Significance and Use
4.1 Based on the measurements of force and displacement at the pile top, possibly combined with those from accelerometers or strain transducers located further down the pile, these test methods measure the pile top deflection in response to an axial compressive force pulse. The relatively long duration of the force pulse compared to the natural period of the test pile causes the pile to compress and translate approximately as a unit during a portion of the pulse, simultaneously mobilizing compressive axial static resistance and dynamic resistance at all points along the length of the pile for that portion of the test.
4.2 The compressive axial static resistance is derived from the test data and is therefore an indirect result. Test Method provides a direct and therefore more reliable measurement of static resistance.
4.3 The Engineer should ensure that the test as specified will generate the required peak force to meet the purpose of the test. In case that purpose is to establish geotechnical failure, the Engineer should also ensure that peak force results in significant permanent axial movement during the axial force pulse event.
4.4 The Engineer may analyze the acquired data using engineering principles and judgment to evaluate the performance of the force pulse apparatus, and the characteristics of the pile's response to the force pulse loading. This analysis typically includes a reduction factor to account for the loading rate effect, that is, additional load resistance that occurs as a result of a faster rate of loading than used during a static test. Test results from piles installed in cohesive soils generally require a greater reduction. The Engineer should determine how the type, size, and shape of the pile, and the properties of the soil or rock beneath and adjacent to the pile, affect the rate-of-loading reduction factors and the amount of movement required to mobilize and accurately assess the static resistance by eliminating the dynamic component of the response.
4.5 The scope of this standard does not include analysis for foundation capacity, but in order to analyze the test data appropriately it is important that information on factors that affect the derived axial static capacity is properly documented. These factors may include, but are not limited to, the: (1) pile installation equipment and procedures, (2) elapsed time since initial installation, (3) pile material properties and dimensions, (4) type, density, strength, stratification, and saturation of the soil, or rock, or both adjacent to and beneath the pile, (5) quality of force pulse test data, and (6) final foundation settlement.
4.6 The accuracy of the derived results may improve when using additional strain transducers embedded in the pile. When combined with an appropriate method of analysis, the Engineer may use data from these optional transducers to estimate the relative contribution of side shear and end bearing to the mobilized axial static compressive resistance of the pile, or to infer the relative contribution of certain soil layers to the overall mobilized axial compressive resistance of the pile.
Note 1: The quality of the result produced by these test methods 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 are generally considered capable of competent and objective testing and inspection. Users of these test methods are cautioned that compliance with Practice does not in itself assure reliable results. Reliable results depend on many factors; Practice provides a means of evaluating some of those factors.
1.1 These test methods, commonly referred to as Rapid Load Testing, cover procedures for testing an individual vertical or inclined deep foundation element to determine the displacement response to an axial compressive force pulse applied at its top. These non-static foundation test methods apply to all deep foundation units, referred to herein as “piles,” that function in a manner similar to driven or cast-in-place piles, regardless of their method of installation.
1.2 Two alternative procedures are provided:
1.2.1 Procedure A uses a combustion gas pressure apparatus to produce the required axial compressive force pulse.
1.2.2 Procedure B uses a cushioned drop mass apparatus to produce the required axial compressive force pulse.
1.3 This standard provides minimum requirements for testing deep foundations under an axial compressive force pulse. Plans, specifications, provisions (or combinations thereof) prepared by a qualified engineer, may provide additional requirements and procedures as needed to satisfy the objectives of a particular deep foundation test program. The engineer in responsible charge of the foundation design, referred to herein as the “Engineer,” shall approve any deviations, deletions, or additions to the requirements of this standard.
1.4 The proper conduct and evaluation of the test requires special knowledge and experience. A qualified engineer should directly supervise the acquisition of field data and the interpretation of the test results so as to predict the actual performance and adequacy of deep foundations used in the constructed foundation. A qualified engineer shall approve the apparatus used for applying the force pulse, rigging and hoisting equipment, support frames, templates, and test procedures.
1.5 The text of this standard references notes and footnotes which provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of the standard. The word “shall” indicates a mandatory provision, and the word “should” indicates a recommended or advisory provision. Imperative sentences indicate mandatory provisions.
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.7 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice .
1.7.1 The procedures used to specify how data are collected/recorded or calculated in the 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 data
1.8 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 the design or other uses, or both. How one uses the results obtained using this standard is beyond its scope.
1.9 ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, are entirely their own responsibility.
1.10 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. Section provides a partial list of specific hazards and precautions.
1.11 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.