Ground Penetrating Radar Surveys Research Articles

Ground-penetration radar detection of Root-mass in a Tree Groove in Southwestern Nigeria

In this study, we present the results of a ground-penetrating radar (GPR) survey aimed at imaging the lateral root systems of a section of  a tree groove lined by the Tectona Grandis (Teak) species. This was to set the basis for deploying a multi-frequency GPR system for the  non-invasive monitoring of rootmass development and evaluation of plant development and health. The survey involved a single GPR Transect with a total length of 60.1 m established along the middle of a line of matured Teak trees. Data was collected at 250 MHz, 500  MHz and 1000 MHz, simultaneously using a wheel-triggered Utsi Trivue system. Data processing involved a dewow, static corrections,  gain application and background removal. A root zone consisting of two layers was delineated and a total of 159 hyperbolae were interpreted as roots. The roots were limited to the shallow subsurface, the upper 1.1 m of a potential root zone 1.6 m deep. Imaged roots  generally occur in clusters that create much disturbance of the otherwise continuous reflections in the root zone. Often, roots may be  laterally offset from the location of tree bases on the Transect. We further identified a potential set of laterally migrating roots in a zone of undisturbed ground outside the main groove indicating the lateral reach of the usually shallow roots of the Teak tree. The results set  the basis for further work in root-mass estimation and monitoring tree health within our team. 

3D ground-penetrating radar data analysis and interpretation using attributes based on the gradient structure tensor

In near-surface geophysics, ground-penetrating radar (GPR) surveys are routinely employed in a variety of applications including those from archaeology, civil engineering, hydrology, and soil science. Thanks to recent technical developments in GPR instrumentation and antenna design, 3D surveys comprising several 100.000 traces can be performed daily. Especially in complex environments such as sedimentary systems, analyzing and interpreting the resulting GPR volumes is a time-consuming and laborious task that is still largely performed manually. In the last decades, several data attributes have been proposed to guide and improve such tasks and assure a higher degree of reproducibility in the resulting interpretations. Many of these attributes have been developed in image processing or computer vision and are routinely used, for example, in reflection seismic data interpretation. Especially in sedimentary systems, variations in the subsurface are accompanied by variations of GPR reflections in terms of amplitudes, continuity, and geometry in view of dip angle and direction. A promising tool to analyze such structural features is known as the gradient structure tensor (GST). Up to today, the application of the GST approach is limited to a few 2D GPR examples. Thus, we take up the basic idea of GST analysis and introduce and evaluate the corresponding attributes to analyze 3D GPR data. We apply the proposed GST approach to one synthetic and two field data sets imaging diverse sedimentary structures. Our results demonstrate that the proposed set of GST-based attributes can be efficiently computed in 3D and that these attributes represent versatile measures to address different typical interpretation tasks and, thus, help for an efficient, reproducible, and more objective interpretation of 3D GPR data.

Structure and chronology of a star dune at Erg Chebbi, Morocco, reveals why star dunes are rarely recognised in the rock record

Star dunes are the tallest dunes on Earth and are amongst the larger and more spectacular aeolian landforms. Although they are widespread in modern sandy deserts, star dunes are rarely recognised in the rock record probably due to a lack of suitable sedimentary models. This paper presents a new sedimentary model for the structure of a star dune at Erg Chebbi in Morocco (Sahara Desert) on the basis of ground-penetrating radar (GPR) surveys. Individual sedimentary structures in star dunes are similar to those in linear or barchanoid dunes, likely leading to misidentification in the rock record. However, the suite of features described in this paper will permit identification of star dunes in future studies of the rock record. Optically stimulated luminescence (OSL) dating shows that accumulation of the Erg Chebbi star dune post-dates the end of the African Humid Period (AHP). At the base of the dune, there is an ~ 8000-year hiatus in the record. Since then, the dune has grown rapidly to create a 100 m high dune within the past 1000 years and is migrating towards the west. Changes in the cross-strata support the idea that star dune construction was accompanied by a change in the wind directions.

The Dunes of Belvedere–San Marco of Aquileia: Integrating High-Resolution Digital Terrain Models and Multispectral Images with Ground-Penetrating Radar Survey to Map the Largest System of Continental Dunes of Northern Italy

The interpretation of high-resolution remote-sensed data (i.e., LiDAR-derived DTMs, aerial photos and satellite images), compared with ground-penetrating radar surveys, historical cartography, geomorphological surveys and stratigraphic data, allowed us to map a large system of dunes near the Grado-Marano Lagoon (NE Italy) and reconstruct its evolution. Remote sensing investigations allowed us to recognize, map and interpret the sandy reliefs as a field of continental aeolian landforms extending for over 15 km2 and consisting of parabolic dunes elongated in the WSW direction. Radar soundings, together with the description of stratigraphic sections and cores, documented the internal clinostratification of the dunes, supporting their aeolian origin. Radiocarbon dating documents that the dunes formed 22 ka ago, at the end of the Last Glacial Maximum, and probably evolved until the first part of the Late Glacial, when vegetation was scarce. The landforms were fed by the sands blown from a paleochannel of Isonzo River flowing eastward of the dune’s field and blown by Bora. This is a very strong katabatic wind, still characterizing the area, but that was likely much stronger during last glaciation, when it was probably sustained by a stronger wind pattern in Central Europe.

A Case Study of Pavement Foundation Support and Drainage Evaluations of Damaged Urban Cement Concrete Roads

Surface cracks and joint deteriorations are typical premature failures of urban cement concrete pavement. However, traffic loads on the urban pavement are much lower than those on highways. Limited research has been conducted to investigate the causes of accelerated damage in urban cement concrete roads. To investigate the foundation issues that may cause the accelerated damage of urban cement concrete pavements, in this study, field evaluations were conducted to assess pavement foundation support and drainage conditions. Field visual inspections, Ground Penetrating Radar (GPR) survey, Dynamic Cone Penetrometer (DCP) test, and the Core-Hole Permeameter (CHP) test were performed. In urban residential areas with inadequate subgrade bearing capacity, cement concrete pavements are prone to early damage. Foundations with a higher content of coarse particles exhibit a higher CBR value, which can extend the service life of the pavement. The compaction of foundation materials near sewer pipelines and manholes is insufficient, leading to non-uniform support conditions. Moreover, the permeability of the foundation material can influence the service life of pavement surface structures. Foundation materials with fewer fine particles enhance drainage performance, contributing to a longer service life for PCC pavements. In areas with inadequate drainage, water accumulation reduces the bearing capacity of the foundation, thereby accelerating pavement deterioration. The poor bearing capacity and drainage conditions of the foundation lead to cavities between the surface layer and foundation material thus yielding stress concentrations on the pavement surface, which cause the formation of pavement surface cracks.

MULTI-MODAL/MULTI-RESOLUTION 3D DATA ACQUISITION AND PROCESSING FOR A NEW UNDERSTANDING OF THE HISTORICAL CITY OF SIENA (ITALY)

Abstract. The paper presents the acquisition and data processing approach for the Ground Penetrating Radar (GPR) and laser scanner surveys carried out within the SOS project (the acronym comes from ‘SOtto Siena’, in English ‘Beneath Siena’). SOS is a program aimed to overcome some of the problems and limitations currently present in the study of cities with long-term continuity of life, responding in particular to the need for a better understanding of the city’s ancient fabric and hence to improvements in its conservation by: GPR city survey full coverage (of all the public spaces, streets, squares, courtyards, gardens, etc.), GIS data entry of the historical-archaeological and geoarchaeological knowledge and the development of a 3D Archaeological WEBGIS.The paper discusses the procedure for the creation of a 3D viewer within an already active WEBGIS platform, specifically created for the visualisation and management of archaeological data. The GPR data, once acquired, were exported in 3D in the form of point clouds and subjected to a procedure of cleaning and filtering from noise, so as to eliminate geometries not referable to anomalies and therefore to the presence of buried structures or cavities, and then transformed into mesh to meet the needs of the subsequent process of semantic enrichment. The GPR survey of the underground was flanked by laser scanning of some of the most significant structures in the historic centre (e.g. the cathedral). All 3D geometries were then inserted into the new visualiser via a pipeline using open-source tools and libraries.

A simple method for estimating the coarse lateral root biomass of shrubs using ground-penetrating radar: Validation by Caragana microphylla Lam. in Inner Mongolia

The potential increases in carbon stocks in arid regions due to recent shrub encroachment have attracted extensive interest among both ecologists and carbon policy analysts. Quantifying the shrub root biomass amount in these ecosystems is essential to understanding the ecological changes occurring. In this paper, we proposed a simple nondestructive method for estimating the coarse lateral root biomass of shrubs based on the root counts obtained from ground-penetrating radar (GPR) radargrams. Root data were gathered via field experiments using GPR with antenna center frequencies of 900 MHz and 400 MHz. Five Caragana microphylla Lam. shrubs of different sizes were selected for measuring objects, and a total of 40 GPR survey lines were established for GPR data acquisition. The soil profile wall excavation method was used to obtain the total root biomass from each radargram. A model for estimating the root biomass was built by establishing the relationship between the root biomass in each profile and the root counts interpreted from the radargrams. According to the mathematical relationship between the root diameter and root biomass, the proxy root radius was derived, which could explain the rationality of the proposed model from the biological mechanism. The established model provided high confidence in estimating the root dry biomass using the GPR data obtained at the two antenna frequencies (R2= 0.73 for 900 MHz and R2= 0.71 for 400 MHz). The leave-one-out cross-validation results showed that the model exhibits satisfactory performance. This study expands the application of geophysical methods in root research and offers a new simplified method for estimating the root biomass from GPR data under field conditions.

Ground Penetrating Radar Survey of Arctic Polygonal Wedge Structures

Ground Penetrating Radar Survey of Arctic Polygonal Wedge Structures

Ground Penetrating Radar Scanning and Historical Interpretation of the Location of Kyiv Confraternal Monastery’s Epiphany Cathedral

In 2021, we performed a ground penetrating radar survey at the place of the Epiphany Cathedral of the Kyiv Confraternal Monastery, destroyed in 1936, in order to precisely locate its foundations. The collection and analysis of archival information from open sources was carried out, which became the basis for the interpretation of the results of geophysical measurements. Publications and written testimonies of archaeologists who personally saw the foundations of the Cathedral became especially valuable. The set of historical data covers the period from 1615, that is, from the beginning of the construction of the wooden Epiphany Church, the predecessor of the Cathedral, to the present day. Original documents, blueprints, stock sources, photographs, and cartographic materials of the 17th––19th centuries, as well as historical works of the 19th–21st centuries, were analyzed. The information about the construction, restoration after the fire, functioning, and destruction of the Cathedral, as well as about the construction on its site in the 20th century, archaeological research in the 20th–21st centuries was generalized. Ground penetrating radar survey revealed the best-preserved group of foundations of the western wall of the Cathedral, which are proposed for archaeological excavations.

Ground-penetrating radar (GPR) survey and spatial analysis of the George and Addie Giddens Cemetery, Opelika, Alabama

ABSTRACT Interest in locating and preserving the cemeteries of enslaved African Americans has increased the need for new methodologies coupled with efficient, noninvasive geophysical techniques, such as ground-penetrating radar (GPR). The southeast United States, where many of such sites are located, provides many challenges to using GPR due to its humid climate and abundant vegetation, which deteriorates burial remains, disguises burial shafts, and forms physical obstacles to GPR surveys. These challenges make it difficult for GPR alone to locate caskets or burial shafts. To address these issues, this study uses GPR combined with an innovative spatial and observational methodology to locate burials in a humid climate and determine their burial conditions. These mixed methods led to the location of 129 potential graves. Knowing the spatial distribution of burial features provides a context for analyzing the relative burial ages and decay rates within the cemetery site.

A geospatial and archaeological investigation of an African–American cemetery in Raleigh, North Carolina, USA

AbstractOberlin Cemetery, located near downtown Raleigh, North Carolina, USA, was founded in 1873 following the American Civil War (1861–1865). This 3.2 ac (~1.29 ha) parcel of land served as the main cemetery for the people of Oberlin Village—the largest freedmen's community in Wake County. Today, descendants of the village founders and other neighbourhood residents, organized as the Friends of Oberlin Village (FOV), are preserving this community landmark and working to have its historical significance recognized. In support of these efforts, terrestrial laser scanning, global‐positioning‐system‐enabled pedestrian and ground‐penetrating radar (GPR) surveys were conducted during the winter and summer of 2016. We inventoried 276 formal grave markers identifying 221 individuals, 296 elongate depressions without a formal marker interpreted as sunken graves, and 130 fieldstones interpreted as burial markers, resulting in an estimate of 517‐to‐660 persons interred within the cemetery. The GPR survey supported the interpretation of topographic depressions as sunken graves; however, the undulating topography, as well as the density of trees and shrubs, limited this survey to ~12% of the site. Based on the birth dates listed on monuments, ~23% of these persons were born before the end of the Civil War. Death dates show the community's continued use of the cemetery throughout the early 1970s and less frequent use after that, with the most recent burials in 2009. A comparison with a 2012 inventory of monuments within Oberlin Cemetery suggests that ~3% of the markers were lost or displaced in 4 years, highlighting the importance of survey and preservation efforts. This work contributed to the FOV's successful nomination of the cemetery to the US National Register of Historic Places and was used to support several grants received for its preservation.

Detection for severe caves and sinkholes in non-clastic rock type using GPR technique

ABSTRACT This study examines the application of Ground Penetrating Radar (GPR) to the detection of severe caverns and sinkholes in non-clastic rock formations. Due to the presence of vertically sloping bedrock, cavities, and sinkholes, geotechnical engineers face significant challenges when designing and constructing foundations in karstic formations such as limestone. The territory under investigation is located close to the Giza limestone plateau, the northern side of which has experienced severe stability issues. The ground-penetrating radar (GPR) method was used to identify the presence and extent of exposed caves and caverns in the studied region. The research area’s geological and geomorphological background is explored, including the creation of primary and secondary caves, as well as solution caves generated by the breakdown of soluble rocks like limestone. Data collecting, processing, and interpretation procedures used in the GPR survey are described. GPR survey findings revealed the existence of a severe cave and many minor sinkholes in the studied region. GPR has shown to be a useful and efficient tool for determining geometric karst features in the subsurface, helping to a better evaluation of the dangers associated with this geological environment.

Ground penetrating radar investigations of buried remnants at ancient capital cities of Panchala and Vatsa kingdoms spread along Ganga-Yamuna doab of India from 600 BCE to 1100 CE

Ahichhatra and Kaushambi, ancient settlements located in Uttar Pradesh, comprise differential cultural deposits and architectural remnants from 2500 BCE to 1200 CE. These settlements flourished as the capital cities of once-prosperous urban kingdoms known as Panchala and Vatsa Mahajanapadas but remain abandoned in the present day. To provide ancillary data for the simplification of traditional archaeological explorational practices, a few portions located in and around the fortified areas of both settlements were considered for subsurface investigations using Ground Penetrating Radar (GPR). In Ahichhatra and Kaushambi, 2D and 3D GPR survey was carried out in the open areas devoid of vegetation for the understanding of the spatial alignment of the buried features within the fortified walls. The subsurface investigations at Ahichhatra have shown high amplitude reflections referring to buried wall structures, residential complexes, raised platforms, past-used surfaces and structural continuity. Also, the partial excavation carried out at Ahichhatra has revealed walls and compacted floors validating our findings. From Kaushambi, the findings include wall structures and interconnected chambered structures. The anomalies obtained in the data collected from considered survey sites located in Ahichhatra are 1–2 m wide and 2–4 m deep whereas in Kaushambi they are 0.5–1 m wide and 2–4 m deep. These findings helped us to determine the progressive urban relics of the ancient kingdoms which were known for their second phase of urbanism in Ganga Valley that prevailed until their abandonment. For a better understanding of the cultural history, detailed mapping of the contemporary sites can be carried out using integrated survey methods.

An Approach for Easy Detection of Buried FRP Composite/Non-Metallic Pipes Using Ground-Penetrating Radar.

Pipelines remain the safest means of transporting natural gas and petroleum products. Nonetheless, the pipeline infrastructure in the US is facing major challenges, especially in terms of corrosion of steel/metallic pipes and excavation damage of onshore pipelines (leading to oil spills, explosions, and deaths). Corrosion of metallic pipelines can be avoided by using non-corrosive materials such as plastic pipes for low-pressure applications and glass-fiber-reinforced polymer (GFRP) composite pipes for transporting high-pressure oil and natural gas. However, buried non-metallic pipelines are not easily detectable, which can lead to increased excavation damage during construction and rehabilitation work. Alternative strategies for making buried non-metallic pipes easily locatable using ground-penetrating radar (GPR) were investigated in this study. Results from this study have shown that using carbon fabric or an aluminum foil overlay on non-metallic pipes before burying in soil significantly increases the reflected GPR signal amplitude, thereby making it easier to locate such pipelines. The reflected GPR signal amplitude for pipe sections with carbon fabric or aluminum foil overlays was found to have increased by a factor of up to 4.5 over the control samples. The results also highlight the importance of selecting the appropriate antenna frequency for GPR surveys, since wet silt loam soil and clay significantly reduce the penetration depths of the radar signals produced by the GPR antennae.

Integration of in‐mine seismic and GPR surveys to gain advanced knowledge of Bushveld Complex orebodies

AbstractImproving the exploration of deep‐seated mineral deposits and assessing the stability of the mine pillars require that geophysical techniques are deployed in a fast and cost‐effective manner with minimal environmental impact. This research presents results from in‐mine reflection seismic experiments and a ground penetrating radar (GPR) survey conducted at the Maseve platinum mine, South Africa. The research aims to develop and implement methods to image platinum group metal (PGM) deposits and geological structures near mine tunnels and assess the stability of pillars. The seismic experiments were conducted using a sledgehammer source (10 lb), conventional cabled geophones (14 Hz), and a landstreamer with 4.5 Hz vertical component geophones. The GPR survey was conducted using a Noggin 500 GPR system with 500 MHz centre frequency. An image of the underlying orebody and geological structures down to 100 m from the mine tunnel floor (∼500 m below ground surface) was produced. We correlated the coherent reflections beneath the tunnel floor with a known Upper Group (UG2) PGM orebody. The final seismic section shows that the UG2 mineralisation is dissected by near‐vertical dykes, faults and fractures. These structures, faults in particular, are interpreted to have been active post‐mineralisation, implying that they may have contributed to the current complex geometry of the deposit. Four GPR profiles were collected around a stability pillar adjacent to the seismic lines. The radargram sections were processed to improve the signal‐to‐noise ratio (S/N). The results show different patterns of fracturing and stress‐induced structures. These fractures were shown to be sub‐vertical and, possibly, constitute complex micro‐structures within the pillar, which could compromise the pillar stability and integrity. The study demonstrates that in‐mine seismic and GPR surveys can be cost‐effective and valuable for mineral exploration.

Integration of Ground Penetrating Radar and Electrical Resistivity Methods to Investigate Subsurface Features at Kish Archaeological site, Babylon, Iraq

Several geophysical techniques, including magnetic, Electrical Resistivity Imaging (ERI), and Ground Penetrating Radar (GPR), have been used to investigate archaeological features because they are non-destructive and inexpensive compared to traditional methods such as excavation. GPR has been used in the Governorate of Babylon, Kish archeological site to investigate the subsurface ancient features.The GPR survey carried out on three parallel profiles. The length of each profile is 29 m and the spacing between each adjacent profile is 15 meters. The antennas 450 MHz and 750 MHz were used. The data was processed using GPR SliceV7 software. The GPR profiles indicate the presence of buried features, which may be an ancient wall. The wall is buried at a depth range between 0.5 and 3 m. Outside the study area, some part of the wall is visible on the surface. Three Electrical resistivity image (ERI) profiles (1, 2 and 3) were carried out by using wenner array to check the main features detected by GPR method. The ERI results are confirmed the GPR profiles (1, 2, and 3). Both methods indicate the existence of an ancient wall trending NW-SE. The thickness of the wall is approximately 3m and is located at distance 7.5-10.5 meters at profile 1 in the south and at distance 10-13 m in profiles 2 and 3. The depth of the wall ranges from 3–3.5 m. Another deep wall was also detected in the GPR profile 1 and in the three profiles of ERI method. The current work confirmed the importance of using ERI method with GPR method to investigate shallow subsurface features.

Geophysical surveys and satellite imaging for the evaluation of near‐surface terrain dynamic – A case study on Grand Portage, MN, USA

AbstractFlooding, erosion and increases in the water level in Lake Superior have contributed to changes in the stem location and width of the Grand Portage Creek. Those events threaten parts of the Grand Portage National Monument, a historically significant site on the North Shore of Lake Superior, Minnesota. We performed geophysical surveys to investigate these dynamic effects. We studied the near‐surface geological deposits, the mechanisms associated with creek stem dynamics and sediment transport, as well as deposition along the lakeshore in Grand Portage Bay. We deployed ground‐penetrating radar (GPR), sub‐bottom profiler, side scan sonar, Geoprobe coring and Van Veen grab samplers and evaluated time‐lapse satellite images to assess the interaction of the Grand Portage Creek with the Grand Portage Bay. The onshore GPR surveys next to the national monument, the creek and the shoreline showed the presence of a complex deposition with eroded ground surfaces and sediment layers across the creek valley. Results from the offshore geophysical campaigns and the interpretations of satellite images also document a heterogeneous deposition sequence environment with fine‐grained sediment deposits present south and southwest of the creek mouth. In addition, we documented an exposed boulder bed towards the east of the creek mouth that was exposed by the current and wave‐driven erosion process in the Grand Portage Bay. Time‐lapse satellite images and hydraulic current velocity simulations validate these observations and provide insight into how anthropogenic activities and natural events interact and might contribute to the long‐term stability of a site of historical and cultural importance.

Reflection characteristics of typical road defects in 3D GPR images for collapse mitigation

Road collapses pose dangerous threats to traffic safety in urban cities. Typically, these collapses result from under-road defects such as cavities, loose soil, and voids. With the development of multi-channel 3D ground penetrating radar (GPR) systems, GPR has become a routine method for inspecting the subsurface conditions of roads. However, the reflection characteristics of hidden defects in 3D GPR results have not been well studied due to the complexity of urban road structures. Consequently, accurately detecting all subsurface defects in GPR survey areas remains challenging. In this paper, numerical models of road structures with typical types of hidden defects are constructed, and their reflection characteristics in GPR B-scan profiles and C-scan depth slices are analyzed. Then, the field results obtained using a car-mounted 3D GPR system are presented to confirm the reflection characteristics of these hidden defects. Finally, the reflections of manhole covers and underground pipelines, which are the most prevalent forms of clutter in GPR images in urban environments, are compared with those of hidden defects. The findings of this paper will facilitate the accurate interpretation of field 3D GPR data for road inspections and the mitigation of road collapse accidents.

Delamination characterization in thin asphalt pavement structure using dispersive GPR data

Detection of delamination in asphalt pavement by non-destructive ground penetrating radar (GPR) is useful for effective maintenance and repair. However, limitations of GPR survey resolution and multiple wave interferences have made thin delamination layer characterization a challenging task in conventional common offset profiling (COP) mode. In this paper, a new method is proposed for characterizing delamination layers in asphalt pavement using the GPR waveguide dispersion model in a wide-angle reflection and refraction (WARR) configuration. The approach was validated through synthetic experiments and laboratory experiments using an asphalt pavement model. The results show that the cutoff frequencies of all modes are sensitive to air-filled delamination, while water-filled delamination leads to a significant decrease in the phase velocity of GPR waves. By observing these trends, we are able to detect delamination layers with 1 cm thickness and identify delamination layers with different properties. This new method can aid in the detection and identification of delamination layers in asphalt pavement structures.

Processing GPR Surveys in Civil Engineering to Locate Buried Structures in Highly Conductive Subsoils

Many studies have illustrated the great benefit of ground-penetrating radar (GPR) in civil engineering. However, in some cases, this geophysical survey method does not produce the desired results due to the electromagnetic characteristics of the subsoil. This study presents the results obtained in two locations near Linares (southern Spain), evaluating the detection of structures buried in conductive host materials (0.02 S/m in site 1 and 0.015 S/m in site 2) characterized by strong signal attenuation. Accounting for the study depth, which was 1.5 m, a 500 MHz shielded GPR antenna was used at both sites. At the first site, a controlled experiment was planned, and it consisted of burying three linear elements. An iron pipe, a PVC pipe, and a series of precast blocks were buried at a depth of 0.5 m in a subsoil composed of highly conductive clayey facies. To eliminate additional multiples caused by other superficial structures and increasing the high-frequency content, the predictive deconvolution flow was applied. In the 3D processing, the cover surfaces technique was used. Once the acquired GPR signals was analyzed and the optimal processing flow established, a second site in which different infrastructures in a conductive host medium formed by marly facies was explored. The 2D flow and 3D processing applied in this work allows to detect and see the continuity of some structures not visible for the default processing.