Non-destructive Geophysical Methods Research Articles

Evaluation of Mangroves Effectiveness in Strengthening Coastal Bund Using Geophysical Method (Non-Destructive Testing) at Tanjong Laboh, Batu Pahat, Johor

In recent years, mangrove forests have rapidly become an endangered ecosystem in the world. On the coastal shorelines, the saltwater intrusion (SI) phenomenon is a main concern that can affect the quality of water. The saltwater intrusion might occur due to sea level rise, and extreme natural disasters along with changes in mangrove ecosystem distribution. The purpose of this research is to evaluate the effectiveness of mangroves for strengthening coastal bunds in Tanjong Laboh, Batu Pahat, Johor. By using the non-destructive geophysical method, the presence of saltwater intrusion and subsurface profile of the survey line in the coastal area with and without mangroves was determined. The coastal bund conditions with and without mangroves were also compared in order to evaluate how the mangrove forest acts as coastal protection. The result shows that the resistivity values of 0.1 to 1.0 ohm are more dominant in the mangrove bund area than in the engineered coastal bund and rock outcrop areas. The saltwater intrusion integrity map was produced from the 2D subsurface image profiles for both survey lines. The comparison of the coastal bund conditions for two different scenarios, which with and without mangroves, has shown that the coastal bund without the mangroves experienced cracking and erosion compared to the coastal bund with the presence of mangroves. This indicates the importance of mangroves in protecting the coastal regions.

Utilizing Ground-Penetrating Radar for Water Leak Detection and Pipe Material Characterization in Environmental Studies: A Case Study

Detecting and mapping subsurface utilities in urban areas is crucial for identifying defects or damages in drinking and sewage pipes that can cause leaks. These leaks make it difficult to accurately characterize the pipes due to changes in their reflective properties. This study focused on detecting leaks originating from underground pipes and distinguishing between these various types of pipes. It also aimed to create a visual fingerprint model that displays the reflection characteristics of these pipes during different leak conditions, enabling efficient maintenance and handling procedures on the pipes. To achieve this, a finite-difference time-domain (FDTD) method was used to simulate two types of pipe materials with and without leak areas to construct different scenarios. Additionally, a ground-penetrating radar (GPR) field survey was conducted using a 600 MHz antenna in a part of the El Hammam area on Egypt’s northwest coast. The simulated images produced with numerical modeling were compared with the radar profiles obtained using GPR at particular locations. The numerical simulations and radar profiles demonstrated the noticeable influence of water leaks from the different pipes, wherein the reflection of saturated soil waves was interrupted due to the presence of saturated soil. Envelope and migration techniques were employed in a new application to accurately distinguish between different pipe types, specifically focusing on leak areas. The strong correlation between the real radar profile and the specific signal of a water pipe leak in the simulated models suggests that GPR is a reliable non-destructive geophysical method for detecting water pipe leaks and distinguishing between the different pipe materials in various field conditions. The simulated models, which serve as image-matching fingerprints to identify and map water pipe leaks, help us to comprehend reality better.

Application of non-destructive geophysical methods for testing concrete structures

Non-destructive testing of reinforced concrete structures is of utmost importance in construction and civil engineering, where many factors can cause internal and external deterioration of reinforced concrete structures: the environment, nuclear radiation, and structural defects, among others. Geophysical non-destructive testing methods such as ultrasonic and radar have been increasingly used in civil engineering in recent years. Improvements in the ultrasonic testing of concrete have produced detailed images of the interiors of even the most complex structures and allowed for the earliest possible detection of deterioration. In this study, three geophysical methods were applied to inspect concrete structures: parallel seismic, sonic echo, and ultra-seismic. These three testing methods are applied to concrete foundations of two depths, namely 5, and 7 m; the deep foundation has a fracture at a depth of 4.5 m. The collected data are processed using a low-pass filter to remove the higher frequencies. These results of parallel seismic tests accurately predict foundation depths of 5.0 and 6.6 m and P-wave velocities of 2551 and 1097 m/s, respectively. Sonic echo tests yield depth predictions of 5.07 and 7.01 m for the tested foundations and 4.44 m for the depth of the crack. Meanwhile, ultra-seismic tests give depth predictions of 7.1 and 4.6 m for the foundation and fracture, respectively, while clarifying the P-wave velocities of the corresponding reflections: 3447 m/s exiting the 7-m foundation and 2668 m/s exiting the embedded fracture. Depth estimates based on each method show strong agreement with true depths. In conclusion, these three geophysical methods have great potential to provide quantitative data to drive quality assurance and remediation for concrete structures.

Imaging the water content of rammed earth materials with induced polarization

Rammed earth is a traditional building material characterized by its low environmental impact. The variation of the moisture content of rammed earth can affect its mechanical properties. Therefore, the non-intrusive evaluation of the water content and its distribution inside rammed earth structures is of high interest to anticipate the risk of failure. A non-destructive geophysical method called induced polarization is used to evaluate its sensitivity to the water content distribution. Measurements are first performed on small cylindrical core samples of rammed earth in order to test a physical model developed to connect induced polarization properties to saturation. Then, the model is used to estimate the water content at 3 distinct heights in 3 cylindrical core samples undergoing capillarity rise. Finally, these samples were cut and their water contents were independently determined and compared to that estimated from induced polarization measurements. A good correlation between the two estimates was obtained. In the second part of this study, induced polarization is used to image the water content distribution and its evolution over time in a rammed earth structural element undergoing desiccation. The monitoring is done for a period of 25 days starting from saturated conditions. We assess the evolution of the 3D distribution of the water content and we demonstrate that the water content obtained through induced polarization tomography is in agreement with independent data from a Time Domain Reflectometry (TDR) probe. Such a probe provides a local measurement of the water content thanks to the measurement of the dielectric constant of the material.

Water Sowing and harvesting application for water management on the slopes of a volcano

The present study aims to elaborate a hydrogeological characterisation in the Water Sowing and Harvesting context. The study is focused on rural parishes in the Ecuadorian Andes that, despite their proximity to snow sources (Chimborazo glaciers), need more supply of this resource, to satisfy the demand of a population of 70,466 inhabitants. The study is based on hydrology and geomorphological analysis, a geophysical exploration, and a definition of water management strategies. The application of non-destructive geophysical methods and Geographic Information Systems support the hydrogeological study and the proposal of strategies for sustainable water management on the slopes of the Chimborazo volcano. An aquifer potential was identified (sand, gravel and fractured porphyritic andesites) with resistivity values between 51.3 and 157 Ω m at an approximate depth of 30 m from the geophysical characterisation addressed. This potential saturated zone is on the southern slope of the Chimborazo volcano within the hydrographic watershed, with favourable drainage networks for water accumulation. The aquifer shows a high-water saturation level but uncontrolled losses. As a consequence of these characteristics, alternatives for managing water resources are proposed, such as wells construction, using Water Sowing and Harvesting system methods (“camellones”) based on Nature-Based Solutions, dam construction and environmental education. The different proposals are associated with the four sustainability axes of Brundtland (economic, social, environmental and cultural axis) and contribute to the sixth objective of the Sustainable Development Goal 2030 Agenda.

Study on Rapid Inversion of Soil Water Content from Ground-Penetrating Radar Data Based on Deep Learning

Ground-penetrating radar (GPR) is an efficient and nondestructive geophysical method with great potential for detecting soil water content at the farmland scale. However, a key challenge in soil detection is obtaining soil water content rapidly and in real-time. In recent years, deep learning methods have become more widespread in the earth sciences, making it possible to use them for soil water content inversion from GPR data. In this paper, we propose a neural network framework GPRSW based on deep learning of GPR data. GPRSW is an end-to-end network that directly inverts volumetric soil water content (VSWC) through single-channel GPR data. Synthetic experiments show that GPRSW accurately identifies different VSWC boundaries in the model in time depth. The predicted VSWC and model fit well within 40 ns, with a maximum error after 40 ns of less than 0.10 cm3 × cm−3. To validate our method, we conducted GPR measurements at the experimental field of the Academy of Agricultural Sciences in Gongzhuling City, Jilin Province and applied GPRSW to VSWC measurements. The results show that predicted values of GPRSW match with field soil samples and are consistent with the overall trend of the TDR soil probe samples, with a maximum difference not exceeding 0.03 cm3 × cm−3. Therefore, our study shows that GPRSW has the potential to be applied to obtain soil water content from GPR data on farmland.

Capabilities of auxiliary techniques for low strain impact testing of piles foundations

Introduction. An increase in the complexity of tasks arising from the quality control of geotechnical structures ultimately increases the role of indirect methods as part of the survey set. Low strain impact testing of piles length and integrity is currently one of the most common non-destructive geophysical methods used in the state diagnostics of foundations. The capabilities and limitations of the method are associated with the peculiarities of its basic theoretical model describing the propagation of elastic waves in a thin rod. In this regard, specialists often have recourse to the auxiliary techniques of field research.Aim. To inform test engineers, designers and employees of supervisory organizations about the potential of auxiliary methods for the low strain impact quality control of pile foundations.Methods and materials. The features of the theoretical model of the low strain impact pile quality control, as well as the associated capabilities and limitations of the method are described. The auxiliary methods of data collection and analysis were used for the survey of pile foundations, including those in the composition of existing structures.Results. The results of the work are represented by additional information obtained about the foundations surveyed using the auxiliary methods of data collection and analysis. An alternative arrangement of sensors relative to the surveyed structure was used for determining the depth of piles in the composition of grade beam footings and existing structures. The common shot point profiling (ultra-seismic method) was used to assess the velocity of rod wave propagation in the body of the structure. The options of data presentation in the parallel seismic method were used to demonstrate its potential for the quality control of foundation concrete.Conclusion. The auxiliary methods of data collection and analysis used in the low strain impact survey of pile foundations can significantly increase the reliability of conclusions about the depth and integrity of a structural material.

Partitioning a rock mass based on electrical resistivity data: the choice of clustering method

SUMMARY The goal of data classification is to organize them into relevant groups using algorithms. In this study, two clustering algorithms are applied to classify a set of geophysical measurements performed around the Lascaux Cave (Dordogne, France). Based on a non-destructive geophysical method, electrical resistivity tomography (ERT), the data (resistivity values) are supposed to characterize the rock mass around the cave. The rock mass must be divided into an optimal number of homogeneous domains with specific thermal properties to integrate them in the future thermo-aeraulic simulations of the cave. Since the data are georeferenced, a given resistivity cluster corresponds to a specific spatial domain of the rock mass. This study aims to compare two different clustering methods, the Hierarchical Agglomerative Clustering (HAC) and the K-means methods, on the resistivity data set. Thus, the objective of this study is to determine which of the two methods leads to a partition of the massif with an optimal number of classes, allowing us to find the geological structures partially known thanks to previous studies. The results of these methods are analyzed in light of two different indices, the Silhouette Index (SI) and the Coefficient of Variation (CV). Based on these indices alone, K-means might seem to be the best algorithm, but a fine analysis of each cluster shows that the HAC method gives better results. Indeed, only the HAC method highlights areas already known to be either waterlogged or clayey. Our partial geological knowledge, which is of paramount importance in such a study, also supports the choice of the HAC method.

A New Electrical Resistivity Tomography Scheme of Borehole-to-Surface-to-Cliff Detection and Imaging for Grotto Rock Structure

Grotto rock structure detection is precondition of the grotto protection and restoration. As a stable and non-destructive geophysical method, electrical resistivity tomography (ERT) is extensively used to detect the geological structure of the grottoes. However, the traditional ERT measurement scheme is challenging to satisfy the requirements of high accuracy and high resolution in the cliff region. Therefore, we propose a new borehole-to-surface-to-cliff ERT (BSC-ERT) scheme for grotto detection. The sensitivity patterns of five ERT schemes using three configurations (A-MN array, AB-MN array, and AM-BN array) are tested to show the detection capability of different configurations. Two numerical experiments show that the combination of borehole-to-surface ERT (BS-ERT) and surface-to-cliff ERT (SC-ERT) schemes using AM-BN array have better imaging effects and a more reasonable detection range, which is recommended to be implemented for future work. In addition, the numerical experiment also proves that the symmetric effect generated in the AM-BN array in BS-ERT scheme can be suppressed with the combination of the SC-ERT scheme.

Broadband spectral induced polarization for the detection of Permafrost and an approach to ice content estimation – a case study from Yakutia, Russia

Abstract. The reliable detection of subsurface ice using non-destructive geophysical methods is an important objective in permafrost research. The ice content of the frozen ground is an essential parameter for further interpretation, for example in terms of risk analysis and for the description of permafrost carbon feedback by thawing processes. The high-frequency induced polarization method (HFIP) enables the measurement of the frequency-dependent electrical conductivity and permittivity of the subsurface, in a frequency range between 100 Hz and 100 kHz. As the electrical permittivity of ice exhibits a strong characteristic behaviour in this frequency range, HFIP in principle is suitable to estimate ice content. Here, we present methodological advancements of the HFIP method and suggest an explicit procedure for ice content estimation. A new measuring device, the Chameleon-II (Radic Research), was used for the first time. Compared to a previous generation, the new system is equipped with longer cables and higher power, such that we can now achieve larger penetration depths up to 10 m. Moreover, it is equipped with technology to reduce electromagnetic coupling effects which can distort the desired subsurface signal. The second development is a method to estimate ice content quantitatively from five Cole–Cole parameters obtained from spectral two-dimensional inversion results. The method is based on a description of the subsurface as a mixture of two components (matrix and ice) and uses a previously suggested relationship between frequency-dependent electrical permittivity and ice content. In this model, the ice relaxation is considered the dominant process in the frequency range around 10 kHz. Measurements on a permafrost site near Yakutsk, Russia, were carried out to test the entire procedure under real conditions at the field scale. We demonstrate that the spectral signal of ice can clearly be identified even in the raw data and show that the spectral 2-D inversion algorithm is suitable to obtain the multidimensional distribution of electrical parameters. The parameter distribution and the estimated ice content agree reasonably well with previous knowledge of the field site from borehole and geophysical investigations. We conclude that the method is able to provide quantitative ice content estimates and that relationships that have been tested in the laboratory may be applied at the field scale.

Příklady uplatnění nedestruktivních geofyzikálních měření při průzkumech raně středověkých hradišť na území Přemyslovské domény i širších Čech

For several decades, the Institute of Archaeology in Prague has used non-destructive geophysical methods to research fortifications. New cooperation between archaeologists and geophysicist as part of a Czech-Polish project resulted in a more systematic and targeted survey of early medieval fortifications. The results of this cooperation were presented at a workshop Use of non-destructive and destructive methods in archaeological research of early medieval hillforts, held in Prague in 2019. The mainpart of this article contains different examples of geophysical prospecting used in connection with archaeological research into the early medieval fortifications in Bohemia. Selected examples illustrate various conditions, combinations and possibilities of application of non-destructive geophysical methods. In several cases, the results of geophysical measurements can also be supplemented by the results of archaeological research or surveys.

Automatic Hyperbola Detection and Apex Extraction Using Convolutional Neural Network on GPR Data

Ground Penetrating Radar (GPR) is a non-destructive geophysical method used for subsurface mapping. It is frequently used for detecting buried cylindrical objects such as underground pipes and cables. Buried cylindrical objects show a hyperbolic signal pattern on a radargram. The typical shape of the hyperbolic reflections depends on the depth and material of the buried objects and the surrounding materials. In many cases, detecting buried cylindrical objects is quite a time-consuming task, thus limiting further interpretation procedures. In this paper, we propose a new method for automating hyperbola detection and apex extraction on radargram. Our work consists of two modules that take radargram as input in a form of images. In the first module, we used the Faster-RCNN to extract the hyperbola segments as a set of rectangular boundary boxes. The network was trained using synthetic radargram data simulated by the gprMax software. The second module is to estimate the coordinates of the hyperbola apex using an image processing technique. We had correctly detected all hyperbola on the simulated radargram from the test set. For the test on field radargram, the framework is capable of processing radargram that is similar to the simulated radargram data. The problem with the second module occurs on interference hyperbola as the searching window is disturbed by the noise. Apart from those problems, by using these two modules, the detection of buried cylindrical objects using GPR can be automated with a minimal amount of time.

Background clutter amplitude and frequency of GPR signals to analyse water content in sedimentary deposits: Urban infrastructure environment

Soil site studies are crucial in the analysis of seismic hazard in populated areas. This study focusses on the use of the Ground Penetrating Radar as a non-destructive geophysical method to analysis the water content of a sedimentary basin of a local urban area in Cervantes Parks in Barcelona city. Main objective of this work is to understand further the local seismic soil site, and analysis the background clutter amplitude and frequency of the GPR signal applied on the seasonal changes of the underground water content. Changes produces in the GPR signal could be associated to the changes of the ground material due to the existence of water content and water flow, which influence the grain size distribution of the soil characterisation.Previously, several methodologies have been applied to determine the changes of the ground material due to the existence of water content and most importantly effect of the seasonal changes on the soil characterisation. GPR has been applied as a new technology and non-invasive to further analysis water content in shallow geology. Methodology applied on this study compromised in four different phases; Two seasonal data collection using 100 MHz centre frequency shielded antenna in both dry and wet season, radar images are proceeded with common post-processing approaches, following more innovative processing approach based on the Fast Fourier Transform (FFT) method in order to analysis background clutter amplitude and frequency spectrum to achieve an accurate interpretation of underground water content activities, in conclusion a comparative study of the results driven from radar images are elaborated considering historical knowledge. Results show that GPR is an efficient technique to analysis water content invasively considering low frequency antennas to achieve deeper penetration depth in sedimentary deposits, and predict shifting and increasing of the underground streams due to changes in weather conditions. Results could contribute to the enhancing local seismic site behaviour in populated areas considering continuous monitoring of underground water activities in sedimentary basin sites.

Self-Supervised Deep Learning for 3D Gravity Inversion

The gravity method is one of the non-destructive geophysical methods, which aims to estimate the 3D subsurface density distribution of geological bodies from the observed 2D surface gravity anomalies. Recently, deep learning has achieved great success in solving ill-posed problems including gravity inversion. The limitation of the current deep learning methods for gravity inversion is the difference between synthetic and field data. Thus, we introduce a self-supervised estimation method for 3D gravity inversion (SSGI). SSGI learns the field data directly by closed-loop of the inversion model and forward model. The proposed inversion model contains an encoder, an expander, a decoder, and a 3D refiner. Since the forward model is built according to the law of universal gravitation, SSGI can optimize the inversion model by minimizing the mean absolute error of the original and reconstructed gravity anomalies. Besides, SSGI constrains the inversion model by a guide-line in the auxiliary loop. Since the guide-line corresponds to the sampling or average of the density matrix, minimizing the mean absolute error between the original guide-line and the generated guide-line can reduce the uncertainty of inversion. The experimental results demonstrate that the proposed SSGI achieves state-of-the-art performance in 3D gravity inversion.

Laboratory Assessment of Chemical Characteristics using Electrical Resistivity (ER) Technique in Highway Construction

Electrical Resistivity (ER) technique was applied for simulation model constructed at University of Technology / Civil Engineering Department Laboratories, Baghdad-Iraq. The study aims to determine the relationship between changing the chemical properties of the soil and the resistivity of soil layers using 1-D VES. ER has been chosen as a nondestructive geophysical survey method to identify some soil characteristics without destructing the soil by making surface measurements using Wenner configuration. The obtained data results showed that there is a relationship between ER and some soil characteristics. The ER values change with the change of soil properties. Two models were created. In the first model, the ER was measured without changing any of the soil characteristics, and it was with optimum water content. In the second model, 5% of the sodium chloride salt was added to the soil after dissolving with water then the ER was measured. It was found that after adding the salt, the ER is decreased significantly, and thus the ER was affected by the addition of the salt.

Hydrogeophysical Assessment of the Critical Zone below a Golf Course Irrigated with Reclaimed Water close to Volcanic Caldera

The geometry and the hydraulic properties of the unsaturated zone is often difficult to evaluate from traditional soil sampling techniques. Soil samples typically provide only data of the upper layers and boreholes are expensive and only provide spotted information. Non-destructive geophysical methods and among them, electrical resistivity tomography can be applied in complex geological environments such as volcanic areas, where lavas and unconsolidated pyroclastic deposits dominate. They have a wide variability of hydraulic properties due to textural characteristics and modification processes suh as compaction, fracturation and weathering. To characterize the subsurface geology below the golf course of Bandama (Gran Canaria) a detailed electrical resistivity tomography survey has been conducted. This technique allowed us to define the geometry of the geological formations because of their high electrical resistivity contrasts. Subsequently, undisturbed soil and pyroclastic deposits samples were taken in representative outcrops for quantifying the hydraulic conductivity in the laboratory where the parametric electrical resistivity was measured in the field. A statistical correlation between the two variables has been obtained and a 3D model transit time of water infiltration through the vadose zone has been built to assess the vulnerability of the aquifers located below the golf course irrigated with reclaimed water.

Georadar method for detecting underground septic tank

The Ground Penetrating Radar (GPR) method commonly known as Georadar, a nondestructive geophysical method that uses electromagnetic waves. This method is widely used to determine conditions under the surface such as mapping structures and subsurface lithology or buried objects. In this study, the GPR measurement using Geoscanners AKULA A9000 + Antenna GCB3070 is conducted to detect the presence or capacity of a septic tank. The GPR data were initially processed using matGPR based on MATLAB. GPR data on each measuring line is processed first, a series of filters and gaining have been conducted such as Adjust Signal Position, Remove DC, Dewow, Inverse Amplitude Decay, Remove Global Background, Karhunen-Loeve Filter, then time to depth conversion with adjusted parameters. From the result of parameter analysis in processing data, found that the GPR data can be interpreted which show the underground septic tank in the study area with the presence of diffraction signatures.

QUALITY ASSURANCE OF DIAPHRAGM AND PILE WALLS BY GEOPHYSICS

Underground structures like diaphragm and pile walls are constructed to organize waterproof curtains, protect pit sides, and transfer loads from the structures. Violations of the construction technological process can lead to the formation of defects. To prevent adverse consequences, before excavation, it is necessary to control the integrity of the slurry walls using non-destructive geophysical methods. A review of geophysical slurry wall quality control methods based on the excitation and registration of physical fields through access tubes installed in the reinforcement cage, in wells drilled near the structure or on the surface of the structure, is presented. The main capabilities and limitations of the methods are given. Cross-hole ultrasonic logging was used to study the section of the slurry wall during the construction of the Moscow Metro station. The results of parallel soundings made it possible to identify anomalous zones, interpreted as defects. The geometric dimensions of one of the major defects were refined by ultrasonic tomography. For the first time in Russian testing practice, thermal integrity profiling was applied to study the diaphragm wall at the base of a residential building. The results of temperature monitoring during the concrete hardening are presented. According to the method, a major flaw, excess of the design mark of the wall bottom and bulging of the structure were revealed. The results of thermal integrity profiling were verified by ultrasonic logging. The combined use of thermal and ultrasonic methods can be recommended as a reliable tool for integrity testing of diaphragm and pile walls. To carry out the measurements, the access tubes shall be included in the reinforcement cage of the structure at the design stage.

Archaeological Investigation at the Urartian Sites of Bastam Castle Using Magnetics Method

Archaeological Investigation at the Urartian Sites of Bastam Castle Using Magnetics Method

Assessment of the Contact between Piles and Soil via the Dynamic Attributes of Acoustic Signals

Abstract—The low-strain impact method is one of the most commonly used nondestructive geophysical methods in pile integrity testing. Data analysis of the low-strain method in the frequency domain allows a researcher to obtain additional information about a foundation. The authors of this article propose a methodology for assessing the contact of piles with soils based on an analysis of the dynamic attributes of the frequency response. Conclusions drawn from using the above-described method can be used by engineers to study the quality of piles and to plan direct static load tests to determine the bearing capacity of piles.