1、Designation: D 6760 02Standard Test Method forIntegrity Testing of Concrete Deep Foundations byUltrasonic Crosshole Testing1This standard is issued under the fixed designation D 6760; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、 the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 a deep found
3、ationsuch as bored piles, drilled shafts, concrete piles or augercastpiles. This method can also be extended to diaphragm walls,barrettes, dams etc. The test measures the propagation time andrelative energy of an ultrasonic pulse between parallel accessducts installed in the pile or structure. This
4、method is mostapplicable when performed between tubes that are installedduring pile construction.1.2 Similar techniques with different excitation sources orsingle access ducts, or both, exist, but these techniques areoutside the scope of this test method.1.3 All observed and calculated values shall
5、conform to theguidelines for significant digits and rounding established inPractice D 6026.1.3.1 The method used to specify how data are collected,calculated, or recorded in this standard is not directly related tothe accuracy to which data can be applied in design or otheruses, or both. How one app
6、lies the results obtained using thisstandard is beyond its scope.1.4 LimitationsProper installation of the access ducts isessential for effective testing and interpretation. The methoddoes not give the exact type of defect (for example, inclusion,honeycombing, lack of cement particles, etc.) but rat
7、her onlythat a defect exists. The method is limited primarily to testingthe concrete between the access ducts and thus gives littleinformation about the concrete outside the reinforcement cageto which the access ducts are attached when the tubes areattached to the inside of the reinforcement cage.1.
8、5 This standard does not purport to address all of thesafety concerns, 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 Doc
9、uments2.1 ASTM Standards:D 1143 Test Method for Piles Under Static Axial Compres-sive Load2D 3740 Practice for Minimum Requirements for AgenciesEngaged in the Testing and/or Inspection of Soil and Rockas Used in Engineering Design and Construction2D 4945 Test Method High Strain Dynamic Testing of Pi
10、les2D 5882 Test Method for Low Strain Integrity Testing ofPiles2D 6026 Practice for Using Significant Digits in Calculatingand Reporting Geotechnical Test Data23. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 access ducts, npreformed steel or plastic tubes, ordrilled boreholes,
11、 placed in the concrete to allow probe entry inpairs to measure pulse transmission in the concrete between theprobes.3.1.2 anomaly, nirregularity or series of irregularitiesobserved in an ultrasonic profile indicating a possible defect.3.1.3 depth interval, nthe maximum incremental spacingalong the
12、pile shaft between ultrasonic pulses.3.1.4 integrity evaluation, nthe qualitative evaluation ofthe concrete continuity and consistency between the accessducts or boreholes.3.1.5 specifier, nthe party requesting that the tests arecarried out, for example, the engineer or client.3.1.6 ultrasonic profi
13、le, na combined graphical output ofa series of measured or processed ultrasonic pulses with depth.3.1.7 ultrasonic pulse, ndata for one specific depth of ashort duration generated by a transmitter probe or sensed by thereceiver probe.4. Principle of the Test Method4.1 The actual velocity of sound wa
14、ve propagation inconcrete is dependent on the concrete material properties,geometry of the element and wavelength of the sound waves.When ultrasonic frequencies (for example, 20 000 Hz) aregenerated, Pressure (P) waves and Shear (S) waves travelthough the concrete. Because S waves are relatively slo
15、w, theyare of no further interest in this method. In good qualityconcrete the P-wave velocity would typically range between1This test method is under the jurisdiction of ASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.11 on Deep Foundations.Current edition app
16、roved Jan 10, 2002. Published April 2002.2Annual Book of ASTM Standards, Vol 04.08.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3600 to 4400 m/s. Poor quality concrete containing anomalies(for example, soil inclusion, gravel, wate
17、r, drilling mud,bentonite, voids, contaminated concrete, or excessive segrega-tion of the constituent particles) has a comparatively lowerP-wave velocity. By measuring the transit time of an ultrasonicP-wave signal between an ultrasonic transmitter and receiver intwo parallel water-filled access duc
18、ts cast into the concreteduring construction and spaced at a known distance apart, suchanomalies may be detected. Usually the transmitter and re-ceiver are maintained at equal elevations as they are moved upor down the access ducts. In some cases and for specialprocessing the probes may be deliberat
19、ely offset in relativeelevation and the use of multiple receivers either in the sameaccess duct or in multiple access ducts can also be allowed. Theprinciples and limitations of the test and interpretation of theresults are described in the References section.4.2 Two ultrasonic probes, one a transmi
20、tter and the other areceiver, are lowered and lifted usually in unison in theirrespective water-filled access ducts to test the full shaft lengthfrom top to bottom. The transmitter probe generates ultrasonicpulses at frequent and regular intervals during the probescontrolled travel rate. The probe d
21、epth and receiver probesoutput (timed relative to the transmitter probes ultrasonicpulse generation) are recorded for each pulse. The receiversoutput signals are sampled and saved as amplitude versus time(see Fig. 1).4.3 Alternately, the signals may be modulated to a series ofblack and white lines c
22、orresponding respectively to the positiveand negative peaks of the signal. In either case, the data arefurther processed and presented to show the first arrival of theultrasonic pulse and the relative energy of the signal to aidinterpretation. The processed data are plotted versus depth as agraphica
23、l representation of the ultrasonic profile of the testedstructure. Special test methods to further investigate anomaliesare employed where the probes are not raised together. TheReferences section lists further sources of information aboutthese special test techniques.5. Significance and Use5.1 This
24、 method uses data from ultrasonic probes loweredinto parallel access ducts in the pile or structure to assess thehomogeneity and integrity of concrete between the probes. Thedata are used to confirm adequate concrete quality or identifyzones of poor quality. If defects are detected, then furtherinve
25、stigations should be made by excavation or coring theconcrete as appropriate, or by other testing such as Test MethodD 1143, D 4945 or D 5882, and measures taken to remediatethe structure if a defect is confirmed.NOTE 1The quality of the result produced by this standard isdependent on the competence
26、 of the personnel performing it, and thesuitability of the equipment and facilities used. Agencies that meet thecriteria of Practice D 3740 are generally considered capable of competentand objective testing and inspection. Users of this standard are cautionedthat compliance with Practice D 3740 does
27、 not in itself assure reliableresults. Reliable results depend on many factors; Practice D 3740 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
28、preferably installed during the pileor structure installation. The tubes shall preferably be mildsteel. Plastic tubes, while not preferred, can be used in specialcircumstances if approved by the test agency but require morefrequent attachment to the reinforcing cage to maintain align-ment. The plast
29、ic material must not deform during the hightemperatures of concrete curing. If no tubes are installed duringconstruction, boreholes drilled into the pile or structure can beinstalled after installation. The internal diameter of the accessducts shall be sufficient to allow the easy passage of theultr
30、asonic probes over the entire access duct length. If theaccess duct diameter is too large it influences the precision ofarrival time and calculated concrete wave speed. Access ductstypically have an internal diameter from 38 to 50 mm.6.2 Apparatus for Determining Physical Test Parameters:6.2.1 Weigh
31、ted Measuring TapeA plumb bob connectedto a measuring tape shall be used as a dummy probe to checkfree passage through and determine the unobstructed length ofeach access duct to the nearest 100 mm. The plumb bob shallhave a diameter similar to the diameter of the probes.6.2.2 Magnetic CompassA magn
32、etic compass accurate towithin 10 shall be used to document the access duct designa-tions compared with the site layout plan. Alternately, accessducts can be labeled based on the site plan, structure orienta-tion or other methods to document access duct designationsassigned and used for reporting te
33、st results.6.3 Apparatus for Obtaining Measurements:6.3.1 ProbesProbes shall allow a generated or detectedpulse within 100 mm of the bottom of the access duct. Theweight of each probe shall in all cases be sufficient to allow itto sink under its own weight in the access ducts. The probehousing shall
34、 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 minimum frequency of 30 000Hz.6.3.3 Receiver ProbeThe receiver probe shall be of asimilar size and compatible design to the transmitter probe andus
35、ed 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 access duct diameter,each probe shall be fitted with centralizers with effectivediameter equivalent to at least 50 % of the
36、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 usedto deploy the probes and transmit data from the probes shall besufficiently robust to support the probes weight. The cables
37、hall 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 watertight.FIG.11msDuration Ultrasonic Pulse from ReceiverD 67602Where the signal transmission cables exit the access duct,suitabl
38、e 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 passed over or through a pulley with a depth-encodingdevice to determine t
39、he 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-measuring device, such as direct markings on the cables,shall monitor ea
40、ch probe separately so the exact depth of eachprobe is known at all times. (Alternately a single pulley can beconnected to one electronic depth encoder, but then the probesmust remain at the same known relative elevation differencefor the entire test.) The depth-measuring device shall beaccurate to
41、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, dc battery powered, computerizedap
42、paratus for recording, processing and displaying the data inthe form of an ultrasonic profile. A typical schematic arrange-ment for the test apparatus is illustrated in Fig. 2. The apparatusshall generate pulses from the transmitter probe either at fixeddepth intervals or at fixed time intervals. In
43、 the latter case, thedepth shall be recorded and assigned to each pulse captured bythe apparatus for the instant of pulse generation. The rate ofpulse generation by either method shall generate at least oneultrasonic pulse for every required depth interval, typically 50mm or less. The apparatus shal
44、l have adjustable gain tooptimize detection of the transmitted pulse by the receiverprobe for the concrete under test.6.4.2 Recording ApparatusEach transmitted ultrasonicpulse shall immediately start the data acquisition for thereceiver probe. Analog signals of an ultrasonic pulse measuredby the rec
45、eiving probe shall be digitized by an analog to digitalconverter with a minimum amplitude resolution of 12 bits anda minimum sampling frequency of 250 000 Hz. The apparatusshall read the depth-measuring device and assign a depth toeach digitized ultrasonic pulse. The apparatus shall store theseraw d
46、igitized ultrasonic pulses and the processed data fromeach ultrasonic profile for each pair of access ducts. All storeddata shall have identifying header information attached to itdescribing the test location, profile identifier, date stamp and allpertinent information regarding the test.6.4.3 Appar
47、atus for Processing DataThe apparatus forprocessing the data shall be a digital computer or micropro-cessor capable of analyzing all data to identify at least the firstarrival and energy of the transmitted ultrasonic pulse at thereceiver probe for each depth interval. The data shall then becompiled
48、into a single ultrasonic profile for each duct pair.6.4.4 Apparatus for Display of Measured DataThe appa-ratus shall be capable of displaying the raw receiver ultrasonicpulses to confirm data quality during acquisition. After dataacquisition, the apparatus shall be capable of displaying theraw data
49、of each ultrasonic pulse along the entire pile length.The apparatus shall also display the processed ultrasonicprofile. The apparatus may optionally include a printer for onsite output of results.7. Procedure7.1 Installation of Preformed Access Ducts:7.1.1 GeneralThe access ducts shall be supplied andinstalled during construction by or in cooperation with thecontractor of the pile or structure to be tested. The total numberof installed access ducts in the pile or structure should bechosen consistent with good coverage of the cross section. Asa guide, the number
