1.1 本试验方法通过使水流过试样上的小孔，直接测量粘土的分散性和由此产生的胶体可蚀性。测试结果是定性的，为分散性和可蚀性提供了一般指导。本试验方法由试验方法补充 D4221 . 1.2 本试验方法和评估试验数据的标准基于从路堤、渠道和其他粘土侵蚀或抵抗侵蚀的区域收集的数百个样品的试验结果 ( 1. ) . 2. 1.3 提供了三种分类粘土分散性的替代程序，如下所示: 1.3.1 方法A和方法C，改编自参考文献 ( 1. ), 将土壤分为六类分散性:分散性（D1、D2）、轻度至中度分散性（ND4、ND3）和非分散性（ND2、ND1）。 1.3.2 方法B将土壤分为三类分散性:分散性（D）、微分散性（SD）和非分散性（ND）。 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 . 1.5 单位- 以国际单位制或英寸-磅单位表示的数值应单独视为标准值。每个系统中规定的值可能不是精确的等效值；因此，每个系统应相互独立使用。将两个系统的值合并可能会导致不符合标准。 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 针孔试验提供了一种识别拟用于或已用于土方施工的粘土分散特性的方法。 许多均质土坝的管涌破坏、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 ( 2. ) . 5.2 该试验方法模拟了沿着土堤裂缝流动的水的作用。其他间接试验，如双比重计试验（试验方法 D4221 )，碎屑测试 ( 3. , 4. ) ，将悬浮粘土胶体云的浊度作为粘土分散性的指标，将钠与土壤总可溶性盐含量的百分比相关的化学试验也用作粘土分散性的指标试验 ( 2. ) . 对数百个样品进行的针孔试验和其他间接试验结果的比较表明，针孔试验结果与自然界中粘土的侵蚀性能具有最佳相关性。 5.3 针孔试验的方法A和方法C要求评估出水的浊度、针孔的最终尺寸，并计算通过针孔的流速，以便对土壤的分散特性进行分类。方法B只需要评估出水的浊度和针孔的最终尺寸，以分类土壤的分散特性。方法A中通过针孔的流速计算主要用于指导在试验期间施加顺序压力下的适当设备和试样性能。所有方法都会产生类似的结果，任何方法都可以用于识别分散性粘土。 5.4 方法A或方法C的使用导致与通过针孔的顺序流量相关的数据积累，并导致孔扩大或侵蚀。 针孔侵蚀试验是为了识别分散性土壤而开发的，不打算成为原型结构的几何比例模型。由于针孔试验设计中未使用相似理论，因此未获得定量数据。通过针孔的流量、土壤侵蚀量或土壤侵蚀率不应外推到实际现场条件 ( 3. ) . 然而，这些数据可能有助于定性评估此类侵蚀在大坝破坏、生命和财产损失方面的后果。它们也可用于考虑必要的防御设计措施的成本效益，以最大限度地减少分散粘土造成的破坏影响。例如，在相当长的一段时间内，被归类为ND2（非常轻微分散）的土壤中发生的胶体侵蚀量将非常小。 在不涉及公共安全或正常维护程序将处理问题的项目中，这种侵蚀在评估成本效益关系时可能并不重要。在这种情况下，使用针孔试验的方法B将土壤分类为ND（非分散性）就足够了。 5.5 针孔试验将土壤分类为轻微分散性（方法A的ND3或方法C或方法B的SD）表明，对于结构设计或稳定性中需要考虑的重大问题的存在，存在高度不确定性。在这种情况下，建议对同一地区的许多其他土壤进行重新采样和测试，以生成足够的统计样本，用于问题评估。原始微分散样品可能来自更高分散性土壤边缘的区域。 5.6 在一些自然地理区域或地质气候条件下，或两者兼而有之，针孔测试或其他指示剂测试都不能提供分散粘土的一致识别 ( 5. , 6. , 7. ) . 在这种情况下，测试结果 ( 8. , 9 ) 应根据成本效益和设计判断进行评估 ( 7. ) . 5.7 对于某些项目，可能需要使用蒸馏水以外的腐蚀液进行针孔测试 ( 8. , 10 ) . 在这种情况下，可以使用方法A、方法B或方法C来确定土壤的分散特性，并将结果与使用蒸馏水获得的结果进行比较。 注1: 尽管这些试验方法中包含精度和偏差声明:这些试验方法的精度取决于执行人员的能力以及所用设备和设施的适用性。 符合执业标准的机构 D3740 通常认为能够胜任和客观测试。这些试验方法的使用者应注意遵守规程 D3740 本身不能保证可靠的测试。可靠的测试取决于几个因素；实践 D3740 提供了一种评估其中一些因素的方法。

1.1 This test method presents a direct, measurement of the dispersibility and consequent colloidal erodibility of clay soils by causing water to flow through a small hole punched in a specimen. The results of the tests are qualitative and provide general guidance regarding dispersibility and erodibility. This test method is complemented by Test Method D4221 . 1.2 This test method and the criteria for evaluating test data are based upon results of several hundred tests on samples collected from embankments, channels, and other areas where clay soils have eroded or resisted erosion in nature ( 1 ) . 2 1.3 Three alternative procedures for classifying the dispersibility of clay soils are provided as follows: 1.3.1 Method A and Method C, adapted from Ref ( 1 ), classify soils into six categories of dispersiveness as: dispersibility (D1, D2), slight to moderately dispersive (ND4, ND3), and nondispersive (ND2, ND1). 1.3.2 Method B classifies soils into three categories of dispersiveness as: dispersibility (D), slightly dispersive (SD), and nondispersive (ND). 1.4 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026 . 1.5 Units— The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with 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 pinhole test provides one method of identifying the dispersive characteristics of clay soils that are to be or have been used in earth construction. The piping failures of a number of homogeneous earth dams, erosion along channel or canal banks, and rainfall erosion of earthen structures have been attributed to the colloidal erosion along cracks or other flow channels formed in masses of dispersive clay ( 2 ) . 5.2 This test method models the action of water flowing along a crack in an earth embankment. Other indirect tests, such as the double hydrometer test (Test Method D4221 ), the crumb test ( 3 , 4 ) , that relates the turbidity of a cloud of suspended clay colloids as an indicator of the clay dispersivity, and chemical tests that relate the percentage of sodium to total soluble salt content of the soil are also used as indicator tests of clay dispersibility ( 2 ) . The comparison of results from the pinhole test and other indirect tests on hundreds of samples indicates that the results of the pinhole test have the best correlation with the erosional performance of clay soils in nature. 5.3 Method A and Method C of the pinhole test require the evaluation of cloudiness of effluent, final size of the pinhole, and computation of flow rates through the pinhole in order to classify the dispersive characteristics of the soil. Method B requires only the evaluation of the cloudiness of effluent and final size of the pinhole to classify the dispersive characteristics of the soil. The computation of flow rates through the pinhole in Method A serves primarily as a guide to the proper equipment and specimen performance under sequential pressures applied during the test. All methods produce similar results and any method can be used to identify dispersive clays. 5.4 The use of Method A or Method C results in the accumulation of data relative to sequential flow rates through the pinhole and consequent enlargement or erosion of the hole. The pinhole erosion test was developed for the purpose of identifying dispersive soils and is not intended to be a geometrically scaled model of a prototype structure. Since the theory of similitude was not used in the design of the pinhole test, quantitative data are not obtained. The quantity of flow through the pinhole, amount of soil erosion, or the rate of soil erosion should not be extrapolated to actual field conditions ( 3 ) . However, such data may be useful in performing qualitative evaluations of the consequences of such erosion in terms of dam failure, loss of life and property. They also may be used in considering the cost effectiveness of defensive design measures necessary to minimize the effects of failure due to dispersive clays. For example, the amount of colloidal erosion that will occur in a soil classed as ND2 (very slightly dispersive) will be very small for a relatively long period of time. Such erosion may not be significant in evaluating the cost-benefit relationships in projects where public safety is not involved or where normal maintenance procedures will handle the problem. In such cases, classifying the soil as ND (nondispersive) using Method B of the pinhole test should be adequate. 5.5 Pinhole tests that result in classifying soil as slightly dispersive (ND3 by Method A or Method C or SD by Method B) indicate high uncertainty about the existence of significant problems to be considered in the design or stability of a structure. In such cases, it is advisable to resample and test a number of other soils from the same area to generate an adequate statistical sample for problem evaluation. The original slightly dispersive sample may come from an area on the edge of a more highly dispersive soil. 5.6 In a few physiographic areas or geoclimatic conditions, or both, neither the pinhole test nor the other indicator tests provide consistent identification of dispersive clays ( 5 , 6 , 7 ) . In such cases, the results of the tests ( 8 , 9 ) should be evaluated in terms of cost effectiveness and design judgment ( 7 ) . 5.7 For some projects, it may be desirable to perform the pinhole test using eroding fluids other than distilled water ( 8 , 10 ) . In such cases, Method A, Method B, or Method C may be used to identify the dispersive characteristics of the soil and compare the results with those obtained using distilled water. Note 1: Notwithstanding the statement on precision and bias contained in these test methods: The precision of these test methods is dependent on the competence of the personnel performing it, and the suitability of the equipment and facilities used. Agencies which meet the criteria of Practice D3740 are generally considered capable of competent and objective testing. Users of these test methods are cautioned that compliance with Practice D3740 does not in itself assure reliable testing. Reliable testing depends on several factors; Practice D3740 provides a means of evaluating some of those factors.