1.1本规程描述了一种基于实验室测定粒度特征、液限和塑性指数的工程用矿物和有机矿物土壤分类系统，并应在需要精确分类时使用。 注1 使用本标准将产生单一分类组符号和组名，除非土壤中含有5%至12%的细粒，或液限和塑性指数值的绘图位于塑性图的交叉阴影区域。在这两种情况下，使用双重符号，例如GP-GM、CL-ML。当实验室测试结果表明土壤接近另一个土壤分类组时，可以用斜线分隔的两个符号表示边界条件。第一个符号应是基于本标准的符号，例如CL/CH、GM/SM、SC/CL。 当粘性土的液限值接近50时，边界符号特别有用。这些土壤可能具有膨胀特性，使用边界符号（CL/CH，CH/CL）将提醒用户指定的膨胀潜力分类。 1.2本系统的组码部分基于对通过3-in。（75 mm）筛（见规范E 11）。 1.3作为一个分类系统，本标准仅限于天然土壤。 注释2 本试验方法中使用的组名和符号可用作适用于页岩、粘土岩、贝壳、碎石等材料的描述系统。请参阅。 1.4本标准仅用于定性应用。 附注3 当重要结构的详细设计需要定量信息时，必须通过实验室试验或其他定量数据来补充该试验方法，以确定预期现场条件下的性能特征。 1.5本标准是统一土壤分类系统的ASTM版本。分类方案的基础是A.Casagrande在20世纪40年代早期开发的机场分类系统。1952年，当几个美国政府机构采用机场系统的修改版本时，它被称为统一土壤分类系统。 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和健康实践，并确定监管限制的适用性。 1.6 本实践提供了一组用于执行一个或多个特定操作的说明。本文件不能取代教育或经验，应与专业判断一起使用。 并非本惯例的所有方面都适用于所有情况。本ASTM标准不代表或取代必须根据其判断给定专业服务的充分性的谨慎标准，也不应在不考虑项目的许多独特方面的情况下应用本文件。本文件标题中的“标准”一词仅表示该文件已通过ASTM共识程序获得批准。 ====意义和用途====== 本标准将任何地理位置的土壤分类为代表规定实验室试验结果的类别，以确定粒度特征、液限和塑性指数。 指定组名和符号以及实施规程D 2488中要求的描述性信息 可用于描述土壤，以帮助评估其工程使用的重要特性。 设计了该分类系统的各种分组，以在一般情况下与土壤的工程行为相关联。本标准为岩土工程目的的任何现场或实验室调查提供了有用的第一步。 本标准也可用于帮助培训人员使用规程D 2488 . 本标准可与实施规程D 4083结合使用 处理冻土时。 笔记 5-尽管本标准中包含精度和偏差声明:本试验方法的精度取决于执行该方法的人员的能力以及所用设备和设施的适用性。符合实践D 3740标准的机构 通常认为能够胜任和客观测试。本试验方法的使用者应注意遵守实施规程D 3740 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D 3740 提供了评估其中一些因素的方法。

1.1 This practice describes a system for classifying mineral and organo-mineral soils for engineering purposes based on laboratory determination of particle-size characteristics, liquid limit, and plasticity index and shall be used when precise classification is required. Note 1 Use of this standard will result in a single classification group symbol and group name except when a soil contains 5 to 12 % fines or when the plot of the liquid limit and plasticity index values falls into the crosshatched area of the plasticity chart. In these two cases, a dual symbol is used, for example, GP-GM, CL-ML. When the laboratory test results indicate that the soil is close to another soil classification group, the borderline condition can be indicated with two symbols separated by a slash. The first symbol should be the one based on this standard, for example, CL/CH, GM/SM, SC/CL. Borderline symbols are particularly useful when the liquid limit value of clayey soils is close to 50. These soils can have expansive characteristics and the use of a borderline symbol (CL/CH, CH/CL) will alert the user of the assigned classifications of expansive potential. 1.2 The group symbol portion of this system is based on laboratory tests performed on the portion of a soil sample passing the 3-in. (75-mm) sieve (see Specification E 11). 1.3 As a classification system, this standard is limited to naturally occurring soils. Note 2 The group names and symbols used in this test method may be used as a descriptive system applied to such materials as shale, claystone, shells, crushed rock, etc. See. 1.4 This standard is for qualitative application only. Note 3 When quantitative information is required for detailed designs of important structures, this test method must be supplemented by laboratory tests or other quantitative data to determine performance characteristics under expected field conditions. 1.5 This standard is the ASTM version of the Unified Soil Classification System. The basis for the classification scheme is the Airfield Classification System developed by A. Casagrande in the early 1940's. It became known as the Unified Soil Classification System when several U.S. Government Agencies adopted a modified version of the Airfield System in 1952. 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 and health practices and determine the applicability of regulatory limitations prior to use. 1.6 This practice offers a set of instructions for performing one or more specific operations. This document cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this practice may be applicable in all circumstances. This ASTM standard is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied without consideration of a project's many unique aspects. The word "Standard" in the title of this document means only that the document has been approved through the ASTM consensus process. ====== Significance And Use ====== This standard classifies soils from any geographic location into categories representing the results of prescribed laboratory tests to determine the particle-size characteristics, the liquid limit, and the plasticity index. The assigning of a group name and symbol(s) along with the descriptive information required in Practice D 2488 can be used to describe a soil to aid in the evaluation of its significant properties for engineering use. The various groupings of this classification system have been devised to correlate in a general way with the engineering behavior of soils. This standard provides a useful first step in any field or laboratory investigation for geotechnical engineering purposes. This standard may also be used as an aid in training personnel in the use of Practice D 2488 . This standard may be used in combination with Practice D 4083 when working with frozen soils. Note 5—Notwithstanding the statements on precision and bias contained in this standard: The precision of this test method 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 D 3740 are generally considered capable of competent and objective testing. Users of this test method are cautioned that compliance with Practice D 3740 does not in itself assure reliable testing. Reliable testing depends on several factors; Practice D 3740 provides a means for evaluating some of those factors.