1.1 本试验方法允许测定土壤在浸没蒸馏水时的膨胀潜力。 2. 该测试方法测量土壤的定性指标特性，而不是用于计算实际膨胀量的设计参数。膨胀指数， 工程安装 ，提供了土壤膨胀潜力的指示。 1.2 该试验方法提供了一种简单但敏感的方法，用于使用指数参数评估实际工程应用中土壤的膨胀潜力。 1.3 单位- 以国际单位制表示的数值应视为标准值。括号中给出的值仅供参考，不被视为标准值。 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标准。 1.3.1 在处理英寸磅单位时，使用英寸磅单位的重力系统。在该系统中，磅（lbf）表示力（重量）的单位，而质量的单位是段塞。除非涉及动态（F=ma）计算，否则未给出缓动单元。 1.3.2 为仪器提供的国际单位制是英寸磅单位的替代品，如果其他类似的国际单位制满足英寸磅仪器制定的技术要求，则可以接受。 1.3.3 工程/建筑行业的常见做法是同时使用磅来表示质量单位（lbm）和力（lbf）。 这种做法隐含地结合了两个独立的单位制；绝对系统和引力系统。在一个标准中结合使用两套独立的英寸-磅单位在科学上是不可取的。如前所述，本标准包括英寸-磅单位的重力系统，不使用/表示段塞质量单位。然而，使用天平和天平记录质量磅（lbm）或记录密度（lbm/ft） 3. 不应视为不符合本标准。 1.3.4 术语密度和单位重量经常互换使用。密度是单位体积的质量，而单位重量是单位体积的力。 在本标准中，密度仅以国际单位制表示。密度确定后，单位重量以国际单位制或英寸-磅单位计算，或以两者为单位计算。 1.4 所有观察值和计算值应符合实践中确定的有效数字和舍入准则 D6026 ，除非被本试验方法取代。 1.4.1 为了将测量值或计算值与规定限值进行比较，应将测量值或计算值四舍五入到规定限值中有效数字的最近小数点。 1.4.2 用于指定如何在标准中收集/记录或计算数据的程序被视为行业标准。 此外，它们代表了通常应保留的有效数字。使用的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；通常的做法是增加或减少报告数据的有效位数，以与这些考虑因素相称。考虑工程数据分析方法中使用的有效数字超出了本标准的范围。 1.5 本标准的文本引用了提供解释材料的注释和脚注。这些注释和脚注（不包括表和图中的注释和脚注）不应视为本标准的要求。 1.6 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。 1.7 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 膨胀指数， 工程安装 ，该值被工程师和其他专业人员用作土壤膨胀潜力的指标。它也可用于确定土壤的适宜性，以满足指定机构设定的要求。 5.2 这个 工程安装 试验不用于复制任何特定的现场条件，如土壤密度、含水量、荷载、原位土壤结构或土壤水化学。然而，在制备压实试样时使用了一致的试验条件，以便可以直接关联数据。 5.3 根据膨胀土的经验，推荐的土壤潜在膨胀的定性分类基于 工程安装 在中提供 表1 . 5.4 试验方法包括在不同垂直（轴向）压力下测量一维润湿引起的膨胀或坍塌（水压）的大小，以及膨胀压力的大小和自由膨胀的大小，以及确定润湿引起的膨胀或坍塌后应力引起的压缩数据 D4546 . 方法中还包括测试完整样本以测量一维润湿引起的膨胀或塌陷的能力 D4546 . 注1: 本标准产生的结果的质量取决于执行该标准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/采样/检查等。本标准的用户应注意遵守惯例 D3740 本身并不能保证可靠的结果。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 This test method allows for determination of expansion potential of soils when inundated with distilled water. 2 This test method measures a qualitative index property of the soil rather than a design parameter to be used for calculation of the actual amount of expansion. The expansion index, EI , provides an indication of swelling potential of a soil. 1.2 This test method provides a simple, yet sensitive, method for evaluation of expansion potential of soils for practical engineering applications using an index parameter. 1.3 Units— The values stated in SI units are to be regarded as standard. The values given in parentheses are provided for information only and are not considered standard. Reporting of test results in units other than SI shall not be regarded as nonconformance with this standard. 1.3.1 The gravitational system of inch-pound units is used when dealing with inch-pound units. In the system, the pound (lbf) represents a unit of force (weight), while the units for mass is slugs. The slug unit is not given, unless dynamic (F = ma) calculations are involved. 1.3.2 The SI units presented for apparatus are substitutions of the inch-pound units, other similar SI units should be acceptable providing they meet the technical requirements established by the inch-pound apparatus. 1.3.3 It is common practice in the engineering/construction profession to concurrently use pounds to represent both a unit of mass (lbm) and of force (lbf). This practice implicitly combines two separate systems of units; the absolute and the gravitational systems. It is scientifically undesirable to combine the use of two separate sets of inch-pound units within a single standard. As stated, this standard includes the gravitational system of inch-pound units and does not use/present the slug unit of mass. However, the use of balances and scales recording pounds of mass (lbm) or recording density in lbm/ft 3 shall not be regarded as nonconformance with this standard. 1.3.4 The terms density and unit weight are often used interchangeably. Density is mass per unit volume, whereas unit weight is force per unit volume. In this standard, density is given only in SI units. After the density has been determined, the unit weight is calculated in SI or inch-pound units, or both. 1.4 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026 , unless superseded by this test method. 1.4.1 For purposes of comparing a measured or calculated value(s) with specified limits, the measured or calculated value(s) shall be rounded to the nearest decimal of significant digits in the specified limit. 1.4.2 The procedures used to specify how data are collected/recorded or calculated in the standard are regarded as the industry standard. In addition, they are representative of the significant digits that generally should be retained. The procedures used do not consider material variation, purpose for obtaining the data, special purpose studies, or any considerations for the user’s objectives; and it is common practice to increase or reduce significant digits of reported data to be commensurate with these considerations. It is beyond the scope of this standard to consider significant digits used in analysis methods for engineering data. 1.5 The text of this standard references notes and footnotes that provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of the standard. 1.6 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. 1.7 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 expansion index, EI , value is used by engineers and other professionals as an indicator of the soil’s swelling potential. It may also be used to determine the suitability of a soil to satisfy requirements set by specifying agencies. 5.2 The EI test is not used to duplicate any particular field conditions such as soil density, water content, loading, in-place soil structure, or soil water chemistry. However, consistent test conditions are used in preparation of compacted specimens such that direct correlation of data can be made. 5.3 Based on experience with expansive soils, the recommended qualitative classification of potential expansion in a soil based on EI is provided in Table 1 . 5.4 The measurement of the magnitude of one-dimensional wetting-induced swell or collapse (hydrocompression) under different vertical (axial) pressures, as well as the magnitude of swell pressure and the magnitude of free swell, and also the determination of data for stress-induced compression following wetting-induced swell or collapse are covered by Test Methods D4546 . The ability to test intact specimens for measuring one-dimensional wetting-induced swell or collapse is also covered in Methods D4546 . Note 1: The quality of the result produced by this standard is dependent on the competence of the personnel performing it 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 assure reliable results. Reliable results depend on many factors; Practice D3740 provides a means of evaluating some of those factors.