1.1本试验方法描述了使用核设备测量土壤和土壤骨料就地密度和水分的程序。材料密度可通过直接透射、反向散射或反向散射/气隙比方法测量。无论用于密度的模式是什么，在后向散射模式下测量表面的水（水分）含量。本小组委员会的目的是，本标准取代D 2922和D 3017。 1.1.1有关限制，请参阅第5节“干扰”。 1.2土壤和土壤骨料的总密度或湿密度通过伽马辐射的衰减来测量，在直接传输中，辐射源放置在300 mm（12 in.）以下的已知深度并且探测器保持在表面上（一些仪表可能会反转此方向）； 或者在后向散射或后向散射/气隙中，光源和探测器都保留在表面上。 1.2.1通过将检测到的γ辐射率与先前建立的校准数据进行比较，计算出以单位体积质量计的试样密度。 1.2.2通过从试样湿密度中减去每单位体积的水质量来获得试样的干密度（第11节）。大多数仪表直接显示该值。 1.3校准仪表，以读取每单位体积土壤或土壤骨料的水质量。当除以水的密度，然后乘以100时，单位体积的水质量等于体积含水量。每单位体积的水质量是由氢（水的一种成分）使快中子受热或减慢而确定的。 中子源和热中子探测器均位于被测材料表面。工程和施工活动中最常见的含水量称为重量含水量w，是孔隙中的水质量与固体总质量的比值，以百分比表示。 1.4提供了两种替代程序。 1.4.1 程序A 描述了一种直接传输方法，在该方法中，伽马射线源棒穿过量规底座，延伸到预成型孔中，达到所需深度。直接传输是首选方法。 1.4.2 程序B 涉及在后向散射位置使用专用的后向散射计或源棒。这将伽马和中子源以及探测器放置在同一平面上。 1.5 国际单位制 — 以国际单位制表示的数值应视为标准。数值单位为英寸-磅（ft – lb单元）仅供参考。 1.6所有观察值和计算值应符合实施规程D 6026中制定的有效数字和舍入指南 . 1.6.1本标准中用于规定如何收集、记录和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的任何考虑因素 ’ s目标；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。 1.7 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====== 所述试验方法是一种快速、无损技术，可用于现场测量土壤和土壤骨料的湿密度和含水量，并测定干密度。 该测试方法用于施工中使用的压实土壤和土壤骨料混合物的质量控制和验收测试，也用于研究和开发。 无损性质允许在单个测试位置重复测量并对结果进行统计分析。 密集 — 这些方法固有的基本假设是康普顿散射是主要的相互作用，并且材料是均匀的。 含水量 — 试验方法固有的基本假设是，土壤或土壤团聚体中存在的氢离子以水的形式存在，由试验方法D 2216得出的含水量定义 ，并且材料是均匀的。（见5.2） 笔记 1-本标准试验方法产生的结果的质量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的测试/采样/检查等。本标准的用户应注意遵守实施规程D 3740 本身并不能保证可靠的结果。可靠的结果取决于许多因素；实践D 3740 提供了一种评估其中一些因素的方法。

1.1 This test method describes the procedures for measuring in-place density and moisture of soil and soil-aggregate by use of nuclear equipment. The density of the material may be measured by direct transmission, backscatter, or backscatter/air-gap ratio methods. Measurements for water (moisture) content are taken at the surface in backscatter mode regardless of the mode being used for density. It is the intent of this subcommittee that this standard replace D 2922 and D 3017. 1.1.1 For limitations see Section 5 on Interferences. 1.2 The total or wet density of soil and soil-aggregate is measured by the attenuation of gamma radiation where, in direct transmission, the source is placed at a known depth up to 300 mm (12 in.) and the detector (s) remains on the surface (some gauges may reverse this orientation); or in backscatter or backscatter/air-gap the source and detector(s) both remain on the surface. 1.2.1 The density of the test sample in mass per unit volume is calculated by comparing the detected rate of gamma radiation with previously established calibration data. 1.2.2 The dry density of the test sample is obtained by subtracting the water mass per unit volume from the test sample wet density (Section 11). Most gauges display this value directly. 1.3 The gauge is calibrated to read the water mass per unit volume of soil or soil-aggregate. When divided by the density of water and then multiplied by 100, the water mass per unit volume is equivalent to the volumetric water content. The water mass per unit volume is determined by the thermalizing or slowing of fast neutrons by hydrogen, a component of water. The neutron source and the thermal neutron detector are both located at the surface of the material being tested. The water content most prevalent in engineering and construction activities is known as the gravimetric water content, w, and is the ratio of the mass of the water in pore spaces to the total mass of solids, expressed as a percentage. 1.4 Two alternative procedures are provided. 1.4.1 Procedure A describes the direct transmission method in which the gamma source rod extends through the base of the gauge into a pre-formed hole to a desired depth. The direct transmission is the preferred method. 1.4.2 Procedure B involves the use of a dedicated backscatter gauge or the source rod in the backscatter position. This places the gamma and neutron sources and the detectors in the same plane. 1.5 SI Units — The values stated in SI units are to be regarded as the standard. The values in inch-pound units (ft – lb units) are provided for information only. 1.6 All observed and calculated values shall conform to the guide for significant digits and rounding established in Practice D 6026 . 1.6.1 The procedures used to specify how data are collected, recorded, and calculated in this standard are regarded as the industry standard. In addition, they are representative of the significant digits that should generally 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 analysis methods for engineering design. 1.7 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 ====== The test method described is useful as a rapid, nondestructive technique for in-place measurements of wet density and water content of soil and soil-aggregate and the determination of dry density. The test method is used for quality control and acceptance testing of compacted soil and soil-aggregate mixtures as used in construction and also for research and development. The nondestructive nature allows repetitive measurements at a single test location and statistical analysis of the results. Density — The fundamental assumptions inherent in the methods are that Compton scattering is the dominant interaction and that the material is homogeneous. Water Content — The fundamental assumptions inherent in the test method are that the hydrogen ions present in the soil or soil-aggregate are in the form of water as defined by the water content derived from Test Methods D 2216 , and that the material is homogeneous. (See 5.2) Note 1—The quality of the result produced by this standard 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/sampling/inspection, and the like. Users of this standard are cautioned that compliance with Practice D 3740 does not in itself assure reliable results. Reliable results depend on many factors; Practice D 3740 provides a means of evaluating some of those factors.