soil and rock medium more effectively; and (iii) the coherence attributes can identify the reflection interface between complete bedrock and bedrock containing fissure and grikes (epikarst). In addition, using the 50 MHz antenna we were able to determine the soil depth in depression with coherence attributes indicating a depth of 3.6 m, very close to the real depth (3.58 m) measured by our auger verification work. GPR attributes provide evidence that the epikarst has developed a large number of fissures filled with soil or other materials, but that the bedrock under the epikarst has few fractures. GPR attributes are therefore helpful for increasing our confidence of studying the structure of slope epikarst structure and depression soil depth.

Comparison of Multichannel Ground Penetrating Radar Equipment for Detecting Road Cavities

Comparison of Multichannel Ground Penetrating Radar Equipment for Detecting Road Cavities

Void detection in two-component annulus grout behind a pre-cast segmental tunnel liner using Ground Penetrating Radar

Ground Penetrating Radar (GPR) is being considered as a potential non-destructive technique for ensuring complete annulus grout backfill behind pre-cast segmental tunnel liners. Current methods for ensuring grout backfill involve drilled verification holes through the waterproof liner. The Rondout bypass tunnel, in Newburgh, NY, where void formation behind the tunnel liner is possible due to high groundwater pressures, provided an example project to evaluate GPR capabilities. While the application of GPR for void detection in one component grouts behind tunnel liners has been well-documented, site specific calibration of the GPR equipment and the application to two-component grouts is necessary. Experiments were conducted on actual tunnel segments to determine the most appropriate antenna frequency that can penetrate through the steel-reinforced segments and produce the best resolution. Mock air and water voids were embedded within areas of complete grout behind the segment to demonstrate the GPR signatures. Steel reflectors buried within the grout provided indirect measurements of the electromagnetic (EM) properties of the two-component grout. All field results were compared against analytical evaluation and numerical models to validate void detection. The findings of this research allow for direct implementation of the GPR technique for detection of voids behind segmental tunnel liners with two-component grout backfill.

Ballast fouling evaluation with ground penetrating radar

In the transport infrastructures context, the support layers have a fundamental role in the degradation of the track condition, both in structural aspects and in terms of fouling of the materials that comprise them. Particularly in the field of railway research, ballast is the key element, and its fouling leads to track deterioration. Thus, the main focus of this work is based on the evaluation of the ballast fouling using Ground Penetrating Radar (GPR). In order to determine the applicability of the method on the evaluation of railway characteristics, laboratory samples and measurements carried out in situ, on sections of two railways in operation were analysed. In both cases the different ballast fouling levels were evaluated, using specialized software for this approach (temporal analysis); and then comparing these results with results of a frequency analysis in an automatic calculation program. This paper presents the possibilities of testing with GPR equipment by analysing an electromagnetic wave, in the temporal and frequency domain for the purpose of investigating the level of degradation of a railway track. Some recommendations are also made regarding the use of this method, adding the need for future developments in an attempt to reduce the number of destructive tests still practiced nowadays.

Aplicación de la técnica del georradar en ingeniería civil: evaluación de la variación del contenido de agua en el hormigón

The non-destructive ground-penetrating radar (GPR) technique is based on the pulsation of electromagnetic waves in the microwave range. This technique is currently used in a large number of studies in the field of civil engineering, such as the analysis of state of pavements, bridges, tunnels, buildings, in the detection and location of installations, as well as in the characterization of building materials. This article describes, as an example, a complete experimental study in which the sensitivity of the non-destructive technique of GPR to assess the variation of the water content is demonstrated. The evaluation is performed by analysing electromagnetic wave parameters recorded using commercial ground-penetrating radar equipment.