共查询到20条相似文献，搜索用时 31 毫秒
1.
Chemseddine Fehdi Fethi Baali Djamel Boubaya Abdelkader Rouabhia 《Arabian Journal of Geosciences》2011,4(1-2):181-187
Sinkhole collapse is one of the main limitations on the development of karst areas, especially where bedrock is covered by unconsolidated material. Studies of sinkhole formation have shown that sinkholes are likely to develop in cutter (enlarged joint) zones as a result of subterranean erosion by flowing groundwater. Electrical resistivity imaging or tomography (RESTOM) is well suited to mapping sinkholes because of the ability of the technique for detecting resistive features and discriminating subtle resistivity variations. Two-dimensional electrical resistivity tomography surveys were conducted at two sinkhole sites near Cheria city where limestone is covered by about 10 m of clayey soils. A Wenner transect was conducted between the two sinkholes. The electrode spacing was 2 m. The length of transect is about 80 m. The survey results suggest that RESTOM is an ideal geophysical tool to aid in the detection and monitoring of sinkholes and other subsurface cavities. 相似文献
2.
Gökhan Göktürkler Çağlayan Balkaya Zülfikar Erhan Ayça Yurdakul 《Environmental Geology》2008,54(6):1283-1290
Near-surface geophysical methods are commonly used to solve a wide class of geological, engineering and environmental problems. In this study, a geoelectrical survey was performed to investigate an alluvial aquifer. The study area is located in the southwest of the Çubukluda? graben, situated in the south of ?zmir, Turkey. The geophysical studies included the electrical resistivity imaging and self-potential (SP) methods. The resistivity data were acquired along eight profiles in the northern part of the study area by a Wenner-Schlumberger electrode configuration and the data processing was achieved by a tomographic inversion technique. The SP data were collected by gradient technique along 16 profiles. Total field values were calculated for each profile by addition of the successive gradient values, then a total field SP map was obtained. The water-saturated zone in the northern part of the study area was clearly revealed by the electrical resistivity imaging and the SP survey yielded useful information on the subsurface fluid movement. 相似文献
3.
I. Nouioua Aek. Rouabhia Ch. Fehdi M. L. Boukelloul L. Gadri D. Chabou R. Mouici 《Environmental Earth Sciences》2013,68(6):1661-1672
Sinkhole collapse is one of the main limitations in the development of karst areas, especially where bedrock is covered by unconsolidated material. Studies of sinkhole formation have shown that sinkholes are likely to develop in cutter (enlarged joint) zones as a result of subterranean erosion by flowing groundwater. Ground-penetrating radar (GPR) and electrical resistivity imaging or tomography (RESTOM) are well suited to mapping sinkholes because of the ability of these two techniques for detecting voids and discriminating subtle resistivity variations. Nine GPR profiles and two-dimensional electrical resistivity tomography have been applied, with relative success, to locate paleo-collapses and cavities, and to detect and characterize karst at two sinkhole sites near Cheria City where limestone is covered by about 10 m of clayey soils. The survey results suggest that GPR and RESTOM are ideal geophysical tools to aid in the detection and monitoring of sinkholes and other subsurface cavities. 相似文献
4.
Ahzegbobor P. Aizebeokhai Kehinde D. Oyeyemi Emmanuel S. Joel 《Arabian Journal of Geosciences》2016,9(7):496
Geoelectrical resistivity techniques are increasingly being applied in addressing a wide range of hydrological, environmental, and geotechnical problems. This is due to their effectiveness in near-surface characterization. In the present study, a suite of vertical electrical soundings (VESs) was integrated with 2D geoelectrical resistivity and time-domain induced polarization (IP) imaging to characterize the near-surface and delineate the underlying aquifer in a sedimentary terrain. The geophysical survey was conducted as part of preliminary studies to evaluate the potential of groundwater resource in Iyana-Iyesi and Canaan Land area of Ota, southwestern Nigeria. A high-yield confined sandy aquifer overlain by a low-yield aquitard was delineated; overlying the aquitard is a very resistive and thick layer that is predominantly composed of kaolinitic swelling clay intercalated with phosphate mineral. 相似文献
5.
通过有限元数值模拟方法,研究了电阻率法监测地下地质变化的可行性,提出了基于多期次观测的地下电阻率监测方法,应用二维电阻率正、反演程序对模型进行了数值模拟。结果表明,电阻率相对变化率可以较好地指示电阻率变化的区域和位置。高精度、大数据量的地电阻率观测,以及基于2D或3D的电阻率正、反演计算使得应用电阻率法监测地下地质变化成为可能。 相似文献
6.
This paper demonstrates the capabilities and limitations of a miniaturised electrical imaging technique (resistivity tomography) developed at Cardiff University to image contaminant plumes in scaled centrifuge models of the vadose zone. For this purpose a generic model of contaminant infiltration into unsaturated sand was designed. The imaging technique produces two-dimensional contoured plots of the resistivity distribution before and during contaminant infiltration experiments. During the experiments, dyed NaCl solution was released into the model and the change in resistivity associated with the contaminant plume evolution was imaged as a function of time and g-level. Capillary pressure was monitored constantly by matrix potential probes (tensiometers) in order to investigate the effect of capillary forces on plume evolution. Tests at 1g (static conditions) and 10g are described in this paper. Comparison of resulting two-dimensional tomography with observed plume geometry at the end of the 1g test showed this imaging technique to be highly effective.
Contaminant plume evolution in the unsaturated sand model was observed to be mainly gravity-driven, with plume migration and geometry being strongly affected by a tenfold increase in gravity in the centrifuge experiment. It is concluded that miniaturised electrical imaging can be a useful tool for monitoring pollution plume evolution during centrifuge tests, but when plume evolution is rapid, the time taken to interrogate each array restricts the effectiveness of the technique in monitoring changes in plume geometry. However, in such cases, resistivity tomography does provide valuable information on residual levels of contaminant fluid retained within the soil after passage of the plume. 相似文献
7.
A hydrogeophysical model of the relationship between geoelectric and hydraulic parameters of anisotropic aquifers 总被引：1，自引：0，他引：1
An electrical resistivity method has been used to determine aquifer parameters in the Ganga-Yamuna interfluve in northern India. An existing relationship between the geoelectrical and hydraulic parameters has been modified for the case of an anisotropic aquifer. The hydrogeological framework in the upper part of the Ganga-Yamuna interfluve is evaluated by using existing relationships between hydraulic parameters and geoelectrical parameters for alluvial aquifers. On the basis of aquifer geometry, the area has been divided into two hydraulic units: the western Yamuna flood plain and the Ganga flood plain towards the east. The resistivity data collected in parts of the study area are first interpreted in terms of true resistivity and thicknesses of subsurface layers. The electrical parameters (resistivity and thicknesses) are subsequently correlated with the available pumping test data. Distinct correlations between transmissivity and modified transverse resistance are obtained for the two hydraulic units. A four-parameter model consisting of hydraulic conductivity, modified longitudinal resistivity, modified transverse resistance and hydraulic anisotropy is presented for the anisotropic aquifer underlain by conductive fine grained sediments. The model has been validated at a number of locations, where aquifer parameters are known from pumping test data. 相似文献
8.
The use of resistivity sounding and two-dimensional (2-D) resistivity imaging was investigated with the aim of delineating and estimating the groundwater potential in Keffi area. Rock types identified are mainly gneisses and granites. Twenty-five resistivity soundings employing the Schlumberger electrode array were conducted across the area. Resistivity sounding data obtained were interpreted using partial curve matching approach and 1-D inversion algorithm, RESIST version 1.0. The 2-D resistivity imaging was also carried out along two traverses using dipole–dipole array, and the data obtained were subjected to finite element method modeling using DIPRO inversion algorithm to produce a two-dimensional subsurface geological model. Interpretation of results showed three to four geoelectrical layers. Layer thickness values were generally less than 2 m for collapsed zone, and ranged from 5 to 30 m for weathered bedrock (saprolite). Two major aquifer units, namely weathered bedrock (saprolite) aquifer and fractured bedrock (saprock) aquifer, have been delineated with the latter usually occurring beneath the former in most areas. Aquifer potentials in the area were estimated using simple schemes that involved the use of three geoelectrical parameters, namely: depth to fresh bedrock, weathered bedrock (saprolite) resistivity and fractured bedrock (saprock) resistivity. The assessment delineated the area into prospective high, medium and low groundwater potential zones. 相似文献
9.
Ahzegbobor Philips Aizebeokhai A. I. Olayinka V. S. Singh 《Environmental Earth Sciences》2010,61(7):1481-1492
Orthogonal set of 2D geoelectrical resistivity field data, consisting of six parallel and five perpendicular profiles, were
collected in an investigation site using the conventional Wenner array. Seven Schlumberger soundings were also conducted on
the site to provide ID layering information and supplement the orthogonal 2D profiles. The observed 2D apparent resistivity
data were first processed individually and then collated into 3D data set which was processed using a 3D inversion code. The
3D model resistivity images obtained from the inversion are presented as horizontal depth slices. Some distortions observed
in the 2D images from the inversion of the 2D profiles are not observed in the 2D images extracted from the 3D inversion.
The survey was conducted with the aim of investigating the degree of weathering and fracturing in the weathered profile, and
thereby ascertaining the suitability of the site for engineering constructions as well as determining its groundwater potential. 相似文献
10.
Gyesoon Park Samgyu Park Myeong-Jong Yi Hyoungrae Rim Seong-Jun Cho Jung-Ho Kim 《Environmental Earth Sciences》2010,60(5):965-974
Two-dimensional (2-D) electrical resistivity and three-dimensional (3-D) gravity explorations were undertaken to estimate
the 3-D distribution of karst cavities at the area of Yongweol-ri in Korea where ground subsidence has occurred. Although
the gravity method is a low-cost way of analyzing a 3-D continuous structure, its vertical resolving power is poor. In contrast,
the electrical resistivity method can provide a 2-D and/or 3-D subsurface structure with a much higher lateral and vertical
resolution than the gravity method. Accordingly, geostatistical methods and density information were used to enhance the 2-D
resistivity structure revealed by the electrical resistivity method into a 3-D structure. The assumptions are, first, that
each data set senses the same underlying geological structure in terms of different material properties and, secondly, that
two different material properties are correlated locally or globally throughout the entire target area. As a result, the distribution
of limestone cavities can be estimated under the assumption that they are mostly filled with groundwater and clayey soils
and have abnormally low levels of resistivity and density. The estimated distribution corresponds with the grouting, borehole
imaging and monitoring data. In this example, it can be seen that the integration analysis of 2-D electrical resistivity and
3-D gravity methods is a very powerful tool for 3-D subsurface imaging and that the method can provide enhanced imaging capabilities
for 3-D cavities. 相似文献
11.
利用ICCG迭代技术加快电阻率三维正演计算 总被引：2，自引：2，他引：0
一般而言,有限差分法求解点源三维地电场正问题所形成的大型稀疏线性方程组Ａｘ＝ｂ,直接解法的计算效率极低。本文从系数矩阵Ａ的不完全Ｃｈｏｌｅｓｋｙ分解及矩阵特征值的特点等角度,说明了不完全Ｃｈｏｌｅｓｋｙ共轭梯度（ＩＣＣＧ）迭代技术可大大提高电阻率三维正演速度的内在原因。结合矩阵Ａ的稀疏存储模式,使得内存需求也大大减少。 相似文献
12.
The effectiveness of inversion apparent resistivity data to determine accurately the true resistivity distribution over 2D structures has been investigated using a common inversion scheme based on smoothness-constrained nonlinear least-squares optimization with enhancing horizontal resolution (EHR) technique by numerical simulation. The theoretical model generates in RES2DMOD software at specific distance and depth using Wenner, Wenner–Schlumberger, and pole–dipole arrays were inverted. The inversion model was compared with the original 2D model in RES2DINV software. The study model includes horizontal layering, vertical resolution, and horizontal two layers with different resistivity. Also, the response to variations in data density of these arrays was investigated. The study shows the best array suitable to be used in the survey was chosen for real data acquisition at the actual site. Subsequently, the results from borehole were used to verify the results of 2D resistivity imaging method with and without EHR technique. Saturated zone (0–40 Ω-m) was found scattered at the depth of 10–20 m. The borehole is located at 63 m at 2D resistivity imaging survey which shows at depth 10–20 m is sandy silt. Highly weathered sandstone was found at 6 m depth with resistivity value of 800 Ω-m and SPT N value of 20. The bedrock was found at 27 m depth with resistivity value of 3,000 Ω-m and SPT N value of 50. The application of 2D resistivity imaging with EHR technique indicate the ability of the proposed approach in terms of density, depth, and resistivity value of anomalous and layer in a computationally and numerically efficient manner and to exhibit good performance in the data inversion. 相似文献
13.
A series of 2D apparent resistivity data were generated over two synthetic models representing different geological or environmental
conditions commonly associated with geophysical applications for hydrogeological, environmental and engineering investigations.
The apparent resistivity data were generated for the following arrays: Wenner-alpha (WA), Wenner-beta (WB), Wenner–Schlumberger
(WSC), dipole–dipole (DDP), pole–dipole (PDP) and pole–pole (PP) arrays, which were paired such that apparent resistivity
data for 2D profiles in a parallel direction are obtained with a particular array type and those in a perpendicular direction
are observed with a different array type. The 2D apparent resistivity data for the orthogonal paired-arrays were then collated
to 3D data sets. The effectiveness and efficiency of the orthogonal paired-arrays in 3D geoelectrical resistivity imaging
were evaluated by determining the mean absolute anomaly effects of the electrode configurations on the synthetic models. The
results show that DDP–PDP, DDP–PP, DDP–WSC, PDP–PP, DDP–WB, PDP–WB and WB–WSC orthogonal paired-arrays produced higher anomaly
effects on the synthetic models. This indicates that DDP–PDP, DDP–PP, DDP–WSC, PDP–PP, DDP–WB, PDP–WB and WB–WSC orthogonal
paired-arrays are more sensitive to 3D features of the geologic models than the other orthogonal paired-arrays investigated. 相似文献
14.
Electrical geophysical surveys in the mode of vertical electrical soundings (VES) and continuous vertical electrical soundings (CVES) were conducted in the León-Chinandega plains, northwestern Nicaragua, in order to obtain detailed information about the geometry of the different hydrogeological layers in the aquifer and depth to the basement. A total of 51 VES were carried out within the plains. The results show a complex structure towards the north east of the area, and the southwestern part of the plains presents a smoother stratification. The geoelectrical measurements and borehole information indicate that the basement topography is characterized by hills and deep valleys with highly variable basement depths. Fifty CVES where done in a smaller area in the center of the plain. The resistivity data yielded considerable information revealing the existence of two main geo-electrical units. The combined interpretation of geological and geophysical data shows an environment typical of sedimentary volcanic coastal plains. The information collected during this investigation provides valuable data for estimating the fresh-water resources of the León-Chinandega aquifer system and for development of a groundwater management plan. 相似文献
15.
16.
Khaled S. Gemail Mohamed Attwa Mohamed Eleraki Sara Zamzam 《Environmental Earth Sciences》2017,76(19):666
The objective of this study is to evaluate the effectiveness of DC resistivity surveys for imaging the wastewater percolation around the stabilization ponds in the Tenth of Ramadan City, the desert fringes of East Nile Delta, Egypt. Detailed resistivity surveys, including DC soundings and electrical resistivity tomography (ERT), were carried out along several profiles. Furthermore, synthetic modeling of ERT was designed to optimize the survey configurations and interpretation of the results. A 2D modeling of smoothness-constrained least-squares inversion scheme was applied to delineate the possible wastewater infiltration zones from oxidation ponds. Because the geoelectrical interpretation has a degree of non-uniqueness, the resistivity inversion was constrained using borehole lithological information and soil sample laboratory measurements. The DC inversion results indicate decreasing resistivity down to a depth of 15 m around waste disposal sites. The inferred soil zone close to the oxidation ponds was a mixture of sand, silt and clay. Moreover, the clay minerals were characterized by moderate swelling that could have reduced the vertical infiltration speed, causing wastewater seepage, especially around unlined disposal sites and open surface drains. Accordingly, the medium-to-low resistivity values can be attributed to wastewater leakage in clayey sand soil. Because the area slopes generally toward the northeast, the surface seepage was dominant in the shallow impermeable sandy clay subsoil. Therefore, measuring soil parameters is a complementary method to optimize resistivity interpretation, with potential for mitigating environmental hazards from wastewater leakage around disposal ponds. 相似文献
17.
Integrated geoelectrical resistivity and hydrogeochemical methods for delineating and mapping heavy metal zone in aquifer system 总被引：1，自引：0，他引：1
Nur Islami Samsudin Hj Taib Ismail Yusoff Azman Abdul Ghani 《Environmental Earth Sciences》2018,77(10):383
A novel study on using geoelectrical resistivity, soil property, and hydrogeochemical analysis methods for delineating and mapping of heavy metal in aquifer system is presented in this paper. A total of 47 surveys of geoelectrical resistivity with Wenner configuration were conducted to determine the subsurface and the groundwater characteristics. The groundwater sample from 53 existing wells and 2 new wells has been analyzed to derive their water chemical content. The chemical analysis was done on the soil sample obtained from new two wells and from selected locations. The water and soil chemical analysis results from the new two wells were used as calibration in resistivity interpretation. The occurrence of heavy metal in aquifer system was expected to detect using the geoelectrical resistivity survey for the whole study area. The result of groundwater analysis shows that the groundwater sample contains a relatively low concentration of Fe (<?0.3 mg/L) elongating from the south up to the middle region. While in the middle and the northwestern, Fe concentration is relatively high (around 12 mg/L). Chemical analysis of soil sample shows that in the lower resistivity zone (<?18 Ωm), Al and Fe concentrations are comparatively high with an average of 68,000 and 40,000 mg/kg, respectively. Starting from the middle to the northwestern zone, the resistivity value appears to be low. It is definitely caused by higher Al and Fe concentration within the soil, and it is supported also by lower total anion content in the groundwater. While the resistivity value of more than 40 Ωm in aquifers is obtained in the zone which Fe concentration is relatively lower in the soil but not present in the groundwater. Correlation Fe concentration in the soil and Fe concentration in the groundwater sample shows the trend of positively linear; however, the Al concentration in soil has no correlation with Al content in groundwater. Finally, the probability of high heavy metal zone in the aquifer system is easily delineated by the distribution of geoelectrical resistivity presented in depth slice shapes which extend from the Boundary Range Composite Batholith in the north to the northwest. 相似文献
18.
V.S. Mogilatov 《Russian Geology and Geophysics》2012,53(5):484-490
The accuracy (detail, resolution) of controlled-source electrical prospecting is a combination of several disparate elements. They include the model framework used in the interpretation. A real geologic medium has a complex structure. Sedimentary rocks have a layered structure with fractal properties: The layers split into smaller ones. Large-scale geoelectrical studies (for example, electrical prospecting) require a proper geoelectrical model. By necessity, the 1D geoelectrical model in electrical prospecting is horizontally layered, with thick (hundreds of meters) homogeneous layers, whereas a fine structure is neglected. To study some aspects of this problem, we performed a set of numerical experiments. They were aimed at studying the TEM response from a formation consisting of many thin layers with random geoelectric parameters, mainly resistivity. 相似文献
19.
20.
We propose a discretization technique using non-fitting grids to simulate magnetic field-based resistivity logging measurements. Non-fitting grids are convenient because they are simpler to generate and handle than fitting grids when the geometry is complex. On the other side, fitting grids have been historically preferred because they offer additional accuracy for a fixed problem size in the general case. In this work, we analyse the use of non-fitting grids to simulate the response of logging instruments that are based on magnetic field resistivity measurements using 2.5D Maxwell’s equations. We provide various examples demonstrating that, for these applications, if the finite element matrix coefficients are properly integrated, the accuracy loss due to the use of non-fitting grids is negligible compared to the case where fitting grids are employed. 相似文献