Ground Penetrating Radar Method Research Articles

Parallel Implenetation of the GPR Techniques for Detecting and Mapping Ancient Buildings by Using CUDA

Ground-penetrating radar (GPR) is an ultra-wideband electromagnetic sensor used for the detection of objects which may be hidden behind a wall or inserted within the wall. The GPR method works on the principle of recording the reflection of electromagnetic waves sent to the underground at high speed from the interfaces by an antenna located in the horizontal direction, again by the receiver in the horizontal direction. Embedded structures are detected using collected data, computer programs, and various filters. Search for the presence of designated targets hidden between the walls, such as air pockets is help to archaeologists. In this work the Lorentz model was used for the distribution of the soil. The perfectly matched layer (PML) used for absorbing boundary conditions to simulate an open space and its expanded to match dispersive media. The finite-difference time-domain (FDTD) method is used to decompose partial differential equations for time cascading of the electromagnetic fields. FDTD calculation works very slowly. General-purpose programming can be done on the graphics processing unit (GPGPU) to solve this problem. In this work, the 3-D FDTD method was applied to the GPU by using CUDA and it was 10 times faster.

Characterizing a decametre-scale granitic reservoir using ground-penetrating radar and seismic methods

Abstract. Ground-penetrating radar (GPR) and seismic imaging have proven to be important tools for the characterization of rock volumes. Both methods provide information about the physical rock mass properties and geological structures away from boreholes or tunnel walls. Here, we present the results from a geophysical characterization campaign that was conducted as part of a decametre-scale hydraulic stimulation experiment in the crystalline rock volume of the Grimsel Test Site (central Switzerland). For this characterization experiment, we used tunnel-based GPR reflection imaging as well as seismic travel-time tomography to investigate the volumes between several tunnels and boreholes. The interpretation of the GPR data with respect to geological structures is based on the unmigrated and migrated images. For the tomographic analysis of the seismic first-arrival travel-time data, we inverted for an anisotropic velocity model described by the Thomsen parameters v0, ϵ and δ to account for the rock mass foliation. Subsequently, the GPR and seismic images were interpreted in combination with the geological model of the test volume and the known in situ stress states. We found that the ductile shear zones are clearly imaged by GPR and show an increase in seismic anisotropy due to a stronger foliation, while they are not visible in the p-wave (v0) velocity model. Regions of decreased seismic p-wave velocity, however, correlate with regions of high fracture density. For geophysical characterization of potential deep geothermal reservoirs, our results imply that wireline-compatible borehole GPR should be considered for shear zone characterization, and that seismic anisotropy and velocity information are desirable to acquire in order to gain information about ductile shear zones and fracture density, respectively.

The Use of Wavelet Analysis to Improve the Accuracy of Pavement Layer Thickness Estimation Based on Amplitudes of Electromagnetic Waves.

The article discusses one of the methods of dielectric constant determination in a continuous way, which is the determination of its value based on the amplitude of the wave reflected from the surface. Based on tests performed on model asphalt slabs, it was presented how the value of the dielectric constant changes depending on the atmospheric conditions of the measured surface (dry, covered with water film, covered with ice, covered with snow, covered with de-icing salt). Coefficients correcting dielectric constants of hot mix asphalt (HMA) determined in various surface atmospheric conditions were introduced. It was proposed to determine the atmospheric conditions of the pavement with the use of wavelet analysis in order to choose the proper dielectric constant correction coefficient and therefore improve the accuracy of the pavement layer thickness estimation based on the ground penetrating radar (GPR) method.

Prospecting and Evaluation of Underground Massive Ice by Ground-Penetrating Radar

Data from geocryological studies of soil and rock massifs in permafrost zone are very important as a basis for predicting possible negative consequences associated with climate change. A promising technique for studying geocryological structures (various types of underground ice) is the ground-penetrating radar (GPR) method. This paper presents the applications of the GPR method to prospect and evaluate massive ice in a frozen rock mass. To study the features of GPR signals received during sounding of underground ice, a model of a single GPR trace for the structure “frozen rock-ice-frozen rock” was developed. As a result, regularities were established in the kinematic and dynamic characteristics of GPR signals at the upper and lower boundaries of massive ice, depending on its geometric parameters. The established features were confirmed by the results of computer and physical simulation of GPR measurements of a frozen rock mass model. The main result of the study was to obtain a set of criteria for identifying massive ice according to GPR measurements. The developed criteria will allow the use of GPR for a detailed study of the structure of permafrost rocks to prevent the development of dangerous cryogenic processes in undisturbed and urban areas of the Arctic.

Using ground penetrating radars to detect internal defects in concrete foundation slabs

Introduction. The co-authors have analyzed a monolithic reinforced concrete piled raft foundation of a multi-storied residential building under construction. The mission of this research effort is to obtain trustworthy information about the internal structure of a foundation slab, to detect and survey internal defects, if any. This research project is to capture potential problems that may accompany the inspection of a foundation, to generate awareness about ground penetrating radar surveys and their methods that can help to optimize operating processes in the process of inspection.
 Materials and methods. The co-authors have employed a method of ground penetrating radar surveying, performed using a regular mesh of orthogonal projections over an easily accessible surface area of a raft foundation and several antennas producing sounding signals with centre frequencies varying within the range of 1,500 and 2,000 MHz.
 Results. A number of internal defects has been detected in the structure of a foundation slab, including several horizontal cold joints, cavity pockets and honeycombs. Their presence was later confirmed by control drilling and core material sampling. The information thus obtained was later generalized and entered into surface maps of cold joints, that depicted both the relief and the layout of detected defects in space. The analysis of core material chips has proven that reflecting boundaries are the same as those of the core material destruction; it has also demonstrated the presence of air pockets and the proofs of poor quality concrete mix compaction.
 Conclusions. The resolution of the ground penetrating radar method is sufficient to identify features of reinforced concrete slabs significant for their structure; it enables researchers to obtain trustworthy information about the internal structure of a foundation slab and make conclusions about the presence or absence of internal defects inside it, including cold joints, cavity pockets or honeycombs.

Non-Destruction Method for Detecting Corroded Underground Pipe Using Ground Penetrating Radar

Ground-penetrating radar (GPR) is a geophysical method that can accurately map the spatial extent of near-surface objects or changes in soil. It also produce radargram of those features. The demand for underground utility mapping in Malaysia is increasing rapidly for construction and non-construction activities. However, implementation of GPR in detecting corroded underground pipe in Malaysia can considered unpopular due to less exposure and exploration. Over the time, underground utility pipe will undergo corrosion process. Thus, is it relevant to detect old corroded pipe using GPR? On this basis, the aim of this experimental study was to validate the condition of corroded pipe by comparing its radagram profiles and to evaluate the significant signal reflectivity which were tested on three different pipe condition, namely new, average and old corroded pipe. The result of GPR calibration and data on GPR were processed using Reflex 2D software. In this study, with the aid of Time-Domain Reflectometry (TDR) sensor was used to obtain the soil moisture as it is one of the biggest in fluent to corrosion activity. In the GPR method, radar antennas moved along the ground in transects (B-scan), and two-dimensional profiles of a large number of periodic reflections (A-scan) were obtained. As conclusion, these GPR datasets and soil moisture from TDR reading are evaluated and been analysed thoroughly. At the end of this paper, it is suggested that GPR is efficiently can be used to detect corroded pipe.

The Structure of Quaternary Deposits in the Upper Dnieper Valley According to Integrated (Combined) Geophysical Data

The ground penetrating radar (GPR) and electrical resistivity tomography (ERT) geophysical methods were used for geological mapping, location of lithological boundaries, and description of the inner structure of sediments of the Upper Dnieper zone, as well as for locating optimal sites for drilling and correlating borehole cores. The geophysical information we obtained allowed restructuring of the upper Dnieper valley due to Valdaian glaciation to be identified. The GPR data in the frequency range of 50–250 MHz enabled description of the upper part of the geological section; ERT provided data up to a 80–100-m depth. Modified focusing inversion based on the major boundaries obtained with GPR was performed to correct the ERT inversion model.

Exploring the Consistency of Data Collected in Archaeological Geophysics: A Case Study from the Iron Age Hillfort of Villasviejas del Tamuja (Extremadura, Spain)

Different geophysical methods applied at the settlement of Villasviejas del Tamuja (Botija, Spain) have identified robust anomalies located at the same position, but some anomalies are reflected by only one method. Furthermore, analysing the spatial correlation of these anomalies is of fundamental importance for obtaining a correct archaeological interpretation. In this work, we analysed the main results of electrical resistivity tomography (ERT), ground-penetrating radar (GPR) and magnetic gradiometry methods in a particular area of the archaeological site. In this analysis, we performed graphical and numerical spatial correlation analyses of the anomalies and observed strong agreement among the results provided by each method. Certain anomalies were reflected only in the magnetic and ERT studies. The results highlight the importance of applying several geophysical methods and performing spatial correlational analyses. Furthermore, the methodology that we have applied to evaluate the spatial correlation offers interesting results.

Evaluation of GPR method in identification hidden faults of Alluvial deposits in north of Persian Gulf artificial lake, twenty-two district of Tehran

In this research, to detect hidden faults around Persian Gulf artificial lake (22 District of Tehran), Ground Penetrating Radar (GPR) was used. Three profiles were studied in this method. South of Persian Gulf artificial lake there is a trench of which first profile is designed on top. There are eight observable subsidiary faults which indicate a high seismic potential of the target area. Second and third profiles are close and parallel to each other. They are designed 260 m far from north of Persian Gulf artificial lake. The GPR data prove the existence of faults and fractures in layers. A fault zone with an approximate length of 200 m in the northern part of the lake is found out. Generally, results suggest that second and third profiles in comparison with first profile, have more severe changes in layers conditions. In addition, subsidiary faults recognized are in the same direction of North Tehran fault (most dangers fault of Tehran). Therefore, they are absolutely fault branches of North Tehran fault.

Integrated Application of GPR and Ultrasonic Testing in the Diagnostics of a Historical Floor.

The paper presents the results of integrated ground penetrating radar (GPR) and ultrasonic testing (UT) measurements conducted on a historical floor in St. Nicholas’ Church, Gdańsk, Poland. The described inspection was the first stage of the technical state assessment of the building. The aim of the study was the detection of underfloor air gaps, which were observed in a few trial pits. The condition of the ground under the floor was determined by localizing other inclusions such as rubble, human remains, brick walls and pipes. To identify the phenomenon of electromagnetic and ultrasonic wave propagation within the air gap, laboratory tests were conducted on physical models consisting of two concrete slabs stacked on top of each other and gradually moved apart to simulate a slot of varying thickness. The conducted research was supported by the numerical models of electromagnetic wave propagation. The obtained results showed that the integration of the GPR and UT methods provided an effective imaging of the floor and the area under it. Ultrasonic testing was proved to be a good technique for identifying air voids, while the GPR method allowed detecting concentrated anomalies and determining the degree of ground homogeneity under the floor.

A Survey Method on Groundwater Sources and Preferential Flow Paths In Urban Limestone-Based Residential Districts

Residential districts dominated by limestone are likely to be impacted by undesirable groundwater seepage accidents. Such groundwater seepage can generally give rise to loss of life and property. To control groundwater seepage, increasingly accurate and reliable methods for surveying are becoming indispensable. We proposed a survey method to confirm groundwater sources and preferential flow paths in urban limestone-based residential districts via ground penetrating radar (GPR) and time domain electromagnetic method (TDEM). Firstly, we established the geophysical exploration plan after careful analysis of available hydrogeological survey data including terrain, stratum distribution and water table. Survey lines were designed parallel to existing urban roads and perpendicular to the ground. Next, we used GPR and TDEM to detect gravels in the permeable layer and water-rich regions in the aquifer. Drilling method was adopted for comparisons to resulting images. Finally, integrated interpretation indicated accurate measures of groundwater sources, main preferential flow paths and the preliminary classification of groundwater leakage risk in a study region. The feasibility and effectiveness of the GPR and TDEM survey method were verified in the hydrogeological survey at the Lingxiucheng Residential District in China, where a thick limestone layer existed and groundwater leakage accidents had occurred in basements of houses. The method had high reliability for limestone topographies and was improved to be an effective and low-cost solution to overcome physical limitations of existent buildings and traffic jams in urban areas. Therefore, our research can be extended to similar projects and related problems to help better map urban limestone-based residential districts and reduce groundwater seepage.

Antenna assembly for down-the-hole measuring probe for locating and sizing hydraulic fracturing cracks in rock mass

The authors discuss the problem connected with the assessment of hydraulic fracturing quality in oil-filled formations by means of location and sizing of hydrofractures. The proposed engineering solution is to design a down-the-hole measuring probe based on the ground penetrating radar method in the range of microwaves. The authors select the model and mode of an antenna assembly for the down-the-hole probe. The width of the the major maximum of the antenna assembly pattern is determined.

Analysis of Groundwater Contamination Level in Residential Areas Around Cipayung Landfill Using Ground Penetrating Radar

Cipayung Landfill is the last disposal location of waste processing in Depok City, West Java. In a day, approximately 800 tons of garbage is dumped, which is then processed by being burned and left to decompose for inorganic and organic waste, respectively. However, poor waste management has resulted in an accumulation that continues to this day. This creates a variety of problems, especially leachate contamination that infiltrates to the groundwater, flows along and threaten the health of residents who live in the vicinity. This liquid contains toxins and hazardous materials. Therefore, it is essential for residents to know the level of contamination occurred and its dispersion, along with actions that must be taken to reduce the impact of pollution. In this study, we map the distribution of contaminated groundwater using the geophysical ground penetrating radar method, together with the chemical analysis of water samples. Ground penetrating radar has been useful to detect the change of permittivity and conductivity of layers below the surface. It is possible to mark off the contaminated groundwater to the fresh one indicated from an extensive amount of electromagnetic signal attenuation. This study suggests that there is contamination occurred in radius up to hundreds of meters from the landfill site. The result of this community-based research gives an advisable policy regarding waste management and groundwater usage in this area.

A Neolithic sedentary hunter–gatherer settlement with densely arranged buildings: results of geophysical prospection at Hasankeyf Höyük in south‐eastern Anatolia

AbstractRecent archaeological studies revealed that the Neolithic hunter–gatherers in south‐eastern Anatolia established highly developed settlements with evidence of the production of sophisticated symbolic artefacts, the existence of long‐distance trade, and elaborated burial practices. Their social organization was complex and can even be compared with that of the Levantine Early Pre‐Pottery Neolithic B (PPNB) farming society. The presence of such highly developed hunter–gatherer settlements requires a reconsideration of the neolithization process. However, a complete understanding of the sizes and plans of the settlements remains lacking because excavations so far have only been conducted in limited areas of the sites.This article presents the results of geophysical investigations using magnetometric and ground penetrating radar (GPR) surveys at the hunter–gatherer site of Hasankeyf Höyük in south‐eastern Anatolia. The results showed that a combination of magnetometric and GPR methods complementarily provides better prospection of sub‐surface structures than a single method does. In addition, this research has demonstrated that the Neolithic hunter–gatherers at Hasankeyf Höyük established a sedentary village with densely arranged buildings, which had not previously been substantiated at any other Neolithic site in south‐eastern Anatolia.

Not only the ‘Gold Train' – the ‘Underground Town' of Riese (Poland) – the ambiguity of interpretation ERT and GPR methods

AbstractThis article presents the results of a geophysical survey conducted in the Sowie Mountains within the Walim commune (Poland) in order to verify the discovery of the ‘Underground Town' of Riese. Project Riese was the biggest mining and construction project of Nazi Germany. The facility was designed as a convenient and secure location for a headquarters, an armaments factory, and warehouses for goods stolen during World War II. The discovery was made in 2015 with the application of the mysterious KS‐700 apparatus, the same as was used to ‘discover' the ‘Gold Train', which is ground penetrating radar (GPR) according to the manufacturer. It was one of the reasons why the verification surveys of the underground sites and the KS‐700 apparatus made use of the GPR method. The depth range of the GPR method was limited to 5 m due to the strong attenuation of electromagnetic waves. It was thus concluded that the underground structures detected by the ‘discoverers' were probably a result of apparatus errors, in which near‐surface reflections are received repeatedly and recorded as returning from a depth far greater than the actual object.Therefore, the electrical resistivity tomography (ERT) method proved to be conclusive. The three obtained characteristics and extremely high‐resistivity anomalies indicated the existence of underground tunnels. A thorough analysis of the results and acquired data, as well as of the literature, has proven that it is impossible to interpret them unambiguously as data from the subsurface but as a result of the influence of the surrounding objects. At other sites where the KS‐700 apparatus recorded numerous ‘underground cavities', the ERT cross‐sections did not yield a correlated image. Additionally, neither the analysis of the local geological structure with regard to the existence of an underground town nor the drilled boreholes confirmed the ‘discoverer's' results.

Non-destructive Method of the Assessment of Stone Masonry by Artificial Neural Networks

Background: In this study , a methodology based on non-destructive tests was used to characterize historical masonry and later to obtain information regarding the mechanical parameters of these elements. Due to the historical and cultural value that these buildings represent, the maintenance and rehabilitation work are important to maintain the appreciation of history. The preservation of buildings classified as historical-cultural heritage is of social interest, since they are important to the history of society. Considering the research object as a historical building, it is not recommended to use destructive investigative techniques. Objective: This work contributes to the technical-scientific knowledge regarding the characterization of granite masonry based on geophysical, mechanical and neural networks techniques. Methods: The database was built using the GPR (Ground Penetrating Radar) method, sonic and dynamic tests, for the characterization of eight stone masonry walls constructed in a controlled environment. The mechanical characterization was performed with conventional tests of resistance to uniaxial compression, and the elastic modulus was the parameter used as output data of ANNs. Results: For the construction and selection of network architecture, some possible combinations of input data were defined, with variations in the number of hidden layer neurons (5, 10, 15, 20, 25 and 30 nodes), with 122 trained networks. Conclusion: A mechanical characterization tool was developed applying the Artificial Neural Networks (ANN), which may be used in historic granite walls. From all the trained ANNs, based on the errors attributed to the estimated elastic modulus, networks with acceptable errors were selected.

Which fractures are imaged with Ground Penetrating Radar? Results from an experiment in the Äspö Hardrock Laboratory, Sweden

Identifying fractures in the subsurface is crucial for many geomechanical and hydrogeological applications. Here, we assess the ability of the Ground Penetrating Radar (GPR) method to image open fractures with sub-mm apertures in the context of future deep disposal of radioactive waste. GPR experiments were conducted in a tunnel located 410 m below sea level within the Äspö Hard Rock Laboratory (Sweden) using 3-D surface-based acquisitions (3.4 m × 19 m) with 160 MHz, 450 MHz and 750 MHz antennas. The nature of 17 identified GPR reflections was analyzed by means of three new boreholes (BH1-BH3; 9–9.5 m deep). Out of 21 injection and outflow tests in packed-off 1-m sections, only five provided responses above the detection threshold with the maximum transmissivity reaching 7.0 × 10−10 m2/s. Most GPR reflections are situated in these permeable regions and their characteristics agree well with core and Optical Televiewer data. A 3-D statistical fracture model deduced from fracture traces on neighboring tunnel walls show that the GPR data mainly identify fractures with dips between 0 and 25°. Since the GPR data are mostly sensitive to open fractures, we deduce that the surface GPR method can identify 80% of open sub-horizontal fractures. We also find that the scaling of GPR fractures in the range of 1–10 m2 agrees well with the statistical model distribution indicating that fracture lengths are preserved by the GPR imaging (no measurement bias). Our results suggests that surface-GPR carries the resolution needed to identify the most permeable sub-horizontal fractures even in very low-permeability formations, thereby, suggesting that surface-GPR could play an important role in geotechnical workflows, for instance, for industrial-scale siting of waste canisters below tunnel floors in nuclear waste repositories.

Application of invasive and non-invasive methods of geo-environmental investigation for determination of the contamination behavior by organic compounds

One of the main steps in assessing contamination in an area with confirmed contamination is the delimitation, behavior and preferential direction of plume flow from subsurface contamination. Contaminated areas present increasing challenges in their understanding, making it necessary to associate invasive and non-invasive investigation techniques to understand the conditions of the geological conditions and the lateral variations resulting from the lithological changes and the development and direction of the contamination plume. Geophysical methods have been shown to be a very effective non-invasive technique for the identification of areas contaminated by various types of pollutants, mainly due to the fact that it is a qualitative technique that allows the delimitation of major contamination focus, such as the source area of the process and the subsurface contaminant mass. The present work presents a 3D modeling of the geophysical methods of electrical tomography and ground penetrating radar (GPR) associated with an invasive method, membrane interface probe (MIP) in the delimitation of the plume of contamination by creosote in an area located near the Institute for Technological Research of the State of São Paulo (IPT), which housed an old railway line and the contaminating material was used in the treatment of wooden sleepers without due environmental care. This organic pollutant is widely used in the preservation of wood. The area, located near the Technological Research Institute of the State of São Paulo (IPT), housed an old railway line and the contaminating material was used in the treatment of wooden sleepers without due environmental care. The 3D model generated by the geophysical data was interpreted considering the punctual data of the MIP survey, which had the intention to refine the values of electrical resistivity in subsoil. The whole interpreted model was confirmed by collecting samples of groundwater in the area, ensuring the effectiveness of the association of the methods for detailed investigation.

An experimental and numerical approach to combine Ground Penetrating Radar and computational modeling for the identification of early cracking in cement concrete pavements

Road pavements are subject to traffic and temperature variations producing cracks that propagate to the pavement surface, which reduces its life and decreases circulation comfort. Early identification of pavement cracks allows for suitable maintenance and rehabilitation decreasing life cycle cost and increasing pavement life. For the development of an approach to identify early cracking using Ground Penetrating Radar (GPR), a laboratory simulation of different types of cracking was carried out, using a GPR system equipped with a ground-coupled antenna with a 2.3 GHz central frequency. Additionally, numerical simulations were elaborated using a Finite-Difference Time-Domain (FDTD) method-based software package (gprMax2D). Field GPR measurements were also carried out on a cracked rigid pavement of a road section overlaid with an asphalt layer. The results of this work proved the capability of the GPR method to detect cracks in rigid pavements and allowed to develop an approach for application in the identification of early cracking in rigid pavements.

Non-destructive Detection of the Anomalies and Thickness of a Shaft Using GPR

Ground penetrating radar (GPR) has been proven to be one of the most promising non-destructive methods that has been widely used in engineering quality inspections and condition assessments of underground structures. This paper reports an application study of GPR that presents a comprehensive survey of the auxiliary shaft of the Anli coal mine in China. During shaft installation, water gushing with a maximum inflow rate of approximately 16.0 m3/h occurred, and thus, it was urgent to determine the distribution range of anomalies and evaluate the lining thickness of the shaft to provide precise technical guidance for later treatments. A GPR grid scan was carried out by towing the antenna along 6 vertical measuring lines and 11 orthogonal circular measuring lines on the shaft surface. The GPR results show that the anomalies experienced by the shaft are voids, uncompacted areas and water bodies. Most anomalies were located in the outer shaft lining and surrounding soil. A vast majority of the shaft lining thickness reach its designed value, with a qualified rate of 91.2% for the inner shaft lining and 89.9% for the outer shaft lining, and the outer shaft lining exhibited inferior smoothness and uniformity. Under the guidance of the GPR results, a grouting treatment was carried out to water seal and strengthen the shaft lining, which, consequently, reduced the water inflow rate by 90%. The favourable grouting effect demonstrates that the GPR method can feasibly and successfully reflect the shaft lining and anomalies in shaft assessments. This engineering practice could serve as a case study reference for investigating any similar underground structure in the future.