1.1 平千斤顶测试测量地表露头或地下开挖面岩石表面的自然或变化地应力。变形模量和长期变形特性（蠕变）也可以在施加的应力范围内进行评估，但长期蠕变不包括在该方法中。 1.2 这种方法包括放置在岩石槽中的方形扁平千斤顶，如果需要，可以封装在槽中。 1.3 变形读数是在表面上采集的，但本标准不排除在表面下采集的变形读数，例如使用设置用于获取内部位移数据的平千斤顶。 1.4 所有观察值和计算值应符合实践中确定的有效数字和舍入准则 D6026 . 1.4.1 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。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标准的范围。 1.5 限制- 平千斤顶试验测量垂直于试验箱表面、地下开挖或露头的平均应力。地应力水平必须通过对这些数据的理论解释来确定。 1.6 影响数据的假设和因素: 1.6.1 假设应力消除是一个弹性可逆过程。 在非均质或高度断裂的材料中，这可能并不完全正确。 1.6.2 方程假设岩体各向同性且均匀。各向异性效应可以通过不同方向的测试来估计。 1.6.3 假设平千斤顶为100 % 有效率的设计和尺寸要求 7.1 确定满足这一要求在几%以内。 1.6.4 假设千斤顶与被测表面上的主应力对齐。剪切应力不会被千斤顶压力抵消。在每个测试平面的三个方向上定位测试可以防止至少一个测试的错位过大。 1.7 单位- 以英寸-磅为单位的数值应视为标准值。括号中给出的值是到国际单位制的数学转换，仅供参考，不被视为标准值。 如适用，添加“以英寸磅以外的单位报告试验结果不应视为不符合本标准。” 1.7.1 在处理英寸磅单位时，使用英寸磅单位的重力系统。在这个系统中，磅（lbf）表示力（重量）的单位，而质量的单位是段塞。除非涉及动态（F=ma）计算，否则不会给出缓动单元。对于涉及质量测定或密度和单位重量使用的标准，包括以下编号段落。 1.7.2 缓动质量单位通常不用于商业实践；即密度、平衡等。因此，本标准中质量的标准单位为千克（kg）或克（g）或两者兼有。此外，括号中未给出/显示等效英寸-磅单位（slug）。 1.7.3 工程/建筑行业的常见做法是同时使用磅来表示质量单位（lbm）和力（lbf）。这种做法隐含地结合了两个独立的单位制；绝对系统和引力系统。在一个标准中结合使用两套独立的英寸-磅单位在科学上是不可取的。如前所述，本标准包括英寸-磅单位的重力系统，不使用/呈现质量的段塞单位。然而，使用天平或天平记录磅质量（lbm）或记录密度（lbm/ft） 3. 不应视为不符合本标准。 1.8 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。 1.9 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 平顶试验有助于评估项目设计阶段的岩体变形性和应力，以及现有项目的问题；例如，地下开口周围的应力。地应力值可作为解释和验证测试结果和分析模型的重要参数。 5.2 该测试方法已成功用于其他应用，如混凝土坝和砌体结构。 该试验方法类似于试验中使用的技术和设备 C1196 和 C1197 . 然而，本标准更多地针对岩石编写，其中可能涉及不规则表面，并且在一次测试中获得了地应力和变形性。 注1: 尽管本试验方法中包含精度和偏差声明；该测试方法的精度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 本身不能保证可靠的测试。可靠的测试取决于许多因素；实践 D3740 提供了一种评估其中一些因素的方法。

1.1 The flat jack test measures the natural or altered in situ stress at a rock surface either for a surface outcrop or an underground excavation surface. The modulus of deformation and the long-term deformational properties (creep) may also be evaluated for the applied stress range, however long-term creep is not covered by this method. 1.2 This method covers square flat jacks that are placed in a rock slot and if required encapsulated in the slot. 1.3 Deformation readings are taken at the surface, but this standard does not exclude deformation readings being taken below the surface, such as using a flat jack which is set up to obtain displacement data internally. 1.4 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice D6026 . 1.4.1 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; 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. 1.5 Limitation— The flat jack test measures the average stress normal to the surface of the test chamber, underground excavation, or outcrop. In situ stress levels must be determined by theoretical interpretations of these data. 1.6 Assumptions and Factors Influencing the Data: 1.6.1 The stress relief is assumed to be an elastic, reversible process. In nonhomogeneous or highly fractured materials, this may not be completely true. 1.6.2 The equations assume that the rock mass is isotropic and homogeneous. Anisotropic effects may be estimated by testing in different orientations. 1.6.3 The flat jack is assumed to be 100 % efficient. The design and size requirements of 7.1 were determined to satisfy this requirement to within a few percent. 1.6.4 The jack is assumed to be aligned with the principal stresses on the surface being measured. Shear stresses are not canceled by jack pressure. Orientating the tests in three directions in each plane tested prevents the misalignment from being excessive for at least one of the tests. 1.7 Units— The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard. Add if appropriate, “Reporting of test results in units other than inch-pounds shall not be regarded as nonconformance with this standard.” 1.7.1 The gravitational system of inch-pound units is used when dealing with inch-pound units. In this system, the pound (lbf) represents a unit of force (weight), while the unit for mass is slugs. The slug unit is not given unless dynamic (F=ma) calculations are involved. For standards involving the determination of mass or the use of density and unit weight, include the following numbered paragraph. 1.7.2 The slug unit of mass is typically not used in commercial practice; that is, density, balances, and so on. Therefore, the standard unit for mass in this standard is either kilogram (kg) or gram (g) or both. Also, the equivalent inch-pound unit (slug) is not given/presented in parentheses. 1.7.3 It is common practice in the engineering/construction profession to concurrently use pounds to represent both a unit of mass (lbm) and of force (lbf). This practice implicitly combines two separate systems of units; the absolute and the gravitational systems. It is scientifically undesirable to combine the use of two separate sets of inch-pound units within a single standard. As stated, this standard includes the gravitational system of inch-pound units and does not use/present the slug unit for mass. However, the use of balances or scales recording pounds of mass (lbm) or recording density in lbm/ft 3 shall not be regarded as nonconformance with this standard. 1.8 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. 1.9 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 Flat jack tests are useful to assess rock mass deformability and stresses in the design stages of projects as well as for issues with existing projects; for example, stresses around an underground opening. The in situ stress values can be used as an important parameter for interpretation and validation of test results and analytical models. 5.2 This test method has been successfully used for other applications such as concrete dams and masonry structures. This test method is similar to the techniques and equipment used in C1196 and C1197 . However, this standard is written more for rock and where irregular surfaces may be involved and both in situ stress and deformability are obtained in one test. 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 and objective testing. Users of this test method are cautioned that compliance with Practice D3740 does not in itself assure reliable testing. Reliable testing depends on many factors; Practice D3740 provides a means of evaluating some of those factors.