1、Designation: D6760 08D6760 14Standard Test Method forIntegrity Testing of Concrete Deep Foundations byUltrasonic Crosshole Testing1This standard is issued under the fixed designation D6760; the number immediately following the designation indicates the year oforiginal adoption or, in the case of rev
2、ision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers procedures for checking the homogeneity and integrity of concrete in deep f
3、oundation such as boredpiles, drilled shafts, concrete piles or augercast piles. This method can also be extended to diaphragm walls, barrettes, dams etc.In this test method, all the above will be designated “deep foundation elements.” The test measures the propagation time andrelative energy of an
4、ultrasonic pulse between parallel access ducts (crosshole) or in a single tube (single hole) installed in the deepfoundation element. This method is most applicable when performed in tubes that are installed during construction.1.2 Similar techniques with different excitation sources exist, but thes
5、e techniques are outside the scope of this test method.1.3 All observed and calculated values shall conform to the guidelines for significant digits and rounding established in PracticeD6026.1.3.1 The method used to specify how data are collected, calculated, or recorded in this standard is not dire
6、ctly related to theaccuracy to which data can be applied in design or other uses, or both. How one applies the results obtained using this standardis beyond its scope.1.4 The method used to specify how data are collected, calculated, or recorded in this test method is not directly related to theaccu
7、racy to which data can be applied in design or other uses, or both. How one applies the results obtained using this standardis beyond its scope.1.5 This standard provides minimum requirements for crosshole (or single hole) testing of concrete deep foundation elements.Plans, specifications, provision
8、s, or combinations thereof prepared by a qualified engineer, and approved by the agency requiringthe test(s), may provide additional requirements and procedures as needed to satisfy the objectives of a particular test program.1.6 The text of this standard references notes and footnotes which provide
9、 explanatory material. These notes and footnotes(excluding those in tables and figures) shall not be considered as requirements of the standard.1.7 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.8 LimitationsProper installa
10、tion of the access ducts is essential for effective testing and interpretation. The method does notgive the exact type of defect (for example, inclusion, honeycombing, lack of cement particles, etc.) but rather only that a defectexists. The method is limited primarily to testing the concrete between
11、 the access ducts and thus gives little information about theconcrete outside the reinforcement cage to which the access ducts are attached when the tubes are attached to the inside of thereinforcement cage.1.9 This standard does not purport to address all of the safety concerns, if any, associated
12、with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D1143 Test Method for Piles Under Static Axial Compressive Load (Wi
13、thdrawn 2005)31 This test method is under the jurisdiction of ASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.11 on Deep Foundations.Current edition approved Jan. 1, 2008June 1, 2014. Published February 2008July 2014. Originally approved in 2002. Last previou
14、s edition approved in 20022008 asD6760 02.D6760 08. DOI: 10.1520/D6760-08.10.1520/D6760-14.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Sum
15、mary page on the ASTM website.3 The last approved version of this historical standard is referenced on www.astm.org.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may n
16、ot be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor
17、Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1D3740 Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used inEngineering Design and ConstructionD4945 Test Method for High-Strain Dynamic Testing of Deep FoundationsD5882 Test
18、Method for Low Strain Impact Integrity Testing of Deep FoundationsD6026 Practice for Using Significant Digits in Geotechnical Data3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 access ducts, npreformed steel tubes, plastic tubes (for example, PVC or equivalent), or drilled bo
19、reholes, placed in theconcrete to allow probe entry in pairs to measure pulse transmission in the concrete between the probes.3.1.2 anomaly, nirregularity or series of irregularities observed in an ultrasonic profile indicating a possible flaw.3.1.3 defect, na flaw that, because of either size or lo
20、cation, may detract from the elements capacity or durability.3.1.4 depth interval, nthe maximum incremental spacing along the pile shaft between ultrasonic pulses.3.1.5 flaw, nany deviation from the planned shape or material (or both) of the element.3.1.6 integrity evaluation, nthe qualitative or qu
21、antitative evaluation of the concrete continuity and consistency between theaccess ducts or boreholes.3.1.7 specifier, nthe party requesting that the tests are carried out, for example, the engineer or client.3.1.8 ultrasonic profile, na combined graphical output of a series of measured or processed
22、 ultrasonic pulses with depth.3.1.9 ultrasonic pulse, ndata for one specific depth of a short duration generated by a transmitter probe and sensed by thereceiver probe.4. Principle of the Test Method4.1 The actual speed of sound wave propagation in concrete is dependent on the concrete material prop
23、erties, geometry of theelement and wavelength of the sound waves. When ultrasonic frequencies (for example, 20 000 Hz) are generated, Pressure (P)waves and Shear (S) waves travel though the concrete. Because S waves are relatively slow, they are of no further interest in thismethod. In good quality
24、concrete the P-wave speed would typically range between 3600 to 4400 m/s. Poor quality concretecontaining defects (for example, soil inclusion, gravel, water, drilling mud, bentonite, voids, contaminated concrete, or excessivesegregation of the constituent particles) has a comparatively lower P-wave
25、 speed. By measuring the transit time of an ultrasonicP-wave signal between an ultrasonic transmitter and receiver in two parallel water-filled access ducts cast into the concrete duringconstruction and spaced at a known distance apart, such anomalies may be detected. Usually the transmitter and rec
26、eiver aremaintained at equal elevations as they are moved up or down the access ducts. In some cases and for special processing the probesmay be deliberately offset in relative elevation and the use of multiple receivers either in the same access duct or in multiple accessducts can also be allowed.
27、Testing of the concrete in the vicinity of the duct can also be made with both probes installed in a singleaccess duct. The principles and limitations of the test and interpretation of the results are described in the References section.4.2 Two ultrasonic probes, one a transmitter and the other a re
28、ceiver, are lowered and lifted usually in unison in their respectivewater-filled access duct(s) to test the full shaft length from top to bottom. The transmitter probe generates ultrasonic pulses atfrequent and regular intervals during the probes controlled travel rate. The probe depth and receiver
29、probes output (timed relativeto the transmitter probes ultrasonic pulse generation) are recorded for each pulse. The receivers output signals are sampled andsaved as amplitude versus time (see Fig. 1) for each sampled depth. These signals can be then nested to produce a “waterfall”diagram (see right
30、 side of Fig. 2).4.3 The data are further processed and presented to show the first arrival of the ultrasonic pulse and the relative energy of thesignal to aid interpretation. The processed data are plotted versus depth as a graphical representation of the ultrasonic profile ofthe tested structure.
31、Special test methods to further investigate anomalies are employed where the probes are not raised together.The References section lists further sources of information about these special test techniques.5. Significance and Use5.1 This method uses data from ultrasonic probes lowered into parallel ac
32、cess ducts, or in a single access duct, in the deepfoundation element to assess the homogeneity and integrity of concrete between the probes. The data are used to confirm adequateconcrete quality or identify zones of poor quality. If defects are detected, then further investigations should be made b
33、y excavationFIG. 1 1 ms Duration Ultrasonic Pulse from ReceiverD6760 142or coring the concrete as appropriate, or by other testing such as Test Method D1143, D4945 or D5882, and measures taken toremediate the structure if a defect is confirmed.NOTE 1The quality of the result produced by this standar
34、d is dependent on the competence of the personnel performing it, and the suitability of theequipment and facilities used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objective testing andinspection. Users of this standard are cautioned that com
35、pliance with Practice D3740 does not in itself assure reliable results. Reliable results depend onmany factors; Practice D3740 provides a means of evaluating some of those factors.6. Apparatus6.1 Apparatus for Allowing Internal Inspection (Access Ducts)To provide access for the probes, access ducts
36、can bepreformed tubes, which are preferably installed during the deep foundation element installation. The tubes shall preferably be mildsteel for crosshole testing, and are required to be PVC or equivalent for single hole testing. Plastic tubes, while not preferred forcrosshole testing, can be used
37、 in special circumstances if approved by the specifier but require more frequent attachment to thereinforcing cage to maintain alignment. The plastic material must not deform during the high temperatures of concrete curing. Ifno tubes are installed during construction, boreholes drilled into the pil
38、e or structure can be installed after installation. The internaldiameter of the access ducts shall be sufficient to allow the easy passage of the ultrasonic probes over the entire access duct length.If the access duct diameter is too large it influences the precision of arrival time and calculated c
39、oncrete wave speed.Access ductstypically have an internal diameter from 38 to 50 mm.6.2 Apparatus for Determining Physical Test Parameters:6.2.1 Weighted Measuring TapeA plumb bob connected to a measuring tape shall be used as a dummy probe to check freepassage through and determine the unobstructed
40、 length of each access duct to the nearest 100 mm. The plumb bob shall have adiameter similar to the diameter of the probes.FIG. 2 Typical Ultrasonic ProfileD6760 1436.2.2 Magnetic CompassA magnetic compass accurate to within 10 shall be used to document the access duct designationscompared with the
41、 site layout plan. Alternately, access ducts can be labeled based on the site plan, structure orientation or othermethods to document access duct designations assigned and used for reporting test results.6.3 Apparatus for Obtaining Measurements : Measurements:6.3.1 ProbesProbes shall allow a generat
42、ed or detected pulse within 125 mm of the bottom of the access duct. The weightof each probe shall in all cases be sufficient to allow it to sink under its own weight in the access ducts. The probe housing shallbe waterproof to at least 1.5 times the maximum depth of testing.6.3.2 Transmitter ProbeT
43、he transmitter probe shall generate an ultrasonic pulse with a frequency of between 30 000 Hz and100 000 Hz.6.3.3 Receiver ProbeThe receiver probe shall be of a similar size and compatible design to the transmitter probe and used todetect the arrival of the ultrasonic pulse generated by the transmit
44、ter probe.6.3.4 Probe CentralizerIf the receiver or transmitter probes, or both, are less than half the access duct diameter, each probeshall be fitted with centralizers with effective diameter equivalent to at least 50 % of the access duct diameter. It shall be designedto minimize any possible snag
45、ging on irregularities in the inner access duct wall.6.3.5 Signal Transmission CablesThe signal cables used to deploy the probes and transmit data from the probes shall besufficiently robust to support the probes weight. The cable shall be abrasion resistant to allow repeated field use and maintainf
46、lexibility in the range of anticipated temperatures. All cable connectors or splices, if any, shall be watertight. Where the signaltransmission cables exit the access duct, suitable cable guides, pulleys or cushioning material shall be fitted inside the access ductsto minimize abrasion and generally
47、 assist with smooth deployment of the probes.6.3.6 Probe Depth-Measuring DeviceThe signal cables shall be passed over or through a pulley with a depth-encoding deviceto determine the depth to the location of the transmitter and receiver on the probes in the access ducts throughout the test. Thedesig
48、n of the depth-measuring device shall be such that cable slippage shall not occur. Preferably a separate depth-measuringdevice shall monitor each probe separately so the exact depth of each probe is known at all times. (Alternately a single pulley canbe connected to one electronic depth encoder, but
49、 then the probes must remain at the same known relative elevation difference forthe entire test.) The depth-measuring device shall be accurate to within 1 % of the access duct length, or 0.25 m, whichever islarger.6.4 Apparatus for Recording, Processing and Displaying Data:6.4.1 GeneralThe signals from the transmitter and receiver probes and the depth-measuring device shall be transmitted to afield rugged, computerized apparatus for recording, processing and displaying the data in the form of an ultrasonic profile.Atypicalschematic arrangement for t
