1.1 本试验方法定义了使用循环荷载模式进行一维固结后，测量循环强度、液化循环次数或土壤循环特性（模量和阻尼）的设备规范和试验程序。 1.2 循环剪切可以使用荷载控制或位移控制。要求进行该试验的机构应负责规定循环荷载的幅值和频率。如果要求测试的机构要求，可以使用其他加载历史。 1.3 本试验方法专门用于测试封闭在钢丝增强膜或刚性环堆内软膜中的圆柱形试样的装置（本试验方法也适用于聚四氟乙烯涂层刚性环）。其他类型的剪切装置不在本试验方法的范围内。 1.4 该试验方法可用于测试无粘性自由排水土或细粒土。然而，在测试大多数土壤类型时，如果注意确保考虑到此类土壤所需的任何特殊考虑因素，则可以遵循本测试方法。 1.5 本试验的剪切阶段在恒定体积条件下进行。由于侧向约束系统可防止径向试样应变，因此恒定体积条件是通过防止剪切过程中试样高度变化来实现的。恒定体积下的剪切可在干燥或饱和试样上进行。恒定体积条件相当于完全饱和试样的不排水条件。可以使用一些简单剪切装置在真正不排水的条件下（限制孔隙水流入和流出试样）进行循环直接单剪试验，但这超出了本标准的范围。 2. 1.6 土壤的循环强度根据达到极限双幅剪切应变或单幅剪切应变所需的循环次数确定，而液化通常定义为100 % 垂直应力比的变化（剪切期间有效垂直应力的变化除以主固结结束时的有效垂直应力）。恒定体积剪切中垂直应力比的变化相当于不排水条件下的超孔隙压力比（剪切期间的超孔隙压力除以主固结结束时的有效垂直应力）。应变准则仅适用于进行荷载控制试验时；100 % 垂直应力比的变化可用于荷载和位移控制。对于位移控制测试，停止测试的标准可以是指定的循环次数。 1.7 本试验方法适用于测试完整、重组或压实的试样；然而，它不包括制备、重组或压实试样的具体指南。 1.8 要求本试验的机构应负责规定剪切前固结应力的大小，如果指定，可能需要卸载固结阶段来过度固结试样。 1.9 所有记录和计算值应符合实践中制定的有效数字和舍入指南 D6026 . 1.9.1 本试验方法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测试方法的范围。 1.9.2 比本标准规定的有效数字或灵敏度更高的测量值不应视为不符合本标准。 1.10 单位- 以国际单位制表示的数值应视为标准。以国际单位制以外的单位报告试验结果应视为符合本试验方法。在工程专业中，除非涉及动态计算（F=Ma），否则通常会交替使用代表质量和力的单位。这隐含地结合了两个独立的单位系统，即绝对系统和重力系统。 在一个标准中结合两个独立的系统在科学上是不可取的。本测试方法使用国际单位制编写；然而，重量分析系统中给出了英寸-磅转换，其中磅（lbf）表示力（重量）的单位。使用天平或天平记录质量磅（lbm），或记录密度磅/英尺 3. 不应视为不符合本试验方法。 1.11 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。 1.12 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 循环直接单剪强度试验结果最常用于评估土壤抵抗地震荷载、海上风暴荷载等期间土体中诱导的剪应力的能力。 5.2 在本试验中，循环强度是在等同于不排水条件的恒定体积条件下测量的；因此，该试验适用于土壤在一组应力下固结，然后在没有时间进行进一步排水的情况下承受应力/应变变化的现场条件。 5.3 循环强度是许多因素的函数，包括密度、围压、应力历史、晶粒结构、试样制备程序、频率和施加的循环载荷的特征。因此，在评估测试结果时应考虑测试因素。 5.4 直接单剪试样内的应力状态没有充分定义，也不够均匀，无法对结果进行严格解释。根据水平面上的剪切应力和垂直有效应力表示数据对于工程目的很有用。可从循环直接单剪试验中得出的一些有效应力参数不得与从具有更好应力状态定义的其他剪切试验（即循环三轴试验）中得出的相应参数混淆。 5.5 通过允许剪切结束时的体积变化，以实现与主固结结束时相同的垂直有效应力，可以从测试结果中评估循环荷载后饱和土壤中的沉降值。 5.6 本试验固结部分的数据与使用试验方法获得的结果具有可比性 D2435/D2435M 前提是试验方法的更严格固结程序 D2435/D2435M 遵循。

1.1 This test method defines equipment specifications and testing procedures for the measurement of cyclic strength, number of cycles to liquefaction or cyclic properties (Modulus and Damping) of soils, after one-dimensional consolidation using a cyclic mode of loading. 1.2 The cyclic shearing can be applied using load control or displacement control. It shall be the responsibility of the agency requesting this test to specify the magnitude and frequency of the cyclic loading. Other loading histories may be used if required by the agency requesting the testing. 1.3 This test method is written specifically for devices that test cylindrical specimens enclosed in a wire-reinforced membrane or a soft membrane within a stack of rigid rings (this test method applies to Teflon coated rigid rings as well). Other types of shear devices are beyond the scope of this test method. 1.4 This test method can be used for testing cohesionless free draining soils or fine grained soils. However, this test method may be followed when testing most soil types if care is taken to ensure that any special considerations required for such soils are accounted for. 1.5 The shearing phase of this test is conducted under constant volume conditions. Since the lateral confinement system prevents radial specimen strains, the constant volume condition is accomplished by preventing specimen height change during shear. Shearing under constant volume can be performed on dry or saturated specimens. The constant volume condition is equivalent to the undrained condition for fully saturated specimens. Cyclic direct simple shear testing with truly undrained conditions (restricting pore water flow from and into the specimen) can be performed using some simple shear devices, but is beyond the scope of this standard. 2 1.6 The cyclic strength of a soil is determined based on the number of cycles required to reach a limiting double amplitude shear strain or a single amplitude shear strain, while liquefaction is more commonly defined as 100 % change in vertical stress ratio (change in effective vertical stress during shearing divided by effective vertical stress at end of primary consolidation). The change in vertical stress ratio in constant volume shearing is equivalent to the excess pore pressure ratio (excess pore pressure during shearing divided by effective vertical stress at end of primary consolidation) under undrained conditions. The strain criterion is only applicable when performing load controlled tests; 100 % change in vertical stress ratio can be used for both, load and displacement control. For displacement control testing, the criterion to stop the test could be a specified number of cycles. 1.7 This test method is applicable to testing intact, reconstituted, or compacted specimens; however, it does not include specific guidance for preparing, reconstituting or compacting test specimens. 1.8 It shall be the responsibility of the agency requesting this test to specify the magnitude of the consolidation stress prior to shear and, if assigned, an unloading consolidation stage may be required for over-consolidating the specimen. 1.9 All recorded and calculated values shall conform to the guide for significant digits and rounding established in Practice D6026 . 1.9.1 The procedures used to specify how data are collected/recorded and calculated in this test method are regarded as the industry standard. In addition, they are representative of the significant digits that shall 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; 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 test method to consider significant digits used in analysis methods for engineering design. 1.9.2 Measurements made to more significant digits or better sensitivity than specified in this standard shall not be regarded as nonconformance with this standard. 1.10 Units— The values stated in SI units are to be regarded as the standard. Reporting test results in units other than SI shall be regarded as conformance with this test method. In the engineering profession it is customary practice to use, interchangeably, units representing both mass and force, unless dynamic calculations (F=Ma) are involved. This implicitly combines two separate systems of units, that is, the absolute system and the gravimetric system. It is scientifically undesirable to combine two separate systems within a single standard. This test method has been written using SI units; however, inch-pound conversions are given in the gravimetric system, where the pound (lbf) represents a unit of force (weight). The use of balances or scales recording pounds of mass (lbm), or the recording of density in lb/ft 3 shall not be regarded as nonconformance with this test method. 1.11 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. 1.12 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 Cyclic direct simple shear strength test results are used most often for evaluating the ability of a soil to resist shear stresses induced in a soil mass during earthquake loading, offshore storm loading, etc. 5.2 In this test, the cyclic strength is measured under constant volume conditions that are equivalent to undrained conditions; hence, the test is applicable to field conditions in which the soils have consolidated under one set of stresses, and then are subjected to changes in stress/strain without time for further drainage to take place. 5.3 The cyclic strength is a function of many factors including density, confining pressure, stress history, grain structure, specimen preparation procedure, frequency, and characteristics of the cyclic loading applied. Therefore, test factors shall be considered during evaluation of test results. 5.4 The state of stress within the direct simple shear specimen is not sufficiently defined nor uniform enough to allow rigorous interpretation of the results. Expressing the data in terms of the shear stress and vertical effective stress on the horizontal plane is useful for engineering purposes. Some effective stress parameters that could be derived from a cyclic direct simple shear test shall not be confused with corresponding parameters derived from other shear tests having better defined states of stress (that is, cyclic triaxial tests). 5.5 The values of settlement in saturated soil after cyclic loading can be assessed from the test results by allowing volume change at the end of the shearing to achieve same vertical effective stresses as at end of primary consolidation. 5.6 The data from the consolidation portion of this test are comparable to results obtained using Test Method D2435/D2435M provided that the more rigorous consolidation procedure of Test Method D2435/D2435M is followed.