1.1 提供了两种测试方法来定性说明粘性土的自然分散特性:方法a和方法B。 1.1.1 方法A- 中所述的天然土壤碎屑处理程序 10.1 . 1.1.2 方法B- 中所述的重塑土屑程序 10.2 . 1.2 碎屑试验虽然是分散性土壤的良好、快速指示，但通常应结合针孔试验和双比重计试验、试验方法进行 D4647/D4647M 和 D4221 分别地由于本试验方法可能无法识别所有分散性粘土，其他试验，如针孔分散（试验方法 D4647/D4647M )，双比重计（试验方法 D4221 )和孔隙水提取分析（试验方法 D4542 )可以单独执行或一起使用，以帮助验证分散性。 1.3 碎屑试验作为分散性土壤的指标有一些局限性。 分散性土壤有时可能在碎屑试验中产生非分散反应。含有已知现场分散问题的高岭石的土壤在碎屑试验中显示出非分散反应 ( 1. ) . 2. 然而，如果碎屑测试表明分散，则土壤可能是分散的。 1.4 这些试验方法仅适用于塑性指数位置与液限图（试验方法）相对应的土壤 D4318 )落在“A”线上或以上（练习 D2487 )超过12个 % 根据试验方法测定，土壤部分的厚度小于2μm D7928 . 1.5 烘箱干燥的土壤不应用于制备碎屑试样，因为导致分散的土壤孔隙水理化性质可能会发生不可逆转的变化 ( 2. ) . 注1: 在某些情况下，针孔、碎屑和双比重计测试方法的结果可能不一致。 碎屑试验是分散性土壤比非分散性土壤更好的指标 ( 3. ) . 1.6 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。 1.7 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 . 1.7.1 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。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。 考虑工程设计分析方法中使用的有效数字超出了本标准的范围。 1.8 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。 1.9 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 碎屑试验为现场或实验室鉴定分散性粘性土提供了一种简单、快速的方法。 许多均质土坝的内部侵蚀破坏、沿渠道或渠岸的侵蚀以及土结构的降雨侵蚀都归因于分散粘土块中形成的裂缝或其他流道的胶体侵蚀 ( 5. ) . 5.2 碎屑测试最初由艾默生开发 ( 6. ) ，被称为聚合一致性测试，有七种不同类型的土壤-水反应。谢拉德 ( 5. ) 后来通过结合一些土壤-水反应简化了试验，以便在试验期间仅观察到四类或四级土壤分散。碎屑测试是土壤中分散性存在的相对准确的阳性指标。然而，碎屑测试并不是土壤不分散的完全可靠的负面指标。碎屑试验很少能作为确定分散性粘土存在的唯一试验方法。 双比重计试验（试验方法 D4221 )和针孔试验（试验方法 D4647/D4647M )是对粘土可能的分散行为提供有价值的额外见解的测试方法。 注2: 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 Two test methods are provided to give a qualitative indication of the natural dispersive characteristics of clayey soils: Method A and Method B. 1.1.1 Method A— Procedure for Natural Soil Crumbs described in 10.1 . 1.1.2 Method B— Procedure for Remolded Soil Crumbs described in 10.2 . 1.2 The crumb test, while a good, quick indication of dispersive soil, should usually be run in conjunction with a pinhole test and a double hydrometer test, Test Methods D4647/D4647M and D4221 , respectively. Since this test method may not identify all dispersive clay soils, other tests such as, pinhole dispersion (Test Methods D4647/D4647M ), double hydrometer (Test Method D4221 ) and the analysis of pore water extraction (Test Methods D4542 ) may be performed individually or used together to help verify dispersion. 1.3 The crumb test has some limitations in its usefulness as an indicator of dispersive soil. A dispersive soil may sometimes give a non-dispersive reaction in the crumb test. Soils containing kaolinite with known field dispersion problems, have shown non-dispersive reactions in the crumb test ( 1 ) . 2 However, if the crumb test indicates dispersion, the soil is probably dispersive. 1.4 These test methods are applicable only to soils where the position of the plasticity index versus liquid limit plots (Test Methods D4318 ) falls on or above the “A” line (Practice D2487 ) and more than 12 % of the soil fraction is finer than 2-μm as determined in accordance with Test Method D7928 . 1.5 Oven-dried soil should not be used to prepare crumb test specimens, as irreversible changes could occur to the soil pore-water physicochemical properties responsible for dispersion ( 2 ) . Note 1: In some cases, the results of the pinhole, crumb, and double-hydrometer test methods may disagree. The crumb test is a better indicator of dispersive soils than of non-dispersive soils ( 3 ) . 1.6 Units— The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.7 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026 . 1.7.1 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 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 analytical methods for engineering design. 1.8 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. 1.9 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 crumb test provides a simple, quick method for field or laboratory identification of a dispersive clayey soil. The internal erosion failures of a number of homogeneous earth dams, erosion along channel or canal banks, and rainfall erosion of earthen structures have been attributed to colloidal erosion along cracks or other flow channels formed in masses of dispersive clay ( 5 ) . 5.2 The crumb test, as originally developed by Emerson ( 6 ) , was called the aggregate coherence test and had seven different categories of soil-water reactions. Sherard ( 5 ) later simplified the test by combining some soil-water reactions so that only four categories, or grades, of soil dispersion are observed during the test. The crumb test is a relatively accurate positive indicator of the presence of dispersive properties in a soil. The crumb test, however, is not a completely reliable negative indicator that soils are not dispersive. The crumb test can seldom be relied upon as a sole test method for determining the presence of dispersive clays. The double-hydrometer test (Test Method D4221 ) and pinhole test (Test Method D4647/D4647M ) are test methods that provide valuable additional insight into the probable dispersive behavior of clay soils. Note 2: 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 depends on several factors; Practice D3740 provides a means of evaluating some of those factors.