1、Designation: D 6760 08Standard 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 deep foundat
3、ion suchas bored piles, drilled shafts, concrete piles or augercast piles.This method can also be extended to diaphragm walls, bar-rettes, dams etc. In this test method, all the above will bedesignated “deep foundation elements.” The test measures thepropagation time and relative energy of an ultras
4、onic 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 techniqu
5、es are outside the scope of this testmethod.1.3 All observed and calculated values shall 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
6、 tothe 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.1.4 The method used to specify how data are collected,calculated, or recorded in this test method is not directly relatedto the accuracy to which
7、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, provisions, or combinatio
8、nsthereof 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 provide explanatory mater
9、ial. 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 installation of the access du
10、cts 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 rather onlythat a defect exists. The method is limited primarily to testingthe concrete between the access ducts and th
11、us 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.1.9 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theres
12、ponsibility 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:2D 1143 Test Method for Piles Under Static Axial Compres-sive Load3D 3740 Practice for Mini
13、mum Requirements for AgenciesEngaged in the Testing and/or Inspection of Soil and Rockas Used in Engineering Design and ConstructionD 4945 Test Method for High-Strain Dynamic Testing ofPilesD 5882 Test Method for Low Strain Impact Integrity Test-ing of Deep FoundationsD 6026 Practice for Using Signi
14、ficant Digits in Geotechni-cal Data3. Terminology3.1 Definitions of Terms Specific to This Standard:1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.11 on Deep Foundations.Current edition approved Jan. 1, 2008. Publ
15、ished February 2008. Originallyapproved in 2002. Last previous edition approved in 2002 as D 6760 02.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards D
16、ocument Summary page onthe ASTM website.3Withdrawn.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.1 access ducts, npreformed steel tubes, plastic tubes(for example, PVC or equivalent), or drilled boreholes, placedin the concrete
17、 to allow probe entry in pairs to measure pulsetransmission in the concrete between the probes.3.1.2 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 detract from the elem
18、ents capacity or durability.3.1.4 depth interval, nthe maximum 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 concret
19、e continuity and consistency betweenthe access ducts or boreholes.3.1.7 specifier, nthe party requesting that the tests arecarried out, for example, the engineer or client.3.1.8 ultrasonic profile, na combined graphical output ofa series of measured or processed ultrasonic pulses with depth.3.1.9 ul
20、trasonic pulse, ndata for one specific depth of ashort duration generated by a transmitter probe and sensed bythe receiver probe.4. Principle of the Test Method4.1 The actual speed of sound wave propagation in concreteis dependent on the concrete material properties, geometry ofthe element and wavel
21、ength of the sound waves. Whenultrasonic frequencies (for example, 20 000 Hz) are gener-ated, Pressure (P) waves and Shear (S) waves travel though theconcrete. Because S waves are relatively slow, they are of nofurther interest in this method. In good quality concrete theP-wave speed would typically
22、 range between 3600 to 4400m/s. Poor quality concrete containing defects (for example, soilinclusion, gravel, water, drilling mud, bentonite, voids, con-taminated concrete, or excessive segregation of the constituentparticles) has a comparatively lower P-wave speed. By mea-suring the transit time of
23、 an ultrasonic P-wave signal betweenan ultrasonic transmitter and receiver in two parallel water-filled access ducts cast into the concrete during constructionand spaced at a known distance apart, such anomalies may bedetected. Usually the transmitter and receiver are maintained atequal elevations a
24、s they are moved up or down the accessducts. In some cases and for special processing the probes maybe deliberately offset in relative elevation and the use ofmultiple receivers either in the same access duct or in multipleaccess ducts can also be allowed. Testing of the concrete in thevicinity of t
25、he duct can also be made with both probes installedin a single access duct. The principles and limitations of the testand interpretation of the results are described in the Referencessection.4.2 Two ultrasonic probes, one a transmitter and the other areceiver, are lowered and lifted usually in uniso
26、n in theirrespective water-filled access duct(s) 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 depth and receiver probesoutput (timed relative to the transmitter p
27、robes ultrasonicpulse generation) are recorded for each pulse. The receiversoutput signals are sampled and saved as amplitude versus time(see Fig. 1) for each sampled depth. These signals can be thennested to produce a “waterfall” diagram (see right side of Fig.2).4.3 The data are further processed
28、and presented to show thefirst arrival of the ultrasonic pulse and the relative energy of thesignal to aid interpretation. The processed data are plottedversus depth as a graphical representation of the ultrasonicprofile of the tested structure. Special test methods to furtherinvestigate anomalies a
29、re employed where the probes are notraised together. The References section lists further sources ofinformation about these special test techniques.5. Significance and Use5.1 This method uses data from ultrasonic probes loweredinto parallel access ducts, or in a single access duct, in the deepfounda
30、tion element to assess the homogeneity and integrity ofconcrete between 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 ot
31、hertesting such as Test Method D 1143, D 4945 or D 5882, andmeasures taken to remediate the structure if a defect isconfirmed.NOTE 1The quality of the result produced by this standard isdependent on the competence of the personnel performing it, and thesuitability of the equipment and facilities use
32、d. 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 not in itself assure reliableresults. Reliable results depend on many factors; Practic
33、e 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 preferably installed during the deepfoundation element installation. The tubes shall pr
34、eferably 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 frequentattachment to the reinforcing cage to mai
35、ntain 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 the access ducts shall besufficient to allow th
36、e 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 mm.6.2 Apparatus for Determining Physical Tes
37、t Parameters:6.2.1 Weighted Measuring TapeA plumb bob connectedto a measuring tape shall be used as a dummy probe to checkFIG.11msDurationUltrasonic Pulse from ReceiverD6760082free passage through and determine the unobstructed length ofeach access duct to the nearest 100 mm. The plumb bob shallhave
38、 a diameter 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, accessducts can be labeled based on the site plan, structure orienta-tion or other
39、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 in all cases be sufficient to al
40、low 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 100 000 Hz.6.3.3 Receiver ProbeThe
41、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 access duct diameter,each probe
42、 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 usedto deploy the probes and trans
43、mit 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 watertight.Where the signal transmiss
44、ion 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 passed over or through a pulley wit
45、h 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-measuring device shall monitor ea
46、ch probe separately sothe exact depth of each probe is known at all times. (Alter-nately a single pulley can be connected to one electronic depthencoder, but then the probes must remain at the same knownrelative elevation difference for the entire test.) The depth-measuring device shall be accurate
47、to within 1 % of the accessduct 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 apparatus for reco
48、rding,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, t
49、he 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, typically 50 mm or less. The apparatusshall have adjustable gain to optimize detection of the trans-mitted pulse by the receiver probe 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 pu
