1、Designation: D6951/D6951M 09 (Reapproved 2015)Standard Test Method forUse of the Dynamic Cone Penetrometer in ShallowPavement Applications1This standard is issued under the fixed designation D6951/D6951M; the number immediately following the designation indicates theyear of original adoption or, in
2、the case of revision, the year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the measurement of the pen-etration rate of the Dynamic Cone
3、 Penetrometer with an 8-kg17.6-lb hammer (8-kg 17.6-lb DCP) through undisturbedsoil or compacted materials, or both. The penetration rate maybe related to in situ strength such as an estimated in situ CBR(California Bearing Ratio). A soil density may be estimated(Note 1) if the soil type and moistur
4、e content are known. TheDCP described in this test method is typically used forpavement applications.1.2 The test method provides for an optional 4.6-kg 10.1-lb sliding hammer when the use of the 8-kg 17.6-lb slidingmass produces excessive penetration in soft ground conditions.1.3 The values stated
5、in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.4 This
6、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. Terminology2.1 Defini
7、tions of Terms Specific to This Standard:2.1.1 8-kg 17.6-lb DCP dynamic cone penetrometer withan 8-kg 17.6-lb hammer (see Fig. 1)a device used to assessthe in situ strength of undisturbed soil or compacted materials,or both.2.1.2 sliding attachment (see Fig. 1)an optional deviceused in reading the d
8、istance the DCP tip has penetrated. It maybe fastened to the anvil or lower rod to hold/slide along aseparate measuring rod, or it may be fastened to the separaterod and slide along a graduated drive rod.3. Summary of Test Method3.1 The operator drives the DCP tip into soil by lifting thesliding ham
9、mer to the handle then releasing it. The totalpenetration for a given number of blows is measured andrecorded in mm/blow, which is then used to describe stiffness,estimate an in situ CBR strength from an appropriate correla-tion chart, or other material charcharacteristics.4. Significance and Use4.1
10、 This test method is used to assess in situ strength ofundisturbed soil and compacted materials (or both). Thepenetration rate of the 8-kg 17.6-lb DCP can be used toestimate in-situ CBR (California Bearing Ratio), to identifystrata thickness, shear strength of strata, and other materialcharacteristi
11、cs.4.1.1 Other test methods exist for DCPs with differenthammer weights and cone tip sizes, which have correlationsthat are unique to the instrument.4.2 The 8-kg 17.6-lb DCP is held vertically and thereforeis typically used in horizontal construction applications, suchas pavements and floor slabs.4.
12、3 This instrument is typically used to assess materialproperties down to a depth of 1000 mm 39 in. below thesurface. The penetration depth can be increased using drive rodextensions. However, if drive rod extensions are used, careshould be taken when using correlations to estimate otherparameters si
13、nce these correlations are only appropriate forspecific DCP configurations. The mass and inertia of the devicewill change and skin friction along drive rod extensions willoccur.4.4 The 8-kg 17.6-lb DCP can be used to estimate thestrength characteristics of fine- and coarse-grained soils, granu-lar c
14、onstruction materials and weak stabilized or modifiedmaterials. The 8-kg 17.6-lb DCP cannot be used in highlystabilized or cemented materials or for granular materialscontaining a large percentage of aggregates greater than 50 mm2 in.1This test method is under the jurisdiction of ASTM Committee E17
15、on Vehicle- Pavement Systems and is the direct responsibility of Subcommittee E17.41 onPavement Testing and Evaluation.Current edition approved May 1, 2015. Published July 2015. Originally approvedin 2003. Last previous edition approved in 2009 as D6951/D6951M 09. DOI:10.1520/D6951_D6951M-09R15.Copy
16、right ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14.5 The 8-kg 17.6-lb DCP can be used to estimate thestrength of in situ materials underlying a bound or highlystabilized layer by first drilling or coring an access hole.NOTE 1The DCP may be
17、 used to assess the density of a fairly uniformmaterial by relating density to penetration rate on the same material. Inthis way undercompacted or “soft spots” can be identified, even thoughthe DCP does not measure density directly.24.5.1 A field DCP measurement results in a field or in situCBR and
18、will not normally correlate with the laboratory orsoaked CBR of the same material. The test is thus intended toevaluate the in situ strength of a material under existing fieldconditions.5. Apparatus5.1 The 8-kg 17.6-lb DCP is shown schematically in Fig.1. It consists of the following components: a 1
19、6-mm 58-in.diameter steel drive rod with a replaceable point or disposablecone tip, an 8-kg 17.6-lb hammer which is dropped a fixedheight of 575 mm 22.6 in., a coupler assembly, and a handle.The tip has an included angle of 60 degrees and a diameter atthe base of 20 mm 0.79 in. (See Fig. 2.)5.1.1 Th
20、e apparatus is typically constructed of stainlesssteel, with the exception of the replacement point tip, whichmay be constructed from hardened tool steel or a similarmaterial resistant to wear.5.2 The following tolerances are recommended:5.2.1 Hammer weight-measurement of 8.0 kg 17.6 lb;tolerance is
21、 0.01 kg 0.02 lb,5.2.2 Hammer weight-measurement of 4.6 kg 10.1 lb.;tolerance is 0.01 kg 0.02 lb,5.2.3 Drop of hammer-measurement of 575 mm 22.6 in.;tolerance is 1.0 mm 0.04 in.,5.2.4 Tip angle measurement of 60 degrees included angle;tolerance is 1 degree, and5.2.5 Tip base diameter measurement of
22、20 mm 0.79 in.;tolerance is 0.25 mm 0.01 in.NOTE 2A disposable cone tip may be used. The deposable cone tip isheld in place with an o-ring, which allows the cone tip to be easilydetached when the drive rod is pulled upward after completion of the test.The disposable cone tip is shown schematically i
23、n Fig. 3.5.3 In addition to the DCP, the following equipment isneeded:5.3.1 Tools for assembling the DCP,5.3.2 Lubricating Oil,5.3.3 Thread Locking Compound, and5.3.4 Data Recording form (see Table 1).5.4 Depending on the circumstances, the following equip-ment may also be needed or is recommended:5
24、.4.1 A vertical scale graduated using increments of 1.0 mm0.04 in., or measuring rod longer than the longest drive rod ifthe drive rod(s) are not graduated,5.4.2 An optional sliding attachment for use with a separatescale or measuring rod,2“METHOD ST6: Measurement of the In Situ Strength of Soils by
25、 the DynamicCone Penetrometer (DCP), Special Methods for Testing Roads,” Draft TMH6,Technical Methods for Highways (TMH), Pretoria, SouthAfrica, ISBN 0 7988 22899, 1984, p. 20.FIG. 1 Schematic of DCP DeviceFIG. 2 Replaceable Point TipD6951/D6951M 09 (2015)25.4.3 A rotary hammer drill or coring appar
26、atus capable ofdrilling a minimum diameter hole of 25 mm 1 in. A largerhole may be required depending on the underlying material orthe need for addition tests or sampling,5.4.4 A wet/dry vacuum or suitable alternative to removeloose material and fluid if an access hole is made beforetesting,5.4.5 Fi
27、eld power supply to power items in 5.4.3 and 5.4.4,5.4.6 Disposable cone tips,5.4.7 Dual mass hammer (see Fig. 4), and5.4.8 Extraction jack, recommended if disposable cone tipsare not used (see Fig. 5).NOTE 3A 4.6-kg 10-lb hammer (see Fig. 4) may be used in place ofthe 8-kg 18-lbf hammer provided th
28、at the standard drop height ismaintained. The 4.6-kg 10-lbf hammer is used in weaker materialswhere the 8-kg 18-lbf hammer would produce excessive penetration.NOTE 4An automated version of the DCP (ADCP) may be usedprovided all requirements of this standard with respect to the apparatusand procedure
29、 are met.NOTE 5An automated data collection system may be used provided itmeasures and records to the nearest 1 mm 0.04 in. and does not interferewith the operation/results of the devise.6. Procedure6.1 Equipment CheckBefore beginning a test, the DCPdevice is inspected for fatigue-damaged parts, in
30、particular thecoupler and handle, and excessive wear of the drive rod andreplaceable point tip. All joints must be securely tightenedincluding the coupler assembly and the replaceable point tip (orthe adapter for the disposable cone tip) to drive rod.6.2 Basic OperationThe operator holds the device
31、by thehandle in a vertical or plumb position and lifts and releases thehammer from the standard drop height. The recorder measuresand records the total penetration for a given number of blowsor the penetration per blow.6.3 Initial Reading:6.3.1 Testing a Surface LayerThe DCP is held verticallyand th
32、e tip seated such that the top of the widest part of the tipis flush with the surface of the material to be tested. An initialreading is obtained from the graduated drive rod or a separatevertical scale/measuring rod. The distance is measured to thenearest 1 mm 0.04 in. Some sliding reference attach
33、mentsallow the scale/measuring rod to be set/marked at zero whenthe tip is at the zero point shown in Fig. 2.6.3.2 Testing Below a Bound LayerWhen testing materialsunderlying a bound layer, a rotary hammer drill or coringapparatus meeting the requirements given in 5.4.3 above isused to provide an ac
34、cess hole to the layer to be tested. Wetcoring requires that coring fluid be removed immediately andthe DCP test be performed as soon as possible, but not longerthan 10 minutes following completion of the coring operation.The coring fluid must not be allowed to soak into or penetratethe material to
35、be tested. A wet/dry vacuum or suitablealternative is used after completion of drilling or coring toremove loose materials and fluid from the access hole beforetesting. To minimize the extent of the disturbance from therotary hammer, drilling should not be taken completely throughthe bound layer, bu
36、t stopped short by about 10 to 20 mm 0.4to 0.8 in. The DCP is then used to penetrate the bottomportion of the bound layer. This can be a repetitive processbetween drilling and doing DCP tests to determine the thick-ness of the layer.6.3.3 Testing Pavement With Thin SealsFor pavementswith thin seals,
37、 the tip is advanced through the seal until thezero point (see Fig. 4) of the tip is flush with the top of the layerto be tested.6.3.4 Once the layer to be tested has been reached, areference reading is taken with the zero point at the top of thatlayer and the thickness of the layer(s) cored through
38、 recorded.This reference reading is the point from which the subsequentpenetration is measured.6.4 Testing Sequence:6.4.1 Dropping the HammerThe DCP device is held in avertical or plumb position. The operator raises the hammeruntil it makes only light contact with the handle. The hammershall not imp
39、act the handle when being raised. The hammer isthen allowed to free-fall and impact the anvil coupler assembly.The number of blows and corresponding penetrations arerecorded as described in 6.5.6.4.2 Depth of PenetrationThe depth of penetration willvary with application. For typical highway applicat
40、ions, apenetration less than 900 mm 35 in. will generally beadequate.6.4.3 RefusalThe presence of large aggregates or rockstrata will either stop further penetration or deflect the driverod. If after 5 blows, the device has not advanced more than 2mm 0.08 in. or the handle has deflected more than 75
41、 mm 3in. from the vertical position, the test shall be stopped, and thedevice moved to another test location. The new test locationshould be a minimum of 300 mm 12 in. from the priorlocation to minimize test error caused by disturbance of thematerial.6.4.4 ExtractionFollowing completion of the test,
42、 thedevice should be extracted using the extraction jack whenusing a replaceable point tip. When using a disposable cone,the device is extracted by driving the hammer upward againstthe handle.6.5 Data Recording:6.5.1 A form like the one shown in Table 1 is suggested fordata recording. The recorder e
43、nters the header informationbefore the test. The actual test data are recorded in column 1(Number of Blows) and column 2 (Cumulative Penetration inFIG. 3 Disposable Cone TipD6951/D6951M 09 (2015)3mm); if the moisture content is available, it is entered incolumn 8. When testing a subsurface layer tho
44、ugh a drilled orcored access hole, the first reading corresponds to the refer-enced reading at the top of the layer to be tested as per 6.3.2.The number of blows between readings may be varied depend-ing on the resistance of the material. Normally readings will betaken after a fixed number of blows,
45、 that is, 1 blow for softmaterial, 5 blows for “normal” materials and 10 blows for veryresistive materials. The penetration to the nearest 1 mm 0.04in. corresponding to a specific number of blows is recorded. Areading is taken immediately when the material properties orpenetration rate change signif
46、icantly.7. Calculations and Interpretation of Results7.1 The estimated in situ CBR is computed using the DCPindex (column 6, Table 1) and Table 2 for each set of readings.The penetration per blow may then be plotted against scalereading or total depth. The penetration per blow is then used toestimat
47、e in situ CBR or shear strength using the appropriatecorrelation. For example, the correlation of penetration perblow (DCP) in Table 2 is derived from the following equationrecommended by the US Army Corps of Engineers:3CBR 5 292/DCP1.12for DCP in mm/blow (1)CBR 5 292/DCP 325.4!1.12for DCP in in./bl
48、ow (2)The above equation is used for all soils except for CL soilsbelow CBR 10 and CH soils. For these soils, the followingequations are recommended by the US Army Corps of Engi-neers:4CBR 5 1/0.017019 3DCP!2for DCP in mm/blow (3)CBR 5 1/0.432283 3DCP!2for DCP in in./blow (4)for CL soils with CBR 32
49、4 0.5AFor DCP Index in units of in./blow, divide by 25.4.D6951/D6951M 09 (2015)510. Keywords10.1 ADCP; aggregate base testing; California bearing ra-tio; CBR; DCP; disposable cones; dual-mass hammer; dynamiccone penetrometer; in situ testing; paving material testing;shear strength; subgrade testingBIBLIOGRAPHY(1) Ayers, M. E., “Rapid Shear Strength of In Situ Granualr MaterialsUtilizing the Dynamic Cone Penetrometer,” Ph.D. Theses, Univer-sity of Illinois, Urbana, IL, 1990.(2)
