Ground Penetrating Radar Technique Research Articles

Ground-Penetrating Radar and Electromagnetic Induction: Challenges and Opportunities in Agriculture

Information on the spatiotemporal variability of soil properties and states within the agricultural landscape is vital to identify management zones supporting precision agriculture (PA). Ground-penetrating radar (GPR) and electromagnetic induction (EMI) techniques have been applied to assess soil properties, states, processes, and their spatiotemporal variability. This paper reviews the fundamental operating principles of GPR and EMI, their applications in soil studies, advantages and disadvantages, and knowledge gaps leading to the identification of the difficulties in integrating these two techniques to complement each other in soil data studies. Compared to the traditional methods, GPR and EMI have advantages, such as the ability to take non-destructive repeated measurements, high resolution, being labor-saving, and having more extensive spatial coverage with geo-referenced data within agricultural landscapes. GPR has been widely used to estimate soil water content (SWC) and water dynamics, while EMI has broader applications such as estimating SWC, soil salinity, bulk density, etc. Additionally, GPR can map soil horizons, the groundwater table, and other anomalies. The prospects of GPR and EMI applications in soil studies need to focus on the potential integration of GPR and EMI to overcome the intrinsic limitations of each technique and enhance their applications to support PA. Future advancements in PA can be strengthened by estimating many soil properties, states, and hydrological processes simultaneously to delineate management zones and calculate optimal inputs in the agricultural landscape.

Radar Observation of the Lava Tubes on the Moon and Mars

The detection of lava tubes beneath the surfaces of the Moon and Mars has been a popular research topic and challenge in planetary radar observation. In recent years, the Moon–based ground penetrating radar (GPR) carried by the Chinese Chang’e–3/–4 mission, the RIMFAX radar carried by the Mars mission Perseverance, and the RoSPR radar and MOSIR radar carried by China’s Tianwen–1 orbiter have extensively promoted the exploration of the underground space of extraterrestrial bodies, which is crucial for the future utilization and development of these spaces. This paper expounds on the principles, methods, and detection results of using GPR to detect lava tubes on the Moon and Mars. First, lava tubes’ formation mechanism and morphological characteristics are outlined, followed by an introduction to GPR’s working principles and classification. The advantages, disadvantages, and prospects of different types of radar in detecting the lava tubes are analyzed. Finally, the distribution of lava tubes on the Moon and Mars is briefly summarized, and the potential utilization of lava tubes is discussed. We believe that the GPR technique is an effective geophysical method for exploring the underground structures of the Moon and Mars, and the lava tubes beneath the surface of extraterrestrial bodies can provide important references for selecting future Moon and Mars bases.

Three-Dimensional Modeling and Non-Invasive Diagnosis of a Huge and Complex Heritage Building: The Patriarchal Basilica of Santa Maria Assunta in Aquileia (Udine, Italy)

Three-dimensional modeling and non-invasive diagnosis are fundamental prerequisites for planning reliable assessments of the seismic vulnerability, renovation and conservation of heritage buildings. In the case of multi-layered, huge and complex ancient constructions, various problems can be encountered in the early design phases of interventions, among which there is often a lack of an adequate building documentation. Such issues include drawings that are without a metric scale, not detailed, not updated or not reflecting the real situation. In addition, the fragility of these constructions requires an accurate census of every sign of deterioration in order to prepare an ad hoc intervention for the site. As an example, in this paper, the results of a survey regarding the Patriarchal Basilica of Santa Maria Assunta (Aquileia, Italy) are reported. The basilica has a rich history of about two thousand years. in which each era has marked the actual architectural layout with its own culture and art. The result is an intricate association of complementary and/or interdependent elements that make the building very complex. Given the need to obtain accurate documentation, a realistic representation and a simulation of the criticalities of the structure, which previously did not exist or were not sufficiently accurate, a multi-methodological and multi-scale diagnosis was performed. In detail, the ground-penetrating radar (GPR) technique was applied to verify the presence of structures still buried under some internal surfaces, and a topographic survey, terrestrial laser scanning (TLS), and structure for motion (SfM) aerial and terrestrial photogrammetry were integrated for the detailed survey of the entire internal and external macro-structure. The resulting outcome provided the comprehensive information needed for preparing projects for the preservation, management and restoration of the basilica and the buildings connected to it.

Machine learning-based detection of transportation infrastructure internal defects using ground-penetrating radar: a state-of-the-art review

Abstract Early detection of internal defects is crucial to ensure the long-term performance and stability of transportation infrastructure. Researchers and practitioners have developed various nondestructive testing (NDT) methods for this purpose. Among them, the ground-penetrating radar (GPR) technique has been widely implemented due to its advantages such as large coverage, traffic-speed survey, and rich subsurface information. In addition, machine learning (ML) algorithms have been frequently applied to achieve automatic GPR data interpretations, which are essential for field applications. However, the fundamental concepts, architectures, and appropriate application scenarios of these algorithms are often questionable to practitioners and researchers. This paper presents a state-of-the-art review of ML applications in the internal defect detection of transportation infrastructure using GPR. In particular, pavements and bridges are covered. The basic knowledge of GPR working principles and ML algorithms is documented. The critical features of the ML algorithms for each detection task are presented. The drawbacks that may hinder the application of ML algorithms using GPR are indicated, including the insufficiency of labeled GPR data, unavailability of GPR dataset, customized ML architecture, and field validation. Finally, possible transfer learning, integrated robotic platform, and data fusion with other NDT methods are discussed. This review paper is expected to serve as a reference for practitioners to choose appropriate ML algorithms to detect internal defects in transportation infrastructure using GPR.

Detection and quantitative evaluation of pumping distress on bridge deck pavement through field and laboratory experiments

Pumping distress refers to the phenomenon of dynamic water entering a pavement, soaking the cement concrete layer to form slurry, and being pumped out of the pavement void under the action of traffic loading. Pumping distress is frequently reported in high temperature and rainy regions, such as Sichuan province in China. Various factors contribute to pumping distress on bridge decks, but most of these factors have merely been subjected to qualitative assessment. The aim of the study is to conduct a comprehensive quantitative analysis through three years of field investigations and laboratory experiments. The field investigations include ground penetrating radar (GPR), pavement permeability tests, skid resistance tests, and drainage facilities surveys. The quantitative analysis of the field and laboratory inspections revealed that the formation reason, deterioration rate, and damage degree of pumping distress were different between the truck and emergency lanes. The occurrence of pumping distresses was significantly related to the uneven construction of the bridge deck leveling layer, compaction segregation, and poor drainage. Additionally, the influence of pavement thickness uniformity on pumping distress was evaluated by incorporating GPR techniques. Failure in the waterproof adhesion layer resulted in the barrier between the cement concrete deck and the asphalt mixture breaking, which allowed alkaline sources to move and transfer to the pavement layer easily. The outcomes of this study can help bridge authorities and construction contractors choose appropriate design and construction measures to prevent pumping distress.

Archaeological prospection of a prehistoric lithic workshop site using ground penetrating radar with a high‐frequency antenna unit

AbstractWe surveyed in detail the Chalcolithic lithic workshop Fofanovo XIII an East Fennoscandian region by ground‐penetrating radar (GPR). A high‐frequency antenna unit was applied to map small‐scale features, mainly waste flakes. To substantiate the efficiency of the GPR technique, we performed a primary analysis of a set of equivalent models in a sandbox. The laboratory‐scale GPR investigation highlights differences in GPR patterns depending on the spatial arrangement of small features and supports the further interpretation of real‐life data. The GPR survey in the field covered 2200 m2, revealing areas with a high density of artefacts in the cultural layer and locating individual structural elements of the Fofanovo XIII archaeological site. We suggested using microdebitage samples from manual probing to verify the detected anomalous values of GPR attributes. The results point to a significant correlation between microdebitage and the envelope peak amplitude of the echo signal. Ultimately, our study confirmed the cultural layer in the Fofanovo XIII workshop site to be rich in lithic production wastes, indicating it was a place of mass‐scale production of lithic chopping tools.

Numerical Study on Urban Infrastructure Diagnosis in Laterally Heterogenous Soils Using Resistivity and Ground Penetrating Radar Techniques

Urban environment can be considered a complex system consisting of the engineered pavement physical structure over the buried utilities (water, gas, sewer) network embedded in the background soil environment. Assessment of buried pipeline civil infrastructures using proximal geophysical methods in such instances has to consider possible interferences, difficulties, and incorrect inferences. In this study, we have conducted a numerical modelling investigation to understand and evaluate how electrical resistivity profiling (ERP) and ground penetrating radar (GPR) can be utilised to provide subsurface information that otherwise may not be possible if either one of the techniques is used. A model geometry consisting of a typical pavement structure (asphalt, base/subbase, and background soil) with a single 2 m pipe buried at a depth of 1 m was used. Strong lateral variations in soil type were incorporated over the short pipe section in order to understand the complexities that can arise, especially with ERP measurements. The 3D electrical resistivity measurements were simulated in Comsol using the 4-probe method, while the 2D GPR measurements were simulated in gprMax to obtain the subsurface information. The results from both ERP and GPR were used to develop a practical framework that can be utilised by relevant authorities for proximal condition assessment of their buried assets. It was suggested that ERP can be used as a first level screening tool over the whole pipeline length, followed by discretely selected GPR scans in order to further gain information on the pipe health. This is attractive practically since, following delineations of a large pipe section into shorter subsections, advanced condition assessment approaches that are generally intrusive in nature can then be economically deployed within the subsections suspected of experiencing significant corrosion damage.

Assessing concrete strength loss at elevated temperatures as a function of dielectric variation measured by GPR: an empirical study

ABSTRACT Reinforced concrete (RC) parts, which are exposed to high temperatures for a certain period, undergo physical-chemical changes that deteriorate their mechanical properties. To this end, this study investigates the efficiency of using ground-penetrating radar (GPR) as a non-destructive testing (NDT) method in assessing the core compressive strength loss, elastic modulus decrease, and tensile strength loss of concrete under extreme temperatures. RC specimens are fabricated and exposed to elevated temperatures (300°C, 400°C, 500°C, 600°C, and 700°C). GPR measurements are performed to estimate the relative dielectric permittivity (RDP) of the specimens before fire exposure (BFE) and after fire exposure (AFE). The compressive strengths of the cores extracted from the specimens are obtained also for BFE and AFE cases. Attained RDP values are in conformance with the previous research results and contribute additional evidence to the published literature. As the temperature levels are increased, RDP and strength-related values of concrete specimens decrease. The strength-related parameters are more sensitive to elevated temperatures, whereas the change in the RDP values is rather gradual. Through multiple correlations within 95% confidence intervals, core compressive strength loss, elastic modulus decrease, and tensile strength loss are, individually, estimated as a function of relative RDP change and applied temperature levels. Empirical formulas are obtained with high coefficients of correlation. The relative effects of RDP change and temperature are more pronounced in elastic modulus decrease and tensile strength loss compared to compressive strength loss. Overall, the outcomes of this paper confirm the viability of using the GPR technique for concrete dielectric characterisation in estimating the strength-related properties of concrete exposed to high temperatures, which might reduce the need for destructive testing.

Geoarchaeological Investigation of Abydos Area Using Land Magnetic and GPR Techniques, El-Balyana, Sohag, Egypt

Abydos Temple is one of Egypt’s most significant sites which has a long history that dates back to the ancient monarchy and continued until the coming of Islam and also served as one of Egypt’s most significant ancient royal and high-ranking official burial sites. The main objective of this work was discovering more archaeological features buried underground such as ancient walls, monuments, and tombs. This objective was achieved using two near surface sophisticated geophysical techniques, namely ground magnetic survey and ground penetrating radar (GPR). This site was surveyed firstly using ground magnetic survey as reconnaissance stage and the locations which contain potential anomalies were resurveyed using GPR technique for determination the depth and the geometry of this potential targets. This site was divided into four regular grids and GPR model SIR-4000 equipment with 200 MHz central frequency antenna was used in this survey. The output of the magnetic survey is a total magnetic anomaly map which was filtered using High pass (HP) and first vertical derivative (VFD) techniques to extract the residual component of the shallow objects which may be archaeological targets. The results of the magnetic methods showed a group of anomalies which appeared on the residual map and were attributed to archaeological features by comparing them with the current excavated objects in and around the site. Their geometrical shapes and depths were estimated using source parameter imaging (SPI) and analytical signal (AS) techniques in Geosoft Oasis Montag Software. The estimated depth of these objects is between 1–3 m. Several hyperbolic shapes appeared in the radargram sections, indicating the possibility of probable buried archaeological objects. These potential objects can be found at depths of 2 to 4 m below the ground surface. The presence of eight probable targets associated with archaeological features at depths between 1–4 m is therefore the most likely outcome from both magnetic and GPR approaches. Therefore, this site contains potential archaeological targets which need confirmation by excavation. These results will influence domestic and foreign tourism in Egypt, leading to an increase in visitors and a rise in Economy.

Mapping Decomposition: A Preliminary Study of Non-Destructive Detection of Simulated body Fluids in the Shallow Subsurface

The processes of decomposition that the body will have after the time of death are peculiar and complex. The body swells and expels gases and fluids, and the flesh decays. It also attracts many insects and scavengers. We know that these fluids are nutrients for the vegetation, and if the body is inhumed in the subsurface, they allow a rapid crop growth that remote sensors can mark. During forensic investigations, mapping the fluid migration in the subsurface can help reconstruct the genesis of a clandestine grave. Several studies show how different remote sensors and analyses can be sensitive to human burials. This paper presents a preliminary experiment studying the fluid dispersion in the subsurface using simulated body fluids in a shallow grave and detecting it through the ground penetrating radar (GPR) technique (given its ability to detect dielectric constant changes in the investigated media) and other remote sensing techniques. Although the simulation of the body fluids related to the dielectric constant was accurate and allowed us to better understand how decomposition in the subsurface does not always migrate in the way that was initially expected (toward gravity), other typical characteristics of the body fluids, other soils and external factors were left out and would be studied in future simulations.

Validation of wireless impact echo prototype for condition assessment of concrete structures

A new wireless impact echo prototype was developed for the condition assessment of reinforced concrete slabs. The new system includes a wireless handheld sensing device which connects by Bluetooth to a tablet equipped with a user-friendly software for managing the testing grid, recording measurements, processing and transforming the data to a frequency domain, and presenting the results in real time. To validate the device, three large-scale concrete slabs of dimensions 2000 mm x 2000 mm x 300 mm were fabricated with artificial defects including voids, delamination, vertical cracks, and geometric discontinuities. The influence of slab boundaries, defect depth and location, overall thickness, steel reinforcement, and an internal conduit on the obtained measurements were investigated. The results were also compared with other commercial non-destructive testing devices including ground penetrating radar (GPR) and ultrasonic pulse velocity (UPE), and the advantages and disadvantages of each method are discussed. Overall, the results suggest that the impact echo technique using the new wireless prototype is able to accurately detect and characterise various defect types provided that the right size of impactor is used. Use of improper impactor sizes can result in alternative vibration modes depending on the slab thickness and defect depth; in that case, multiple readings may be required. The new system greatly improved the ease-of-use of the impact echo technique, although the inspector should be trained to properly interpret the results. Compared with the GPR technique, the impact echo system was not as rapid and unable to detect the location of steel reinforcement; on the other hand, it was better able to detect defects in the presence of steel bars which tended to obscure readings using GPR. UPE measurements were also faster than the impact echo tests and performed well for slab thickness measurements and detection of certain defect types; however, readings were found to be affected by the presence of steel reinforcement and in some cases were inconsistent. Overall, it may be concluded that each technique presents certain strengths and weaknesses that should be considered in the condition assessment strategy. The results obtained from each technique are complementary and may be used to develop a complete understanding of the internal state of the structure.

GPR Technique and Data for Achievement 4D Cadaster

This article proposes to strengthen the connection of data about constructions made underground and what is built above ground for the development of the concept of multidimensional GIS. We emphasize here the importance and need to use GPR (Ground Penetrating Radar) systems for the fast and accurate acquisition of information about underground utility networks and the geological and geotechnical structure of the land, useful information for new construction investments (buildings, roads, highways, subway, etc.). Also here is presented a variant of integrating this data into a GIS platform.

Synthetic modeling and field GPR survey to understand the near-surface deformation induced by coseismic groundwater dynamics following the 2019 Mirpur earthquake in Pakistan

The Mirpur earthquake of Mw 5.8 on 24 September 2019 severely damaged villages in the epicentral area. The earthquake-triggered ground dynamics produced widespread liquefaction features on the surface (e.g., fractured road structure and sand boils) and in the shallow subsurface (e.g., elevated groundwater table, fractures, and sand dikes). Due to complexity of liquefaction-induced deformation and timing of field surveys, the structural and hydrogeologic features that develop in the near surface during seismic events are often poorly resolved on ground-penetrating-radar (GPR) profiles. To track and delineate the internal architecture and coseismic changes in groundwater levels and/or pressures due to liquefaction, a GPR survey was carried out soon after the Mirpur earthquake. The sudden pore water pressure changes in the shallow aquifer system caused a rise in the water table via upward groundwater movement and fracturing followed by rapid infiltration. This cascade phenomenon has adverse effects on soil, water resources, civil infrastructure, and public health and safety. To better understand induced changes in the physical properties of road infrastructure and the shallow subsurface, we performed synthetic modeling of electromagnetic wave propagation by employing the finite-difference time-domain method. Based on the available information at multiple scales (borehole and geophysical), subsurface physical models representing the most common and important coseismic features were considered for synthetic modeling. Likewise, synthetic tests of paved road were conducted to simulate the radar response of structural discontinuities (fractures) developed at different angles. To validate synthetic results by identifying a similar dynamic response of the induced hydrogeologic changes in the form of coseismic liquefaction features, a field GPR survey was conducted. Our results clearly demonstrate that the GPR technique is a potential candidate for hydrogeophysical detection and characterization of features of interest in the case of paved roads as well as agricultural and residential areas. Additionally, the successful application of GPR proves it to be a cost-effective, high-resolution, and speedy tool for better assessment of hydrogeologic hazard, socioeconomic consequences, and mitigation in the Mirpur area. The proposed approach may find applications in other seismically active regions around the world.

Precise estimation of subsurface moisture content based on laboratory measurement and 3D GPR field survey

The Sponge City construction currently undergoing in China aims to enhance the moisture capacity of urban pedosphere, and subsurface moisture content (SMC) is proposed to evaluate the effect of improvement. Different ground-penetrating radar (GPR) techniques have been used in previous studies to estimate moisture content, however, very few has assessed the potential of combing 2D common offset (CO) GPR with 3D multichannel GPR to resolve SMC estimates at the complex filed scale. In this paper, modified velocity analysis of in-situ 3D GPR common-midpoint (CMP) datasets was used together with 2D GPR laboratory calibration procedure to investigate spatial moisture variation and the impact of surface pavement and soil heterogeneity on subsurface water dynamics. Precise and reliable moisture information under two field sites (i.e., sponge pavement site and asphalt pavement site) was obtained, which further allowed us to quantitative characterize SMC distribution and its associated dynamics within the shallow vadose zone, and most importantly to investigate the coupling mechanism between subsurface water fluctuations with surface pavement conditions and subsoil moisture capacity in urban near surface environment. Additionally, through contrastive analysis, the superior performance of novel sponge material to detain and transit rainwater was highlighted. Data and results presented in this research provide pioneer reference for Sponge City construction and other engineering applications.

3D Sedimentary Architecture of Sandy Braided River, Based on Outcrop, Unmanned Aerial Vehicle and Ground Penetrating Radar Data

Ground Penetrating Radar (GPR) is a geophysical method that uses antennas to transmit and receive high-frequency electromagnetic waves to detect the properties and distribution of materials in media. In this paper, geological observation, UAV detection and GPR technology are combined to study the recent sediments of the Yungang braided river study area in Datong. The application of the GPR technique to the description of fluvial facies and reservoir architecture and the development of geological models are discussed. The process of GPR detection technology and application includes three parts: GPR data acquisition, data processing and integrated interpretation of GPR data. The geological surface at different depths and scales can be identified by using different combinations of frequencies and antenna configurations during acquisition. Based on outcrop observation and lithofacies analysis, the Yandong Member of the Middle Jurassic Yungang Formation in the Datong Basin has been identified as a typical sandy braided river sedimentary system. The sandy braided river sandbody changes rapidly laterally, and the spatial distribution and internal structure of the reservoir are very complex, which has a very important impact on the migration and distribution of oil and gas as a reservoir. It is very important to make clear the characteristics of each architectural unit of the fluvial sand body and quantitatively characterize them. The architectural elements of the braided river sedimentary reservoir in the Datong-Yungang area can be divided into three types: Channel unit, bar unit and overbank assemblages. The geological radar response characteristics of different types of sedimentary units are summarized and their interfaces are identified. The channel sediments form a lens-shaped wave reflection with a flat at the top and convex-down at the bottom in the radar profile, and the angles of the radar reflection directional axes are different on both sides of the sedimentary interface. In the radar profile, the deposit of the unit bar is an upward convex reflection structure. The overbank siltation shows a weak amplitude parallel reflection structure. The flood plain sediments are distributed continuously and stably in the radar profile, showing weak reflection characteristics. Different sedimentary units are identified by GPR data and combined with Unmanned Aerial Vehicle (UAV) detection data, and the establishment of the field outcrop geological model is completed. The development pattern of the diara is clarified, and the swing and migration of the channel in different stages are identified.

Upscaling digital outcrop models to infer well connectivity in carbonates with karstic features

We construct an innovative static–dynamic integrated workflow capable of bridging the gap between input geological data, inherent to a lacustrine carbonate outcrop containing karst geobodies, and the description of the flow patterns and quantification of the multi-well productivity index (MWPI) for a particular well configuration in the outcrop. The workflow incorporates additional features stemming from the use of Machine Learning-based methods to mitigate lack of data in the locations away from the sections of input signals, along with the construction of new upscaling methods to assess the MWPI matrix. The ML-enhanced geostatic model hinges upon shallow surface geophysical data collected using Ground-Penetrating Radar (GPR) techniques. Furthermore, by discretizing the flow equations and adopting a flow-based upscaling method, we construct correlations between well flow rates and pressure drawdown in a typical five-spot well configuration. In this setting, we analyze the sensitivity of each well productivity with respect to heterogeneity distribution and correlations in the karst system within the outcrop. Computational simulations illustrate the ability of the integrated workflow proposed herein to improve prediction of hydraulic-connectivity between well pairs, which appear manifested in the entries of the MWPI matrix, whose magnitude aims at quantifying the effects of the karst geobodies upon geofluid production.

An Assessment of Geophysical Survey Techniques for Characterising the Subsurface Around Glacier Margins, and Recommendations for Future Applications

Geophysical surveys provide an efficient and non-invasive means of studying subsurface conditions in numerous sedimentary settings. In this study, we explore the application of three geophysical methods to a proglacial environment, namely ground penetrating radar (GPR), seismic refraction and multi-channel analysis of surface waves (MASW). We apply these geophysical methods to three glacial landforms with contrasting morphologies and sedimentary characteristics, and we use the various responses to assess the applicability and limitations of each method for these proglacial targets. Our analysis shows that GPR and seismic (refraction and MASW) techniques can provide spatially extensive information on the internal architecture and composition of moraines, but careful survey designs are required to optimise data quality in these geologically complex environments. Based on our findings, we define a number of recommendations and a potential workflow to guide future geophysical investigations in analogous settings. We recommend the initial use of GPR in future studies of proglacial environments to inform (a) seismic survey design and (b) the selection of seismic interpretation techniques. We show the benefits of using multiple GPR antenna frequencies (e.g., 25 and 100 MHz) to provide decimetre scale imaging in the near surface (e.g., < 15 m) while also enabling signal penetration to targets at up to ∼40 m depth (e.g., bedrock). This strategy helps to circumvent changes in radar signal penetration resulting from variations in substrate conductivity or abundant scatterers. Our study also demonstrates the importance of combining multiple geophysical methods together with ground-truthing through sedimentological observations to reduce ambiguity in interpretations. Implementing our recommendations will improve geophysical survey practice in the field of glacial geology and allow geophysical methods to play an increasing role in the interpretation of glacial landforms and sediments.

Research on the Dynamic Monitoring Technology of Road Subgrades with Time-Lapse Full-Coverage 3D Ground Penetrating Radar (GPR)

Road safety is important for the rapid development of the economy and society. Thus, it is of great significance to monitor the dynamic changing processes of road diseases, such as cavities, to provide a basis for the daily maintenance of roads and prevent any possible car accidents. The ground penetrating radar (GPR) technology is widely used in road disease detection due to its advantages of nondestructiveness, rapidness, and high resolution. Traditionally, one-time 2D GPR detection cannot obtain the 3D spatial changes of subgrades. Thus, we developed a road subgrade monitoring method based on the time-lapse full-coverage (TLFC) 3D GPR technique by focusing on solving the key problems of time and spatial position mismatches in experimental data. Moreover, we used the time zero consistency correction, 3D data combination, and spatial position matching methods, as they greatly improve the 3D imaging quality of underground spaces. Finally, the time-lapse attribute analysis method was used in the TLFC 3D GPR data to obtain detailed characteristics and an overall rule of the dynamic subgrade change. Overall, this research proves that TLFC 3D GPR is an optimal choice for road subgrade monitoring.

Investigating the sensitivity of mineral aggregate size on the dielectric response of asphalt concrete based on a multiscale experiment

Investigation of the dielectric properties of asphalt pavement materials is critical for the application of the ground penetrating radar non-destructive testing techniques. This study focused on the effect of each part with different particle sizes in mineral aggregates on the bulk dielectric response of asphalt concrete materials. Multiscale experiments were conducted with different mineral aggregate particle mixtures (mastic, mortar, and asphalt concrete materials). By combining the multi-scale test data and micromechanical method, the sensitivity of the mineral’s aggregate size, including the size effect induced by the interface behaviors of the asphalt–mineral aggregate, was analyzed. The results indicate that (i) the dielectric response of asphalt concrete is mainly dominated by its mineral aggregates, and the particle size is one of the main factors affecting the polarization of asphalt–particle mixtures; (ii) the interface effects increase the polarization of the filler and fine aggregates in asphalt; and (iii) the cumulative effect of unit volume of the filler and fine aggregate on the overall dielectric response of the asphalt mixture, i.e., the cumulative weight, shows a natural logarithmic growth.

Geophysical and Geochemical Characterization of Solidwaste Dumpsite: A Case Study of Chowa Gujar, Peshawar (Part of Indus Basin)

Open and non-engineered dumping is a typical method for solid waste disposal in most cities of Pakistan. This practice of waste dumping poses a serious threat to the surrounding ecosystem and human population due to the release and transport of decomposed organic matter, i.e., leachate from dumpsite into the groundwater. The present study was conducted over a non-engineered and open dumpsite (Chowa Gujar), located in the outskirts of the highly populated city of Peshawar by using integrated geophysical techniques such as electrical resistivity tomography (ERT) and ground-penetrating radar (GPR) and geochemical techniques. The main goal was to delineate the characterization and depth of buried waste, to map the subsurface extension of contaminant plumes towards agricultural land and groundwater table and the concentration of heavy metals (HMs) in dump and agricultural soil. Geophysical results showed that the thickness of buried waste (predominantly composed of domestic waste) was around 4 m and the leachate plumes have percolated to the adjacent agricultural land. A range of heavy metals (mg/kg) such as Cr (20.5–26.6), Cd (2.6–5.7), Pb (0.35–21.25), Ni (2.5–53.05), Cu (29–68.3), Zn (45.7–77), and Co (18.9–23.2) have been found in the agricultural land adjacent to the dumpsite. The findings demonstrated that combined use of ERT and GPR successfully characterize the buried waste and spread of pollutant plumes spatially and vertically from Chowa Gujar dumpsite. The anomalous geophysical signatures were confirmed by geochemical characterization. The movement of leachate plumes towards agricultural land and groundwater table and the concentration of HMs in soil show that Chowa Gujar dumpsite is a potential source of contamination not only to the surrounding population but also to the agricultural land, surface (Bara River), and subsurface water bodies. In the study region, there is an urgency to take remediation and mitigation measures to reduce the level of pollution created by the dumpsite.