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
Assessment of fractured rock aquifers in many parts of the world is complicated given their strong heterogeneity. Delineation of the subsurface geological formation in the weathered terrain is essential for groundwate...Assessment of fractured rock aquifers in many parts of the world is complicated given their strong heterogeneity. Delineation of the subsurface geological formation in the weathered terrain is essential for groundwater exploration. To achieve this goal, 2D electrical resistivity tomography(ERT) and self-potential(SP) in combination with joint profile method(JPM) and boreholes have been carried out to delineate the subsurface geological units, detect the fracture/fault zones in hard rock, monitor the groundwater flow, and estimate the groundwater reserves contained within the weathered terrain at a complex heterogeneous site of Huangbu, South Guangdong of China. The integration of resistivity images with the borehole lithology along three profiles delineates three subsurface distinct layers namely topsoil cover, weathered and unweathered layers. The incorporation of ERT and SP with JPM reveal five fractures/faults, i.e., F_1, F_2, F_3, F_4 and F_5. 2D ERT models interpret the less resistive anomalies as the fractures/faults zones, and high resistive anomalies as the fresh bedrock. The inversion program based on the smoothness-constraint is used on the resistivity field data to get more realistic three layered model. SP measurements are obtained along the same electrical profiles which provide the negative anomalies clearly indicating the groundwater preferential flow pathways along the fracture/fault zones. Hydraulic parameters namely hydraulic conductivity and transmissivity were determined to estimate the groundwater resources contained within the fractures/faults. The integrated results suggest that the fractures/faults zones are most appropriate places of drilling for groundwater exploration in the investigated area. Geophysical methods coupled with the upfront borehole data provides better understanding about the conceptual model of the subsurface geological formations. The current investigation demonstrates the importance of the integrated geophysical methods as a complementary approach for groundwater assessment in the hard rock weathered areas.展开更多
Nonlinear resistivity inversion requires efficient artificial neural network(ANN)model for better inversion results.An evolutionary BP neural network(BPNN)approach based on differential evolution(DE)algorithm was pres...Nonlinear resistivity inversion requires efficient artificial neural network(ANN)model for better inversion results.An evolutionary BP neural network(BPNN)approach based on differential evolution(DE)algorithm was presented,which was able to improve global search ability for resistivity tomography 2-D nonlinear inversion.In the proposed method,Tent equation was applied to obtain automatic parameter settings in DE and the restricted parameter Fcrit was used to enhance the ability of converging to global optimum.An implementation of proposed DE-BPNN was given,the network had one hidden layer with 52 nodes and it was trained on 36 datasets and tested on another 4 synthetic datasets.Two abnormity models were used to verify the feasibility and effectiveness of the proposed method,the results show that the proposed DE-BP algorithm has better performance than BP,conventional DE-BP and other chaotic DE-BP methods in stability and accuracy,and higher imaging quality than least square inversion.展开更多
Electrical resistivity tomography survey was deployed at a solid waste landfill in southwest Missouri USA with the intent to map variations in moisture content through the solid waste and underlying subsurface, and to...Electrical resistivity tomography survey was deployed at a solid waste landfill in southwest Missouri USA with the intent to map variations in moisture content through the solid waste and underlying subsurface, and to map the top of bedrock. Multichannel analyses of surface waves survey was also deployed to map variations in engineering properties of the solid waste and underlying subsurface, and to constrain the interpretations of top of bedrock. The 2-D resistivity images through the waste suggest rainwater seeps through the cap cover system of the solid waste landfill, and moisture content within the solid waste increases with solid waste burial depth. The resistivity anomalies displayed by the soil and bedrock directly underneath the solid waste suggests a lateral component to moisture infiltrating at the toe of the landfill, which is flowing inward to the base of solid waste structural low. The 1-D shear wave velocity profiles obtained from the multichannel analyses of surface waves survey helped interpret the top of bedrock underneath the solid waste, where top of bedrock is difficult to map using electrical resistivity tomography, as shallow fractured bedrock is moist and displays comparable resistivity values to that of overlying soil. Not surprisingly, the top of bedrock is readily identified on the electrical resistivity tomography profiles in places where subsurface is relatively dry. The deployment of the combined non- invasive, cost and time effective geophysical surveys, along with engineering judgement on available site history data, has reasonably identified potential landfill seepage pathways. The methodology presented could be used in similar site investigation settings.展开更多
In order to ensure access to drinking water for Benin populations by 2021, the Emergency Measure program for the reinforcement of the drinking water supply system of Savalou city was initiated in 2018. This program fo...In order to ensure access to drinking water for Benin populations by 2021, the Emergency Measure program for the reinforcement of the drinking water supply system of Savalou city was initiated in 2018. This program focuses on densification and extension of hydraulic infrastructures. Therefore, it is prominent to use rigorous approach for implementation and execution of drilling activities. The present work has the advantage of combining the use of electrical resistivity tomography and borehole technique to locate ten high flow drilling in Savalou city. The electrical resistivity tomography (ERT) panels were made based on the dipole-dipole arrays with 48 electrodes with 5 m inter-electrode spacing. The drilling was carried out over ten selected points and in two stages: confirmation test using piezometer and borehole diameter enlargement. Moreover, only piezometers with flow rate greater than 10 m3/h were enlarged. The tomography processing has identified 10 fractured zones that are defined by 250 - 1000 ohm.m resistivity values and a width between 15 - 55 m. The confirmation test carried out over ten piezometers exhibits high flow rates ranging from 9 to 35 m3/h with depths of 30 to 68 m. Nine over the ten boreholes with a flow rate equal or greater than 10 m3/h, have improved their flow rates by 50% to 100% after the boring technique. Thus, the cumulative flow rate has reached 252. 7 m3/h for Savalou city and his surrounding areas.展开更多
Experiments using electrical resistivity tomography(ERT) have shown promising results in reducing the uncertainty of solute plume characteristics related to estimates based on the analysis of local point measurements ...Experiments using electrical resistivity tomography(ERT) have shown promising results in reducing the uncertainty of solute plume characteristics related to estimates based on the analysis of local point measurements only.To explore the similarities and differences between two cross-borehole ERT inversion approaches for characterizing salt tracer plumes,namely the classical smoothness-constrained inversion and a geostatistically based approach,we performed two-dimensional synthetic experiments.Simplifying assumptions about the solute transport model and the electrical forward and inverse model allowed us to study the sensitivity of the ERT inversion approaches towards a variety of basic conditions,including the number of boreholes,measurement schemes,contrast between the plume and background electrical conductivity,use of a priori knowledge,and point conditioning.The results show that geostatistically based and smoothness-constrained inversions of electrical resistance data yield plume characteristics of similar quality,which can be further improved when point measurements are incorporated and advantageous measurement schemes are chosen.As expected,an increased number of boreholes included in the ERT measurement layout can highly improve the quality of inferred plume characteristics,while in this case the benefits of point conditioning and advantageous measurement schemes diminish.Both ERT inversion approaches are similarly sensitive to the noise level of the data and the contrast between the solute plume and background electrical conductivity,and robust with regard to biased input parameters,such as mean concentration,variance,and correlation length of the plume.Although sophisticated inversion schemes have recently become available,in which flow and transport as well as electrical forward models are coupled,these schemes effectively rely on a relatively simple geometrical parameterization of the hydrogeological model.Therefore,we believe that standard uncoupled ERT inverse approaches,like the ones discussed and assessed in this paper,will continue to be important to the imaging and characterization of solute plumes in many real-world applications.展开更多
Electrical resistivity tomography data were acquired in proximity to the coal combustion residual landfill in an effort to image and analyze seepage pathways through the shallow residual soil and underlying karsted li...Electrical resistivity tomography data were acquired in proximity to the coal combustion residual landfill in an effort to image and analyze seepage pathways through the shallow residual soil and underlying karsted limestone bedrock. The water table is at a depth of more than 45 m. The most prominent subsurface seepage pathways identified on the acquired electrical resistivity tomography data are located immediately adjacent to the toe of the landfill and are attributed to stormwater run-off. The moisture content of the limestone appears to decrease gradually with increasing distance from the toe of the landfill, suggesting there is also a horizontal component of moisture flow in the subsurface. Shallow limestone with higher moisture content generally underlies or is in close proximity to anthropogenic features such as drainage ditches and clay berms that are designed to channel run-off. At one location, electrical resistivity tomography data were acquired along essentially the same traverse at different times of the year, and the resistivity of shallow limestone overall was lower on the data acquired after heavy rains.展开更多
Laboratory visual detection on the hydrate accumulation process provides an effective and low-cost method to uncover hydrate accumulation mechanisms in nature.However,the spatial hydrate distribution and its dynamic e...Laboratory visual detection on the hydrate accumulation process provides an effective and low-cost method to uncover hydrate accumulation mechanisms in nature.However,the spatial hydrate distribution and its dynamic evolutionary behaviors are still not fully understood due to the lack of methods and experimental systems.Toward this goal,we built a two-dimensional electrical resistivity tomography(ERT)apparatus capable of measuring spatial and temporal characteristics of hydrate-bearing porous media.Beach sand(0.05–0.85 mm)was used to form artificial methane hydrate-bearing sediment.The experiments were conducted at 1°C under excess water conditions and the ERT data were acquired and analyzed.This study demonstrates the utility of the ERT method for hydrate mapping in laboratory-scale.The results indicate that the average electrical conductivity decreases nonlinearly with the formation of the hydrate.At some special time-intervals,the average conductivity fluctuates within a certain scope.The plane conductivity fields evolve heterogeneously and the local preferential hydrate-forming positions alternate throughout the experimental duration.We speculate that the combination of hydrate formation itself and salt-removal effect plays a dominant role in the spatial and temporal hydrate distribution,as well as geophysical parameters changing behaviors during hydrate accumulation.展开更多
This research applies Electrical Resistivity Tomography (ERT) and Time Domain Electromagnetic Method (TDEM) to study the hydrogeology of the Taubaté basin, which is characterized by half-grabens with about 850 m ...This research applies Electrical Resistivity Tomography (ERT) and Time Domain Electromagnetic Method (TDEM) to study the hydrogeology of the Taubaté basin, which is characterized by half-grabens with about 850 m of maximum sediments thickness. The study area is in Taubaté city, São Paulo State, Brazil, where the Taubaté aquifer is an important water source. The Taubaté Group is the main sedimentary package of the basin;it is formed mainly by shales that form aquicludes, and thin layers of sandstones that form the aquifer. There are 40 groundwater exploration wells in Taubaté city that provide important information. The study purpose is to characterize the geoelectrical stratigraphy of the subsurface to locate the contact between the Quaternary and Tertiary sediments and to identify the Taubaté aquifer. The ERT is used for shallow investigations (tens of meters) and the TDEM can reach a great investigation depth (hundreds of meters). Therefore, these geophysical methods are complementary. The ERT data were acquired with the pole-dipole array with 20 m of electrodes spacing and 400 m length, and the TDEM data with the central-loop array with a 200 × 200 m transmitter loop. The results permit to define the contact between the Quaternary and Tertiary sediments around 15 m depth, the Pindamonhangaba Formation between 15 m and 30 m depth and the Taubate Group between 30 m and 300 m depth. The TDEM method defined the Taubaté Group as a single geoelectric layer because the shale and the sandstone layers are all very conductive. The basement is formed by gneiss, which is a very resistive rock. The TDEM method is not able to identify a high conductor/resistor contrast. Overall, the results are consistent with the known geology and the wells information.展开更多
Position, width and fragmentation level of fracture zones and position, sig-nificance and characteristic distance of fractures were aimed to determine in a carbonate aquifer. These are fundamental parameters, e.g. in ...Position, width and fragmentation level of fracture zones and position, sig-nificance and characteristic distance of fractures were aimed to determine in a carbonate aquifer. These are fundamental parameters, e.g. in hydrogeological modelling of aquifers, due to their role in subsurface water movements. The description of small scale fracture systems is however a challenging task. In the test area (Kádárta, Bakony Mts, Hungary), two methods proved to be applicable to get reasonable information about the fractures: Electrical Resistivity Tomography (ERT) and Pricking-Probe (PriP). PriP is a simple mechanical tool which has been successfully applied in archaeological investigations. ERT results demonstrated its applicability in this small scale fracture study. PriP proved to be a good verification tool both for fracture zone mapping and detecting fractures, but in certain areas, it produced different results than the ERT. The applicability of this method has therefore to be tested yet, although its problems most probably origin from human activity which reorganises the near-surface debris distribution. In the test site, both methods displayed fracture zones including a very characteristic one and a number of individual fractures and determined their characteristic distance and significance. Both methods prove to be able to produce hydrogeologically important parameters even individually, but their simultaneous application is recommended to decrease the possible discrepancies.展开更多
According to the principle of electrical resistance tomography （ ERT）, the resistivity distribution of the carbon fiber reinforced concrete （CFRC） in the sensing field can be measured by injecting exciting current...According to the principle of electrical resistance tomography （ ERT）, the resistivity distribution of the carbon fiber reinforced concrete （CFRC） in the sensing field can be measured by injecting exciting current and measuring the voltage on the sensor electrode arrays installed on the surface of the object. Therefore, measurement of the resistivity distribution of CFRC is divided into first measuring the boundary conditions and then inversely computing the resistivity distribution. To reach this goal, an ERT system was constructed, which is composed of a sensor array unit, a data acquisition unit and an image reconstruction unit. Simulations of static ERT was performed on set-ups with many objects spread in a homogeneous background, and a simulation of dynamic ERT was also done on a rectangular board, the resistivity of which was changed within a small domain of it. Then, the resistivity distribution of a CFRC sample with a circlar hole as the target was detected by the ERT system. Simulation and experimental results show that the reconstructed ERT image reflects the resistivity distribution or the resistivity change of CFRC structure well. Especially, a small change in resistivity can be identified from the reconstructed images in the simulation of dynamic ERT images.展开更多
The leakage occurs during operation of the dam in Liuhuanggou reservoir. It’s a threat to the safety of the people’s lives and property in downstream. In order to eliminate the hidden danger of reservoir, ensure the...The leakage occurs during operation of the dam in Liuhuanggou reservoir. It’s a threat to the safety of the people’s lives and property in downstream. In order to eliminate the hidden danger of reservoir, ensure the safety of the dam, play better the function of flood control and water storage of the reservoir etc., we apply the 3D electrical resistivity tomography detecting technology and volume rendering image processing technology, make the measurement in field, process the data and combine the field survey to find out the leakage channels inside the dam. The results show that the 3D resistivity images appear the low resistivity zone corresponding with the leakage channels. There are two main leakage channels that come from different location inside the dam. It is feasible to diagnose the leakage in earth rock-fill dam by applying 3D electrical resistivity tomography.展开更多
The weak structure plane is an important factor affecting the stability of rock slope, and detecting the spatial structure of the weak structural plane is beneficial to analyze the stability of the slope and estimate ...The weak structure plane is an important factor affecting the stability of rock slope, and detecting the spatial structure of the weak structural plane is beneficial to analyze the stability of the slope and estimate the quantity of the landslide. Based on 3D electrical resistivity tomography, a model of rock slope with weak structure plane is established, and the characteristics of three-dimensional resistivity imaging of weak structure plane under different ground water conditions are simulated. The results show that the weak structural plane has a better reflection in 3D electrical resistivity tomography;the distribution of weak structural plane of 3D resistivity imaging can be roughly determined under different ground water conditions;the three-dimensional electrical resistivity tomography is feasible in the detection of weak structural plane of rock slope.展开更多
By electrical resistance tomography (ERT) the cross sectional profiles of gas hold-up in a φ56mm bubble column are obtained with four designs of gas sparger. The effect of sparger geometry on the bubble distribution ...By electrical resistance tomography (ERT) the cross sectional profiles of gas hold-up in a φ56mm bubble column are obtained with four designs of gas sparger. The effect of sparger geometry on the bubble distribution is re-vealed by applying a sensitivity conjugated gradients reconstruction method (SCG). Experimental results show that over-all hold-up obtained by ERT is generally in good agreement with those measured with the pressure transducer and the ERT system produces informative evidence that the radial profiles of hold-up is very similar to the sparger design in the lower section of bubble column. Meanwhile, the rise velocity of bubble swarm and the Sauter mean bubble size are evaluated using ERT based on dynamic gas disengagement theory. The experimental results are in good agreement with correlations and conventional estimation obtained using pressure transmitter methods.展开更多
Geophysical surveys are frequently applied in mining prospection to detect the presence and volume of ore bodies of different nature.Particularly,in gypsum ore bodies exploitation,electrical resistivity measurements a...Geophysical surveys are frequently applied in mining prospection to detect the presence and volume of ore bodies of different nature.Particularly,in gypsum ore bodies exploitation,electrical resistivity measurements are usually the most used methodology.However,it has been observed that different electrical resistivity values can be obtained depending on geometrical features and composition of gypsum.Indeed,electrical resistivity of gypsum rocks depends on several parameters,such as gypsum purity,nature of secondary minerals,porosity,saturation and interstitial fluid properties.Saturation and hydrogeological setting,in particular,were recognized as the most influencing parameters.Hydrogeological conditions of gypsum rock masses are also very relevant for exploitability,safety conditions and economic feasibility and should be accurately known during the prospection and planning phases of the quarries.In this work,a relationship between electrical resistivity and saturation degree of gypsum is proposed.The possibility to estimate gypsum porosity with the use of this relationship is also investigated.The reliability of laboratory measurements is finally verified in comparison with field and modelled resistivity data.The reported results underline the potentiality of the proposed approach to obtain a reliable characterization of the studied ore body.展开更多
The all traditional electrical resistance tomography (ERT) sensors have a static structure, which cannot satisfy the intelligent requirements for adaptive optimization to ERT sensors that is subject to flow pattern ch...The all traditional electrical resistance tomography (ERT) sensors have a static structure, which cannot satisfy the intelligent requirements for adaptive optimization to ERT sensors that is subject to flow pattern changes during the real-time detection of two-phase flow. In view of this problem, an adaptive ERT sensor with a dynamic structure is proposed. The electrodes of the ERT sensor are arranged in an array structure, the flow pattern recognition technique is introduced into the ERT sensor design and accordingly an ERT flow pattern recognition method based on signal sparsity is proposed. This method uses the sparse representation of the signal to express the sampling voltage of the ERT system as a sparse combination and find its sparse solution to achieve the classification of different flow patterns. With the introduction of flow identification information, the sensor has an intelligent function of adaptively and dynamically adapting the sensor structure according to the real-time flow pattern change. The experimental results show that the sensor can automatically identify four typical flow patterns: core flow, bubble flow, laminar flow and circulation flow with recognition rates of 91%, 93%, 90% and 88% respectively. For different flow patterns, the dynamically optimized sensor can significantly improve the quality of ERT image reconstruction.展开更多
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sponsored by CAS-TWAS President’s Fellowship for International PhD Studentsfinancially supported by the National Natural Science Foundation of China (NSFC+3 种基金 Grant No. 41772320)the Strategic Priority Research Program of the University of Chinese Academy of Sciences (Grant No.XDB 10030100)CAS-TWAS President’s FellowshipKey Laboratory of Shale Gas and Geoengineering, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing China
文摘Assessment of fractured rock aquifers in many parts of the world is complicated given their strong heterogeneity. Delineation of the subsurface geological formation in the weathered terrain is essential for groundwater exploration. To achieve this goal, 2D electrical resistivity tomography(ERT) and self-potential(SP) in combination with joint profile method(JPM) and boreholes have been carried out to delineate the subsurface geological units, detect the fracture/fault zones in hard rock, monitor the groundwater flow, and estimate the groundwater reserves contained within the weathered terrain at a complex heterogeneous site of Huangbu, South Guangdong of China. The integration of resistivity images with the borehole lithology along three profiles delineates three subsurface distinct layers namely topsoil cover, weathered and unweathered layers. The incorporation of ERT and SP with JPM reveal five fractures/faults, i.e., F_1, F_2, F_3, F_4 and F_5. 2D ERT models interpret the less resistive anomalies as the fractures/faults zones, and high resistive anomalies as the fresh bedrock. The inversion program based on the smoothness-constraint is used on the resistivity field data to get more realistic three layered model. SP measurements are obtained along the same electrical profiles which provide the negative anomalies clearly indicating the groundwater preferential flow pathways along the fracture/fault zones. Hydraulic parameters namely hydraulic conductivity and transmissivity were determined to estimate the groundwater resources contained within the fractures/faults. The integrated results suggest that the fractures/faults zones are most appropriate places of drilling for groundwater exploration in the investigated area. Geophysical methods coupled with the upfront borehole data provides better understanding about the conceptual model of the subsurface geological formations. The current investigation demonstrates the importance of the integrated geophysical methods as a complementary approach for groundwater assessment in the hard rock weathered areas.
基金Project(20120162110015)supported by the Research Fund for the Doctoral Program of Higher Education,ChinaProject(41004053)supported by the National Natural Science Foundation of ChinaProject(12c0241)supported by Scientific Research Fund of Hunan Provincial Education Department,China
文摘Nonlinear resistivity inversion requires efficient artificial neural network(ANN)model for better inversion results.An evolutionary BP neural network(BPNN)approach based on differential evolution(DE)algorithm was presented,which was able to improve global search ability for resistivity tomography 2-D nonlinear inversion.In the proposed method,Tent equation was applied to obtain automatic parameter settings in DE and the restricted parameter Fcrit was used to enhance the ability of converging to global optimum.An implementation of proposed DE-BPNN was given,the network had one hidden layer with 52 nodes and it was trained on 36 datasets and tested on another 4 synthetic datasets.Two abnormity models were used to verify the feasibility and effectiveness of the proposed method,the results show that the proposed DE-BP algorithm has better performance than BP,conventional DE-BP and other chaotic DE-BP methods in stability and accuracy,and higher imaging quality than least square inversion.
文摘Electrical resistivity tomography survey was deployed at a solid waste landfill in southwest Missouri USA with the intent to map variations in moisture content through the solid waste and underlying subsurface, and to map the top of bedrock. Multichannel analyses of surface waves survey was also deployed to map variations in engineering properties of the solid waste and underlying subsurface, and to constrain the interpretations of top of bedrock. The 2-D resistivity images through the waste suggest rainwater seeps through the cap cover system of the solid waste landfill, and moisture content within the solid waste increases with solid waste burial depth. The resistivity anomalies displayed by the soil and bedrock directly underneath the solid waste suggests a lateral component to moisture infiltrating at the toe of the landfill, which is flowing inward to the base of solid waste structural low. The 1-D shear wave velocity profiles obtained from the multichannel analyses of surface waves survey helped interpret the top of bedrock underneath the solid waste, where top of bedrock is difficult to map using electrical resistivity tomography, as shallow fractured bedrock is moist and displays comparable resistivity values to that of overlying soil. Not surprisingly, the top of bedrock is readily identified on the electrical resistivity tomography profiles in places where subsurface is relatively dry. The deployment of the combined non- invasive, cost and time effective geophysical surveys, along with engineering judgement on available site history data, has reasonably identified potential landfill seepage pathways. The methodology presented could be used in similar site investigation settings.
文摘In order to ensure access to drinking water for Benin populations by 2021, the Emergency Measure program for the reinforcement of the drinking water supply system of Savalou city was initiated in 2018. This program focuses on densification and extension of hydraulic infrastructures. Therefore, it is prominent to use rigorous approach for implementation and execution of drilling activities. The present work has the advantage of combining the use of electrical resistivity tomography and borehole technique to locate ten high flow drilling in Savalou city. The electrical resistivity tomography (ERT) panels were made based on the dipole-dipole arrays with 48 electrodes with 5 m inter-electrode spacing. The drilling was carried out over ten selected points and in two stages: confirmation test using piezometer and borehole diameter enlargement. Moreover, only piezometers with flow rate greater than 10 m3/h were enlarged. The tomography processing has identified 10 fractured zones that are defined by 250 - 1000 ohm.m resistivity values and a width between 15 - 55 m. The confirmation test carried out over ten piezometers exhibits high flow rates ranging from 9 to 35 m3/h with depths of 30 to 68 m. Nine over the ten boreholes with a flow rate equal or greater than 10 m3/h, have improved their flow rates by 50% to 100% after the boring technique. Thus, the cumulative flow rate has reached 252. 7 m3/h for Savalou city and his surrounding areas.
文摘Experiments using electrical resistivity tomography(ERT) have shown promising results in reducing the uncertainty of solute plume characteristics related to estimates based on the analysis of local point measurements only.To explore the similarities and differences between two cross-borehole ERT inversion approaches for characterizing salt tracer plumes,namely the classical smoothness-constrained inversion and a geostatistically based approach,we performed two-dimensional synthetic experiments.Simplifying assumptions about the solute transport model and the electrical forward and inverse model allowed us to study the sensitivity of the ERT inversion approaches towards a variety of basic conditions,including the number of boreholes,measurement schemes,contrast between the plume and background electrical conductivity,use of a priori knowledge,and point conditioning.The results show that geostatistically based and smoothness-constrained inversions of electrical resistance data yield plume characteristics of similar quality,which can be further improved when point measurements are incorporated and advantageous measurement schemes are chosen.As expected,an increased number of boreholes included in the ERT measurement layout can highly improve the quality of inferred plume characteristics,while in this case the benefits of point conditioning and advantageous measurement schemes diminish.Both ERT inversion approaches are similarly sensitive to the noise level of the data and the contrast between the solute plume and background electrical conductivity,and robust with regard to biased input parameters,such as mean concentration,variance,and correlation length of the plume.Although sophisticated inversion schemes have recently become available,in which flow and transport as well as electrical forward models are coupled,these schemes effectively rely on a relatively simple geometrical parameterization of the hydrogeological model.Therefore,we believe that standard uncoupled ERT inverse approaches,like the ones discussed and assessed in this paper,will continue to be important to the imaging and characterization of solute plumes in many real-world applications.
文摘Electrical resistivity tomography data were acquired in proximity to the coal combustion residual landfill in an effort to image and analyze seepage pathways through the shallow residual soil and underlying karsted limestone bedrock. The water table is at a depth of more than 45 m. The most prominent subsurface seepage pathways identified on the acquired electrical resistivity tomography data are located immediately adjacent to the toe of the landfill and are attributed to stormwater run-off. The moisture content of the limestone appears to decrease gradually with increasing distance from the toe of the landfill, suggesting there is also a horizontal component of moisture flow in the subsurface. Shallow limestone with higher moisture content generally underlies or is in close proximity to anthropogenic features such as drainage ditches and clay berms that are designed to channel run-off. At one location, electrical resistivity tomography data were acquired along essentially the same traverse at different times of the year, and the resistivity of shallow limestone overall was lower on the data acquired after heavy rains.
基金The Taishan Scholar Special Experts Project of Shandong Province under contract No.ts201712079the National Natural Science Foundation of China under contract No.41976074the National Key Research and Development Program of China under contract No.2018YFE0126400。
文摘Laboratory visual detection on the hydrate accumulation process provides an effective and low-cost method to uncover hydrate accumulation mechanisms in nature.However,the spatial hydrate distribution and its dynamic evolutionary behaviors are still not fully understood due to the lack of methods and experimental systems.Toward this goal,we built a two-dimensional electrical resistivity tomography(ERT)apparatus capable of measuring spatial and temporal characteristics of hydrate-bearing porous media.Beach sand(0.05–0.85 mm)was used to form artificial methane hydrate-bearing sediment.The experiments were conducted at 1°C under excess water conditions and the ERT data were acquired and analyzed.This study demonstrates the utility of the ERT method for hydrate mapping in laboratory-scale.The results indicate that the average electrical conductivity decreases nonlinearly with the formation of the hydrate.At some special time-intervals,the average conductivity fluctuates within a certain scope.The plane conductivity fields evolve heterogeneously and the local preferential hydrate-forming positions alternate throughout the experimental duration.We speculate that the combination of hydrate formation itself and salt-removal effect plays a dominant role in the spatial and temporal hydrate distribution,as well as geophysical parameters changing behaviors during hydrate accumulation.
文摘This research applies Electrical Resistivity Tomography (ERT) and Time Domain Electromagnetic Method (TDEM) to study the hydrogeology of the Taubaté basin, which is characterized by half-grabens with about 850 m of maximum sediments thickness. The study area is in Taubaté city, São Paulo State, Brazil, where the Taubaté aquifer is an important water source. The Taubaté Group is the main sedimentary package of the basin;it is formed mainly by shales that form aquicludes, and thin layers of sandstones that form the aquifer. There are 40 groundwater exploration wells in Taubaté city that provide important information. The study purpose is to characterize the geoelectrical stratigraphy of the subsurface to locate the contact between the Quaternary and Tertiary sediments and to identify the Taubaté aquifer. The ERT is used for shallow investigations (tens of meters) and the TDEM can reach a great investigation depth (hundreds of meters). Therefore, these geophysical methods are complementary. The ERT data were acquired with the pole-dipole array with 20 m of electrodes spacing and 400 m length, and the TDEM data with the central-loop array with a 200 × 200 m transmitter loop. The results permit to define the contact between the Quaternary and Tertiary sediments around 15 m depth, the Pindamonhangaba Formation between 15 m and 30 m depth and the Taubate Group between 30 m and 300 m depth. The TDEM method defined the Taubaté Group as a single geoelectric layer because the shale and the sandstone layers are all very conductive. The basement is formed by gneiss, which is a very resistive rock. The TDEM method is not able to identify a high conductor/resistor contrast. Overall, the results are consistent with the known geology and the wells information.
文摘Position, width and fragmentation level of fracture zones and position, sig-nificance and characteristic distance of fractures were aimed to determine in a carbonate aquifer. These are fundamental parameters, e.g. in hydrogeological modelling of aquifers, due to their role in subsurface water movements. The description of small scale fracture systems is however a challenging task. In the test area (Kádárta, Bakony Mts, Hungary), two methods proved to be applicable to get reasonable information about the fractures: Electrical Resistivity Tomography (ERT) and Pricking-Probe (PriP). PriP is a simple mechanical tool which has been successfully applied in archaeological investigations. ERT results demonstrated its applicability in this small scale fracture study. PriP proved to be a good verification tool both for fracture zone mapping and detecting fractures, but in certain areas, it produced different results than the ERT. The applicability of this method has therefore to be tested yet, although its problems most probably origin from human activity which reorganises the near-surface debris distribution. In the test site, both methods displayed fracture zones including a very characteristic one and a number of individual fractures and determined their characteristic distance and significance. Both methods prove to be able to produce hydrogeologically important parameters even individually, but their simultaneous application is recommended to decrease the possible discrepancies.
基金The National Natural Science Foundation of China (No.50238040)
文摘According to the principle of electrical resistance tomography （ ERT）, the resistivity distribution of the carbon fiber reinforced concrete （CFRC） in the sensing field can be measured by injecting exciting current and measuring the voltage on the sensor electrode arrays installed on the surface of the object. Therefore, measurement of the resistivity distribution of CFRC is divided into first measuring the boundary conditions and then inversely computing the resistivity distribution. To reach this goal, an ERT system was constructed, which is composed of a sensor array unit, a data acquisition unit and an image reconstruction unit. Simulations of static ERT was performed on set-ups with many objects spread in a homogeneous background, and a simulation of dynamic ERT was also done on a rectangular board, the resistivity of which was changed within a small domain of it. Then, the resistivity distribution of a CFRC sample with a circlar hole as the target was detected by the ERT system. Simulation and experimental results show that the reconstructed ERT image reflects the resistivity distribution or the resistivity change of CFRC structure well. Especially, a small change in resistivity can be identified from the reconstructed images in the simulation of dynamic ERT images.
文摘The leakage occurs during operation of the dam in Liuhuanggou reservoir. It’s a threat to the safety of the people’s lives and property in downstream. In order to eliminate the hidden danger of reservoir, ensure the safety of the dam, play better the function of flood control and water storage of the reservoir etc., we apply the 3D electrical resistivity tomography detecting technology and volume rendering image processing technology, make the measurement in field, process the data and combine the field survey to find out the leakage channels inside the dam. The results show that the 3D resistivity images appear the low resistivity zone corresponding with the leakage channels. There are two main leakage channels that come from different location inside the dam. It is feasible to diagnose the leakage in earth rock-fill dam by applying 3D electrical resistivity tomography.
文摘The weak structure plane is an important factor affecting the stability of rock slope, and detecting the spatial structure of the weak structural plane is beneficial to analyze the stability of the slope and estimate the quantity of the landslide. Based on 3D electrical resistivity tomography, a model of rock slope with weak structure plane is established, and the characteristics of three-dimensional resistivity imaging of weak structure plane under different ground water conditions are simulated. The results show that the weak structural plane has a better reflection in 3D electrical resistivity tomography;the distribution of weak structural plane of 3D resistivity imaging can be roughly determined under different ground water conditions;the three-dimensional electrical resistivity tomography is feasible in the detection of weak structural plane of rock slope.
文摘By electrical resistance tomography (ERT) the cross sectional profiles of gas hold-up in a φ56mm bubble column are obtained with four designs of gas sparger. The effect of sparger geometry on the bubble distribution is re-vealed by applying a sensitivity conjugated gradients reconstruction method (SCG). Experimental results show that over-all hold-up obtained by ERT is generally in good agreement with those measured with the pressure transducer and the ERT system produces informative evidence that the radial profiles of hold-up is very similar to the sparger design in the lower section of bubble column. Meanwhile, the rise velocity of bubble swarm and the Sauter mean bubble size are evaluated using ERT based on dynamic gas disengagement theory. The experimental results are in good agreement with correlations and conventional estimation obtained using pressure transmitter methods.
文摘Geophysical surveys are frequently applied in mining prospection to detect the presence and volume of ore bodies of different nature.Particularly,in gypsum ore bodies exploitation,electrical resistivity measurements are usually the most used methodology.However,it has been observed that different electrical resistivity values can be obtained depending on geometrical features and composition of gypsum.Indeed,electrical resistivity of gypsum rocks depends on several parameters,such as gypsum purity,nature of secondary minerals,porosity,saturation and interstitial fluid properties.Saturation and hydrogeological setting,in particular,were recognized as the most influencing parameters.Hydrogeological conditions of gypsum rock masses are also very relevant for exploitability,safety conditions and economic feasibility and should be accurately known during the prospection and planning phases of the quarries.In this work,a relationship between electrical resistivity and saturation degree of gypsum is proposed.The possibility to estimate gypsum porosity with the use of this relationship is also investigated.The reliability of laboratory measurements is finally verified in comparison with field and modelled resistivity data.The reported results underline the potentiality of the proposed approach to obtain a reliable characterization of the studied ore body.
基金Projects(51405381,51674188)supported by the National Natural Science Foundation of China
文摘The all traditional electrical resistance tomography (ERT) sensors have a static structure, which cannot satisfy the intelligent requirements for adaptive optimization to ERT sensors that is subject to flow pattern changes during the real-time detection of two-phase flow. In view of this problem, an adaptive ERT sensor with a dynamic structure is proposed. The electrodes of the ERT sensor are arranged in an array structure, the flow pattern recognition technique is introduced into the ERT sensor design and accordingly an ERT flow pattern recognition method based on signal sparsity is proposed. This method uses the sparse representation of the signal to express the sampling voltage of the ERT system as a sparse combination and find its sparse solution to achieve the classification of different flow patterns. With the introduction of flow identification information, the sensor has an intelligent function of adaptively and dynamically adapting the sensor structure according to the real-time flow pattern change. The experimental results show that the sensor can automatically identify four typical flow patterns: core flow, bubble flow, laminar flow and circulation flow with recognition rates of 91%, 93%, 90% and 88% respectively. For different flow patterns, the dynamically optimized sensor can significantly improve the quality of ERT image reconstruction.
