1.1 这些试验方法涵盖了当土壤受到侧向约束和轴向排水，同时承受增量施加的受控应力载荷时，确定土壤固结程度和速率的程序。提供以下两种替代程序: 1.1.1 试验方法A- 本试验方法在24小时或其倍数的恒定负载增量持续时间下进行。至少需要两个负载增量的时间变形读数。该试验方法仅提供了试样的压缩曲线，结果结合了一次固结和二次压缩变形。 1.1.2 试验方法B- 所有荷载增量都需要时间变形读数。100后施加连续负载增量 % 达到一次固结，或以试验方法A中所述的恒定时间增量。该试验方法提供了压缩曲线和明确的数据，以说明二次压缩、饱和材料的固结系数和二次压缩率。 注1: 当土壤受到控制时，确定土壤固结的速率和幅度- 试验方法涵盖了应变载荷 D4186/D4186M . 1.2 这些试验方法通常在自然沉淀在水中的细粒土的饱和完整样品上进行，然而，基本试验程序也适用于压实土壤的样品和由其他过程（如风化或化学变化）形成的土壤的完整样品。这些试验方法中规定的评估技术假设孔隙空间完全饱和，通常适用于在水中自然沉积的土壤。对其他非饱和材料（如压实和残余（风化或化学变化）土壤）进行的测试可能需要特殊的评估技术。 特别是，固结速率（时间曲线的解释）仅适用于完全饱和的试样。 1.3 要求进行本试验的机构应负责规定每个荷载增量的大小和顺序，包括回弹循环的位置（如需要），以及对于试验方法a，需要时间变形读数的荷载增量。所需的最大应力水平取决于测试目的，并且必须与请求机构达成一致。在没有具体说明的情况下，第节 11 提供标准测试的默认负载增量和负载持续时间计划。 注2: 需要时间变形读数来确定完成初级固结的时间和评估固结系数， c v . 自从 c v 随着应力水平和加载类型（加载或卸载）的不同，必须根据具体项目选择带有定时读数的加载增量。或者，请求机构可以指定试验方法B，其中在所有荷载增量上读取时间变形读数。 1.4 这些试验方法不涉及使用背压使试样饱和。设备可用于使用背压饱和进行固结试验。增加背压饱和并不构成不符合这些试验方法。 1.5 单位- 以国际单位制或英寸-磅单位（括号中给出）表示的值应单独视为标准值。每个系统中规定的值可能不是精确的等效值；因此，每个系统应相互独立使用。将两个系统的值合并可能会导致- 符合标准。 1.5.1 在工程专业中，习惯做法是交替使用表示质量和力的单位，除非进行动态计算( F = 妈妈 )都有牵连。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。 1.6 观察值和计算值应符合实践中制定的有效数字和舍入准则 D6026 ，除非被本试验方法取代。 1.6.1 本标准中用于指定数据收集、计算或记录方式的方法与数据在设计或其他用途中或两者中的应用精度没有直接关系。 如何应用使用本标准获得的结果超出了其范围。 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、健康和环境实践，并确定监管限制的适用性。 1.8 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 固结试验的数据用于估计结构或填土的差异沉降和总沉降的大小和速率。这类估算在工程结构的设计和性能评估中至关重要。 5.2 样本干扰会极大地影响测试结果。需要仔细选择和制备试样，以减少潜在的干扰影响。 注3: 尽管本标准中包含精度和偏差声明，但本试验方法的精度取决于执行试验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测试。本试验方法的使用者应注意遵守规程 D3740 不能保证可靠的测试。可靠的测试取决于许多因素和实践 D3740 提供了一种评估其中一些因素的方法。 5.3 固结试验结果取决于荷载增量的大小。传统上，轴向应力每增加一倍，导致荷载增量比为1。对于完整的样品，该加载程序提供了数据，根据这些数据，使用既定的解释技术估算的先期固结应力与现场观察结果进行了比较。 其他加载时间表可用于模拟特定现场条件或满足特殊要求。例如，为了最好地评估响应，可能需要根据现场预期的湿润或加载模式淹没和加载样本。对于高度敏感或其响应高度依赖于应变率的土壤，可能需要小于1的荷载增量比。 5.4 这些测试方法规定的用于估计预固结应力的解释方法提供了一种简单的技术，以验证在预固结应力之后读取了一组时间读数，并且样本加载到足够高的应力水平。 存在其他几种评估技术，可能会产生不同的预固结应力估计值。经请求机构同意后，可使用估算预固结应力的替代技术，且该技术仍符合这些试验方法。 5.5 固结试验结果取决于每个荷载增量的持续时间。传统上，每个增量的荷载持续时间相同，等于24小时。对于某些土壤，固结速率使得完全固结（多余孔隙压力的消散）需要超过24小时。 一般使用的仪器没有对孔隙压力耗散进行正式验证的规定。有必要使用间接确定固结基本完成的解释技术。这些试验方法规定了两种技术（方法A和方法B）的程序，但是，经请求机构同意，可以使用替代技术，并且仍然符合这些试验方法。 5.6 这些试验方法通常使用的仪器没有验证饱和的规定。 从地下水位以下采集的大多数完整样本将饱和。然而，变形的时间速率对饱和度非常敏感，当部分饱和条件盛行时，必须谨慎估计沉降持续时间。试样浸水不会显著改变试样的饱和度，而是提供边界水，以消除与取样相关的负孔隙压力，并防止试验期间蒸发。部分饱和对测试结果的影响程度可能是测试评估的一部分，可能包括应用传统固结理论以外的理论模型。 或者，可以使用配备有使试样饱和的仪器进行试验。 5.7 这些试验方法使用基于太沙基固结方程的传统固结理论来计算固结系数， c v . 分析基于以下假设: 5.7.1 土壤饱和，性质均匀； 5.7.2 孔隙水沿垂直方向流动； 5.7.3 与土壤骨架的压缩性相比，土壤颗粒和孔隙水的压缩性可以忽略不计； 5.7.4 应力-应变关系与载荷增量呈线性关系； 5.7.5 随着荷载的增加，土壤渗透性与土壤压缩性之比保持不变；和 5.7.6 适用于多孔介质流动的达西定律。

1.1 These test methods cover procedures for determining the magnitude and rate of consolidation of soil when it is restrained laterally and drained axially while subjected to incrementally applied controlled-stress loading. Two alternative procedures are provided as follows: 1.1.1 Test Method A— This test method is performed with constant load increment duration of 24 h, or multiples thereof. Time-deformation readings are required on a minimum of two load increments. This test method provides only the compression curve of the specimen and the results combine both primary consolidation and secondary compression deformations. 1.1.2 Test Method B— Time-deformation readings are required on all load increments. Successive load increments are applied after 100 % primary consolidation is reached, or at constant time increments as described in Test Method A. This test method provides the compression curve with explicit data to account for secondary compression, the coefficient of consolidation for saturated materials, and the rate of secondary compression. Note 1: The determination of the rate and magnitude of consolidation of soil when it is subjected to controlled-strain loading is covered by Test Method D4186/D4186M . 1.2 These test methods are most commonly performed on saturated intact samples of fine grained soils naturally sedimented in water, however, the basic test procedure is applicable, as well, to specimens of compacted soils and intact samples of soils formed by other processes such as weathering or chemical alteration. Evaluation techniques specified in these test methods assume the pore space is fully saturated and are generally applicable to soils naturally sedimented in water. Tests performed on other unsaturated materials such as compacted and residual (weathered or chemically altered) soils may require special evaluation techniques. In particular, the rate of consolidation (interpretation of the time curves) is only applicable to fully saturated specimens. 1.3 It shall be the responsibility of the agency requesting this test to specify the magnitude and sequence of each load increment, including the location of a rebound cycle, if required, and, for Test Method A, the load increments for which time-deformation readings are desired. The required maximum stress level depends on the purpose of the test and must be agreed on with the requesting agency. In the absence of specific instructions, Section 11 provides the default load increment and load duration schedule for a standard test. Note 2: Time-deformation readings are required to determine the time for completion of primary consolidation and for evaluating the coefficient of consolidation, c v . Since c v varies with stress level and loading type (loading or unloading), the load increments with timed readings must be selected with specific reference to the individual project. Alternatively, the requesting agency may specify Test Method B wherein the time-deformation readings are taken on all load increments. 1.4 These test methods do not address the use of a back pressure to saturate the specimen. Equipment is available to perform consolidation tests using back pressure saturation. The addition of back pressure saturation does not constitute non-conformance to these test methods. 1.5 Units— The values stated in either SI units or inch-pound units [given in brackets] are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard. 1.5.1 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 should not be regarded as nonconformance with this test method. 1.6 Observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026 , unless superseded by this test method. 1.6.1 The method used to specify how data are collected, calculated, or recorded in this standard is not directly related to the accuracy to which the data can be applied in design or other uses, or both. How one applies the results obtained using this standard is beyond its scope. 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.8 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 data from the consolidation test are used to estimate the magnitude and rate of both differential and total settlement of a structure or earthfill. Estimates of this type are of key importance in the design of engineered structures and the evaluation of their performance. 5.2 The test results can be greatly affected by sample disturbance. Careful selection and preparation of test specimens is required to reduce the potential of disturbance effects. Note 3: Notwithstanding the statement on precision and bias contained in this standard, the precision of this test method is dependent on the competence of the personnel performing the test and suitability of the equipment and facilities used. Agencies that meet the criteria of Practice D3740 generally are considered capable of competent and objective testing. Users of this test method are cautioned that compliance with Practice D3740 does not assure reliable testing. Reliable testing depends on many factors, and Practice D3740 provides a means of evaluation some of these factors. 5.3 Consolidation test results are dependent on the magnitude of the load increments. Traditionally, the axial stress is doubled for each increment resulting in a load increment ratio of 1. For intact samples, this loading procedure has provided data from which estimates of the preconsolidation stress, using established interpretation techniques, compare favorably with field observations. Other loading schedules may be used to model particular field conditions or meet special requirements. For example, it may be desirable to inundate and load the specimen in accordance with the wetting or loading pattern expected in the field in order to best evaluate the response. Load increment ratios of less than 1 may be desirable for soils that are highly sensitive or whose response is highly dependent on strain rate. 5.4 The interpretation method specified by these test methods to estimate the preconsolidation stress provides a simple technique to verify that one set of time readings are taken after the preconsolidation stress and that the specimen is loaded to a sufficiently high stress level. Several other evaluation techniques exist and may yield different estimates of the preconsolidation stress. Alternative techniques to estimate the preconsolidation stress may be used when agreed to by the requesting agency and still be in conformance with these test methods. 5.5 Consolidation test results are dependent upon the duration of each load increment. Traditionally, the load duration is the same for each increment and equal to 24 h. For some soils, the rate of consolidation is such that complete consolidation (dissipation of excess pore pressure) will require more than 24 h. The apparatus in general use does not have provisions for formal verification of pore pressure dissipation. It is necessary to use an interpretation technique which indirectly determines that consolidation is essentially complete. These test methods specify procedures for two techniques (Method A and Method B), however alternative techniques may be used when agreed to by the requesting agency and still be in conformance with these test methods. 5.6 The apparatus in general use for these test methods do not have provisions for verification of saturation. Most intact samples taken from below the water table will be saturated. However, the time rate of deformation is very sensitive to degree of saturation and caution must be exercised regarding estimates for duration of settlements when partially saturated conditions prevail. Inundation of the test specimen does not significantly change the degree of saturation of the test specimen but rather provides boundary water to eliminate negative pore pressure associated with sampling and prevents evaporation during the test. The extent to which partial saturation influences the test results may be a part of the test evaluation and may include application of theoretical models other than conventional consolidation theory. Alternatively, the test may be performed using an apparatus equipped to saturate the specimen. 5.7 These test methods use conventional consolidation theory based on Terzaghi's consolidation equation to compute the coefficient of consolidation, c v . The analysis is based upon the following assumptions: 5.7.1 The soil is saturated and has homogeneous properties; 5.7.2 The flow of pore water is in the vertical direction; 5.7.3 The compressibility of soil particles and pore water is negligible compared to the compressibility of the soil skeleton; 5.7.4 The stress-strain relationship is linear over the load increment; 5.7.5 The ratio of soil permeability to soil compressibility is constant over the load increment; and 5.7.6 Darcy's law for flow through porous media applies.