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Results of apparent resistivity imaging and DTV imaging for model 3. Results of apparent resistivity imaging for (a) case 1, (b) case 2, and (c) case 3. Results of DTV imaging for (d) case 1, (e) case 2, and (f) case 3. In case 1, one of the anomalous bodies is resistive and the other is conductive. In case 2, both anomalous bodies are conductive. In case 3, both anomalous bodies are resistive. White dashed lines indicate the position of the anomalous bodies.
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The ground–airborne frequency–domain electromagnetic (GAFDEM) method is a recently developed rapid detection approach for underground structures. However, the conventional apparent resistivity imaging in this method cannot meet the requirements of high precision and high efficiency detection for 3D targets. Therefore, we introduce the divergence of...
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Context 1
... DTV imaging is more effective for detecting anomalous bodies compared with apparent resistivity imaging. Figure 7 shows the imaging results of model 3. Figure 7(a-c) are the results of apparent resistivity imaging, and Figure 7(d-f) are the results of DTV imaging. There are no evident features around the two atypical bodies in apparent resistivity imaging. ...
Context 2
... DTV imaging is more effective for detecting anomalous bodies compared with apparent resistivity imaging. Figure 7 shows the imaging results of model 3. Figure 7(a-c) are the results of apparent resistivity imaging, and Figure 7(d-f) are the results of DTV imaging. There are no evident features around the two atypical bodies in apparent resistivity imaging. ...
Context 3
... DTV imaging is more effective for detecting anomalous bodies compared with apparent resistivity imaging. Figure 7 shows the imaging results of model 3. Figure 7(a-c) are the results of apparent resistivity imaging, and Figure 7(d-f) are the results of DTV imaging. There are no evident features around the two atypical bodies in apparent resistivity imaging. ...
Context 4
... the simulation, the distance between adjacent observation points is set to be 5 m. Thus, each subgraph contains 81 × 81 data points in Figure 6, and contains 81 × 121 data points in Figure 7. For each subgraph in Figure 7, the apparent resistivity imaging time is 1140 s and the DTV imaging time is 6 s. ...
Context 5
... each subgraph contains 81 × 81 data points in Figure 6, and contains 81 × 121 data points in Figure 7. For each subgraph in Figure 7, the apparent resistivity imaging time is 1140 s and the DTV imaging time is 6 s. The DTV imaging time is considerably shorter than the apparent resistivity imaging time. ...
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Citations
... Relying solely on drilling methods for landslide investigations in complex mountainous terrains is inefficient, costly, and not feasible on a large scale. In recent years, geophysical exploration methods have made significant strides in developing exploration instruments, as well as in digital signal acquisition, processing, and analysis techniques [11][12][13][14][15]. The signal-to-noise ratio and resolution have gradually improved, and the application fields are continuously expanding. ...
The Meijiayan landslide in Pengshui County within Chongqing City is a medium-scale soil landslide triggered by the excavation of roadbeds. To delve into the influencing factors and assess the stability of this landslide, it is crucial to meticulously map the subterranean geological framework of the area. Such an analysis lays the groundwork for evaluating and mitigating the risks of future landslide instabilities. In this context, the semi-airborne transient electromagnetic method (SATEM), which is complemented by a receiving system mounted on an aerial platform, stands out as an innovative geophysical exploration technique. This method is adept at conducting swift measurements across complex terrains, making it particularly valuable for areas prone to such geological events. This paper presents the utilization of a cutting-edge loop source SATEM system, which was operationalized via a rotor-based unmanned aerial vehicle (UAV). The system was employed to conduct shallow geological structure detection experiments on the Meijiayan landslide. The SATEM detection outcomes have unveiled fluctuations in the electrical distribution across the upper strata, which are indicative of the subsurface geological boundaries, faults, and areas potentially rich in water within the landslide region. These discoveries affirm the viability of utilizing loop source SATEM for the identification of shallow geological structures in regions susceptible to landslides. The findings indicate that while the landslide is currently in a stable condition, it poses a significant risk of movement, especially during the rainy season, with the potential for landslides to be exacerbated by extreme or sustained rainfall events.
... On the other hand, airborne electromagnetic methods can swiftly detect geological structures without being hindered by ground factors. However, the detection depth of the airborne electromagnetic method is relatively shallow due to limitations such as the drone load capacity and launch power [8]. To enhance the detection depth, the semi-airborne electromagnetic method (SAEM) was employed. ...
The development of underground artificial cavities plays an important role in the exploitation of urban spatial resources. As the rapidly growing number of underground artificial cavities with different depths and scales increases, the detection and identification of underground artificial cavities has become a key issue in underground engineering studies. Geophysical techniques have been widely used for the construction, management, and maintenance of underground artificial cavities. In this study, we present two identification methods for underground artificial cavities. Apparent resistivity imaging is the most popular technique for quickly identifying underground artificial cavities, using the forward simulation results of a three-dimensional earth model and comparing these with the preset positions of artificial cavities, as demonstrated in the experiment. To further improve the efficiency of underground artificial cavity identification, we developed a fast recognition approach for underground artificial cavities based on the Bayesian convolutional neural network (BCNN). Compared to a traditional convolutional neural network, the performance of the BCNN method was greatly improved in terms of the classification accuracy and efficiency of identifying underground artificial cavities with apparent resistivity image datasets.
... Mineral resources became an important basis for social development [2]. The ground-airborne frequency domain electromagnetic (GAFDEM) method is suitable for detecting resource distribution and geological structure by a grounded electrical source and an airborne receiver [3]. This technique is practical and suitable for large surveying areas with challenging ground conditions that are difficult or dangerous to access for traditional ground surveys [4]. ...
The vertical component magnetic field signal in the ground–airborne frequency domain electromagnetic (GAFDEM) method is detected by the air coil sensor, which is parallel to the ground. Unfortunately, the air coil sensor has low sensitivity in the low-frequency band, making it challenging to detect effective low-frequency signals and causing low accuracy and large error for interpreted deep apparent resistivity in actual detection. This work develops an optimized weight magnetic core coil sensor for GAFDEM. The cupped flux concentrator is used in the sensor to reduce the weight of the sensor while maintaining the magnetic gathering capacity of the core coil. The winding of the core coil is optimized to resemble the shape of a rugby ball, taking full advantage of the magnetic gathering capacity at the core center. Laboratory and field experiment results show that the developed optimized weight magnetic core coil sensor for the GAFDEM method is highly sensitive in the low-frequency band. Therefore, the detection results at depth are more accurate compared with those obtained using existing air coil sensors.
... The secondary field is the response of the anomaly body excited by the background field. The total field is defined as the sum of the background and secondary fields [13,14]. The GAFDEM apparent resistivity imaging method provides rapid imaging of subsurface electrical structures, but the method cannot effectively recognize anomaly boundaries. ...
Ground-airborne frequency domain electromagnetic (GAFDEM) is an important tool for mineral resource exploration and geological surveys in complex mountainous areas. The rapid and high-precision calculation of background resistivity is the foundation for high-resolution imaging. Due to the influence of attitude noise, the current accuracy of background resistivity calculations is not high. Furthermore, when the measurement area is large and the terrain is complex, the need to establish a terrain model for the measurement area leads to a decrease in efficiency. To solve the above problems, this paper proposes a method to calculate the background resistivity using the total magnetic intensity. Firstly, the magnetic field component is analyzed for its ability to identify anomalies, then the effects of transmitting frequency and source-receiver distance parameters are analyzed, and finally, simulation experiments and field experiments are conducted. Simulation experiments show that the method of calculating background resistivity using total magnetic intensity can accurately calculate the background resistivity of the double anomaly model and the model with topographic relief compared with the current method. Field experiments show that compared with the current method, the total magnetic intensity method of calculating background resistivity is not affected by attitude noise, and the results of background resistivity calculation are consistent with the real results with higher accuracy. The method in this paper supports GAFDEM to realize high-resolution and fast exploration of underground structures.
Marine controlled source electromagnetic (MCSEM) detection is an effective technique for detecting submarine mineral resources. Aiming at the problems of weak transmission energy and low signal-to-noise ratio due to the double suppression of high-frequency signals by inductive coils and strong attenuation of seawater as well as the low efficiency of conventional single-frequency transmitting methods, we propose a three-component coupled transmission system with resonance compensation applied to MCSEM detection. This system can transmit three-frequency signals with significantly higher electric current main frequency energy. The proposed scheme is effective in increasing the magnetic field strength. The superiority of the proposed scheme in terms of less impact when the component value deviates is demonstrated. Firstly, the MCSEM detection method is introduced, and the magnetic field in the space generated by the three-component coupled coil is analyzed by means of mathematical analysis. Secondly, the circuit model of the three-component coupled transmitting system is given, and compared with the conventional scheme and three-frequency resonance scheme. Finally, simulations and laboratory experiments are conducted on the proposed three-component transmitting system to verify its feasibility and effectiveness. The results show that the proposed scheme can significantly increase the current mains frequency energy, and the maximum gain rate can reach 373.0 %. Compared with the three-frequency resonance scheme, the proposed scheme can achieve a maximum gain rate of 29.8 %.
Ground-airborne frequency-domain electromagnetic (GAFDEM) rapid imaging method holds the potential for swiftly detecting underground anomalies in complex terrains at great depths. However, the current GAFDEM rapid imaging methods have not yet achieved satisfactory detection results in actual complex terrains. This is primarily due to two reasons: 1. The detection environment in complex terrain involves non-horizontal land and significant relief caused by the presence of mountains. However, current GAFDEM rapid imaging methods fail to consider the influence of terrain on imaging effectiveness. 2. In controlled-source electromagnetic detection, the design of the observation scheme directly affects the detection effectiveness of imaging methods. In actual detection, terrain constraints limit the design of observation schemes. For GAFDEM, the design of its transmitting sources is greatly influenced by terrain since these sources need to be deployed on the ground. Addressing these issues, this study analyzes the challenges faced by the Space Magnetic Gradient Anomaly (SMGA) in complex terrains, which exhibits effective detection under a horizontal ground model. Based on the analysis results, an optimization method for SMGA in complex terrains is proposed. This method achieves rapid correction of the background field in SMGA, thereby enhancing its detection efficacy in complex terrains and enabling the effective identification of underground electrical anomalies. Furthermore, performance testing of the optimized SMGA (O-SMGA) demonstrated that O-SMGA exhibits excellent applicability. Subsequently, an examination is performed on multiple parameters of the transmitting source assessing their effects on the imaging performance of O-SMGA. Based on the analysis results, design guidelines for GAFDEM transmitting sources in complex terrains applicable to O-SMGA are provided to further enhance its detection effectiveness in actual detection. Finally, a synthetic test of O-SMGA and the transmitting source design guidelines is conducted using models with actual terrain data and actual experimental results. The results indicate that these methods still exhibit excellent performance in actual detection applications.
