1.1 这些测试方法涵盖了适用于定义非饱和土壤水力传导函数（HCF）的数据点的定量测量。HCF定义为导水率和基质吸力之间的关系，或导水率和体积含水量、重量含水量或饱和度之间的关系。达西定律为HCF上点的测量提供了基础，其中土壤样本的导水率等于通过样本的水流量与穿过样本的水力梯度之间的比例系数。 为了定义HCF上的一个点，在土壤样本上施加水力梯度，测量相应的瞬态或稳态水流量（反之亦然），使用达西定律计算的导水率与土壤样本中基质吸力或体积含水量的独立测量相结合。 1.2 这些测试方法描述了一系列测试方法，可用于定义不同类型土壤的HCF上的点。不幸的是，由于测试时间和应力控制的需要，没有一种测试可以应用于所有土壤来测量HCF。 测试请求者有责任选择最适合给定土壤类型的方法。这些测试方法的重要性和使用部分提供了指导。 1.3 与定义为体积含水量和基质吸力之间关系的土壤水分保持曲线（SWRC）类似，HCF可能不是唯一的函数。无论是湿润还是干燥非饱和土壤，SWRC和HCF都可能遵循不同的路径。应选择一种能够复制现场流动过程的测试方法。 1.4 这些试验方法描述了直接测量HCF的三类方法（A到C类）。A类（柱试验）涉及使用在施加瞬态和稳态水流过程中压实到刚性壁渗透仪中的土柱中体积含水量或吸力随高度的测量一维剖面来定义HCF的方法。A类中的不同方法描述了施加水流过程的不同方法。B类（轴平移测试）涉及使用饱和高压下土壤样本的流出测量来定义HCF的方法- 在施加瞬态水流过程中，空气进入渗透计中的多孔圆盘。刚性壁渗透计或柔性壁渗透计的使用在B类中的单独方法中描述。C类（离心渗透计测试）包括在施加的稳态水流过程中，使用离心渗透计中限制的土壤柱中测量的体积含水量或吸力剖面来定义HCF的方法。本标准中的方法可用于测量土壤饱和导水率至约10%的导水率值 -11 米/秒。 1.5 这些试验方法中描述的数据分析方法包括测量水流量和水力梯度，以及使用达西定律（直接法）计算导水率 ( 1. ) . 2. 或者，也可以使用逆方法来定义HCF ( 2. ) . 这些方法采用迭代的、基于回归的方法来估计土壤样本需要给出测量水流响应的导水率。然而，由于它们需要专门的工程分析，因此不包括在这些试验方法的范围内。 1.6 这些试验方法适用于在体积含水量或吸力或两者变化期间体积变化不显著的土壤（即膨胀粘土或坍塌土壤）。这意味着这些方法应用于低塑性的砂、粉土和粘土。 1.7 这些方法仅适用于含有两种孔隙流体的土壤:气体和液体。液体通常是水，气体通常是空气。如果需要，也可以使用其他液体。如果使用的液体导致土壤收缩或膨胀，则应小心。 1. 8. 报告中使用的单位应为国际单位制，以与非饱和土壤中水流分析的文献一致。应以[m/s]为单位报告渗透系数，以[kPa]为单位报告基质吸力，以[m]为单位报告体积含水量 3. /m 3. ]或[%]，饱和度以[m]为单位 3. /m 3. ]. 1.9 所有观察值和计算值应符合实践中制定的有效数字和舍入指南 D6026 . 实践中的程序 D6026 用于指定如何收集、记录和计算数据的标准被视为行业标准。 此外，它们代表了通常应保留的有效数字。这些程序不考虑材料变化、获取数据的目的、特殊目的研究或用户目标的任何考虑因素。增加或减少报告数据的有效位数以符合这些考虑是常见做法。考虑工程设计分析方法中使用的有效数字超出了这些测试方法的范围。 1.10 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。 1.11 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 导水率函数（HCF）是非饱和土壤水文特性的基础，也是大多数非饱和土壤水分运动分析所必需的。 例如，HCF是分析土壤样本渗透或蒸发过程中水分运动的关键参数。这与评估垃圾填埋场覆盖系统中的水运动、因水运动引起的路面刚度变化、向含水层补水以及从土壤中提取孔隙水进行采样有关。 5.2 技术文献中报告的HCF示例如所示 图1 ( 一 ), 图1 ( b )，和 图1 ( c )，分别适用于粘土、粉土和砂。根据吸力或体积含水量报告HCF的决定取决于用于测量HCF的测试方法和仪器。 A类和C类方法将提供吸力或体积含水量方面的HCF，而B类方法将提供吸力方面的HCF。 图1 不同土壤的实验HCF:( 一 ) k -ψ表示粘土；( b ) k -θ表示粉土；( c ) k -θ表示砂( 3- 14 ) 5.3 水力传导率测量中涉及的一个主要假设是，它用于量化液态水通过非饱和土壤的运动（即，它是液态水流量和水力梯度之间的比例系数）。 水也可以以蒸汽形式通过土壤，但土壤对水蒸汽流（扩散）的阻抗取决于不同的机制。因此，HCF仅适用于工程实践中水相连续的饱和度（即没有“未连接”的水）。尽管这取决于土壤类型和质地，但这大致对应于大于50到60的饱和度 %. 5.4 土壤的HCF可能对孔隙度、土壤结构、压实（压实重量含水量和干容重）、有效应力、温度和测试流动路径（湿润或干燥）敏感。 然而，并非所有工程问题都需要考虑这些变量的影响。在第节中列出的试验方法之外 4. ，没有一种方法最适合测量所有这些变量的影响。此外，不同的测试在测试时间上可能有很大的差异。 表1 为给定土壤和应用选择最佳试验提供了指南。提供低塑性粉质粘土的测试时间作为基线参考。粗粒土的测试时间通常为1至2天。 5.5 尚未对使用本文所述实验室方法获得的HCF与原位材料的HCF之间的相关性进行全面调查。因此，应由合格人员小心地将试验方法获得的结果应用于现场情况。 注1: 本标准产生的结果的质量取决于执行测试的人员的能力以及所用设备和设施的适用性。符合实践标准的机构 D3740 通常认为能够胜任和客观的测试、抽样、检查等。 本标准的用户应注意遵守惯例 D3740 本身不能确保可靠的结果。可靠的结果取决于许多因素。实践 D3740 提供了一种评估其中一些因素的方法。

1.1 These test methods cover the quantitative measurement of data points suitable for defining the hydraulic conductivity functions (HCF) of unsaturated soils. The HCF is defined as either the relationship between hydraulic conductivity and matric suction or that between hydraulic conductivity and volumetric water content, gravimetric water content, or the degree of saturation. Darcy’s law provides the basis for measurement of points on the HCF, in which the hydraulic conductivity of a soil specimen is equal to the coefficient of proportionality between the flow rate of water through the specimen and the hydraulic gradient across the specimen. To define a point on the HCF, a hydraulic gradient is applied across a soil specimen, the corresponding transient or steady-state water flow rate is measured (or vice versa), and the hydraulic conductivity calculated using Darcy’s law is paired with independent measurements of matric suction or volumetric water content in the soil specimen. 1.2 These test methods describe a family of test methods that can be used to define points on the HCF for different types of soils. Unfortunately, there is no single test that can be applied to all soils to measure the HCF due to testing times and the need for stress control. It is the responsibility of the requestor of a test to select the method that is most suitable for a given soil type. Guidance is provided in the significance and use section of these test methods. 1.3 Similar to the Soil Water Retention Curve (SWRC), defined as the relationship between volumetric water content and matric suction, the HCF may not be a unique function. Both the SWRC and HCF may follow different paths whether the unsaturated soil is being wetted or dried. A test method should be selected which replicates the flow process occurring in the field. 1.4 These test methods describe three categories of methods (Categories A through C) for direct measurement of the HCF. Category A (column tests) involves methods used to define the HCF using measured one-dimensional profiles of volumetric water content or suction with height in a column of soil compacted into a rigid wall permeameter during imposed transient and steady-state water flow processes. Different means of imposing water flow processes are described in separate methods within Category A. Category B (axis translation tests) involves methods used to define the HCF using outflow measurements from a soil specimen underlain by a saturated high-air entry porous disc in a permeameter during imposed transient water flow processes. The uses of rigid-wall or flexible-wall permeameters are described in separate methods within Category B. Category C (centrifuge permeameter test) includes a method to define the HCF using measured volumetric water content or suction profiles in a column of soil confined in a centrifuge permeameter during imposed steady-state water flow processes. The methods in this standard can be used to measure hydraulic conductivity values ranging from the saturated hydraulic conductivity of the soil to approximately 10 -11 m/s. 1.5 The methods of data analysis described in these test methods involve measurement of the water flow rate and hydraulic gradient, and calculation of the hydraulic conductivity using Darcy’s law (direct methods) ( 1 ) . 2 Alternatively, inverse methods may also be used to define the HCF ( 2 ) . These employ an iterative, regression-based approach to estimate the hydraulic conductivity that a soil specimen would need to have given a measured water flow response. However, as they require specialized engineering analyses, they are excluded from the scope of these test methods. 1.6 These test methods apply to soils that do not change significantly in volume during changes in volumetric water content or suction, or both (that is, expansive clays or collapsing soils). This implies that these methods should be used for sands, silts, and clays of low plasticity. 1.7 The methods apply only to soils containing two pore fluids: a gas and a liquid. The liquid is usually water and the gas is usually air. Other fluids may also be used if requested. Caution shall be exercised if the liquid being used causes shrinkage or swelling of the soil. 1.8 The units used in reporting shall be SI units in order to be consistent with the literature on water flow analyses in unsaturated soils. The hydraulic conductivity shall be reported in units of [m/s], the matric suction in units of [kPa], the volumetric water content in [m 3 /m 3 ] or [%], and the degree of saturation in [m 3 /m 3 ]. 1.9 All observed and calculated values shall conform to the guide for significant digits and rounding established in Practice D6026 . The procedures in Practice D6026 that are used to specify how data are collected, recorded, and calculated are regarded as the industry standard. In addition, they are representative of the significant digits that should generally be retained. The procedures do not consider material variation, purpose for obtaining the data, special purpose studies, or any considerations for the objectives of the user. Increasing or reducing the significant digits of reported data to be commensurate with these considerations is common practice. Consideration of the significant digits to be used in analysis methods for engineering design is beyond the scope of these test methods. 1.10 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. 1.11 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 The hydraulic conductivity function (HCF) is fundamental to hydrological characterization of unsaturated soils and is required for most analyses of water movement in unsaturated soils. For instance, the HCF is a critical parameter to analyze the movement of water during infiltration or evaporation from soil specimens. This is relevant to the evaluation of water movement in landfill cover systems, stiffness changes in pavements due to water movement, recharge of water into aquifers, and extraction of pore water from soils for sampling. 5.2 Examples of HCFs reported in the technical literature are shown in Fig. 1 ( a ), Fig. 1 ( b ), and Fig. 1 ( c ), for clays, silts, and sands, respectively. The decision to report a HCF in terms of suction or volumetric water content depends on the test method and instruments used to measure the HCF. The methods in Categories A and C will provide a HCF in terms of either suction or volumetric water content, while the methods in Category B will provide a HCF in terms of suction. FIG. 1 Experimental HCFs for Different Soils: ( a ) k -ψ for Clays; ( b ) k -θ for Silts; ( c ) k -θ for Sands ( 3- 14 ) 5.3 A major assumption involved in measurement of the hydraulic conductivity is that it is used to quantify movement of water in liquid form through unsaturated soils (that is, it is the coefficient of proportionality between liquid water flow and hydraulic gradient). Water can also move through soil in vapor form, but different mechanisms govern impedance of a soil to water vapor flow (diffusion). Accordingly, the HCF is only applicable in engineering practice for degrees of saturation in which the water phase is continuous (that is, no pockets of “unconnected” water). Although this depends on the soil type and texture, this approximately corresponds to degrees of saturation greater than 50 to 60 %. 5.4 The HCFs of soils may be sensitive to the porosity, soil structure, compaction (compaction gravimetric water content and dry unit weight), effective stress, temperature, and testing flow path (wetting or drying). However, not all engineering problems need to account for the effects of these variables. Out of the test methods listed in Section 4 , there is not a single method that is best suited to measure the effects of all of these variables. In addition, the different tests may have a wide range in testing times. Table 1 is provided as a guide for selection of the best test for a given soil and application. Test times for low plasticity, silty clays are provided as a baseline reference. Testing times for coarse-grained soils are typically on the order of 1 to 2 days. 5.5 A full investigation has not been conducted regarding the correlation between HCFs obtained using the laboratory methods presented herein and HCFs of in-place materials. Thus, results obtained from the test methods should be applied to field situations with caution and by qualified personnel. Note 1: The quality of the result produced by this standard depends on the competence of the personnel performing the test and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing, sampling, inspection, etc. Users of this standard are cautioned that compliance with Practice D3740 does not in itself ensure reliable results. Reliable results depend on many factors. Practice D3740 provides a means of evaluating some of these factors.