1.1 本试验方法涵盖从实验室压实样本中测定路面路基、底基层和基层材料的加州承载比（CBR）。该试验方法主要用于但不限于评估最大粒径小于 3. / 4. 在里面（19毫米）。 1.2 当材料的最大粒径大于 3. / 4. 在里面（19 mm），该试验方法规定修改材料的级配，以便用于试验的材料均通过 3. / 4. -在中。（19 mm）筛，而总砾石（3 in.（75 mm）至+4号（4.75 mm））分数保持不变。虽然传统上使用这种试样制备方法是为了避免CBR试验装置中含有大颗粒的试验材料固有的误差，但改性材料可能具有与原始材料显著不同的强度特性。 然而，已经使用该试验方法开发了一个大型经验数据库，用于修改级配的材料，并且基于使用该程序的试验结果，正在使用令人满意的设计方法。 1.3 过去的实践表明，对于那些在4号（4.75 mm）筛网上保留大量颗粒的材料，CBR结果比更细的材料更可变。因此，可能需要对这些材料进行更多试验，以建立可靠的CBR。 1.4 本试验方法规定了在最佳含水量或规定压实试验和规定干容重的含水量范围内测定材料的CBR。干容重通常以试验方法确定的最大干容重的百分比表示 D698 或 D1557 . 1.5 要求测试的客户可以指定需要CBR的含水量或含水量范围以及干容重。 1.6 除非提出要求的客户另有规定，或除非已证明对被测材料的测试结果没有影响，否则所有试样均应在渗透前浸泡。 1.7 关于现场材料CBR的测定，请参见试验方法 D4429 . 1.8 单位- 以英寸-磅为单位的数值应视为标准值。括号中给出的国际单位是数学转换，仅供参考，不被视为标准。以英寸-磅单位以外的单位报告试验结果不应视为不符合本试验方法。 1.8.1 在处理英寸磅单位时，使用英寸磅单位的重力系统。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 段塞质量单位几乎从未在商业实践中使用过；即密度、平衡等。因此，本标准中的质量标准单位为千克（kg）或克（g），或两者兼有。此外，括号中未给出/显示等效英寸-磅单位（slug）。 1.8.3 在美国，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组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。 1.8.4 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。 1.9 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。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，通常做法是增加或减少有效数字或报告数据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和健康实践，并确定监管限制的适用性。 ====意义和用途====== 5.1 本试验方法用于评估路基、底基层和基层材料的潜在强度，包括用于道路和机场路面设计的再生材料。本试验中获得的CBR值构成了几种柔性路面设计方法的组成部分。 5.2 对于压实含水量对承载比影响较小的应用，如无粘性粗粒材料，或在设计程序中考虑了不同压实含水量的影响，可在指定压实力的最佳含水量下确定承载比。规定的干容重通常是使用客户现场压实规范允许的最小压实百分比。 5. 3. 对于压实含水量对CBR的影响未知或需要考虑其影响的应用，CBR是针对一系列含水量确定的，通常是通过使用客户的现场压实协议或规范来确定现场压实允许的含水量范围。 5.4 自胶结（和其他）材料的试样制备标准必须基于岩土工程评估。按照客户的指示，自胶结材料应适当固化，直到可以测量代表长期使用条件的承载比。 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 本身不能确保可靠的结果。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 covers the determination of the California Bearing Ratio (CBR) of pavement subgrade, subbase, and base course materials from laboratory compacted specimens. The test method is primarily intended for, but not limited to, evaluating the strength of materials having maximum particle size less than 3 / 4 in. (19 mm). 1.2 When materials having a maximum particle size greater than 3 / 4 in. (19 mm) are to be tested, this test method provides for modifying the gradation of the material so that the material used for tests all passes the 3 / 4 -in. (19-mm) sieve while the total gravel (3 in. (75 mm) to plus No. 4 (4.75 mm)) fraction remains the same. While traditionally this method of specimen preparation has been used to avoid the error inherent in testing materials containing large particles in the CBR test apparatus, the modified material may have significantly different strength properties than the original material. However, a large experience database has been developed using this test method for materials for which the gradation has been modified, and satisfactory design methods are in use based on the results of tests using this procedure. 1.3 Past practice has shown that CBR results for those materials having substantial percentages of particles retained on the No. 4 (4.75 mm) sieve are more variable than for finer materials. Consequently, more trials may be required for these materials to establish a reliable CBR. 1.4 This test method provides for the determination of the CBR of a material at optimum water content or a range of water content from a specified compaction test and a specified dry unit weight. The dry unit weight is usually given as a percentage of maximum dry unit weight determined by Test Methods D698 or D1557 . 1.5 The client requesting the test may specify the water content or range of water contents and the dry unit weight for which the CBR is desired. 1.6 Unless specified otherwise by the requesting client, or unless it has been shown to have no effect on test results for the material being tested, all specimens shall be soaked prior to penetration. 1.7 For the determination of CBR of field in-place materials, see Test Method D4429 . 1.8 Units— The values stated in inch-pound units are to be regarded as standard. The SI units given in parentheses are mathematical conversions, which are provided for information purposes only and are not considered standard. Reporting of test results in units other than inch-pound units shall not be regarded as nonconformance with this test method. 1.8.1 The gravitational system of inch-pound units is used when dealing with inch-pound 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 The slug unit of mass is almost never used in commercial practice; that is, density, balances, etc. Therefore, the standard unit for mass in this standard is either kilogram (kg) or gram (g), or both. Also, the equivalent inch-pound unit (slug) is not given/presented in parentheses. 1.8.3 It is common practice in the engineering/construction profession, in the United States, 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 inchpound 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. 1.8.4 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. 1.9 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 considerations for the user’s objectives, and it is common practice to increase or reduce significant digits or 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. 1.10 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 and health practices and determine the applicability of regulatory limitations prior to use. ====== Significance And Use ====== 5.1 This test method is used to evaluate the potential strength of subgrade, subbase, and base course materials, including recycled materials for use in the design of road and airfield pavements. The CBR value obtained in this test forms an integral part of several flexible pavement design methods. 5.2 For applications where the effect of compaction water content on CBR is small, such as cohesionless, coarse-grained materials, or where an allowance is made for the effect of differing compaction water contents in the design procedure, the CBR may be determined at the optimum water content of a specified compaction effort. The specified dry unit weight is normally the minimum percent compaction allowed by the using client’s field compaction specification. 5.3 For applications where the effect of compaction water content on CBR is unknown or where it is desired to account for its effect, the CBR is determined for a range of water contents, usually the range of water content permitted for field compaction by using the client’s protocol or specification for field compaction. 5.4 The criteria for test specimen preparation of self-cementing (and other) materials which gain strength with time must be based on a geotechnical engineering evaluation. As directed by the client, self-cementing materials shall be properly cured until bearing ratios representing long term service conditions can be measured. Note 1: The quality of the results 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 ensure reliable results. Reliable results depend on many factors; Practice D3740 provides a means of evaluating some of those factors.