1.1 本试验方法提供了在排水条件下进行扭转环剪切试验的程序，以测量细粒土的完全软化剪切强度和应力相关强度包络线（使用重组正常固结试样）。完全软化强度和相应的应力相关有效应力强度包络线用于评估没有预先存在的剪切面但受到环境条件和剪切应力影响的边坡的稳定性，这些剪切应力会导致土壤软化、土壤组构劣化和强度损失。 已显示（Skempton 1970） 2. 和1977年 3. )在这些条件下，在经历软化的深度区域内，首次边坡破坏可能发生在与完全软化强度包络线对应的有效应力水平。经验也证明了这一点（Skempton 1970） 2. 和1977年 3. )细粒土的完全软化强度可以近似为重组和正常固结试样的峰值强度。在本试验方法中，以受控恒定位移速率剪切重组和正常固结试样，直到获得峰值剪切阻力。 通常，在三个或三个以上的有效法向应力下确定排水全软化破坏包络线。对于每个法向应力，必须使用单独的试样来测量完全软化的强度，否则，如果由于存在先前的剪切面，在相同或另一有效法向应力下使用相同的试样，则将测量峰值后甚至排水的残余强度。 1.2 环形剪切装置允许在排水剪切之前，在所需的法向应力下对重组试样进行正常固结。试验结果紧密模拟了刚性天然细骨料的完全软化强度- 颗粒土（Skempton 1970） 2. 和1977年 3. )细粒土的压实填土（Gamez和Stark 2014） 4. ). 这模拟了土壤完全软化并达到完全软化强度条件后，自然边坡中的超固结粘土、粘土岩、泥岩和页岩以及人造边坡（如大坝、堤防和公路路堤）中的压实填土中的动员抗剪强度。 1.3 可从该试验方法中获得剪切应力-位移关系。然而，剪切应力-应变关系或任何相关量（如模量）无法通过该试验方法确定，因为在剪切应变计算中很难确定剪切带的高度。 因此，该剪切带的高度未知，因此无法确定准确或具有代表性的剪切应变。 1.4 设计分析中法向应力的选择和剪切强度包络线的最终确定以及解释和评估测试结果的标准由要求测试的工程师或实体负责。 1.5 单位- 以国际单位制表示的数值应视为标准。括号中给出的值是英寸-磅单位的数学转换，仅供参考，不被视为标准值。 1.6 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。 1.7 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 环形剪切装置在剪切过程中保持剪切表面的横截面积恒定，并在一个旋转方向上沿整个试样横截面积连续剪切任意大小的剪切位移。 5.2 环形剪切装置允许在排水剪切之前，在所需的法向应力下固结重组试样。这模拟了现场条件，在此条件下，在没有预固结的超固结粘土、粘土岩、泥岩和页岩中形成完全软化- Skempton（1970）描述的现有剪切面、剪切层理面、节理或断层 2. 和1977年 3. )和不稳定压实填土边坡（Gamez和Stark，2014年） 4. )因为全软化强度对应于正常固结细粒土的峰值剪切强度。完全软化强度仅适用于受环境恶化和施加剪切应力影响的土壤区域，这些剪切应力会导致土壤软化、土壤组构恶化和强度损失，这可能与所有边坡和所有深度无关。 对于没有事先剪切的边坡，应使用应力相关强度包络线进行有效应力/排水稳定性分析。 5.3 环形剪切试验适用于测定排水完全软化的剪切强度，因为通过薄试样的排水路径短，正常固结试样中峰后强度损失小，横截面积恒定。 5.4 环形剪切试样是环形的，因此角位移在内径和外径之间不同。这并不重要，因为正常固结的样本不会显示出较大的柱- 峰值强度损失，因此在不同位移下，内半径和外半径处的峰值抗剪强度差异不显著，根据Hvorslev（1936）的规定，环的内外半径比大于0.5 6. . 注1: 尽管本试验方法中包含精度和偏差声明:本试验方法的精度取决于执行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 通常认为能够进行合格测试。 本试验方法的使用者应注意遵守规程 D3740 无法确保可靠的测试。可靠的测试取决于几个因素；实践 D3740 提供了一种评估其中一些因素的方法。

1.1 This test method provides a procedure for performing a torsional ring shear test under a drained condition to measure the fully softened shear strength and stress dependent strength envelope of fine-grained soils (using a reconstituted normally consolidated specimen). The fully softened strength and the corresponding stress dependent effective stress strength envelope are used to evaluate the stability of slopes that do not have a pre-existing shear surface but have been subjected to environmental conditions and shear stresses that lead to soil softening, deterioration of the soil fabric, and strength loss. It has been shown (Skempton 1970 2 and 1977 3 ) that under these conditions and within the depth zones that have undergone softening, first-time slope failures can occur at effective stress levels that correspond to a fully softened strength envelope. It has also been shown empirically (Skempton 1970 2 and 1977 3 ) that fully softened strength of fine grained soils can be approximated by the peak strength of a reconstituted and normally consolidated specimen. In this test method, reconstituted and normally consolidated specimens are sheared at a controlled and constant displacement rate until the peak shear resistance has been obtained. Generally, the drained fully softened failure envelope is determined at three or more effective normal stresses. A separate test specimen must be used for each normal stress to measure the fully softened strength otherwise a post-peak or even drained residual strength will be measured if the same specimen is used at the same or at another effective normal stress because of the existence of a prior shear surface. 1.2 The ring shear apparatus allows a reconstituted specimen to be normally consolidated at the desired normal stress prior to drained shearing. The test results closely simulate the fully softened strength of stiff natural fine-grained soils (Skempton 1970 2 and 1977 3 ) and compacted fills of fine-grained soils (Gamez and Stark 2014 4 ). This simulates the mobilized shear strength in overconsolidated clays, claystones, mudstones, and shales in natural slopes and compacted fill in manmade slopes, such as, dams, levees, and highway embankments, after the soil has fully softened and attained the fully softened strength condition. 1.3 A shear stress-displacement relationship may be obtained from this test method. However, a shear stress-strain relationship or any associated quantity, such as modulus, cannot be determined from this test method because defining the height of the shear zone is difficult and needed in the shear strain calculations. As a result, the height of this shear zone is unknown, so an accurate or representative shear strain can therefore not be determined. 1.4 The selection of normal stresses and final determination of the shear strength envelope for design analyses and the criteria to interpret and evaluate the test results are the responsibility of the engineer or entity requesting the test. 1.5 Units— The values stated in SI units are to be regarded as the standard. The values given in parentheses are mathematical conversions to inch-pound units that are provided for information only and are not considered standard. 1.6 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. 1.7 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 The ring shear apparatus maintains the cross-sectional area of the shear surface constant during shear and shears the specimen continuously in one rotational direction for any magnitude of shear displacement and along the entire specimen cross-sectional area. 5.2 The ring shear apparatus allows a reconstituted specimen to be consolidated at the desired normal stress prior to drained shearing. This simulates the field conditions under which complete softening develops in overconsolidated clays, claystones, mudstones, and shales that do not have a pre-existing shear surface, sheared bedding planes, joints, or faults as described by Skempton (1970 2 and 1977 3 ) and unfailed compacted fill slopes (Gamez and Stark 2014 4 ) because the fully softened strength corresponds to the peak shear strength of a normally consolidated fine-grained soil. The fully softened strength is only applicable to the soil zones that are subject to the environmental deterioration and applied shear stresses that lead to soil softening, deterioration of soil fabric, and strength loss, which may not be relevant to all slopes and all depths. The fully softened strength should be used in an effective stress/drained stability analysis using a stress dependent strength envelope for slopes with no prior shearing. 5.3 The ring shear test is suited to the determination of the drained fully softened shear strength because of the short drainage path through the thin specimen, small post-peak strength loss in a normally consolidated specimen, and the constant cross-sectional area. 5.4 The ring shear test specimen is annular so the angular displacement differs from the inner radius to the outer radius. This is not significant because a normally consolidated specimen does not exhibit a large post-peak strength loss so the difference in peak shear resistance at the inner radius and outer radius at different displacements is not significant and the ratio of the inner to outer radii of the ring is greater than 0.5 in accordance with Hvorslev (1936) 6 . Note 1: Notwithstanding the statements on precision and bias contained in this test method: 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 D3740 are generally considered capable of competent testing. Users of this test method are cautioned that compliance with Practice D3740 does not ensure reliable testing. Reliable testing depends on several factors; Practice D3740 provides a means of evaluating some of those factors.