AASHTO TP 104-2013 Standard Method of Test for Rapid Axial Compressive Load Testing of Deep Foundation Units.pdf

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1、Standard Method of Test for Rapid Axial Compressive Load Testing of Deep Foundation Units AASHTO Designation: TP 104-13 (2015)1American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-1b TP 104-1 AASHTO Standard Method of T

2、est for Rapid Axial Compressive Load Testing of Deep Foundation Units AASHTO Designation: TP 104-13 (2015)11. SCOPE 1.1. This method covers the procedure for testing a vertical or inclined pile to determine the displacement response of the pile to an axial compressive load pulse of a preselected tar

3、get peak force. 1.2. This test method is applicable to all deep foundation units that function in a manner similar to piles, regardless of their method of installation. 1.3. Two alternative procedures are provided: 1.3.1. Procedure A uses a combustion gas pressure apparatus to produce the required a

4、xial compression force pulse. 1.3.2. Procedure B uses a cushioned drop mass apparatus to produce the required axial compression force pulse. 1.4. All observed and calculated values shall conform to the guidelines for significant digits and rounding established in ASTM D6026. 1.5. The method used to

5、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. 1.6. AASHTO takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in

6、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. 1.7. The values stated in SI units shall be regarded as the standard. The inch-pound equivalen

7、ts of the SI units may be approximate. 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 rationalized slug unit is not given unless dynamic (F = ma

8、) calculations are involved. 1.8. This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety concerns associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health p

9、ractices and determine the applicability of regulatory limitations prior to its use. For specific hazards and precautions, refer to Section 6. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1b TP 104

10、-2 AASHTO 2. REFERENCED DOCUMENTS 2.1. AASHTO Standard: R 13, Conducting Geotechnical Subsurface Investigations 2.2. ASTM Standards: D653, Standard Terminology Relating to Soil, Rock, and Contained Fluids D1143/D1143M, Standard Test Methods for Deep Foundations Under Static Axial Compressive Load D3

11、689, Standard Test Methods for Deep Foundations Under Static Axial Tensile Load D3740, Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction D5882, Standard Test Method for Low Strain Impact Integr

12、ity Testing of Deep Foundations D6026, Standard Practice for Using Significant Digits in Geotechnical Data D6760, Standard Test Method for Integrity Testing of Concrete Deep Foundations by Ultrasonic Crosshole Testing 3. TERMINOLOGY 3.1. Except as defined in Section 3.2, the terminology used in this

13、 test method conforms to ASTM D653. 3.2. Descriptions of Terms Specific to This Standard: 3.2.1. force pulsefor the purposes of this standard, a “force pulse” shall result in a force-time event similar to Figure 1. The applied force shall exceed the preload for a duration time of at least twelve tim

14、es the test pile length (L) divided by the strain wave speed (c), or 12L/c. The applied force shall also exceed 50 percent of the actual peak force for a minimum duration time of four times L/c. The force pulse shall increase smoothly and continuously to the peak force and then decrease smoothly and

15、 continuously. Typical force pulse durations range from 90 to 250 ms. Note 1A force pulse duration of less than 12L/c may be acceptable to the engineer when using supplemental transducers. 3.2.2. preloadthe load applied to the pile head due to the static weight of the test apparatus prior to the tes

16、t and may be negligible depending on the design of the test apparatus. 3.2.3. strain wave speed (or wave speed)the speed with which a strain wave propagates through a pile. It is a property of the pile composition and is represented herein by c. For one-dimensional wave propagation, c is equal to th

17、e square root of elastic modulus divided by mass density: c = (E/)1/2. Typical values of c are 4000 m/s for concrete piles and 5100 m/s for steel piles. 3.2.4. target peak forcea predetermined target value for the desired amplitude of the force pulse as defined by the project requirements. This valu

18、e should typically exceed the sum of the required ultimate axial static capacity plus the dynamic resistance of the pile by an amount determined by the engineer based on factors including, but not limited to, pile type, soil type, structural strength of the pile, type of structural load, physical re

19、strictions, or other project requirements. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1b TP 104-3 AASHTO Figure 1Typical Axial Compressive Force Pulse 4. SIGNIFICANCE AND USE 4.1. This test metho

20、d is used to measure the pile head displacement response of an individual pile when the pile is subjected to an axial compressive force pulse. Response data obtained from this test may be used to estimate axial static capacity when the pile displacement is sufficient to cause a pile-soil failure and

21、 to estimate soil-pile damping characteristics. 4.2. When used in conjunction with additional transducers embedded in the pile, this test method may also be used to measure the pile response to the axial force pulse along the pile length. When combined with an appropriate method of analysis, the eng

22、ineer may use data from these optional transducers to estimate the relative contribution of side shear and end bearing to the mobilized axial static capacity of the pile, or to infer the relative contribution of certain soil layers to the overall axial capacity of the pile. Note 2Factors that may af

23、fect the axial static capacity estimated from force pulse tests include, but are not limited to the following: (1) pile installation equipment and procedures; (2) elapsed time since initial installation; (3) pile material properties and dimensions; (4) type, density, strength, stratification, and sa

24、turation of the soil, or rock, or both, adjacent to and beneath the pile; (5) quality of force pulse test data; (6) analysis method; and (7) engineering judgment and experience. Engineering experience is required to analyze the force pulse test data to estimate the axial static capacity and the load

25、 distribution along the pile length. A static load test, conducted in accordance with ASTM D1143/D1143M, may be used to verify the axial static capacity estimated by force pulse tests. Axial static capacity determination utilizing ASTM D1143/D1143M provides a direct and more reliable measurement tha

26、n other methods. Note 3If a force pulse test produces insufficient axial movement, subsequent analysis may overestimate the axial static capacity because of difficulty in separating the static and dynamic components of the response. The analysis of a force pulse test to estimate axial static capacit

27、y also typically includes a reduction factor to account for the additional load resistance that occurs as a result of a faster rate of loading than used during a static test. Force pulse test results from cohesive soils generally require a greater reduction factor due to the rate-of-loading effect,

28、chosen TimeForceTarget PeakForceActual Peak Force50% of ActualPeak ForcePre-Load4L/c ofDurationDuration (12L/c) 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1b TP 104-4 AASHTO conservatively to pro

29、duce a lower axial static capacity estimate. 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 a

30、ssess the axial static capacity. Correlations between actual measurements and force pulse estimates of the ultimate axial static capacity generally improve when using additional transducers embedded in the pile. Axial static capacity may also change over time after the pile installation, especially

31、for driven piles. Both static and force pulse tests represent the capacity at the time of the respective test, and correlation attempts should provide results for a similar time of testing after pile installation or include analysis to account for changes in the soil strength during the time between

32、 the two tests. For further explanation into rate-of-loading effects, soil damping and related phenomena associated with rapid load testing, a list of references has been provided in Section 12. Note 4The quality of the result produced by this test method is dependent on the competence of the person

33、nel performing it and the suitability of the equipment and facilities used. Agencies that meet the criteria of ASTM D3740 are generally considered capable of competent and objective testing and inspection. Users of this test method are cautioned that compliance with ASTM D3740 does not in itself ass

34、ure reliable results. Reliable results depend on many factors; ASTM D3740 provides a means of evaluating some of those factors. 5. APPARATUS 5.1. GeneralAny apparatus capable of applying a force pulse to a pile foundation that is in accordance with Section 3 shall be considered acceptable. The appar

35、atus selected shall be capable of applying a target peak force in accordance with the project requirements. This section describes two specific types of equipment used to generate an axial compressive force pulse: a combustion gas pressure apparatus as shown in Figure 2 and a cushioned drop-mass app

36、aratus as shown in Figure 3. 5.2. Combustion Gas Pressure Apparatus (for Procedure A): 5.2.1. Piston and cylinder jack capable of confining the operating pressure, and capable of centering the force pulse application to the pile. 5.2.2. Fuel and ignition mechanism to create gas pressure in the combu

37、stion chamber. 5.2.3. Reaction beam, supported by the cylinder portion of the jack to transfer the combustion force to the inertial or other reaction system. 5.2.4. Reaction mass or other means to resist the combustion forces. A reaction mass system will typically weigh between 5 and 15 percent of t

38、he target peak force and be comprised of concrete, steel, or contained water. 5.2.5. Accumulator or plenum to receive the combustion gas. 5.2.6. Venting apparatus for the release of combustion gas from the plenum. 5.2.7. Silencer apparatus to muffle the noise of the venting combustion gas. 2015 by t

39、he American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1b TP 104-5 AASHTO Figure 2Typical Combustion-Type Apparatus 5.2.8. Means or mechanism to protect the pile from damage caused by the fall of the reaction mass sy

40、stem (this will typically consist of a gravel-filled enclosure or a mechanism for arresting the reaction mass, such as a hydraulic or mechanical system). 5.2.9. Means or mechanism, such as a rupture valve or disk, to release the combustion gas in the event of an accidental increase in system pressur

41、e or malfunction of the system. 5.3. Cushioned Drop Mass Apparatus (for Procedure B): 5.3.1. A drop mass comprised of concrete, steel, or another material, typically weighing between 5 and 15 percent of the target peak force. 5.3.2. A cylinder jack, crane, or winch, capable of lifting the drop mass

42、to the required height. 5.3.3. Release mechanism for the drop mass. 5.3.4. A guiding system for the fall of the drop mass to properly center the force pulse application to the pile. 5.3.5. Springs or cushion material of sufficient strength and stiffness to transfer a force pulse to the test pile. 5.

43、3.6. Optional secondary springs or cushion material to further cushion the force pulse at the beginning and end of the force pulse application. 5.3.7. Optional clamping or catching mechanism on the drop mass, guide system, or lift cylinder to catch the rebounding drop mass after the application of t

44、he force pulse, preventing the application of 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-1b TP 104-6 AASHTO additional force and improving the verification of the permanent pile head displacement

45、 by means of an elevation check. This clamping or catching mechanism is preferred but not required. 5.3.8. Accessibility for the measurement of the drop height. 5.3.9. Accumulator or plenum to receive the hydraulic fluids used to raise and to catch the drop mass. Figure 3Typical Drop Mass Apparatus

46、5.4. Apparatus for Force and Displacement Measurements: 5.4.1. The apparatus for measuring the force pulse applied to the pile shall consist of a calibrated force transducer mounted directly between the test apparatus and the pile head and in alignment with the central longitudinal axis of the test

47、pile. The force transducer shall have a rated service capacity at least 10 percent greater than the target peak force and shall be calibrated to a minimum of the target peak force plus 10 percent. The force transducer shall have a response time of less than 0.1 ms. 5.4.2. The primary apparatus for m

48、easuring the axial displacement at the pile head shall consist of a calibrated displacement transducer(s). The device shall be capable of measuring displacements directly and continuously over a range of not less than the larger of: (a) 50 mm plus the theoretical elastic shortening of the pile; or (

49、b) D/20 plus the theoretical elastic shortening of the pile, where D is the pile diameter. The transducer shall have a precision of at least 0.25 mm and a response time of less than 0.1 ms. The displacement transducer shall be positioned at and parallel to the central longitudinal axis of the pile. If a single transducer cannot be located at the central axis, then position two or more transducers parallel to and at symmetrical locations with respect to the central longitudinal axis so that the average of their measurements cancels the rotational 2015 by