1.1 目的和应用: 1.1.1 本指南总结了使用直流电阻率法评估地下材料及其孔隙流体电性能的设备、现场程序和解释方法。从地表测量地下材料的电性能，并得出视电阻率。然后，可以对这些数据进行解释，以估算地下层的深度、厚度、孔隙和电阻率。 1.1.2 本指南中所述的电阻率测量适用于地质、岩土工程、环境和水文调查。 电阻率法用于绘制岩性、构造、裂缝和地层等地质特征；水文特征，如地下水位深度、隔水层深度和地下水盐度；并圈定地下水污染物。一般参考文献包括Keller和Frischknecht ( 1. ) , 2. Zohdy等人 ( 2. ) ，Koefeed ( 3. ) ，美国环保局 ( 4. ) 病房 ( 5. ) 、格里菲斯和金 ( 6. ) ，和Telford等人 ( 7. ) . 1.1.3 本指南不涉及使用层析成像解释方法，通常称为电阻率层析成像（ERT）或电阻率成像（ERI）。虽然应用了许多原则，但数据采集和解释与本指南中规定的不同。 1.2 限制: 1.2.1 本指南概述了直流电阻率法。它没有详细阐述理论、现场程序或数据解释。为此目的，包含了大量参考文献，并被视为本指南的重要组成部分。建议电阻率法用户熟悉本文引用的参考文献和指南 D420 实践 D5088 实践 D5608 指导 D5730 ，试验方法 G57 , D6429 和 D6235 . 1.2.2 本指南仅限于使用斯伦贝谢、温纳或偶极子测深和剖面技术进行电阻率测量的常用方法- 偶极子阵列和对这些阵列的修改。它不包括广泛的专用阵列的使用。它也不包括使用自发电位（SP）测量、激发极化（IP）测量或复电阻率方法。 1.2.3 电阻率法已适用于陆地、钻孔内或水中的许多特殊用途。本指南不包括电阻率测量的这些适应性讨论。 1.2.4 本指南中提出的电阻率法方法是最常用、最广泛接受和证明的方法；然而，如果技术上合理且有文件证明，则可以替代技术上合理的电阻率法其他方法或修改。 1.2.5 本指南提供了有组织的信息收集或一系列选项，并不推荐具体的行动方案。本文件不能取代教育或经验，应与专业判断结合使用。并非本指南的所有方面都适用于所有情况。本ASTM标准不代表或取代必须根据其判断给定专业服务的充分性的谨慎标准，也不应在不考虑项目的许多独特方面的情况下应用本文件。本文件标题中的“标准”一词仅表示该文件已通过ASTM共识程序获得批准。 1.3 单位- 以国际单位制表示的数值应视为标准值。本标准不包括其他计量单位。以国际单位制以外的单位报告试验结果不应视为不符合本试验方法。 1.4 注意事项: 1.4.1 本指南的用户有责任遵循设备制造商建议中的任何预防措施，并考虑使用高压和电流时的安全影响。 1.4.2 如果本指南用于有危险材料、操作或设备的场所，则本指南的用户有责任在使用前制定适当的安全和健康做法，并确定法规的适用性。 1.5 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.6 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 5.1 概念- 电阻率技术用于测量地下材料的电阻率。虽然材料的电阻率可以很好地指示存在的地下材料类型，但它不是唯一的指示器。虽然电阻率法用于测量地球材料的电阻率，但解释人员必须在了解当地地质条件和其他数据的基础上解释电阻率数据，并得出合理的地质和水文解释。 5.2 被测参数和代表值: 5.2.1 表1 显示了电阻率值的一些一般趋势。 图2 显示地下材料的电阻率值范围。 5.6.2 斯伦贝谢阵列- 斯伦贝谢阵列由间距不等的串联电极组成( 图3 )，其中 AB公司 > 5 MN公司 . 根据斯伦贝谢测量计算视电阻率的公式为: 哪里: AB公司 = 电流电极之间的距离，以及 MN公司 = 电位电极之间的距离。 5.6.3 偶极-偶极阵列- 偶极-偶极阵列由一对密集的电流电极和一对密集的电位电极组成( 图3 ). 偶极子视电阻率的计算公式- 偶极子测量为: 哪里: 不适用 = 以a间距的数量（n）测量的最内侧电极之间的距离，以及 一 = 电流电极和电位电极之间的距离。 5.6.4 阵列比较: 5.6.4.1 斯伦贝谢阵列: (1) 斯伦贝谢阵列不太容易受到接触问题和可能影响读数的附近地质条件的影响。该方法提供了一种识别横向变化影响并对其进行部分校正的方法。 (2) 斯伦贝谢阵列在现场操作中稍快，因为只有电流电极必须在读数之间移动。 5.6.4.2 温纳阵列: (1) 与其他阵列相比，温纳阵列提供了更高的信噪比，因为其电位电极总是相距较远，并且位于电流电极之间。因此，与其他阵列相比，温纳阵列在给定电流下测量的电压更大。 (2) 该阵列在城市地区等高噪声环境中表现良好。 (3) 对于给定的深度能力，该阵列需要较少的电流。这意味着对给定深度能力的仪器要求不那么严格。 5.6.4.3 偶极-偶极阵列: (1) 探索大深度需要相对较短的电缆长度。 (2) 短电缆长度可减少电流泄漏。 (3) 可以获得有关电层位倾斜方向的更详细信息。 5.6.5 其他阵列- 还有其他几种阵列:Lee分区阵列（Zohdy等人 ( 2. ) )，方形阵列（Lane等人 ( 11 ) )，梯度阵列（Ward ( 2. ) )和极偶极子（Ward ( 5. ) )以及本指南中未讨论的自动数据采集和成像系统。 5.7 测深（深度）测量- 测深测量是电阻率技术最广泛的应用之一。测深提供了一种测量单个位置电阻率随深度变化的方法。 随着电极间距的增加，进行了几次测量。随着电极间距的增加，测量材料的深度和体积也会增加( 图4 ). 随着电气间距的增加，阵列的中心点保持不变。 图4 增加的电极间距使地球的深度和体积更大（来自Benson等人， ( 8. ) ) 5.7.1 测深测量在不同电极间距下产生一系列视电阻率值。这些视电阻率值根据电极间距使用对数刻度绘制( 图5 )并使用反演技术进行解释，以得出地下层的真实电阻率和厚度。 图5 电阻率测深曲线（来自Benson等人， ( 8. ) ) 5.7.2 连续电极间距应（近似）在对数刻度上等距分布。通常，每十年应测量3到6个数据点。从均匀层状介质的测量中获得的电阻率测深曲线应遵循平滑曲线( 图5 ). 通过每十年使用六个点，噪声通常不太显著，可以获得平滑的测深曲线。应在现场绘制数据，以确保进行足够数量的无噪声测量。 5.7.3 不均匀分层地球的穿透深度取决于电极分离和地球各层的电阻率。 通常，总阵列长度可能是勘探深度的许多倍。 5.8 剖面测量- 沿线的一系列剖面测量用于评估给定深度下地下条件的横向变化( 图6 ). 电阻率剖面是通过沿剖面线在多个站点上使用固定电极间距和阵列几何形状进行测量来完成的( 图7 ). 单次剖面测量会导致测站的视电阻率值。一个区域上的多个剖面可用于生成地下条件变化的等高线图( 图8 ). 如果没有测深数据或其他附加信息，这些视电阻率剖面或地图无法根据层电阻率值进行解释。 图6 分析以评估横向变化（来自Zohdy等人， ( 12 ) ) 图7 剖面沿线的站点（来自Benson等人， ( 8. ) ) 图8 视电阻率等值线图（来自Zohdy等人， ( 12 ) ) 5.8.1 垂直测深用于确定适当的电极间距以进行剖面分析。小电极间距可用于强调可能影响深层数据解释的电阻率浅层变化。测量间距控制可从一系列轮廓测量中获得的横向分辨率。

1.1 Purpose and Application: 1.1.1 This guide summarizes the equipment, field procedures, and interpretation methods for the assessment of the electrical properties of subsurface materials and their pore fluids, using the direct current (DC) resistivity method. Measurements of the electrical properties of subsurface materials are made from the land surface and yield an apparent resistivity. These data can then be interpreted to yield an estimate of the depth, thickness, voids, and resistivity of subsurface layer(s). 1.1.2 Resistivity measurements as described in this guide are applied in geological, geotechnical, environmental, and hydrologic investigations. The resistivity method is used to map geologic features such as lithology, structure, fractures, and stratigraphy; hydrologic features such as depth to water table, depth to aquitard, and groundwater salinity; and to delineate groundwater contaminants. General references are, Keller and Frischknecht ( 1 ) , 2 Zohdy et al ( 2 ) , Koefoed ( 3 ) , EPA ( 4 ) , Ward ( 5 ) , Griffiths and King ( 6 ) , and Telford et al ( 7 ) . 1.1.3 This guide does not address the use tomographic interpretation methods, commonly referred to as electrical resistivity tomography (ERT) or electrical resistivity imaging (ERI). While many of the principles apply the data acquisition and interpretation differ from those set forth in this guide. 1.2 Limitations: 1.2.1 This guide provides an overview of the Direct Current Resistivity Method. It does not address in detail the theory, field procedures, or interpretation of the data. Numerous references are included for that purpose and are considered an essential part of this guide. It is recommended that the user of the resistivity method be familiar with the references cited in the text and with the Guide D420 , Practice D5088 , Practice D5608 , Guide D5730 , Test Method G57 , D6429 , and D6235 . 1.2.2 This guide is limited to the commonly used approach for resistivity measurements using sounding and profiling techniques with the Schlumberger, Wenner, or dipole-dipole arrays and modifications to those arrays. It does not cover the use of a wide range of specialized arrays. It also does not include the use of spontaneous potential (SP) measurements, induced polarization (IP) measurements, or complex resistivity methods. 1.2.3 The resistivity method has been adapted for a number of special uses, on land, within a borehole, or on water. Discussions of these adaptations of resistivity measurements are not included in this guide. 1.2.4 The approaches suggested in this guide for the resistivity method are the most commonly used, widely accepted and proven; however, other approaches or modifications to the resistivity method that are technically sound may be substituted if technically justified and documented. 1.2.5 This guide offers an organized collection of information or a series of options and does not recommend a specific course of action. This document cannot replace education or experience and should be used in conjunction with professional judgements. Not all aspects of this guide may be applicable in all circumstances. This ASTM standard is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied without consideration of a project's many unique aspects. The word “Standard” in the title of this document means only that the document has been approved through the ASTM consensus process. 1.3 Units— The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. Reporting of test results in units other than SI shall not be regarded as nonconformance with this test method. 1.4 Precautions: 1.4.1 It is the responsibility of the user of this guide to follow any precautions in the equipment manufacturer's recommendations and to consider the safety implications when high voltages and currents are used. 1.4.2 If this guide is used at sites with hazardous materials, operations, or equipment, it is the responsibility of the user of this guide to establish appropriate safety and health practices and to determine the applicability of regulations prior to use. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 Concepts— The resistivity technique is used to measure the resistivity of subsurface materials. Although the resistivity of materials can be a good indicator of the type of subsurface material present, it is not a unique indicator. While the resistivity method is used to measure the resistivity of earth materials, it is the interpreter who, based on knowledge of local geologic conditions and other data, must interpret resistivity data and arrive at a reasonable geologic and hydrologic interpretation. 5.2 Parameter Being Measured and Representative Values: 5.2.1 Table 1 shows some general trends for resistivity values. Fig. 2 shows ranges in resistivity values for subsurface materials. 5.6.2 Schlumberger Array— The Schlumberger array consists of unequally spaced in-line electrodes ( Fig. 3 ), where AB > 5 MN . The formula for calculating apparent resistivity from a Schlumberger measurement is: where: AB = distance between current electrodes, and MN = distance between potential electrodes. 5.6.3 Dipole-Dipole Array— The dipole-dipole array consists of a pair of closely spaced current electrodes and a pair of closely spaced potential electrodes ( Fig. 3 ). The formula for calculating apparent resistivity from a dipole-dipole measurement is: where: na = distance between innermost electrodes measured as a number (n) of a-spacings, and a = distance between the current electrodes and also the potential electrodes. 5.6.4 Comparison of the Arrays: 5.6.4.1 Schlumberger Arrays: (1) Schlumberger arrays are less susceptible to contact problems and the influence of nearby geologic conditions that may affect readings. The method provides a means to recognize the effects of lateral variations and to partially correct for them. (2) Schlumberger arrays are slightly faster in field operations since only the current electrodes must be moved between readings. 5.6.4.2 Wenner Arrays: (1) The Wenner array provides a higher signal to noise ratio than other arrays because its potential electrodes are always farther apart and located between the current electrodes. As a result, the Wenner array measures a larger voltage for a given current than is measured with other arrays. (2) This array is good in high-noise environments such as urban areas. (3) This array requires less current for a given depth capability. This translates into less severe instrumentation requirements for a given depth capability. 5.6.4.3 Dipole-Dipole Arrays: (1) Relatively short cable lengths are required to explore large depths. (2) Short cable lengths reduce current leakage. (3) More detailed information on the direction of dip of electrical horizons is obtainable. 5.6.5 Other Arrays— There are several other arrays: Lee-partitioning array (Zohdy et al ( 2 ) ), square array (Lane et al ( 11 ) ), gradient array (Ward ( 2 ) ) and pole-dipole (Ward ( 5 ) ) and automated data acquisition and imaging systems that are not discussed in this guideline. 5.7 Sounding (Depth) Measurements— Sounding measurements are one of the most widespread uses for the resistivity technique. Soundings provide a means of measuring changes of electrical resistivity with depth at a single location. Several measurements are made with increasing electrode spacings. As the spacing of the electrodes is increased, there is an increase in the depth and volume of material measured ( Fig. 4 ). The center point of the array remains fixed as the electrical spacing is increased. FIG. 4 Increased Electrode Spacing Samples Greater Depth and Volume of Earth (from Benson et al, ( 8 ) ) 5.7.1 Sounding measurements result in a series of apparent electrical resistivity values at various electrode spacings. These apparent resistivity values are plotted against electrode spacing using a log-log scale ( Fig. 5 ) and are interpreted using inversion techniques to derive true resistivity and thickness of subsurface layers. FIG. 5 Resistivity Sounding Curve (from Benson et al, ( 8 ) ) 5.7.2 Successive electrode spacings should be (approximately) equally spaced on a logarithmic scale. Normally, 3 to 6 data points per decade should be measured. A resistivity sounding curve obtained from measurements of a uniform layered medium should follow a smooth curve, ( Fig. 5 ). By using six points per decade, noise is generally less significant and a smooth sounding curve may be obtained. Data should be plotted in the field to ensure that an adequate number of noise-free measurements are made. 5.7.3 The depth of penetration for an inhomogeneous stratified earth depends upon the electrode separation and the resistivities of the earth's layers. In general, the overall array length could be many times the exploration depth. 5.8 Profiling Measurements— A series of profile measurements along a line is used to assess lateral changes in subsurface conditions at a given depth ( Fig. 6 ). Electrical resistivity profiling is accomplished by making measurements with fixed electrode spacing and array geometry at several stations along a profile line ( Fig. 7 ). A single profile measurement results in an apparent electrical resistivity value at a station. Several profiles over an area can be used to produce a contour map of changes in subsurface conditions ( Fig. 8 ). These apparent resistivity profiles or maps cannot be interpreted in terms of layer resistivity values without sounding data or other additional information. FIG. 6 Profiling to Assess Lateral Changes (from Zohdy et al, ( 12 ) ) FIG. 7 Stations Along a Profile (from Benson et al, ( 8 ) ) FIG. 8 Apparent Resistivity Contour Map (from Zohdy et al, ( 12 ) ) 5.8.1 Vertical soundings are used to determine the appropriate electrode spacing for profiling. Small electrode spacings can be used to emphasize shallow variations in resistivity that may affect the interpretation of deeper data. Spacing between measurements controls the lateral resolution that can be obtained from a series of profile measurements.