1.1 本标准涵盖两种实验室试验方法，用于测量非饱和土壤的一维湿润引起的膨胀或坍塌的幅度，以及一种用于测量湿润引起的变形后的荷载引起的压缩的方法。 1.1.1 试验方法A是一种用于测量模拟压实填土现场条件的重塑试样的一维润湿引起的膨胀或水压（坍塌）的程序。膨胀压力（防止膨胀所需的最小垂直应力）和自由膨胀（1 kPa或20 lbf/ft压力下的膨胀百分比）的大小 2. )也可根据试验方法A的结果确定。 1.1.2 试验方法B是一种测量从自然沉积物或现有压实填料中获得的完整试样的一维润湿引起的膨胀或塌陷变形的程序。膨胀压力和自由膨胀的大小也可以根据试验方法B的结果确定。 1.1.3 试验方法C是在试样经历润湿引起的膨胀或塌陷变形后，测量重组或完整试样上的荷载引起应变的程序。 1.2 在试验方法A中，将一系列再现现场土壤细颗粒压实条件的再造试样（不包括超大颗粒）组装在固结仪单元中。 对不同的试样施加与不同填充深度相对应的不同荷载，使每个试样能够接触到自由水，直到主要膨胀或坍塌过程完成( 图1 )在恒定垂直总应力下( 图2 ). 测量了由此产生的膨胀或坍塌变形。该试验方法可称为 加载试验后润湿 在多个再造标本上。这些测试的数据可用于估计填土施工后由于完全湿润而可能发生的一维地表隆起或沉降。 此外，膨胀压力的大小和自由膨胀的大小可以从测试结果中解释。 图1 时间膨胀曲线 图2 变形与垂直应力，试验方法A 1.3 试验方法B通常用于测量单个完整样品的一维润湿引起的膨胀或水压。这种方法可以称为 加载试验后单点润湿 . 试样润湿时的垂直压力等于与取样深度对应的垂直地应力（表土应力加结构应力，如有）。 测试结果表明，当给定填土深度的土壤从当前水分条件湿润到完全浸水条件时，可能产生的隆起或水压缩量。如果测试不同深度的完整试样，则膨胀或坍塌应变数据可用于估计地表的隆起或沉降。如果试验的目的是测量膨胀土的膨胀压力，则可以在一定压力范围内（类似于试验方法a）湿润给定深度区域的一系列完整试样，并将结果解释为确定膨胀压力的大小。 1.4 试验方法C用于在发生润湿引起的膨胀或坍塌变形后测量荷载引起的应变。这种方法可以称为 湿润试验后加载 . 该测试可以在完整或重组样本上进行，也可以在一个样本或一系列样本上进行。结果将适用于新填土、额外结构荷载或两者同时施加到先前经历过湿陷引起的隆起或沉降的地面的情况。试验的第一部分与试验方法A或B中的相同。在给定垂直荷载下完成膨胀或坍塌后，以与固结试验相同的方式向试样施加额外的垂直荷载增量（试验方法 D2435/D2435M )并测量了荷载引起的应变。 1.5 要求进行本试验的机构应负责规定试验方法A和试验方法B的每个载荷的大小。对于试验方法C，要求进行试验的机构应规定试样润湿时的应力大小，以及润湿后额外应力增量的大小。 1.6 这些试验方法不涉及土壤吸力和吸力控制膨胀-坍塌试验的测量。吸力控制润湿的添加不构成这些试验方法的不符合项。 1.7 这些试验方法有许多局限性，其结果可能受到一个或多个因素的影响，包括大量超大颗粒的影响（在试验方法a中）、采样干扰（在试验方法B中）以及实验室试样和现场润湿程度之间的差异。有关这些限制和其他限制的详细信息，请参阅第节 6. . 1.8 以国际单位制表示的数值应视为标准值。国际单位制后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记录的试验结果不应视为不符合本标准。描述测试结果的数字可以采用国际单位制或英寸-磅单位。 1.8.1 转换后的英寸-磅单位使用重力单位制。在这个系统中，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。 1.8.2 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）。 这隐含地结合了两个独立的单元系统；也就是说，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/呈现质量的段塞单位。然而，使用天平或天平记录磅质量（lbm）或记录密度（lbm/ft） 3. 不应视为不符合本标准。 1.8.3 术语密度和单位重量经常互换使用。 密度是每单位体积的质量，而单位重量是每单位体积的力。在此标准中，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。 1.9 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 . 1.9.1 本标准中用于规定如何收集/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。 所使用的程序不考虑材料变化、获取数据的目的、特殊目的研究或任何对用户目标的考虑；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。考虑工程设计分析方法中使用的有效数字超出了本标准的范围。 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 根据试验方法A和B测得的润湿引起的膨胀/坍塌应变可用于估算受限土壤剖面的隆起或沉降 ( 1- 4. ) . 4. 它们也可用于估计膨胀压力的大小( 图3 )和自由膨胀应变（1 kPa（20 lbf/ft）压力下的膨胀百分比 2. )). 试验方法C中的湿润后荷载引起的应变可用于估计湿润引起的隆起或沉降后的应力引起的沉降。试验方法、加载和淹没顺序的选择应尽可能模拟现场条件，因为密度和含水量的相对较小变化，或加载和湿润顺序可能会显著改变试验结果 ( 1. , 5和 6. ) . 图3 应力与润湿引起的膨胀/坍塌应变，试验方法A 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测试。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。可靠的结果取决于几个因素；实践 D3740 提供了一种评估其中一些因素的方法。

1.1 This standard covers two laboratory test methods for measuring the magnitude of one-dimensional wetting-induced swell or collapse of unsaturated soils and one method for measuring load-induced compression subsequent to wetting-induced deformation. 1.1.1 Test Method A is a procedure for measuring one-dimensional wetting-induced swell or hydrocompression (collapse) of reconstituted specimens simulating field condition of compacted fills. The magnitude of swell pressure (the minimum vertical stress required to prevent swelling), and free swell (percent swell under a pressure of 1 kPa or 20 lbf/ft 2 ) can also be determined from the results of Test Method A. 1.1.2 Test Method B is a procedure for measuring one-dimensional wetting-induced swell or collapse deformation of intact specimens obtained from a natural deposit or from an existing compacted fill. The magnitude of swell pressure and free swell can also be determined from the results of Test Method B. 1.1.3 Test Method C is a procedure for measuring load-induced strains on a reconstituted or intact specimen after the specimen has undergone wetting-induced swell or collapse deformation. 1.2 In Test Method A, a series of reconstituted specimens duplicating compaction condition of the fine fraction of the soil in the field (excluding the oversize particles) are assembled in consolidometer units. Different loads corresponding to different fill depths are applied to different specimens and each specimen is given access to free water until the process of primary swell or collapse is completed ( Fig. 1 ) under a constant vertical total stress ( Fig. 2 ). The resulting swell or collapse deformations are measured. This test method can be referred to as wetting-after-loading tests on multiple reconstituted specimens. The data from these tests can be used to estimate one-dimensional ground surface heave or settlement that can occur due to full wetting after fill construction. In addition, the magnitude of swell pressure and the magnitude of free swell can be interpreted from the test results. FIG. 1 Time-Swell Curve FIG. 2 Deformation Versus Vertical Stress, Test Method A 1.3 Test Method B is commonly used for measuring one-dimensional wetting-induced swell or hydrocompression of individual intact samples. This method can be referred to as single-point wetting-after-loading test . The vertical pressure at wetting for the specimen is chosen equal to the vertical in-situ stress (overburden stress plus structural stress, if any) corresponding to the sampling depth. The test result indicates the amount of heave or hydrocompression that can result when the soil at a given fill depth is wetted from the current moisture condition to full inundation condition. If intact specimens from various depths are tested, the swell or collapse strain data can be used to estimate heave or settlement of the ground surface. If the objective of the test is to measure swell pressure for an expansive soil, a series of intact specimens from a given depth zone can be wetted under a range of pressures (similar to Test Method A) and the results interpreted to determine the magnitude of the swell pressure. 1.4 Test Method C is for measuring load-induced strains after wetting-induced swell or collapse deformation has occurred. This method can be referred to as loading-after-wetting test . The test can be performed on either intact or reconstituted specimens, and can be on one specimen or a series of specimens. The results would apply to situations where new fill, additional structural loads, or both, are applied to the ground that has previously gone through wetting-induced heave or settlement. The first part of the test is the same as in Test Method A or B. After completion of the swell or collapse under a given vertical load, additional vertical load increments are applied to the specimen in the same manner as in a consolidation test (Test Methods D2435/D2435M ) and the load-induced strains are measured. 1.5 It shall be the responsibility of the agency requesting this test to specify the magnitude of each load for Test Method A and Test Method B. For Test Method C, the agency requesting the test should specify the magnitude of the stress under which the specimen is wetted, and the magnitudes of the additional stress increments subsequent to wetting. 1.6 These test methods do not address the measurement of soil suction and suction-controlled swell-collapse tests. The addition of suction-controlled wetting does not constitute nonconformance to these test methods. 1.7 These test methods have a number of limitations and their results can be affected by one or a combination of factors including the effect of significant amounts of oversize particles (in Test Method A), sampling disturbance (in Test Method B) and differences between the degree of wetting in the laboratory test specimens and in the field. For details of these and other limitations, see Section 6 . 1.8 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard. Test results recorded in units other than SI shall not be regarded as nonconformance with this standard. Figures depicting the test results can be either in SI units or in inch-pound units. 1.8.1 The converted inch-pound units use the gravitational system of units. In this system, the pound (lbf) represents a unit of force (weight), while the unit for mass is slugs. The slug unit is not given, unless dynamic (F = ma) calculations are involved. 1.8.2 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 implicitly combines two separate systems of units; that is, the absolute system and the gravitational system. 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 for mass. However, the use of balances or scales recording pounds of mass (lbm) or recording density in lbm/ft 3 shall not be regarded as nonconformance with this standard. 1.8.3 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. 1.9 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026 . 1.9.1 The procedures used to specify how data are collected/recorded, or calculated, in this 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 consideration 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 design. 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 wetting-induced swell/collapse strains measured from Test Methods A and B can be used to develop estimates of heave or settlement of a confined soil profile ( 1- 4 ) . 4 They can also be used to estimate the magnitudes of the swell pressure ( Fig. 3 ) and the free swell strain (percent swell under a pressure of 1 kPa (20 lbf/ft 2 )). The load-induced strains after wetting from Test Method C can be used to estimate stress-induced settlement following wetting-induced heave or settlement. Selection of test method, loading, and inundation sequences should, as closely as possible, simulate field conditions because relatively small variations in density and water content, or sequence of loading and wetting can significantly alter the test results ( 1 , 5 and 6 ) . FIG. 3 Stress Versus Wetting-Induced Swell/Collapse Strain, Test Method A 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. Users of this standard are cautioned that compliance with Practice D3740 does not in itself assure reliable results. Reliable results depends on several factors; Practice D3740 provides a means of evaluating some of these factors.