bluuebunny/crossref_metadata_2025_split huggingface dataset:
Research on highly sensitive electromagnetic method based on balance coil for underground metal detection
Authors: Zhang Bo , Yin Guangyao , Zhang Yang , Lin Jun 
Published: February 2021

Abstract
In order to solve the problem of low signal-to-noise ratio and serious primary field interference of frequency domain electromagnetic system for urban underground metal, a balanced coil structure based on LC resonance technique is proposed in this paper. The proposed technique uses the balance coil to eliminate the interference of the primary field, and LC resonance technique is adopted to increase the signal amplitude and improve the signal sensitivity and signal-to-noise ratio. An experiment was conducted by the system built on this proposed technique. The results show that the primary magnetic field can be suppressed by the balance coil and the signal-to-noise ratio can be improved by LC resonance technique through experiments.
Feasibility study of detecting gas leakage in buried pipeline based on resistivity method
Authors: Sun Binyang , Zhang Pingsong , Guo Liquan , Fu Maoru , Fu Ming , Cheng Wenkang 
Published: February 2021

Abstract
Urban gas pipe networks are mostly buried underground and it is hard to monitor, detect and locate the leakage area effectively. The primary structure of the soil could change before and after aeration, so the detection method of gas leakage based on resistivity method has some physical basis. Based on the theoretical research of the predecessors, corresponding geoelectric model is established by combining two typical gas leakage geological models to study the influences of testing device, leakage mode and leakage intensity on the distribution characteristics of gas leakage geoelectric field. Obtained by using forward and inverse numerical computation methods, the theoretical resistivity profile image is compared with the resistivity profile measured by outdoor gas leakage simulation experiment to evaluate comprehensively the feasibility and effectiveness of detecting gas leakage of buried pipelines based on resistivity differential characteristics. The research results show that resistivity method could describe the spatial distribution location effectively and the electrical resistivity has positive correlation with leakage pressure. And the pressure inside the pipeline also determines the migration path of the gas leakage, which diffuses outwards in the shape of “smoke ring” in high-pressure leakage.
Research on towed TEM on off-centre self-compensation technology for urban underground space detection
Authors: Zhang Yang , Lin Jun 
Published: February 2021

Abstract
Transient electromagnetic (TEM) is a geophysical method that can obtain the electrical information of underground media. It will provide strong technical support for the safe development and operation of urban underground space. However, the coupling effect of the transmitting current on the receiving loop leads to the shallow blind area of TEM. Especially, the coupling effect is more serious when the multi-turn and small-size coil structure is required because of the limitation of urban buildings and ground facilities. To solve these problems, this paper proposes a towed TEM technology based on off-centre self-compensation with the small size structure. The new technology adopts the idea of non-coplanar eccentricity structure to design a self-compensation system, which can eliminate the coupling effect. In this paper, the distribution of primary field in receiving coil is studied, and the key structural parameters of transmitting coil and receiving coil is obtained by theoretical model. The experimental results show that the towed TEM system based on the new technology can directly obtain pure secondary field signal. Compared with other TEM structures, it has higher tolerance for physical size error and higher practicability. The towed TEM technology proposed in this paper will provide a theoretical basis for the realization of blind area free, high-speed and accurate scanning measurement of urban underground space.
Wavefield reconstruction inversion in the frequency domain of on-ground GPR data
Authors: Feng Deshan , Ding Siyuan , Wang Xun 
Published: February 2021

Abstract
Full waveform inversion (FWI) is one of the most promising techniques for the quantitative characterization of the shallow subsurface of the Earth. However, the conventional FWI with the reduced approach is highly nonlinear, a challenging source of which is the cycle skipping. It would drive FWI to spurious local minima as soon as the initial model parameters are not accurate enough. By introducing a non-negative penalty term and a penalty parameter, wavefield reconstruction inversion (WRI) extends the search space of full waveform inversion, relaxes the requirement to satisfy exactly the wave equation at each iteration, and mitigates some of the problems related to poor start models, which leads to the cycle skipping phenomenon. Moreover, WRI breaks down FWI into two linear sub-problems and reconstruct the wavefield and estimate the model parameter in a loop and there is no need to update and store the wavefield. In this paper, we perform the model reconstruction of on-ground GPR using WRI in the frequency domain by inverting data of a limited number of frequency components, and compare the results of it with that of the conventional FWI. With a limited illumination of the subsurface, WRI with small penalty parameters has a positive performance.
Estimating water content of unsaturated sandy soils by GPR during a drainage experiment
Authors: Zhang M. H. , Bano M. , Feng X. , Lesparre N. , Girard J. F. , Razakarisoa O. , Belfort B. , Lehmann F. , Friedmann P. 
Published: February 2021

Abstract
This study shows how to estimate water content of unsaturated sandy soils from ground-penetrating radar (GPR) data acquired during water drainage experiment. Using the Topp equation, water content can be converted to dielectric permittivity. Afterwards, based on 1D forward modeling method a GPR synthetic trace is generated. Finally, a trial-and-error match of modeled and observed GPR traces was performed to estimate the optimum set of parameters characterizing the materials composing the soil. According to the comparison of the modeling signal and the real signal, we go back to update the water content. Repeating the procedure until the modeling signal fits the real signal very well. We used this procedure to obtain the evolution of water content of unsaturated sandy soils. The method is presented on drainage experiment carried out on unsaturated sandy soil of a large-controlled experimental site. In order to follow the change of the water level, we measured GPR profiles at different times and picked up four GPR profiles, then the same trace (No. 700) were picked up on each GPR profile and estimated the water content from each signal.
Calibration of Interface Induced Polarization for Full Polarimetric Ground Penetrating Radar
Authors: Dong Zejun , Feng Xuan , Liu Cai , Liang Wenjing , Zhou Haoqiu 
Published: February 2021

Abstract
The traditional ground penetrating radar (GPR) uses only one type of antenna for data acquisition, and only obtains single polarization data of targets. It can not fully describe the various properties of the target. Full polarimetric GPR is a new technology that uses four different polarization antennas to measure the target and can receive electromagnetic waves of different polarized directions to describe the polarization effect of targets. However, when the plane electromagnetic wave propagates through the ground surface, the polarized direction will rotate, namely interface induced polarization (IIP), which results in the complex interference embedded in the full polarimetric GPR data. In this research, firstly we discuss the generation of the IIP; subsequently how the IIP affect the full polarimetric GPR data is derived; finally the calibration formula is proposed and is applied to the GPR data processing.
Research and design of tripod-shaped UWB antenna for GPR
Authors: Chen Sibo , Jia Wenfeng , Lin Jun , Zhang Yang 
Published: February 2021

Abstract
In recent years, GPR (Ground Penetrating Radar) has developed rapidly and has played an important role in many fields. As a key part of GPR, the antenna directly affects system performance. A suitable antenna can greatly improve the detection results. To this end, this paper introduces the design of GPR tripod-shaped ultra-wideband antenna based on bow tie antenna. The working bandwidth of the antenna is widened by means of structural loading with truncation as the main part and circular slot at the end of the antenna. Antenna optimization and simulation were performed using ANSYS HFSS (High Frequency Structure Simulator), and the effects of antenna arm truncation length on antenna performance were discussed. Simulation results show that the designed antenna has an operation bandwidth of 700MHz ~ 2GHz and good directionality. It is a miniaturized ultra-wideband antenna suitable for shallow underground pipeline detection.
Passive surface wave imaging with ultrashort noise records in urban areas
Authors: Zhang Hongyu , Xia Jianghai , Pang Jingyin , Cheng Feng , Xing Huaixue 
Published: February 2021

Abstract
Passive surface-wave methods are widely used in urban areas because of their economic efficiency. It usually needs long-time observation to provide phase velocity information at frequencies ranging from several Hz to several tens of Hz. A complex urbanized environment, however, leads to a reduction in acquisition time. Consequently, it’s necessary to extract surface waves with ultrashort traffic noise for engineering applications. Although noise segments are limited in the circumstance of ultrashort acquisition, we still need data selection to avoid stacking neutralization of data with a different signal-to-noise ratio (SNR). Then we compare linear stacking, phase-weighted stacking (PWS), and time-frequency phase-weighted stacking (tf-PWS) through processing one-minute noise records after selection. We can obtain clear and continuous dispersion energy with these three methods. Our results indicate that PWS or tf-PWS has better performance than linear stacking by comparing dispersion energy images, and PWS improves SNR most, strongly contrasting before and after selection.
3D FV Simulation of the Orthogonal Azimuth Electromagnetic Tool Response Logging While Drilling with Multi Annular Grooves Using Potentials
Authors: Yu Lei , Wang Haosen , Wang Hongnian , Yang Shouwen , Yin Changchun 
Published: February 2021

Abstract
In this paper, we use the 3D cylindrical finite volume (3D FV) method to simulate the Orthogonal Azimuth Electromagnetic Tool (OAEMT) responses Logging While Drilling (LWD) according to the special structure of the OAEMT with multi annular grooves. The algorithm allows the solution of the 3D Maxwell’s equation in inhomogeneous media with arbitrary conductivity and magnetic permeability distributions. For improvement of the computational efficiency and the modeling accuracy of the responses of OAEMT with annular grooves filled with ferrite material on steel mandrel in a completely anisotropic media, several techniques are applied: 1) a 3-D cylindrical irregular grid to avoid stair-casing discretization errors in the transmitter, receiver, and mandrel geometries; 2)the electric field continuation to approximate the perfectly electric conducting (PEC) boundary condition for enhancement of the discrete accuracy of the Helmholtz equations on the surface of steel mandrel; 3)the standardization technique to determine the equivalent conductivity and permeability in a non-uniform element; 4) PARDISO direct solver to solve the discrete equation as far as possible for increase of solution stability. We validate the 3D FV results against the numerical mode matching method. The comparisons show very good agreement. Results from 3-D borehole problems in several complex formation conditions involving eccentric tools and dipping beds are given to demonstrate the robustness of the method.
A Co-offset GPR Data Inversion Based on Ray Theory
Authors: Xue Meiqi , Liu Sixin , Lu Qi , Li Hongqing , Wang Yuanxin 
Published: February 2021

Abstract
We use Monte Carlo method to establish a randomly undulating homogeneous layered medium model. Then the co-offset GPR data for the built geological model is simulated by FDTD. The ray-tracing based inversion is applied for interval velocity estimation. During the inversion, the offset between antennas, the velocity value of the first layer, the picked amplitudes values of each reflection layer and reference amplitude are the input data. The thickness and velocity of each layer are calculated by this recursive method. It is proved that this inversion method is feasible for the layered geological model with random undulation, and the fact that undulation, i.e. RMS height and correlation length, influences the inversion results is discussed.
Quasi-3D TEM inversion based on lateral constraint
Authors: Yang Yunjian , Wang Xuben , Liu Xuejun , He Zhangxiang , Mi Xiaoli 
Published: February 2021

Abstract
Quasi-2D inversion based on a lateral constraint is an effective technique for the interpretation of the survey data of transient electromagnetic method (TEM). In this paper, the principle of the lateral constraint is introduced to construct a quasi-3D TEM inversion. Considering that the 3D measuring grid is often not strictly regular, the quasi-3D TEM inversion is constructed using the distance-weighted adjacent stations’ lateral constraint, which can suppress the irrational model mutation generated by single-station 1D inversion, and has no requirement concerning the regularity of the 3D measuring grid. The application in the inversion of field TEM data had verified the effectiveness of this method.
Estimation of near-surface shear-wave velocity by joint inversion of dispersion and HVSR curves of Rayleigh waves from multicomponent active-seismic records
Authors: Mi Binbin , Xia Jianghai 
Published: February 2021

Abstract
The multichannel analysis of surface waves (MASW) method has been widely used for near-surface geophysical and geotechnical studies by using the dispersive characteristics of Rayleigh waves to determine subsurface shear-wave velocity. Commonly, Rayleigh waves are obtained only from the vertical component of P-SV waves. However, the multimodal Rayleigh waves estimated from the horizontal (radial) component data have a different energy distribution compared with those estimated from the vertical component data. The horizontal-to-vertical spectral ratio (HVSR) of Rayleigh waves can be calculated from multicomponent active-seismic records after mode separation. The HVSR peak and trough frequencies are very sensitive to model parameters. We propose to estimate near-surface shear-wave velocity by joint inversion of dispersion and HVSR curves of Rayleigh waves from multicomponent active-seismic records. The proposed joint inversion method can combine the strengths of MASW and HVSR analysis methods. A synthetic example demonstrates that our proposed joint inversion method can provide better constrained and more reliable S-wave velocity in the shallow subsurface.
Application of gravity exploration in urban active fault detection
Authors: Ming Yuanyuan , Niu Xue , Xie Xinglong , Han Zhaohong , Li Qiuchen , Sun Sheng 
Published: February 2021

Abstract
Active faults are a major source of danger for destructive earthquakes. It is an important task for urban earthquake disaster prevention to find out the spatial location and structural attributes of active faults. At present, the most effective geophysical exploration method for detecting and locating urban concealed active faults is shallow seismic exploration, while other geophysical exploration methods are seldom used. In the detection of active faults in Shanghai, seismic exploration is greatly influenced by human factors in urban areas and the efficiency is low. In this paper, through the comparison and analysis of the alignment of seismic and gravity, it is found that the interpretation results of gravity exploration have a good correspondence with the fault structures interpreted by shallow seismic exploration. At the same time, gravity method reveals that there may be other fault anomalies near the fault anomalies identified in previous literature. It illustrates the effectiveness and feasibility of high-precision gravity detection methods in the detection of urban active fault, and also provides important reference significance for active fault detection in other regions.
Urban near-surface imaging from ambient noise tomography using dense seismic networks
Authors: Zhou Changjiang , Xia Jianghai , Zhang Hongyu , Pang Jingyin , Liu Ya , Xi Chaoqiang , Ning Ling , Mi Binbin , Xing Huaixue , Chang Xiaojun 
Published: February 2021

Abstract
It is of scientific and engineering significance to extract surface wave signals from urban ambient noise for fine-scale three-dimensional velocity structure imaging of underground medium. A series of issues such as ambient noise characteristics in urban environment, observation system design and resolution of small-scale imaging, have put forward a lot of new requirements and challenges to traditional methods and technologies. We utilized the dense array with its aperture extend below hundred meters in Hangzhou urban area, to carry out the ambient noise data acquisition experiments within one day. Based on the time-frequency analysis of noise cross-correlations, we conducted surface wave travel time tomography. Finally, the phase velocity slices were inverted to build a three-dimensional S-wave velocity structure, and the profiles were compared with the drilling data for validations. We concluded that these geometry and processing parameters adopted in the urban environment are feasible for near-surface tomography and can meet the demands of three-dimensional geological survey in cities efficiently.
Weighted adaptive finite-element method for 3D transient EM modelling
Authors: Zheng Jianbo , Jia Yajuan , Wang Juanjuan , Liu Yunhe , Qi Yanfu 
Published: February 2021

Abstract
As we know, grid quality can produce big effect on the numerical precision of 3D forward modeling. How to generate high-quality grids becomes the key for high-accuracy EM responses. So we develop a weighted adaptive finite-element method based on hybrid posterior error estimation in combination with unstructured vector finite-element method and Backward Euler scheme. We introduce a weighting factor to adjust the relative weight of posterior errors defined by the continuities of normal current density and tangential magnetic field to create an effective mesh. The numerical experiments on a conductive cube model show that our algorithm performs better than the traditional adaptive method.
A new approach for accurate detection of leakage paths from multiple-wenner arrays inverted resistivity imaging in embankment dam
Authors: Jiang Xiaoyi , Tan Lei , Jiang Shuhai , Lai Sheng 
Published: February 2021

Abstract
Aiming at the difference of hidden danger identification of embankment dams by different arrays of high-density electrical method, a combined inversion method of wenner data volume is proposed to improve the resolution capability of target. The response characteristics of α, β and γ array to the preset model are presented by constructing the geoelectric model of the dam body and the potential leakage hazard in the contact zone. According to the simulation results, different arrays have different detection effects on the same target and the same array has different detection effects on different targets. β array reflects better effect of low resistance area, and γ array is more suitable for dividing dam body boundary, but both have weak anti-interference ability. In addition, the spatial feature information of the target by multiple-wenner inversion is more for the preset model and can effectively compensate for the limitation of a single array. The inversion results based on a priori model can suppress boundary interference and improve the effective identification of preset hidden dangers and boundary. The field test also shows that the anomaly determined by multiple-wenner inversion technology is highly consistent with the leakage site, which effectively improves the accuracy of hidden danger diagnosis.
Application of Magnetic Resonance Detection in Goaf Water in Wuhai
Authors: Li Cong , Zeng Zhaofa , Duan Qingming 
Published: February 2021

Abstract
The mine water disaster in our country has always been the key factor restricting the development of coal production. Due to the unreasonable small coal mine development, mining in some mining area, the destruction of the waterproof coal pillar, lead to the formation of the mined-out area, and goaf water. Because the goaf water does great harm to coal field exploration and development, the prevention and control of goaf water disasters are very important. In this study, aiming at a large area of exploration space, the method of magnetic resonance can be used to detect groundwater, and two magnetic resonance instruments are used to work together. In order to ensure the accuracy and effectiveness of the data collected by the two instruments, improve the efficiency of exploration work and save field exploration time, the basic model of detecting groundwater with magnetic resonance sounding (MRS) method instrument is established, the influencing factors of MRS are analyzed, and the effective signal value of detecting groundwater with MRS instrument is calculated. Through numerical simulation, the optimal distance between the coils laid on the ground when the two MRS instruments are working at the same time is determined. Furthermore, the practicability of the method is verified via a field case performed in a mining area in Wuhai, China. This method can be used as a guide for large-scale field exploration in the future.
Efficient 2D Modeling of Gravity Anomaly in Space-wavenumber Mixed Domain
Authors: Wang Xulong , Liu Jianxin , Guo Rongwen , Liu Rong 
Published: February 2021

Abstract
Forward modeling is the basis of inversion. In order to implement refined inversion imaging and quantitative interpretation of gravity exploration, a high-efficiency and high-precision numerical simulation method of gravity anomalies in mixed space-wavenumber domain is proposed in this paper. By performing one-dimensional Fourier transform, the method transforms the partial differential equations of the two-dimensional space domain problem of gravity anomaly into one-dimensional differential equations with different wave numbers independent of each other. The depth direction is reserved as the spatial domain, and the shallow grid can be properly encrypted and the deep grid to be properly sparse, which taking account of the calculation accuracy, calculation efficiency and simulation of complex terrain. The two-dimensional gravity anomaly forward modeling in the mixed space wavenumber domain makes full use of the fast Fourier transform and the chase method to solve the five-diagonal equations quickly, and realizes the numerical simulation of gravity anomaly with high efficiency and high precision.
Technology of detecting deep underground metal pipeline by magnetic gradient method
Authors: Xi Jianjun , Cui Dandan 
Published: February 2021

Abstract
The application of trenchless technology, such as pipe pulling, pipe jacking, directional drilling and so on, makes the deep buried underground pipeline more and more in the project, and most of the geophysical exploration technology has poor detection effect, which makes it become the difficulty in the underground pipeline detection. This paper mainly expounds and analyzes the principle and construction method of magnetic gradient method for detecting deep underground pipelines, and introduces the application of magnetic gradient method in the detection of deep underground pipelines with two natural gas pipelines in Shijiazhuang road project.