1、Designation: D6760 16Standard 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 revision, t
2、he 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 thehomogeneity and integrity of concrete in deep foundation
3、 suchas bored piles, 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 bedesignated “deep foundation elements.” The test measures thepropagation time and relative energy of an ultrasonic
4、pulsebetween parallel access ducts (crosshole) or in a single tube(single hole) installed in the deep foundation element. Thismethod is most applicable when performed in tubes that areinstalled during construction.1.2 Similar techniques with different excitation sourcesexist, but these techniques ar
5、e outside the scope of this testmethod.1.3 All observed and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D6026.1.4 The method used to specify how data are collected,calculated, or recorded in this test method is not directly relatedto th
6、e accuracy to which data can be applied in design or otheruses, or both. How one applies the results obtained using thisstandard is beyond its scope.1.5 This standard provides minimum requirements forcrosshole (or single hole) testing of concrete deep foundationelements. Plans, specifications, provi
7、sions, or combinationsthereof prepared by a qualified engineer, and approved by theagency requiring the test(s), may provide additional require-ments and procedures as needed to satisfy the objectives of aparticular test program.1.6 The text of this standard references notes and footnoteswhich provi
8、de explanatory material. These notes and footnotes(excluding those in tables and figures) shall not be consideredas requirements of the standard.1.7 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.8 LimitationsProper installat
9、ion of the access ducts isessential for effective testing and interpretation. The methoddoes not give the exact type of flaw (for example, inclusion,honeycombing, lack of cement particles, etc.) but rather onlythat a flaw exists.1.9 This standard does not purport to address all of thesafety concerns
10、, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D653 Terminology Relating to Soil, Rock, an
11、d ContainedFluidsD1143 Test Method for Piles Under Static Axial Compres-sive Load (Withdrawn 2005)3D3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD4945 Test Method for High-Strain Dynamic Testing
12、ofDeep FoundationsD5882 Test Method for Low Strain Impact Integrity Testingof Deep FoundationsD6026 Practice for Using Significant Digits in GeotechnicalData3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 access ducts, npreformed steel tubes, plastic tubes(for example, PVC or
13、equivalent), or drilled boreholes, placedin the concrete to allow probe entry in pairs to measure pulsetransmission in the concrete between the probes.1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.11 on Deep Foun
14、dations.Current edition approved Dec. 1, 2016. Published January 2017. Originallyapproved in 2002. Last previous edition approved in 2014 as D6760 14. DOI:10.1520/D6760-16.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For An
15、nual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. Unite
16、d StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers
17、to Trade (TBT) Committee.13.1.2 anomaly, nirregularity or series of irregularitiesobserved in an ultrasonic profile indicating a possible flaw.3.1.3 defect, na flaw that, because of either size orlocation, may significantly detract from the elements capacityor durability.3.1.4 depth interval, nthe m
18、aximum incremental spacingalong the pile shaft between ultrasonic pulses.3.1.5 flaw, nany deviation from the planned shape ormaterial (or both) of the element.3.1.6 integrity evaluation, nthe qualitative or quantitativeevaluation of the concrete continuity and consistency betweenthe access ducts or
19、boreholes.3.1.7 ultrasonic profile, na combined graphical output ofa series of measured or processed ultrasonic pulses with depth.3.1.8 ultrasonic pulse, ndata for one specific depth of ashort duration generated by a transmitter probe and sensed bythe receiver probe.4. Principle of the Test Method4.
20、1 The actual speed of sound wave propagation in concreteis dependent on the concrete material properties, geometry ofthe element and wavelength of the sound waves. Whenultrasonic frequencies (for example, 20,000 Hz) aregenerated, Pressure (P) waves and Shear (S) waves travelthough the concrete. Beca
21、use S waves are relatively slow, theyare of no further interest in this method. In good qualityconcrete the P-wave speed would typically range between 3600to 4400 m/s. Poor quality concrete containing defects (forexample, soil inclusion, gravel, water, drilling mud, bentonite,voids, contaminated con
22、crete, or excessive segregation of theconstituent particles) has a comparatively lower P-wave speed.By measuring the transit time of an ultrasonic P-wave signalbetween an ultrasonic transmitter and receiver in two parallelwater-filled access ducts cast into the concrete during construc-tion and spac
23、ed at a known distance apart, such anomalies maybe detected. Usually the transmitter and receiver are main-tained at equal elevations as they are moved up or down theaccess ducts. In some cases and for special processing theprobes may be deliberately offset in relative elevation and theuse of multip
24、le receivers either in the same access duct or inmultiple access ducts can also be allowed. Testing of theconcrete in the vicinity of the access duct can also be madewith both probes installed in a single access duct.4.2 Two ultrasonic probes, one a transmitter and the other areceiver, are lowered t
25、o the bottom of their respective water-filled access duct(s) to test the full shaft length from bottom totop. The transmitter probe generates ultrasonic pulses atfrequent and regular intervals during the probes controlledtravel rate. The probe depth and receiver probes output (timedrelative to the t
26、ransmitter probes ultrasonic pulse generation)are recorded for each pulse. The receivers output signals aresampled and saved as voltage versus time (see Fig. 1) for eachsampled depth. These signals can be then nested to produce a“waterfall” diagram (see right side of Fig. 2).4.3 The data are further
27、 processed and presented to show theFirstArrival Time (FAT) of the ultrasonic pulse and its RelativeEnergy (RE) to aid interpretation. The processed data areplotted versus depth as a graphical representation of theultrasonic profile of the tested structure (see Fig. 2 left). Specialtest methods to f
28、urther investigate anomalies are employedwhere the probes are not raised together.5. Significance and Use5.1 This method uses data from ultrasonic probes loweredinto parallel access ducts, or in a single access duct, in the deepfoundation element to assess the homogeneity and integrity ofconcrete be
29、tween the probes. The data are used to confirmadequate concrete quality or identify zones of poor quality. Ifdefects are detected, then further investigations should be madeby excavation or coring the concrete as appropriate, or by othertesting such as Test Method D1143, D4945 or D5882, andmeasures
30、taken to remediate the structure if a defect isconfirmed.5.2 Limitations:5.2.1 For crosshole tests, the access ducts should preferablybe made of steel to prevent debonding of the access duct fromthe concrete resulting in an anomaly. This test can assess to theintegrity of the concrete mainly in the
31、area bounded by theaccess ducts, which means typically inside the reinforcementcage.FIG. 1 An Ultrasonic Pulse from ReceiverD6760 1625.2.2 For single hole tests the access tubes must be plastictubes. Testing should therefore be performed as soon aspractical in order to avoid debonding issues. Since
32、the gener-ated waves travel through the concrete around the access duct,unless a flaw is massive enough and very near to the accessduct it may not be detected by this method.NOTE 1The quality of the result produced by this standard isdependent on the competence of the personnel performing it, and th
33、esuitability of the equipment and facilities used. Agencies that meet thecriteria of Practice D3740 are generally considered capable of competentand objective testing and inspection. Users of this standard are cautionedthat compliance with Practice D3740 does not in itself assure reliableresults. Re
34、liable results depend on many factors; Practice D3740 providesa means of evaluating some of those factors.6. Apparatus6.1 Apparatus for Allowing Internal Inspection (AccessDucts)To provide access for the probes, access ducts can bepreformed tubes, which are preferably installed during the deepfounda
35、tion element installation. The tubes shall preferably bemild steel for crosshole testing, and are required to be PVC orequivalent for single hole testing. Plastic tubes, while notpreferred for crosshole testing, can be used in special circum-stances if approved by the specifier but require more freq
36、uentattachment to the reinforcing cage to maintain alignment. Theplastic material must not deform during the high temperaturesof concrete curing. If no tubes are installed during construction,boreholes drilled into the pile or structure can be installed afterinstallation. The internal diameter of th
37、e access ducts shall besufficient to allow the easy passage of the ultrasonic probesover the entire access duct length. If the access duct diameteris too large it influences the precision of arrival time andcalculated concrete wave speed.Access ducts typically have aninternal diameter from 38 to 50
38、mm.6.2 Apparatus for Determining Physical Test Parameters:6.2.1 Weighted Measuring TapeAplumb bob connected toa measuring tape shall be used as a dummy probe to check freepassage through and determine the unobstructed length of eachaccess duct to the nearest 100 mm. The plumb bob shall havea diamete
39、r similar to the diameter of the probes.6.2.2 Magnetic CompassA magnetic compass accurate towithin 10 shall be used to document the access duct designa-tions compared with the site layout plan. Alternately, accessFIG. 2 Typical Ultrasonic ProfileD6760 163ducts can be labeled based on the site plan,
40、structure orienta-tion or other methods to document access duct designationsassigned and used for reporting test results.6.3 Apparatus for Obtaining Measurements:6.3.1 ProbesProbes shall allow a generated or detectedpulse within 125 mm of the bottom of the access duct. Theweight of each probe shall
41、in all cases be sufficient to allow itto sink under its own weight in the access ducts. The probehousing shall be waterproof to at least 1.5 times the maximumdepth of testing.6.3.2 Transmitter ProbeThe transmitter probe shall gen-erate an ultrasonic pulse with a frequency of between 30,000Hz and 60,
42、000 Hz.6.3.3 Receiver ProbeThe receiver probe shall be of asimilar size and compatible design to the transmitter probe andused to detect the arrival of the ultrasonic pulse generated bythe transmitter probe.6.3.4 Probe CentralizerIf the receiver or transmitterprobes, or both, are less than half the
43、access duct diameter,each probe shall be fitted with centralizers with effectivediameter equivalent to at least 50 % of the access ductdiameter. It shall be designed to minimize any possiblesnagging on irregularities in the inner access duct wall.6.3.5 Signal Transmission CablesThe signal cables use
44、dto deploy the probes and transmit data from the probes shall besufficiently robust to support the probes weight. The cableshall be abrasion resistant to allow repeated field use andmaintain flexibility in the range of anticipated temperatures.All cable connectors or splices, if any, shall be watert
45、ight.Where the signal transmission cables exit the access duct,suitable cable guides, pulleys or cushioning material shall befitted inside the access ducts to minimize abrasion and gener-ally assist with smooth deployment of the probes.6.3.6 Probe Depth-Measuring DeviceThe signal cablesshall be pass
46、ed over or through a pulley with a depth-encodingdevice to determine the depth to the location of the transmitterand receiver on the probes in the access ducts throughout thetest. The design of the depth-measuring device shall be suchthat cable slippage shall not occur. Preferably a separatedepth-me
47、asuring device shall monitor each probe so the exactdepth of each probe is known at all times. (Alternately a singlepulley can be connected to one electronic depth encoder, butthen the probes must remain at the same known relativeelevation difference for the entire test.) The depth-measuringdevice s
48、hall be accurate to within 1 % of the access duct length,or 0.25 m, whichever is larger.6.4 Apparatus for Recording, Processing and DisplayingData:6.4.1 GeneralThe signals from the transmitter and re-ceiver probes and the depth-measuring device shall be trans-mitted to a field rugged, computerized a
49、pparatus for recording,processing and displaying the data in the form of an ultrasonicprofile. A typical schematic arrangement for the test apparatusis illustrated in Fig. 3. The apparatus shall generate pulses fromthe transmitter probe either at fixed depth intervals or at fixedtime intervals. In the latter case, the depth shall be recorded andassigned to each pulse captured by the apparatus for the instantof pulse generation. The rate of pulse generation by eithermethod shall generate at least one ultrasonic pulse for everyrequired depth interval, typi
