1.1 这些试验方法包括测定现场或试验模具中土壤的冲击值（IV），如下所示: 1.1.1 现场程序A-- 现场单独测定IV。 1.1.2 现场程序B-- 现场测定IV和含水量。 1.1.3 现场程序C-- 现场测定IV、含水量和干密度。 1.1.4 模具程序-- 在实验室中测定在模具中压实的土壤的IV。 1.2 单位-- 以国际单位制表示的数值应视为标准。括号中给出的值仅供参考，不被视为标准值。以SI以外的单位报告试验结果不应被视为不符合本标准。 1.3 使用4.5 kg（10 lbm）锤子的标准试验方法适用于但不限于评估非饱和压实填土的强度，特别是路面材料、土壤和土壤- 最大粒径小于37.5毫米（1.5英寸）的骨料。 1.4 通过使用重量较轻的0.5 kg（1.1 lbm）或2.25 kg（5 lbm）锤子，本试验方法适用于评估强度较低的土壤，如最大粒径小于9.5 mm（0.375 in.）的细粒无粘性、高度有机、饱和或高度塑性土壤，或天然草坪草。 1.5 通过使用较重的10 kg（22 lbm）或20 kg（44 lbm）锤子，本试验方法适用于评估天平顶端或超出标准和较轻冲击土壤测试仪范围的较硬材料。 1.6 通过使用4.5 kg（10 lbm）锤子对特定土壤进行实验室试验相关性，IV可以与未压实的加州承载比（CBR）相关联，或者可以用于推断压实百分比。0.5 kg（1.1 lbm）和2.25 kg（5 lbm）锤的IV可独立地与未压实CBR相关，或用于推断低强度土壤的压实百分比。 1.7 所有观测值和计算值应符合实践中制定的有效数字和四舍五入指南 D6026 . 1.8 为了将测量或计算值与规定限值进行比较，测量或计算的值应四舍五入至规定限值中最接近的小数或有效数字。 1.8.1 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相称。考虑设计分析方法中使用的有效数字超出了本标准的范围。 注1: 该测试方法中包含的设备和程序与B.Clegg于20世纪70年代在澳大利亚西澳大利亚州珀斯的西澳大利亚大学开发的设备和步骤相似。冲击值也称为克莱格冲击值（CIV）。 1.9 本标准并不旨在解决与其使用相关的所有安全问题（如有）。本标准的使用者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。 1.10 本国际标准是根据世界贸易组织技术性贸易壁垒委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认的标准化原则制定的。 ====意义和用途====== 5. 1. 使用标准4.5 kg（10 lbm）锤确定的冲击值直接应用于路面的设计和施工，并普遍应用于土方工程压实控制和评估各种材料的强度特性，如土壤、土壤骨料和稳定土。冲击值是一种特性，用于使用直径为50 mm（2 in.）的锤子评估厚度达150 mm（6 in.）或使用直径为130 mm（5 in.）的锤评估厚度达380 mm（15 in.）的土壤层的强度，并通过推断指示该层的压实条件。冲击值反映并响应影响强度的物理特性的变化。它是一种动态力穿透特性，可用于设置强度参数。 5.2 该试验方法提供了IV方面的即时结果，可用于路面或填土活动的过程控制，其中避免延误很重要，并且在使用基于统计的质量保证程序时需要确定可变性。 5.3 该试验方法不直接以压实百分比的形式提供结果，而是作为强度指数值，根据该值可以推断出特定水分条件下的压实情况。根据观察，强度要么沿着压实曲线的干燥侧保持不变，要么达到峰值，并且在这两种情况下，随着含水量的增加而迅速下降，超过最佳含水量的略微干燥点（约0.5%）。这通常在95到98之间 % 最大干密度（见 图1 和 图2 ). 根据IV，压实后的目标强度可以通过实验室测试或现场试验指定为在现场达到的强度，作为压实过程的结果，以达到所需的密度和含水量。如果在压实后进行测试，条件是含水量已从临界值变化，则通过实验室测试确定实际含水量，可以使用IV、密度和含水量从回归方程中推断出现场密度。 图1 无峰值材料的目标IV示意图 图2 具有突出峰值的材料的靶标IV图解 注2: 冲击值可用作改善压实过程的一种手段，通过对压路机效率、均匀性进行即时反馈，确认达到目标强度，并推断达到的密度。然而，当仅从IV推断密度时，它被认为仅指示密度。 5.4 该试验方法可用于监测压实过程中或由于季节、环境或交通变化而随时间变化的强度变化。 注3: 对于可能存在干燥坚硬表层（地壳）的现场土壤强度评估，可能需要对地壳和下层进行测试。 5.5 标准仪器基于4.5 kg（10 lbm）的压实锤，使用450 mm（18 in.）的跌落高度。液压锤配有加速度计，并使用峰值保持电子电路进行仪表测量，以读取碰撞时的峰值减速度。 电路经过电子滤波以去除不需要的频率，峰值减速度以10个重力为单位显示( g )其中低于10个重力单位的输出被截断。 5.6 得出IV的峰值减速度表示减速度-时间曲线下的面积，对于大多数土壤，该曲线可以假设为半个正弦曲线。应用二重积分首先提供时间-速度关系，其次提供时间-穿透关系。由于力也与减速度直接相关，因此IV表示应力和穿透力，可以作为刚度或强度的直接测量值（见 图3 ). 图3 从减速到时间的力穿透发展 5.7 影响值可能与未处理的CBR相关。 5.8 冲击值可以表示为锤模量，类似于弹性模量或变形模量。 5.9 较轻的锤子使用与标准锤子相同的加速度计和仪器。 与标准质量相比，使用0.5 kg（1.1 lbm）和2.25 kg（5 lbm）的较轻质量会使强度较低的材料更敏感；也就是说，这些较轻的锤块扩大了标度，并在较软的材料上提供了更多的清晰度，同时材料中的压痕也更少。为了避免混淆，对于0.5 kg（1.1 lbm）的质量，较轻锤的IV表示为IV/L，对于2.25 kg（5 lbm）质量，IV表示为I/M。 5.10 中型锤的灵敏度介于标准锤和轻型锤之间。 5.11 轻度冲击值和中度冲击值适用于沙子、泥炭的测试以及天然和人工娱乐草坪的硬度评估，其中娱乐草坪表面的硬度会影响球的弹跳特性以及参与者的表现或受伤可能性。在评估茅草较厚、草较长的天然草皮时，中等冲击值比轻冲击值更可取，而轻冲击值则适用于需要比中等锤子更小压痕的精细割草表面，例如草地网球场和高尔夫推杆果岭的测试。 5.12 中型锤可用于土方工程材料的测试。 5.13 重型-中型-重型锤使用与标准锤相同的加速度计和仪器，由于其直径质量较大，因此与轻型冲击式土壤测试器相比，重型-中型重型锤在水平和垂直方向上都能通过更大的区域进行测试。重型-中重型锤的IV表示为IV/HMH。 5.14 重型-中型-重型冲击值适用于测试与标准、轻型、中型和重型冲击土壤测试仪测试的材料相同的材料。 5.15 与直径为50 mm（2 in.）的冲击土壤测试器相比，重锤使用与标准锤相同的加速度计和仪器，并在水平和垂直方向上通过更大的区域进行测试。重锤的IV表示为IV/H。 5.16 重型冲击值适用于测试与标准、轻型、中型和重型-中型重型冲击土壤测试仪测试的材料相同的材料，但该冲击土壤测试机的质量越大，输出的灵敏度越低，因此适用于天平顶端或超出轻型冲击土土土测试仪范围的较硬材料。 注4: 该测试方法产生的结果的质量取决于执行该测试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 通常被认为能够胜任和客观的测试。该试验方法的使用者应注意遵守规程 D3740 本身并不能确保可靠的结果。可靠的结果取决于许多因素；实践 D3740 提供了评估其中一些因素的方法。

1.1 These test methods cover the determination of the Impact Value (IV) of a soil either in the field or a test mold, as follows: 1.1.1 Field Procedure A— Determination of IV alone, in the field. 1.1.2 Field Procedure B— Determination of IV and water content, in the field. 1.1.3 Field Procedure C— Determination of IV, water content and dry density, in the field. 1.1.4 Mold Procedure— Determination of IV of soil compacted in a mold, in the lab. 1.2 Units— The values stated in SI units are to be regarded as the standard. The values given in parentheses are provided for information only and are not considered standard. Reporting of test results in units other than SI shall not be regarded as nonconformance with this standard. 1.3 The standard test method, using a 4.5 kg (10 lbm) hammer, is suitable for, but not limited to, evaluating the strength of an unsaturated compacted fill, in particular pavement materials, soils, and soil-aggregates having maximum particle sizes less than 37.5 mm (1.5 in.). 1.4 By using a lighter 0.5 kg (1.1 lbm) or 2.25 kg (5 lbm) hammer, this test method is applicable for evaluating lower strength soils such as fine grained cohesionless, highly organic, saturated, or highly plastic soils having a maximum particle size less than 9.5 mm (0.375 in.), or natural turfgrass. 1.5 By using a heavier 10 kg (22 lbm) or 20 kg (44 lbm) hammer, this test method is applicable for evaluating harder materials at the top end the scales or beyond the ranges of the standard and lighter impact soil testers. 1.6 By performing laboratory test correlations for a particular soil using the 4.5 kg (10 lbm) hammer, IV may be correlated with an unsoaked California Bearing Ratio (CBR) or may be used to infer percentage compaction. The IV of the 0.5 kg (1.1 lbm) and 2.25 kg (5 lbm) hammers may be independently correlated to an unsoaked CBR or used to infer the percentage compaction for lower strength soils. 1.7 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026 . 1.8 For purposes of comparing a measured or calculated value(s) with specified limits, the measured or calculated value(s) shall be rounded to the nearest decimal or significant digits in the specified limits. 1.8.1 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; 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 design. Note 1: The equipment and procedures contained in this test method are similar to those developed by B. Clegg in the 1970s at the University of Western Australia, Perth, Western Australia, Australia. Impact Value is also commonly known as Clegg Impact Value (CIV). 1.9 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. 1.10 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 Impact Value, as determined using the standard 4.5 kg (10 lbm) hammer, has direct application to design and construction of pavements and a general application to earthworks compaction control and evaluation of strength characteristics of a wide range of materials, such as soils, soil aggregates and stabilized soil. Impact Value is one of the properties used to evaluate the strength of a layer of soil up to about 150 mm (6 in.) in thickness using a 50 mm (2 in.) diameter hammer or up to 380 mm (15 in.) in thickness using a 130 mm (5 in.) diameter hammer, and by inference to indicate the compaction condition of this layer. Impact Value reflects and responds to changes in physical characteristics that influence strength. It is a dynamic force-penetration property and may be used to set a strength parameter. 5.2 This test method provides immediate results in terms of IV and may be used for the process control of pavement or earthfill activities where the avoidance of delays is important and where there is a need to determine variability when statistically based quality assurance procedures are being used. 5.3 This test method does not provide results directly as a percentage of compaction but rather as a strength index value from which compaction may be inferred for the particular moisture conditions. From observations, strength either remains constant along the dry side of the compaction curve or else reaches a peak and, for both cases, declines rapidly with increase in water content beyond a point slightly dry of optimum water content, at approximately 0.5 percent. This is generally between 95 and 98 % maximum dry density (see Fig. 1 and Fig. 2 ). An as-compacted target strength in terms of IV may be designated from laboratory testing or field trials as a strength to achieve in the field as the result of a compaction process for a desired density and water content. If testing is performed after compaction when conditions are such that the water content has changed from the critical value, determination of the actual water content by laboratory testing enables the field density to be inferred from regression equations using IV, density and water content. FIG. 1 Illustration of Target IV for Material with No Peak FIG. 2 Illustration of Target IV for Material with Pronounced Peak Note 2: Impact Value may be used as a means to improve the compaction process by giving instant feedback on roller efficiency, uniformity, confirming the achievement of the target strength, and by inference the achieved density. When inferring density solely from IV, however, it is considered as only indicative of density. 5.4 This test method may be used to monitor strength changes during a compaction process or over time due to seasonal, environmental or traffic changes. Note 3: For in-place soil strength evaluation where there may be a dry and hard surface layer (crust), testing both the crust and the underlying layer may be required. 5.5 The standard instrument is based on a 4.5 kg (10 lbm) compaction hammer using a 450 mm (18 in.) drop height. The hammer is equipped with an accelerometer and instrumented using a peak hold electronic circuit to read the peak deceleration on impact. The circuitry is filtered electronically to remove unwanted frequencies and the peak deceleration is displayed in units of ten gravities ( g ) with the output below units of ten gravities truncated. 5.6 The peak deceleration on which IV is derived represents the area under the deceleration versus time curve which for most soils may be assumed as half a sinusoid. Applying double integration provides first the time-velocity relationship and second the time-penetration relationship. As force is also directly related to deceleration, the IV therefore represents both stress and penetration and may be taken as a direct measurement of stiffness or strength (see Fig. 3 ). FIG. 3 Development of Force-Penetration from Deceleration Versus Time 5.7 Impact Value may be correlated with an unsoaked CBR. 5.8 Impact Value may be expressed as a hammer modulus, analogous with elastic modulus or deformation modulus. 5.9 The lighter hammers use the same accelerometer and instrumentation as the standard hammer. Utilization of lighter masses at 0.5 kg (1.1 lbm) and 2.25 kg (5 lbm) results in more sensitivity for lower strength materials compared to the standard mass; that is, the scale is expanded with these lighter hammer masses and provides more definition on softer materials, along with there being less indentation into the material. To avoid confusion, the IV of the lighter hammers is notated as IV/L for the 0.5 kg (1.1 lbm) mass and as IV/M for the 2.25 kg (5 lbm) mass. 5.10 The medium hammer provides a sensitivity between that of the standard hammer and light hammer. 5.11 Light Impact Value and Medium Impact Value have application to testing of sand, peat and for natural and artificial recreation turf hardness evaluation, where it is that the hardness of recreation turf surfaces affects ball bounce characteristics and the performance or injury potential to participants. Medium Impact Value is preferable over Light Impact Value in relation to assessing natural turf where there is thicker thatch and longer grass whereas Light Impact Value is preferable for finely mown grass surfaces where less indentation than that of the medium hammer is desired, such as testing of grass tennis courts and golf putting greens. 5.12 The medium hammer has application to testing of earthworks materials. 5.13 The heavy medium heavy hammer uses the same accelerometer and instrumentation as the standard hammer and tests through a larger zone both horizontally and vertically than the lighter impact soil testers because of its larger diameter mass. The IV of the heavy medium heavy hammer is notated as IV/HMH. 5.14 The Heavy Medium Heavy Impact Value has application to testing the same materials as those tested by the standard, light, medium and heavy impact soil testers. 5.15 The heavy hammer uses the same accelerometer and instrumentation as the standard hammer and tests through a larger zone both horizontally and vertically as compared to the 50 mm (2 in.) diameter impact soil testers. The IV of the heavy hammer is notated as IV/H. 5.16 The Heavy Impact Value has application to testing the same materials as those tested by the standard, light, medium, and heavy medium heavy impact soil testers but the greater mass of this impact soil tester provides less sensitivity of the output so is applicable for harder materials at the top end the scales or beyond the ranges of the lighter impact soil testers. Note 4: The quality of the results produced by 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 D3740 are generally considered capable of competent and objective testing. Users of this test method 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.