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1.
为解决内蒙古白旗地区水资源严重短缺的问题,采用瞬变电磁技术进行水资源勘察.本文通过分析平原地区含水层的矿化度和孔隙度对岩石电阻率的影响,得出在内蒙古干旱牧区浑善达克沙地的含水砂砾岩电阻率值为75~150 Ω·m之间变化.以导电球体为模型来计算地下含水层异常的可分辨时间窗口,确定该区地下含水层异常出现最大值的探测条件.瞬变电磁技术在结合已知自流井的电性差异基础上,可以对地下水的含水层和含水深度进行准确勘察,确定新的水井5位置,经钻孔验证喷水量达到每小时100 m3以上,满足白旗供水需求.验证了瞬变电磁技术在地下水资源勘察中的有效性,为西部地区水资源的评价提供了重要的技术依据. 相似文献
2.
由于人工源电磁探测效果与收发距离有一定关系，本文首先分析了收发距离为零的中心回线源瞬变电磁法（Transient Electromagnetic Method，TEM）视电阻率定义和算法特点，回溯了从圆形回线到矩形的修正式中心回线装置的发展过程；概述了从中心回线发展到接地导线源短偏移瞬变电磁（Short-Offset TEM，SOTEM）理论上的可行性；列举了将LOTEM（Long-Offset TEM）从数倍于探测深度的观测区推进到近源区后的探测实例.对于频率域人工源电磁法，介绍了起源于MT（Magneto-Telluric）的CSAMT（Controlled Source Audio-frequency Magneto-Telluric）与电磁频率测深法不同发展道路.电磁频率测深将观测区从远区推进到了中区；广域电磁法通过全区视电阻率新定义不仅提高了解释精度，而且将传统CSAMT远场观测模式推进到中区探测模式；最后指出，如能采用新的点微元假设计算方法，可有望分离自有场和辐射场，实现频域电磁近源探测. 相似文献
3.
较详细地介绍了近年来国内外地面瞬变电磁法（TEM）的基本原理、特点、影响因素、测量仪器、数据处理、数据解译（数据的正演和反演）方面的研究状况和所取得的进展,简要介绍了其应用前景,由于具有探测深度大、空间分辨率高等优势,TEM在地质灾害、建筑工程、水文地质工程特别是在深部找矿等方面得以广泛应用。 相似文献
4.
诸多研究表明我国深部资源潜力巨大，但目前的开发开采深度普遍停留在500 m以浅，开展"攻深探盲"是构建国家资源安全体系的有效途径.应用最先进的科学技术手段，提取深部地质信息，已成为我国当前地球物理科学研究的发展方向.作为地球物理学的重要分支，电磁法是矿产资源探查的主体手段之一.在分析我国现阶段航空、地面及海洋电磁探测技术进展的基础上，本文重点说明了极低频电磁法（简称WEM法），多通道瞬变电磁法（简称MTEM）和电性源短偏移瞬变电磁法（简称SOTEM）等电磁探测新技术.WEM法建立一套包括岩石层、大气层和电离层在内的全空间电磁传播理论，通过新研制的观测系统，获取地下10 km的地电信息；MTEM方法是地下埋深4 km目标体精细勘查的有效手段；SOTEM实现地下1.5 km深度范围内目标体的精细探测.通过多种电磁探测技术组合，可实现地下10 km深度范围内多尺度探测，达到"望远镜+放大镜+显微镜"探测效果.同时，本文指出进一步研发与新方法配套的装备、资料处理技术和大数据人工智能识别等将是我国电磁法未来的发展方向. 相似文献
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为准确确定露天煤矿地下水分布与类型，根据不同赋存条件电磁差异，基于磁场强度与电阻率参数进行异常划分与类型判别。以新疆某露天煤矿为例，采用高精度磁法通过磁异常强度确定烧变岩边界，并采用高密度电法和瞬变电磁法通过电阻率圈定低阻异常区，结合异常响应差异分别推断地下水分布范围与赋存类型。地面钻探验证探测成果的准确性。结果表明:露天煤矿烧变岩水与砂岩裂隙水电磁响应差异明显，基于磁场强度与电阻率的双参数综合电磁法能准确圈定其分布范围，并判别其赋存类型。 相似文献
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目前，瞬变电磁法（TEM）数据基本都是基于各向同性模型进行反演解释，这对于存在明显电性各向异性的勘探区域会产生较大的反演解释误差.为分析电各向异性对回线源瞬变电磁信号的影响方式与程度，本文通过求解离散化的全张量电导率时间域Helmholtz方程，实现了基于有限体积法的TEM任意各向异性的三维正演算法.该算法采用基于交错网格的拟态有限体积法（MFV）对时域Maxwell方程组进行空间域离散，并利用后退欧拉算法（Backward Euler Method）进行时间域离散.为提高时域电磁场的求解精度与效率，该算法将时间分段等步长算法与方程直接求解法相结合.通过对一维各向异性模型以及三维复杂各向同性模型进行测试，验证了本算法对于回线源瞬变电磁响应计算的正确性及有效性.最后，通过对几类典型电各向异性介质中大回线源瞬变电磁信号响应的分析，总结了不同电各向异性类型对TEM电磁信号的影响模式，结果表明，主轴各向异性情况下TEM信号主要受水平方向电导率的影响，倾斜各向异性对TEM信号的影响程度远大于水平各向异性，而通过水平各向异性信号能较清晰判断出各向异性主轴方向. 相似文献
9.
本文通过在广东省湛江市省级生态农业示范区——南木水地区进行地下水探测拟解决当地的生活用水问题.该区域主要为燕山期花岗岩,本文采用了音频大地电磁法(AMT)勘探方法,从构造分析出发,选择三个有利区域(分别为A、B、C、区),布设了10条AMT勘探线,共166个测点,进行野外数据.对野外数据进行了一系列预处理、反演和电阻率成像得到各线的剖面图.分析研究剖面图和切片图,确定了三个可能含水的低阻带以及三口钻井的位置.其中C区已经打井取水,出水50 m~3/h,很好地验证了AMT方法在硬岩地区进行地下水探测的实用性和有效性. 相似文献
10.
海洋电磁法研究的现状和进展 总被引：17，自引：0，他引：17
海洋电磁法是研究海洋特别是海底的重要手段之一,我国对海洋（海底）资源的开发利用,和科学研究址分重视,已将海洋电磁法研究列入国这“８６３”计划。最近通过了专属经济区和大陆架的有关法规,笔者在广泛收集迄今为止国内外大量资料的基础上,经编,译,整理,撰写了本文,力求全面地介绍这一领域的历史,现状和进展,各种海洋电磁法的基本原理,海洋（海底）电磁法操作的要求和特点,以及应用实例,以推时我国海洋电磁法研究的 相似文献
11.
Usama Massoud Gad El Qady Mohamed Metwaly Fernando Santos 《Pure and Applied Geophysics》2009,166(4):701-719
An azimuthal resistivity survey was conducted at the transition zone between the desert area and the cultivated land near
Lake Qaroun, Egypt. This area has been affected by an east-west trending fault system as indicated from the surface geology.
Apparent resistivity values were plotted along azimuth on a polar diagram. Resistivity anomalies, for most of the AB/2 values
with long axes strike in a direction parallel to the contact between the desert and cultivated lands, indicate the presence
of electrical macro-anisotropy, mainly due to the faulting effect, at this area. Vertical electrical soundings (VES) and transient
electromagnetic (TEM) measurements were conducted at eight stations along a line that crosses the boundary between the desert
and cultivated land. Joint inversion of VES-TEM data was successfully used for identification of the subsurface lithostratigraphic
succession and demonstrated the effect of the fault zone on the investigated subsurface medium. Apparent anisotropy coefficients
at all current electrode spacings were calculated, plotted against AB/2 values and compared with the geoelectrical cross section.
The effect of the fault zone was detected at AB/2 spacings equal to 100 m and extended downward and is largely related to
the depth of the fault, as indicated in the constructed cross section. 相似文献
12.
Klaus-G. Hinzen Stephan Schreiber Claus Fleischer Sharon K. Reamer Isabel Wiosna 《Journal of Seismology》2013,17(2):399-424
The causes of damage observed in archeological records or preserved monuments are often difficult to be determined unequivocally, particularly when the possibility of secondary earthquake damage exists. Such secondary damage has been previously proposed for the Roman Praetorium, the governor’s palace in the center of Cologne. Ongoing excavations since 2007 revealed additional damage. The existing ground that has been uncovered and documented extends the affected area to 175?×?180 m. We present a comprehensive virtual model of the excavation area based on 200 3D laserscans together with a systematic analysis of the damage patterns and an improved model of the terrain during Roman/Medieval times including geotechnical parameters of the subsurface. Five locations with different damage patterns, including a Roman sewer, the octagonal central part of the Praetorium, a section with strongly inclined massive walls, a 13 m deep deformed well, a collapsed hypocaust, and damages in the Medieval mikveh are analyzed in detail. We use site-specific synthetic strong ground motion seismograms to test the possibility of earthquake-induced ground failures as a cause for the observed damage. This subsurface model is also used to test the possibility of hydraulically-induced damages by seepage and erosion of fine-grained material from stray sand. Heavy rainstorms can induce a direct stream of surface water through the fine sand layers to the ground water table. Simulated ground motion for assumed worst-case earthquake scenarios do not provoke slope instability at the level necessary to explain the structural damages. 相似文献
13.
Jose L. Bermejo William A. Sauck Estella A. Atekwana 《Ground Water Monitoring & Remediation》1997,17(4):131-137
Alight nonaqueous phase liquid (LNAPL) ground water contaminant plume has been discovered by purely geophysical means at the former Wurtsmith Air Force Base (AFB) near Oscoda, Michigan. It is located near another plume called FT-02, which is a well-studied area undergoing natural bioremediation. The plume was discovered by ground penetrating radar (GPR) profiling while extending a long line from FT-02 to establish background variability around that plume. The new plume was apparent because of a high-conductivity "shadow' or GPR reflection attenuation observed below the conductive zone at the top of the aquifer, identical to the pattern observed at the FT-02 plume. Further GPR surveys were conducted by students of a Western Michigan University geophysics field course to outline the proximal part of the plume. The GPR survey was supplemented by an electromagnetic induction (EM) survey which showed a group of four cables crossing the area. Finally, a magnetometer survey was conducted to search for any buried steel objects which might have been missed by the EM survey. The results of the three geophysical surveys were then used by students of a University of Michigan field course to guide subsurface soil and fluid sampling, which verified the presence of residual LNAPL product and ground water with conductivities 2.5 to 3.3 times above background. The plume source is in the vicinity of a vaulted underground storage tank (UST) formerly used for the collection of waste solvents and fuels for subsequent use in the fire training exercises at FT-02. This newly discovered LNAPL plume, along with other "mature' plumes, fits the electrical model which predicts conductive ground water below the decomposing but electrically resistive LNAPLs. Finally, this is a fine example of the cooperative use of a dedicated research site for training by students of two different universities. 相似文献
14.
《Ground Water Monitoring & Remediation》2000,20(2):66-77
An in situ redox manipulation (ISRM) method for creating a permeable treatment zone in the subsurface has been developed at the laboratory bench and intermediate scales and deployed at the field scale for reduction/immobilization of chrornate contamination. At other sites, the same redox technology is currently being tested for dechlorination of TCE. The reduced zone is created by injected reagents that reduce iron naturally present in the aquifer sediments from Fe(III) to surface-bound and structural Fe(II) species. Standard ground water wells are used, allowing treatment of contaminants too deep below the ground surface for conventional treneh-and-fill technologies.
A proof-of-principle field experiment was conducted in September 1995 at a chromate (hexavalent chromium) contaminated ground water site on the Hartford Site in Washington. The test created a 15 m (˜50 feet) diameter cylindrical treatment zone. The three phases of the test consisted of (1) injection of 77, 000 L (20, 500 gallons) of buffered sodium dithionite solution in 17.1 hours, (2) reaction for 18.5 hours, and (3) withdrawal of 375, 000 L (99, 600 gallons) in 83 hours. The withdrawal phase recovered 87% to 90% of the reaction products. Analysis of post-experimental sediment cores indicated that 60% to 100% of the available reactive iron in the treated zone was reduced. The longevity of the reduced zone is estimated between seven and 12 years based on the post-experiment core samples. Three and half years after the field test, the treatment zone remains anoxic, and hexavalent chromium levels have been reduced from 0.060 mg/L to below detection limits (0.008 mg/L). Additionally, no significant permeability changes have been detected during any phase of the experiment. 相似文献
A proof-of-principle field experiment was conducted in September 1995 at a chromate (hexavalent chromium) contaminated ground water site on the Hartford Site in Washington. The test created a 15 m (˜50 feet) diameter cylindrical treatment zone. The three phases of the test consisted of (1) injection of 77, 000 L (20, 500 gallons) of buffered sodium dithionite solution in 17.1 hours, (2) reaction for 18.5 hours, and (3) withdrawal of 375, 000 L (99, 600 gallons) in 83 hours. The withdrawal phase recovered 87% to 90% of the reaction products. Analysis of post-experimental sediment cores indicated that 60% to 100% of the available reactive iron in the treated zone was reduced. The longevity of the reduced zone is estimated between seven and 12 years based on the post-experiment core samples. Three and half years after the field test, the treatment zone remains anoxic, and hexavalent chromium levels have been reduced from 0.060 mg/L to below detection limits (0.008 mg/L). Additionally, no significant permeability changes have been detected during any phase of the experiment. 相似文献
15.
Residential areas in Kuwait City have witnessed a dramatic rise in subsurface water tables over the last three decades. This water rise phenomenon is attributed mainly to over irrigation practices of private gardens along with leakage from domestic and sewage networks. This paper presents a comprehensive study for urban drainage in two selected areas representing the two hydrogeological settings encountered in Kuwait City. In the first area, a vertical drainage scheme was applied successfully over an area of 1 km2. The system has been under continuous operation and monitoring for more than 4 years without problems, providing a permanent solution for the water rise problem in this area. The hydrogeological system has approached steady state conditions and the water levels have dropped to about 3·5 m below the ground surface. In the second area a dual drainage scheme, composing of horizontal and vertical elements, is proposed. Horizontal elements are suggested in the areas where the deep groundwater contains hazardous gases that may pose environmental problems. The proposed drainage scheme in the second area has not yet been implemented. Field tests were conducted to assess the aquifer parameters in both areas and a numerical model has been developed to predict the long‐term response of the hydrogeological system in the two areas under consideration. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
16.
James F. Pankow Richard L. Johnson James E. Houck Susan M. Brillante W. Jerry Bryan 《Ground water》1984,22(5):593-601
The hydrogeology of the chemical waste disposal site in the closed basin at Alkali Lake, Oregon has been examined. Interest in the site is due to the burial (November 1976) of 25,000 drums of herbicide manufacturing residues in unlined trenches on the playa of the basin. Included in the wastes were large amounts of chlorophenols and polymeric chlorophenoxyphenols. The flow of the alkaline (pH ∼10) ground water in the site area is driven by: (1) springs which create a mound east of the site; and (2) the sump effect of “West Alkali Lake,” a topographic low to the west of the site. Porosity, bulk mass densities, and grain-size distributions were determined. At one piezometer, the depth to ground water ranged between 0.9 m and 2.2 m. With the bottoms of the trenches in which the chemicals were buried between 0.60 and 0.75 m below the level of the ground surface, the bottom portions of the trenches may, at least occasionally, be in direct contact with the ground water. 相似文献
17.
Quantifying aggregation and change in runoff source in accordance with catchment area increase in a forested headwater catchment 
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下载免费PDF全文 There has been a great deal of research interest regarding changes in flow path/runoff source with increases in catchment area. However, there have been very few quantitative studies taking subscale variability and convergence of flow path/runoff source into account, especially in relation to headwater catchments. This study was performed to elucidate how the contributions and discharge rates of subsurface water (water in the soil layer) and groundwater (water in fractured bedrock) aggregate and change with catchment area increase, and to elucidate whether the spatial variability of the discharge rate of groundwater determines the spatial variability of stream discharge or groundwater contribution. The study area was a 5‐km2 forested headwater catchment in Japan. We measured stream discharge at 113 points and water chemistry at 159 points under base flow conditions. End‐member mixing analysis was used to separate stream water into subsurface water and groundwater. The contributions of both subsurface water and groundwater had large variability below 1 km2. The contribution of subsurface water decreased markedly, while that of groundwater increased markedly, with increases in catchment area. The specific discharge of subsurface water showed a large degree of variability and decreased with catchment area below 0.1 km2, becoming almost constant above 0.1 km2. The specific discharge of groundwater showed large variability below 1 km2 and increased with catchment area. These results indicated that the variabilities of stream discharge and groundwater contribution corresponded well with the variability of the discharge rate of groundwater. However, below 0.1 km2, it was necessary to consider variations in the discharge rates of both subsurface water and groundwater. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
18.
J.A. Morakinyo R. Mackay 《Stochastic Environmental Research and Risk Assessment (SERRA)》2006,20(1-2):106-118
The pattern of ground contamination across a site depends on the historical pattern of contaminant releases at the surface
and the redistribution and the fate of contaminants below the surface. Using these concepts a new site assessment approach
(assessment modelling) is proposed based on the development of three stochastic models: a model of the physical structure
of the ground materials beneath the site; a model of the distribution of surface contaminant spills; and a model of the flow
and transport of spilled material into the heterogeneous underlying ground to construct alternative, equally likely, present
day contaminant distributions. Combining the models within a Monte Carlo framework can, in principle, improve the understanding
of the potential for excess contamination across the site and improve decisions on remediation options and locations. A trial
application has been undertaken in the UK using a particular site to assess the approach. The conditions at the site used
for the trial and the first of the stochastic model developments, the geostatistical modelling of the soil heterogeneity,
are presented in this paper. Non-parametric and parametric geostatistics have been employed to formulate the geostatistical
models of the site soils using lithological information from 146 trial pits and boreholes. The approach to the soil modelling
and the verification and validation of the results are described. The heterogeneity of the subsurface is complicated by the
presence of made-ground, comprised of various inert building wastes, and the non-stationarity of the heterogeneity of the
natural ground. This paper is the first of three describing the assessment modelling methodology and its trial application
to the site. 相似文献
19.
Improved surface-based geophysical technologies that are commercially available provide a new level of detail that can be used to guide ground water remediation. Surface-based multielectrode resistivity methods and tomographic seismic refraction techniques were used to image to a depth of approximately 30 m below the surface at the Natural and Accelerated Bioremediation Research Field Research Center. The U.S. Department of Energy (DOE) established the research center on the DOE Oak Ridge Reservation in Oak Ridge, Tennessee, to conduct in situ field-scale studies on bioremediation of metals and radionuclides. Bioremediation studies are being conducted on the saprolite, shale bedrock, and ground water at the site that have been contaminated with nitrate, uranium, technetium, tetrachloroethylene, and other contaminants (U.S. DOE 1997). Geophysical methods were effective in imaging the high-ionic strength plume and in defining the transition zone between saprolite and bedrock zones that appears to have a significant influence on contaminant transport. The geophysical data were used to help select the location and depth of investigation for field research plots. Drilling, borehole geophysics, and ground water sampling were used to verify the surface geophysical studies. 相似文献
20.
During the past two decades electromagnetic methods have been increasingly applied to problems in hydrocarbon exploration. It has been shown that EM methods achieve satisfactory results which can be supplementary to results of the seismic method. We extend the application of the Long-Offset Transient ElectroMagnetic Sounding (lotem ) to exploration problems in the coal mining industry. A survey was conducted north of the Rhine-Ruhr coal district using a grounded dipole source and receivers laid out along several profile lines giving areal coverage. The strong noise from cultural as well as natural electromagnetic sources was reduced using prestack data processing techniques resulting in reliable data with a good signal-to-noise ratio. The interpretation is self-consistent and matches the well logs and the geological information of the area quite well. The high station density permitted the mapping of the top of the Carboniferous formation to a depth of between 800 and 1000 m below surface. 相似文献