In slowly deforming intraplate regions,identifying active faults is challenging due to their low slip rates or concealment by recent sedimentation and anthropogenic activity,requiring significant time and resources.We...In slowly deforming intraplate regions,identifying active faults is challenging due to their low slip rates or concealment by recent sedimentation and anthropogenic activity,requiring significant time and resources.We focus on the structural features and spatial extent of a buried active reverse fault,central South Korea.Our approach integrates the structural and paleoseismic records from the fault exposure with 2D and 3D electrical resistivity surveys.In the road construction area,electrical resistivity differentiates the fault’s hanging wall from the footwall in granitic bedrock.展开更多
This study addresses the challenge of real-time resistivity gradient measurement in the Czochralski(CZ)silicon production process.Due to the inability to directly measure this parameter,we propose a Long Short-Term Me...This study addresses the challenge of real-time resistivity gradient measurement in the Czochralski(CZ)silicon production process.Due to the inability to directly measure this parameter,we propose a Long Short-Term Memory soft-sensing model based on Convolutional Neural Network(CNN)and attention mechanism(CNN-ALSTM)that enhances traditional LSTM by integrating CNN and attention mechanism to overcome time lag variations during silicon pulling.The CNN module extracts spatial features from multi-source sensor data,while the attention-enhanced LSTM(ALSTM)dynamically adjusts historical parameter weights,enabling accurate resistivity gradient prediction.Experiments with real production data show that CNN-ALSTM outperforms SVR,FNN,RNN,XGBoost,and GRU,improving prediction accuracy by 11.76%,16.67%,21.05%,30.23%,and 9.09%,respectively.This soft-sensing approach enhances real-time monitoring and optimization of monocrystalline silicon growth.展开更多
The 2D data processing adopted by the high-density resistivity method regards the geological structures as two degrees, which makes the results of the 2D data inversion only an approximate interpretation;the accuracy ...The 2D data processing adopted by the high-density resistivity method regards the geological structures as two degrees, which makes the results of the 2D data inversion only an approximate interpretation;the accuracy and effect can not meet the precise requirement of the inversion. Two typical models of the geological bodies were designed, and forward calculation was carried out using finite element method. The forward-modeled profiles were obtained. 1% Gaussian random error was added in the forward models and then 2D and 3D inversions using a high-density resistivity method were undertaken to realistically simulate field data and analyze the sensitivity of the 2D and 3D inversion algorithms to noise. Contrast between the 2D and 3D inversion results of least squares inversion shows that two inversion results of high-density resistivity method all can basically reflect the spatial position of an anomalous body. However, the 3D inversion can more effectively eliminate the influence of interference from Gaussian random error and better reflect the distribution of resistivity in the anomalous bodies. Overall, the 3D inversion was better than 2D inversion in terms of embodying anomalous body positions, morphology and resistivity properties.展开更多
Evaluating the stabilized lead(Pb)-contaminated soils through sampling and laboratory testing involves costly and time-consuming processes.Therefore,this study employed a low-cost and non-destructive resistivity tool ...Evaluating the stabilized lead(Pb)-contaminated soils through sampling and laboratory testing involves costly and time-consuming processes.Therefore,this study employed a low-cost and non-destructive resistivity tool to evaluate the Pb-contaminated soils stabilized by electrolytic manganese residue(EMR)-based geopolymer(EG-OPC)from the strength and environmental benefits perspective.First,unconfined compressive strength(UCS)and leaching tests were conducted to study the stabilization effectiveness of EG-OPC.Results indicated that the UCS values of soil(5000 mg/kg of pollutants)stabilized by 20%EG-OPC were 4.87 MPa and 8.13 MPa after 7 d and 60 d of curing,respectively.After 60 d of curing,the Pb concentration in the leachate reached 44 mg/L,far lower than the control group(321 mg/L).Second,soil,pore water,and leachate resistivity(ERS,ERW,and ERL)were measured to establish fitting relationships with strength parameters and pollution risk.The good fitting results(e.g.ERS/ERW versus UCS/secant modulus(E50):correlation coefficient R2 z 0.9,ERS/ERW versus Pb contents:R2 z 0.9,and ERL versus Pb2þconcentration:R2¼0.92)and well used Archie's law(ERS versus ERW:R2>0.9)indicate that the resistivity can be used to evaluate the stabilization effectiveness.Furthermore,the microscopic results revealed two behaviors,demonstrating the reliability of resistivity:(1)with the hydration process,resistivity increases due to a denser structure and lower amounts of free water and Pb ions,and(2)the addition of Pb reduces resistivity due to its inhibition or even destructive effects on cementation and formation of hydration products.展开更多
Natural gas hydrates are widely distributed in marine and permafrost environments.As a novel energy resource,accurately describing reservoir characteristics and assessing energy potential is crucial for its commercial...Natural gas hydrates are widely distributed in marine and permafrost environments.As a novel energy resource,accurately describing reservoir characteristics and assessing energy potential is crucial for its commercial development.Resistivity logging serves as a valuable approach for achieving these goals.Nevertheless,due to inadequate comprehension of the electrical conductivity mechanism in hydrate-bearing sediments,existing data processing models still encounter certain challenges.This study conducts both core-scale and pore-scale simulation experiments to examine the relationship between resistivity variations and the distribution of gas hydrate porosity.The results indicate that the characteristics of resistivity variation is associated with the gas hydrate formation process,and the gas hydrate saturation index,denoted as‘n',varies between 0 and 3 depending on different gas hydrate distribution patterns.As the saturation increases,gas hydrate distribution in pore spaces transitions from floating to contacting and cementing patterns.It is proposed that the aqueous pore tortuosity can be utilized to correct the saturation index‘n'in Archie's equation.Based on the analysis of experimental data,a correction method for Archie's equation is suggested,and its effectiveness in controlling relative error has been validated.展开更多
To minimize the calculation errors in the sound absorption coefficient resulting from inaccurate measurements of flow resistivity,a simple method for determining the sound absorption coefficient of soundabsorbing mate...To minimize the calculation errors in the sound absorption coefficient resulting from inaccurate measurements of flow resistivity,a simple method for determining the sound absorption coefficient of soundabsorbing materials is proposed.Firstly,the sound absorption coefficients of a fibrous sound-absorbing material are measured at two different frequencies using the impedance tube method.Secondly,utilizing the empirical formulas for the wavenumber and acoustic impedance in the fibrous material,the flow resistivity and porosity of the sound-absorbing materials are calculated using the MATLAB cycle program.Thirdly,based on the values obtained through reverse calculations,the sound absorption coefficient,the real and the imaginary parts of the acoustic impedance of the sound-absorbing material at different frequencies are theoretically computed.Finally,the accuracy of these theoretical calculations is verified through experiments.The experimental results indicate that the calculated values are basically consistent with the measured values,demonstrating the feasibility and reliability of this method.展开更多
Evaluation of backfilling effectiveness plays a crucial role in the geological environment management and restoration of abandoned open-pit quarries,providing a scientific basis for subsequent greening efforts.Backfil...Evaluation of backfilling effectiveness plays a crucial role in the geological environment management and restoration of abandoned open-pit quarries,providing a scientific basis for subsequent greening efforts.Backfill soil,predominantly composed of silty clay,demonstrates high water retention capacity and elevated moisture content,leading to a pronounced resistivity contrast with the bedrock exposed by quarrying activities.To investigate the distribution of backfill soil subsurface and assess backfilling effectiveness in the study area,this study conducted a comprehensive geophysical investigation utilizing the high-density electrical resistivity tomography(ERT).A total of 19 ERT survey lines were deployed across three distinct areas in Liuyao Village,Huaibei City,Anhui Province,China.The inversion results,derived from both two-dimensional(2D)and three-dimensional(3D),reveal distinct electrical properties of the subsurface materials:the backfill soil layer shows low resistivity features,the fill stone layer exhibits medium to high resistivity,and the bedrock shows the highest resistivity.The 2D inversion results,from the data measured using the Wenner array effectively capture the spatial distribution and structural features of the backfill soil layer.The findings indicate a gradual east-west thinning of the clay layer within the quarry.Furthermore,the northern pit area exhibits a uniform distribution of backfill soil layer,indicative of effective backfilling operations.In contrast,the southern pit area lacks a well-defined clay layer,suggesting suboptimal backfilling effectiveness.展开更多
A parallel finite element scheme for 3D resistivity method forward modeling is introduced in this article.The domain decomposition algorithm,along with a message passing interface,is used to implement parallelism.The ...A parallel finite element scheme for 3D resistivity method forward modeling is introduced in this article.The domain decomposition algorithm,along with a message passing interface,is used to implement parallelism.The computational domain is divided into subdomains,and mesh partitioning is combined with load balancing.Unstructured meshes and local mesh refinement strategies are used to realize high precision for complex topography models.Furthermore,an improved linear solver for multi-electrode resistivity method modeling is adopted.Recycling preconditioned conjugate gradient,which is a linear solver,is based on the similarity of linear systems between point sources.The multiple right-hand-side linear systems corresponding to different point source positions are constructed,and the accelerated convergence is obtained through recycling subspace using the linear solver.The computational accuracy and efficiency of the forward scheme for complex topography models are verified using the numerical test results.展开更多
In the leakage detection of reservoir dam bodies,traditional geophysical methods can only achieve one-time detection.Meanwhile,due to the non-uniqueness of geophysicalin version,how to improve the fidelity of geophysi...In the leakage detection of reservoir dam bodies,traditional geophysical methods can only achieve one-time detection.Meanwhile,due to the non-uniqueness of geophysicalin version,how to improve the fidelity of geophysical detection inversion profiles has become a key challenge in the industry.This study aims to construct a long-term real-time monitoring system using the time-lapse resistivity method,reveal the spatiotemporal evolution law of dam leakage,and provide technical support for accurate treatment.By integrating the Internet of Things(IoT),5G technology,and AI technology,real-time data acquisition,real-time transmission,and automatic inversionare realized.Through dynamic imaging analysis of the electrical anomaly characteristics of the leakage area and comparison between corresponding rainfall events,the leakage range and resistivity changes,the reliability and efficiency of dam leakagedete ction are significantly improved.This achieves long-termdynamic monitoring of dam leakage and provides a new perspective for the safe operation and maintenance of reservoirs.展开更多
AlGaN-based LEDs with peak wavelength below 240 nm(far-UVC)pose no significant harm to human health,thus highlighting their broader application potential.While,there is a significant Schottky barrier between the n-ele...AlGaN-based LEDs with peak wavelength below 240 nm(far-UVC)pose no significant harm to human health,thus highlighting their broader application potential.While,there is a significant Schottky barrier between the n-electrode and Alrich n-AlGaN,adversely impeding electron injection and resulting in considerable heat generation.Here,we fabricate V-based electrodes of V/Al/Ti/Au on n-AlGaN with Al content over 80%and investigate the relationship between the metal diffusion and contact properties during the high-temperature annealing process.Experiments reveal that decreasing V thickness in the electrode promotes the diffusion of Al towards the surface of n-AlGaN,which facilitates the formation of VN and thus the increase of local electron concentration,resulting in lower specific contact resistivity.Then,increasing the Al thickness inhibits the diffusion of Au to the n-AlGaN surface,suppressing the rise of Schottky barrier.Experimentally,an optimized n-electrode of V(10 nm)/Al(240 nm)/Ti(40 nm)/Au(50 nm)on n-Al_(0.81)Ga_(0.19)N is obtained,realizing an optimal specific contact resistivity of 7.30×10^(−4)Ω·cm^(2).Based on the optimal n-electrode preparation scheme for Al-rich n-AlGaN,the work voltage of a far-UVC LED with peak wavelength of 233.5 nm is effectively reduced.展开更多
Multiple electrodes are arranged on the surfaces of cubic granite samples of different sizes according to pre-designed patterns. Smples are fully saturated with water in vacuum. Waterproof insulation glue is coated o...Multiple electrodes are arranged on the surfaces of cubic granite samples of different sizes according to pre-designed patterns. Smples are fully saturated with water in vacuum. Waterproof insulation glue is coated on the measuring surfact and asmall parts (including two arrises) of the adjacent surfeces of the saturated sample to ensure that the electric current flows only within the sample through the connection between the electrodes. The multiple electrodes are combined form arrays of different direction and specing with symmetrical four-clectrode method according to need of measuring of resistivity changing anisotropy, electric profiling and electric sounding. The samples are placed into container filled with water. The samples are uniaxially compressed along the direction parallel to the longest dimension of the cubic, and the variation of resistivity during the whole loading process is observed. In the experiments, some samples are loaded to rupture with macro-fractures, some are only loaded to the Stage, which shows obvious Precursors in variation of resistivity associated with the indication of forthcoming rupture. Finally a quantitative comparison batween the dominant orientation of pre-existing cracks in photo-micrography of unruptured Samles and those macro-fractures in ruptured sample is made, together with theirrespective resistivity changing anisotropy behaviors. The experimental results are the following: ① For measuring points in areas that are passed by craks or rupture bands, the directions of principal anisotropy axes dedued from four kinds of combined equation sets are essentially identical with each other, and accord with the orientation of cracks or main rupture bands approximately. For measuring points in areas without crack or rupture band passing through, either the directions of calculated principal anisotropy axes by different combinatorial arrays are inconsistent with each other, or the principal anisotropy axis cannot be determined, especially in the cases where the crack plane is parallel to the measuring surface.② The dominant orientation of microfractures or rupture bands shown from micrographs is close to the direction of principal anisotropy axis along which the variation in resistivity is the greaest.③ The results of electric profiling can be used for detecting the localization of cracks.展开更多
To minimize the number of solutions in 3D resistivity inversion, an inherent problem in inversion, the amount of data considered have to be large and prior constraints need to be applied. Geological and geophysical da...To minimize the number of solutions in 3D resistivity inversion, an inherent problem in inversion, the amount of data considered have to be large and prior constraints need to be applied. Geological and geophysical data regarding the extent of a geological anomaly are important prior information. We propose the use of shape constraints in 3D electrical resistivity inversion, Three weighted orthogonal vectors （a normal and two tangent vectors） were used to control the resistivity differences at the boundaries of the anomaly. The spatial shape of the anomaly and the constraints on the boundaries of the anomaly are thus established. We incorporated the spatial shape constraints in the objective function of the 3D resistivity inversion and constructed the 3D resistivity inversion equation with spatial shape constraints. Subsequently, we used numerical modeling based on prior spatial shape data to constrain the direction vectors and weights of the 3D resistivity inversion. We established a reasonable range between the direction vectors and weights, and verified the feasibility and effectiveness of using spatial shape prior constraints in reducing excessive structures and the number of solutions. We applied the prior spatially shape-constrained inversion method to locate the aquifer at the Guangzhou subway. The spatial shape constraints were taken from ground penetrating radar data. The inversion results for the location and shape of the aquifer agree well with drilling data, and the number of inversion solutions is significantly reduced.展开更多
The dynamic monitoring of landslides in engineering geology has focused on the correlation among landslide stability,rainwater infiltration,and subsurface hydrogeology.However,the understanding of this complicated cor...The dynamic monitoring of landslides in engineering geology has focused on the correlation among landslide stability,rainwater infiltration,and subsurface hydrogeology.However,the understanding of this complicated correlation is still poor and inadequate.Thus,in this study,we investigated a typical landslide in southwestern China via time-lapse electrical resistivity tomography（TLERT） in November 2013 and August 2014.We studied landslide mechanisms based on the spatiotemporal characteristics of surface water infiltration and flow within the landslide body.Combined with borehole data,inverted resistivity models accurately defined the interface between Quaternary sediments and bedrock.Preferential flow pathways attributed to fracture zones and fissures were also delineated.In addition,we found that surface water permeates through these pathways into the slipping mass and drains away as fissure water in the fractured bedrock,probably causing the weakly weathered layer to gradually soften and erode,eventually leading to a landslide.Clearly,TLERT dynamic monitoring can provide precursory information of critical sliding and can be used in landslide stability analysis and prediction.展开更多
There exist different response characteristics in the resistivity measurements of dual laterolog （DLL） and logging while drilling （LWD） electromagnetic wave propagation logging in highly deviated and horizontal we...There exist different response characteristics in the resistivity measurements of dual laterolog （DLL） and logging while drilling （LWD） electromagnetic wave propagation logging in highly deviated and horizontal wells due to the difference in their measuring principles. In this study, we first use the integral equation method simulated the response characteristics of LWD resistivity and use the three dimensional finite element method （3D-FEM） simulated the response characteristics of DLL resistivity in horizontal wells, and then analyzed the response differences between the DLL and LWD resistivity. The comparative analysis indicated that the response differences may be caused by different factors such as differences in the angle of instrument inclination, anisotropy, formation interface, and mud intrusion. In the interface, the curves of the LWD resistivity become sharp with increases in the deviation while those of the DLL resistivity gradually become smooth. Both curves are affected by the anisotropy although the effect on DLL resistivity is lower than the LWD resistivity. These differences aid in providing a reasonable explanation in the horizontal well. However, this can also simultaneously lead to false results. At the end of the study, we explain the effects of the differences in the interpretation of the horizontal well based on the results and actual data analysis.展开更多
Most of the carbonate formation are highly heterogeneous with cavities of different sizes, which makes the prediction of cavity-filled reservoir in carbonate rocks difficult. Large cavities in carbonate formations pos...Most of the carbonate formation are highly heterogeneous with cavities of different sizes, which makes the prediction of cavity-filled reservoir in carbonate rocks difficult. Large cavities in carbonate formations pose serious threat to drilling operations. Logging-whiledrilling （LWD） is currently used to accurately identify and evaluate cavities in reservoirs during drilling. In this study, we use the self-adaptive hp-FEM algorithm simulate and calculate the LWD resistivity responses of fracture-cavity reservoir cavities. Compared with the traditional h-FEM method, the self-adaptive hp-FEM algorithm has the characteristics of the self-adaptive mesh refinement and the calculations exponentially converge to highly accurate solutions. Using numerical simulations, we investigated the effect of the cavity size, distance between cavity and borehole, and transmitted frequency on the LWD resistivity response. Based on the results, a method for recognizing cavities is proposed. This research can provide the theoretical basis for the accurate identification and quantitative evaluation of various carbonate reservoirs with cavities encountered in practice.展开更多
To speed up three-dimensional （3D） DC resistivity modeling, we present a new multigrid method, the aggregation-based algebraic multigrid method （AGMG）. We first discretize the differential equation of the secondar...To speed up three-dimensional （3D） DC resistivity modeling, we present a new multigrid method, the aggregation-based algebraic multigrid method （AGMG）. We first discretize the differential equation of the secondary potential field with mixed boundary conditions by using a seven-point finite-difference method to obtain a large sparse system of linear equations. Then, we introduce the theory behind the pairwise aggregation algorithms for AGMG and use the conjugate-gradient method with the V-cycle AGMG preconditioner （AGMG-CG） to solve the linear equations. We use typical geoelectrical models to test the proposed AGMG-CG method and compare the results with analytical solutions and the 3DDCXH algorithm for 3D DC modeling （3DDCXH）. In addition, we apply the AGMG-CG method to different grid sizes and geoelectrical models and compare it to different iterative methods, such as ILU-BICGSTAB, ILU-GCR, and SSOR-CG. The AGMG-CG method yields nearly linearly decreasing errors, whereas the number of iterations increases slowly with increasing grid size. The AGMG-CG method is precise and converges fast, and thus can improve the computational efficiency in forward modeling of three-dimensional DC resistivity.展开更多
In this paper, responses of a new dual-induction resistivity logging-while-drilling （LWD） tool in 3D inhomogeneous formation models are simulated by the vectorfinite element method （VFEM）, the influences of the bo...In this paper, responses of a new dual-induction resistivity logging-while-drilling （LWD） tool in 3D inhomogeneous formation models are simulated by the vectorfinite element method （VFEM）, the influences of the borehole, invaded zone, surroundingstrata, and tool eccentricity are analyzed, and calibration loop parameters and calibrationcoefficients of the LWD tool are discussed. The results show that the tool has a greater depthof investigation than that of the existing electromagnetic propagation LWD tools and is moresensitive to azimuthal conductivity. Both deep and medium induction responses have linearrelationships with the formation conductivity, considering optimal calibration loop parametersand calibration coefficients. Due to the different depths of investigation and resolution, deepinduction and medium induction are affected differently by the formation model parameters,thereby having different correction factors. The simulation results can provide theoreticalreferences for the research and interpretation of the dual-induction resistivity LWD tools.展开更多
We present a forward-modeling investigation of time-dependent ground magnetometric resistivity （MMR） anomalies associated with transient leachate transport in groundwater systems. Numerical geo-electrical models are...We present a forward-modeling investigation of time-dependent ground magnetometric resistivity （MMR） anomalies associated with transient leachate transport in groundwater systems. Numerical geo-electrical models are constructed based on the hydrological simulation results of leachate plumes from a highly conceptualized landfill system and the resultant MMR responses are computed using a modified finite difference software MMR2DFD. Three transmitter configurations （i.e., single source, MMR-TE, and MMR-TM modes） and two hydrological models （i.e., uniform and faulted porous media） are considered. Our forward modeling results for the uniform porous medium indicates that the magnetic field components perpendicular to the dominant current flow contain the most information of the underground targets and the MMR-TE mode is an appropriate configuration for detecting contaminant plumes. The modeling experiments for the faulted porous medium also confirm that the MMR method is capable of mapping and monitoring the extent of contaminant plumes in aroundwater systems.展开更多
Since the ocean bottom is a sedimentary environment wherein stratification is well developed, the use of an anisotropic model is best for studying its geology. Beginning with Maxwell＇s equations for an anisotropic mo...Since the ocean bottom is a sedimentary environment wherein stratification is well developed, the use of an anisotropic model is best for studying its geology. Beginning with Maxwell＇s equations for an anisotropic model, we introduce scalar potentials based on the divergence-free characteristic of the electric and magnetic （EM） fields. We then continue the EM fields down into the deep earth and upward into the seawater and couple them at the ocean bottom to the transmitting source. By studying both the DC apparent resistivity curves and their polar plots, we can resolve the anisotropy of the ocean bottom. Forward modeling of a high-resistivity thin layer in an anisotropic half-space demonstrates that the marine DC resistivity method in shallow water is very sensitive to the resistive reservoir but is not influenced by airwaves. As such, it is very suitable for oil and gas exploration in shallowwater areas but, to date, most modeling algorithms for studying marine DC resistivity are based on isotropic models. In this paper, we investigate one-dimensional anisotropic forward modeling for marine DC resistivity method, prove the algorithm to have high accuracy, and thus provide a theoretical basis for 2D and 3D forward modeling.展开更多
The electrical resistivity characteristics of cement soil and flyash lime soil are investigated in the laboratory and the field. It is shown that the electrical resistivities of the cement soil and flyash lime s...The electrical resistivity characteristics of cement soil and flyash lime soil are investigated in the laboratory and the field. It is shown that the electrical resistivities of the cement soil and flyash lime soil are sensitive to water content, degree of saturation and unconfined strength. The cement soil and flyash lime soil with higher water content, greater degree of saturation, lower unconfined strength has lower electrical resistivity. Electrical resistivity is also correlated with additives. Based on the tests, it is concluded that the electrical resistivity method is available for checking the effectiveness of the soil improvement by the cement soil and flyash lime soil mixing pile in terms of engineering practice.展开更多
基金supported by a grant(2022-MOIS62-001)for National Disaster Risk Analysis and Management Technology in Earthquakes funded by the Ministry of Interior and Safety(MOIS,South Korea).
文摘In slowly deforming intraplate regions,identifying active faults is challenging due to their low slip rates or concealment by recent sedimentation and anthropogenic activity,requiring significant time and resources.We focus on the structural features and spatial extent of a buried active reverse fault,central South Korea.Our approach integrates the structural and paleoseismic records from the fault exposure with 2D and 3D electrical resistivity surveys.In the road construction area,electrical resistivity differentiates the fault’s hanging wall from the footwall in granitic bedrock.
文摘This study addresses the challenge of real-time resistivity gradient measurement in the Czochralski(CZ)silicon production process.Due to the inability to directly measure this parameter,we propose a Long Short-Term Memory soft-sensing model based on Convolutional Neural Network(CNN)and attention mechanism(CNN-ALSTM)that enhances traditional LSTM by integrating CNN and attention mechanism to overcome time lag variations during silicon pulling.The CNN module extracts spatial features from multi-source sensor data,while the attention-enhanced LSTM(ALSTM)dynamically adjusts historical parameter weights,enabling accurate resistivity gradient prediction.Experiments with real production data show that CNN-ALSTM outperforms SVR,FNN,RNN,XGBoost,and GRU,improving prediction accuracy by 11.76%,16.67%,21.05%,30.23%,and 9.09%,respectively.This soft-sensing approach enhances real-time monitoring and optimization of monocrystalline silicon growth.
基金Projects(41074085,41374118)supported by the National Natural Science Foundation of ChinaProject(20120162110015)supported by Doctoral Fund of Ministry of Education of ChinaProject(NCET-12-0551)supported by Program for New Century Excellent Talents in University,China
文摘The 2D data processing adopted by the high-density resistivity method regards the geological structures as two degrees, which makes the results of the 2D data inversion only an approximate interpretation;the accuracy and effect can not meet the precise requirement of the inversion. Two typical models of the geological bodies were designed, and forward calculation was carried out using finite element method. The forward-modeled profiles were obtained. 1% Gaussian random error was added in the forward models and then 2D and 3D inversions using a high-density resistivity method were undertaken to realistically simulate field data and analyze the sensitivity of the 2D and 3D inversion algorithms to noise. Contrast between the 2D and 3D inversion results of least squares inversion shows that two inversion results of high-density resistivity method all can basically reflect the spatial position of an anomalous body. However, the 3D inversion can more effectively eliminate the influence of interference from Gaussian random error and better reflect the distribution of resistivity in the anomalous bodies. Overall, the 3D inversion was better than 2D inversion in terms of embodying anomalous body positions, morphology and resistivity properties.
基金supported by the National Key R&D Program of China(Grant No.2022YFC3901204)the Foundation for Distinguished Young Scholars of Hubei Province,China(Grant No.2021CFA096)the National Natural Science Foundation of China(Grant No.U20A20320).
文摘Evaluating the stabilized lead(Pb)-contaminated soils through sampling and laboratory testing involves costly and time-consuming processes.Therefore,this study employed a low-cost and non-destructive resistivity tool to evaluate the Pb-contaminated soils stabilized by electrolytic manganese residue(EMR)-based geopolymer(EG-OPC)from the strength and environmental benefits perspective.First,unconfined compressive strength(UCS)and leaching tests were conducted to study the stabilization effectiveness of EG-OPC.Results indicated that the UCS values of soil(5000 mg/kg of pollutants)stabilized by 20%EG-OPC were 4.87 MPa and 8.13 MPa after 7 d and 60 d of curing,respectively.After 60 d of curing,the Pb concentration in the leachate reached 44 mg/L,far lower than the control group(321 mg/L).Second,soil,pore water,and leachate resistivity(ERS,ERW,and ERL)were measured to establish fitting relationships with strength parameters and pollution risk.The good fitting results(e.g.ERS/ERW versus UCS/secant modulus(E50):correlation coefficient R2 z 0.9,ERS/ERW versus Pb contents:R2 z 0.9,and ERL versus Pb2þconcentration:R2¼0.92)and well used Archie's law(ERS versus ERW:R2>0.9)indicate that the resistivity can be used to evaluate the stabilization effectiveness.Furthermore,the microscopic results revealed two behaviors,demonstrating the reliability of resistivity:(1)with the hydration process,resistivity increases due to a denser structure and lower amounts of free water and Pb ions,and(2)the addition of Pb reduces resistivity due to its inhibition or even destructive effects on cementation and formation of hydration products.
基金financially supported by the National Natural Science Foundation of China(No.42376067)the Natural Science Foundation of Shandong Province(No.ZR202011030013)+1 种基金the Laoshan Laboratory(No.LSKJ202203506)the China Geological Survey Program(No.DD20230064)。
文摘Natural gas hydrates are widely distributed in marine and permafrost environments.As a novel energy resource,accurately describing reservoir characteristics and assessing energy potential is crucial for its commercial development.Resistivity logging serves as a valuable approach for achieving these goals.Nevertheless,due to inadequate comprehension of the electrical conductivity mechanism in hydrate-bearing sediments,existing data processing models still encounter certain challenges.This study conducts both core-scale and pore-scale simulation experiments to examine the relationship between resistivity variations and the distribution of gas hydrate porosity.The results indicate that the characteristics of resistivity variation is associated with the gas hydrate formation process,and the gas hydrate saturation index,denoted as‘n',varies between 0 and 3 depending on different gas hydrate distribution patterns.As the saturation increases,gas hydrate distribution in pore spaces transitions from floating to contacting and cementing patterns.It is proposed that the aqueous pore tortuosity can be utilized to correct the saturation index‘n'in Archie's equation.Based on the analysis of experimental data,a correction method for Archie's equation is suggested,and its effectiveness in controlling relative error has been validated.
基金National Natural Science Foundation of China(No.51705545)。
文摘To minimize the calculation errors in the sound absorption coefficient resulting from inaccurate measurements of flow resistivity,a simple method for determining the sound absorption coefficient of soundabsorbing materials is proposed.Firstly,the sound absorption coefficients of a fibrous sound-absorbing material are measured at two different frequencies using the impedance tube method.Secondly,utilizing the empirical formulas for the wavenumber and acoustic impedance in the fibrous material,the flow resistivity and porosity of the sound-absorbing materials are calculated using the MATLAB cycle program.Thirdly,based on the values obtained through reverse calculations,the sound absorption coefficient,the real and the imaginary parts of the acoustic impedance of the sound-absorbing material at different frequencies are theoretically computed.Finally,the accuracy of these theoretical calculations is verified through experiments.The experimental results indicate that the calculated values are basically consistent with the measured values,demonstrating the feasibility and reliability of this method.
基金Supported by National Key Research and Development Program of China(No.2023YFC3707901)。
文摘Evaluation of backfilling effectiveness plays a crucial role in the geological environment management and restoration of abandoned open-pit quarries,providing a scientific basis for subsequent greening efforts.Backfill soil,predominantly composed of silty clay,demonstrates high water retention capacity and elevated moisture content,leading to a pronounced resistivity contrast with the bedrock exposed by quarrying activities.To investigate the distribution of backfill soil subsurface and assess backfilling effectiveness in the study area,this study conducted a comprehensive geophysical investigation utilizing the high-density electrical resistivity tomography(ERT).A total of 19 ERT survey lines were deployed across three distinct areas in Liuyao Village,Huaibei City,Anhui Province,China.The inversion results,derived from both two-dimensional(2D)and three-dimensional(3D),reveal distinct electrical properties of the subsurface materials:the backfill soil layer shows low resistivity features,the fill stone layer exhibits medium to high resistivity,and the bedrock shows the highest resistivity.The 2D inversion results,from the data measured using the Wenner array effectively capture the spatial distribution and structural features of the backfill soil layer.The findings indicate a gradual east-west thinning of the clay layer within the quarry.Furthermore,the northern pit area exhibits a uniform distribution of backfill soil layer,indicative of effective backfilling operations.In contrast,the southern pit area lacks a well-defined clay layer,suggesting suboptimal backfilling effectiveness.
基金supported by the National Natural Science Foundation of China(No:42274182)Guangxi Natural Science Foundation(No:2020 GXNSFAA297079)。
文摘A parallel finite element scheme for 3D resistivity method forward modeling is introduced in this article.The domain decomposition algorithm,along with a message passing interface,is used to implement parallelism.The computational domain is divided into subdomains,and mesh partitioning is combined with load balancing.Unstructured meshes and local mesh refinement strategies are used to realize high precision for complex topography models.Furthermore,an improved linear solver for multi-electrode resistivity method modeling is adopted.Recycling preconditioned conjugate gradient,which is a linear solver,is based on the similarity of linear systems between point sources.The multiple right-hand-side linear systems corresponding to different point source positions are constructed,and the accelerated convergence is obtained through recycling subspace using the linear solver.The computational accuracy and efficiency of the forward scheme for complex topography models are verified using the numerical test results.
文摘In the leakage detection of reservoir dam bodies,traditional geophysical methods can only achieve one-time detection.Meanwhile,due to the non-uniqueness of geophysicalin version,how to improve the fidelity of geophysical detection inversion profiles has become a key challenge in the industry.This study aims to construct a long-term real-time monitoring system using the time-lapse resistivity method,reveal the spatiotemporal evolution law of dam leakage,and provide technical support for accurate treatment.By integrating the Internet of Things(IoT),5G technology,and AI technology,real-time data acquisition,real-time transmission,and automatic inversionare realized.Through dynamic imaging analysis of the electrical anomaly characteristics of the leakage area and comparison between corresponding rainfall events,the leakage range and resistivity changes,the reliability and efficiency of dam leakagedete ction are significantly improved.This achieves long-termdynamic monitoring of dam leakage and provides a new perspective for the safe operation and maintenance of reservoirs.
基金supported by National Key R&D Program of China(2022YFB3605103)National Natural Science Foundation of China(62425408,62121005,U22A2084,12234018)+2 种基金Youth Innovation Promotion Association of the Chinese Academy of Sciences(2023223)Natural Science Foundation of Jilin Province(20230101345JC,20230101360JC,SKL202302026)Young Elite Scientist Sponsorship Program by CAST(YESS20200182).
文摘AlGaN-based LEDs with peak wavelength below 240 nm(far-UVC)pose no significant harm to human health,thus highlighting their broader application potential.While,there is a significant Schottky barrier between the n-electrode and Alrich n-AlGaN,adversely impeding electron injection and resulting in considerable heat generation.Here,we fabricate V-based electrodes of V/Al/Ti/Au on n-AlGaN with Al content over 80%and investigate the relationship between the metal diffusion and contact properties during the high-temperature annealing process.Experiments reveal that decreasing V thickness in the electrode promotes the diffusion of Al towards the surface of n-AlGaN,which facilitates the formation of VN and thus the increase of local electron concentration,resulting in lower specific contact resistivity.Then,increasing the Al thickness inhibits the diffusion of Au to the n-AlGaN surface,suppressing the rise of Schottky barrier.Experimentally,an optimized n-electrode of V(10 nm)/Al(240 nm)/Ti(40 nm)/Au(50 nm)on n-Al_(0.81)Ga_(0.19)N is obtained,realizing an optimal specific contact resistivity of 7.30×10^(−4)Ω·cm^(2).Based on the optimal n-electrode preparation scheme for Al-rich n-AlGaN,the work voltage of a far-UVC LED with peak wavelength of 233.5 nm is effectively reduced.
文摘Multiple electrodes are arranged on the surfaces of cubic granite samples of different sizes according to pre-designed patterns. Smples are fully saturated with water in vacuum. Waterproof insulation glue is coated on the measuring surfact and asmall parts (including two arrises) of the adjacent surfeces of the saturated sample to ensure that the electric current flows only within the sample through the connection between the electrodes. The multiple electrodes are combined form arrays of different direction and specing with symmetrical four-clectrode method according to need of measuring of resistivity changing anisotropy, electric profiling and electric sounding. The samples are placed into container filled with water. The samples are uniaxially compressed along the direction parallel to the longest dimension of the cubic, and the variation of resistivity during the whole loading process is observed. In the experiments, some samples are loaded to rupture with macro-fractures, some are only loaded to the Stage, which shows obvious Precursors in variation of resistivity associated with the indication of forthcoming rupture. Finally a quantitative comparison batween the dominant orientation of pre-existing cracks in photo-micrography of unruptured Samles and those macro-fractures in ruptured sample is made, together with theirrespective resistivity changing anisotropy behaviors. The experimental results are the following: ① For measuring points in areas that are passed by craks or rupture bands, the directions of principal anisotropy axes dedued from four kinds of combined equation sets are essentially identical with each other, and accord with the orientation of cracks or main rupture bands approximately. For measuring points in areas without crack or rupture band passing through, either the directions of calculated principal anisotropy axes by different combinatorial arrays are inconsistent with each other, or the principal anisotropy axis cannot be determined, especially in the cases where the crack plane is parallel to the measuring surface.② The dominant orientation of microfractures or rupture bands shown from micrographs is close to the direction of principal anisotropy axis along which the variation in resistivity is the greaest.③ The results of electric profiling can be used for detecting the localization of cracks.
基金supported by the National Program on Key Basic Research Project of China(973 Program)(No.2013CB036002,No.2014CB046901)the National Major Scientific Equipment Developed Special Project(No.51327802)+3 种基金National Natural Science Foundation of China(No.51139004,No.41102183)the Research Fund for the Doctoral Program of Higher Education of China(No.20110131120070)Natural Science Foundation of Shandong Province(No.ZR2011EEQ013)the Graduate Innovation Fund of Shandong University(No.YZC12083)
文摘To minimize the number of solutions in 3D resistivity inversion, an inherent problem in inversion, the amount of data considered have to be large and prior constraints need to be applied. Geological and geophysical data regarding the extent of a geological anomaly are important prior information. We propose the use of shape constraints in 3D electrical resistivity inversion, Three weighted orthogonal vectors （a normal and two tangent vectors） were used to control the resistivity differences at the boundaries of the anomaly. The spatial shape of the anomaly and the constraints on the boundaries of the anomaly are thus established. We incorporated the spatial shape constraints in the objective function of the 3D resistivity inversion and constructed the 3D resistivity inversion equation with spatial shape constraints. Subsequently, we used numerical modeling based on prior spatial shape data to constrain the direction vectors and weights of the 3D resistivity inversion. We established a reasonable range between the direction vectors and weights, and verified the feasibility and effectiveness of using spatial shape prior constraints in reducing excessive structures and the number of solutions. We applied the prior spatially shape-constrained inversion method to locate the aquifer at the Guangzhou subway. The spatial shape constraints were taken from ground penetrating radar data. The inversion results for the location and shape of the aquifer agree well with drilling data, and the number of inversion solutions is significantly reduced.
基金funded by the National Basic Research Program of China(973 Program)(No.2013CB733203)the National Natural Science Foundation of China(No.41474055)
文摘The dynamic monitoring of landslides in engineering geology has focused on the correlation among landslide stability,rainwater infiltration,and subsurface hydrogeology.However,the understanding of this complicated correlation is still poor and inadequate.Thus,in this study,we investigated a typical landslide in southwestern China via time-lapse electrical resistivity tomography（TLERT） in November 2013 and August 2014.We studied landslide mechanisms based on the spatiotemporal characteristics of surface water infiltration and flow within the landslide body.Combined with borehole data,inverted resistivity models accurately defined the interface between Quaternary sediments and bedrock.Preferential flow pathways attributed to fracture zones and fissures were also delineated.In addition,we found that surface water permeates through these pathways into the slipping mass and drains away as fissure water in the fractured bedrock,probably causing the weakly weathered layer to gradually soften and erode,eventually leading to a landslide.Clearly,TLERT dynamic monitoring can provide precursory information of critical sliding and can be used in landslide stability analysis and prediction.
基金supported by the National Science and Technology Major Project of China(Nos.2016ZX05014-002-001,2016ZX05002-005-001,and 2017ZX05005-005-005)
文摘There exist different response characteristics in the resistivity measurements of dual laterolog （DLL） and logging while drilling （LWD） electromagnetic wave propagation logging in highly deviated and horizontal wells due to the difference in their measuring principles. In this study, we first use the integral equation method simulated the response characteristics of LWD resistivity and use the three dimensional finite element method （3D-FEM） simulated the response characteristics of DLL resistivity in horizontal wells, and then analyzed the response differences between the DLL and LWD resistivity. The comparative analysis indicated that the response differences may be caused by different factors such as differences in the angle of instrument inclination, anisotropy, formation interface, and mud intrusion. In the interface, the curves of the LWD resistivity become sharp with increases in the deviation while those of the DLL resistivity gradually become smooth. Both curves are affected by the anisotropy although the effect on DLL resistivity is lower than the LWD resistivity. These differences aid in providing a reasonable explanation in the horizontal well. However, this can also simultaneously lead to false results. At the end of the study, we explain the effects of the differences in the interpretation of the horizontal well based on the results and actual data analysis.
基金supported by the National Natural Science Foundation of China(No. 41074099)
文摘Most of the carbonate formation are highly heterogeneous with cavities of different sizes, which makes the prediction of cavity-filled reservoir in carbonate rocks difficult. Large cavities in carbonate formations pose serious threat to drilling operations. Logging-whiledrilling （LWD） is currently used to accurately identify and evaluate cavities in reservoirs during drilling. In this study, we use the self-adaptive hp-FEM algorithm simulate and calculate the LWD resistivity responses of fracture-cavity reservoir cavities. Compared with the traditional h-FEM method, the self-adaptive hp-FEM algorithm has the characteristics of the self-adaptive mesh refinement and the calculations exponentially converge to highly accurate solutions. Using numerical simulations, we investigated the effect of the cavity size, distance between cavity and borehole, and transmitted frequency on the LWD resistivity response. Based on the results, a method for recognizing cavities is proposed. This research can provide the theoretical basis for the accurate identification and quantitative evaluation of various carbonate reservoirs with cavities encountered in practice.
基金supported by the Natural Science Foundation of China(Nos.41404057,41674077 and 411640034)the Nuclear Energy Development Project of China,and the‘555’Project of Gan Po Excellent People
文摘To speed up three-dimensional （3D） DC resistivity modeling, we present a new multigrid method, the aggregation-based algebraic multigrid method （AGMG）. We first discretize the differential equation of the secondary potential field with mixed boundary conditions by using a seven-point finite-difference method to obtain a large sparse system of linear equations. Then, we introduce the theory behind the pairwise aggregation algorithms for AGMG and use the conjugate-gradient method with the V-cycle AGMG preconditioner （AGMG-CG） to solve the linear equations. We use typical geoelectrical models to test the proposed AGMG-CG method and compare the results with analytical solutions and the 3DDCXH algorithm for 3D DC modeling （3DDCXH）. In addition, we apply the AGMG-CG method to different grid sizes and geoelectrical models and compare it to different iterative methods, such as ILU-BICGSTAB, ILU-GCR, and SSOR-CG. The AGMG-CG method yields nearly linearly decreasing errors, whereas the number of iterations increases slowly with increasing grid size. The AGMG-CG method is precise and converges fast, and thus can improve the computational efficiency in forward modeling of three-dimensional DC resistivity.
基金supported by the National Oil and Gas Major Projects(No.2011ZX05020-002)
文摘In this paper, responses of a new dual-induction resistivity logging-while-drilling （LWD） tool in 3D inhomogeneous formation models are simulated by the vectorfinite element method （VFEM）, the influences of the borehole, invaded zone, surroundingstrata, and tool eccentricity are analyzed, and calibration loop parameters and calibrationcoefficients of the LWD tool are discussed. The results show that the tool has a greater depthof investigation than that of the existing electromagnetic propagation LWD tools and is moresensitive to azimuthal conductivity. Both deep and medium induction responses have linearrelationships with the formation conductivity, considering optimal calibration loop parametersand calibration coefficients. Due to the different depths of investigation and resolution, deepinduction and medium induction are affected differently by the formation model parameters,thereby having different correction factors. The simulation results can provide theoreticalreferences for the research and interpretation of the dual-induction resistivity LWD tools.
基金Supported by the Program to Sponsor Teams for Innovation in the Construction of Talent Highlands in Guangxi Institutions of Higher Learning (Grant No. 200508)Sponsored by the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry (Grant No. 200889016).
文摘We present a forward-modeling investigation of time-dependent ground magnetometric resistivity （MMR） anomalies associated with transient leachate transport in groundwater systems. Numerical geo-electrical models are constructed based on the hydrological simulation results of leachate plumes from a highly conceptualized landfill system and the resultant MMR responses are computed using a modified finite difference software MMR2DFD. Three transmitter configurations （i.e., single source, MMR-TE, and MMR-TM modes） and two hydrological models （i.e., uniform and faulted porous media） are considered. Our forward modeling results for the uniform porous medium indicates that the magnetic field components perpendicular to the dominant current flow contain the most information of the underground targets and the MMR-TE mode is an appropriate configuration for detecting contaminant plumes. The modeling experiments for the faulted porous medium also confirm that the MMR method is capable of mapping and monitoring the extent of contaminant plumes in aroundwater systems.
基金financially supported by the National Hi-tech Research and Development Program of China(863 Program)(No.2012AA09A20103)
文摘Since the ocean bottom is a sedimentary environment wherein stratification is well developed, the use of an anisotropic model is best for studying its geology. Beginning with Maxwell＇s equations for an anisotropic model, we introduce scalar potentials based on the divergence-free characteristic of the electric and magnetic （EM） fields. We then continue the EM fields down into the deep earth and upward into the seawater and couple them at the ocean bottom to the transmitting source. By studying both the DC apparent resistivity curves and their polar plots, we can resolve the anisotropy of the ocean bottom. Forward modeling of a high-resistivity thin layer in an anisotropic half-space demonstrates that the marine DC resistivity method in shallow water is very sensitive to the resistive reservoir but is not influenced by airwaves. As such, it is very suitable for oil and gas exploration in shallowwater areas but, to date, most modeling algorithms for studying marine DC resistivity are based on isotropic models. In this paper, we investigate one-dimensional anisotropic forward modeling for marine DC resistivity method, prove the algorithm to have high accuracy, and thus provide a theoretical basis for 2D and 3D forward modeling.
文摘The electrical resistivity characteristics of cement soil and flyash lime soil are investigated in the laboratory and the field. It is shown that the electrical resistivities of the cement soil and flyash lime soil are sensitive to water content, degree of saturation and unconfined strength. The cement soil and flyash lime soil with higher water content, greater degree of saturation, lower unconfined strength has lower electrical resistivity. Electrical resistivity is also correlated with additives. Based on the tests, it is concluded that the electrical resistivity method is available for checking the effectiveness of the soil improvement by the cement soil and flyash lime soil mixing pile in terms of engineering practice.
