1、Designation: D 4647 06Standard Test Method forIdentification and Classification of Dispersive Clay Soils bythe Pinhole Test1This standard is issued under the fixed designation D 4647; 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. Scope*1.1 This test method presents a direct, qualitative measure-ment of the dispersibility and consequent collo
3、idal erodibilityof clay soils by causing water to flow through a small holepunched in a specimen. This test method is complemented byTest Method D 4221.1.2 This test method and the criteria for evaluating test dataare based upon results of several hundred tests on samplescollected from embankments,
4、channels, and other areas whereclay soils have eroded or resisted erosion in nature (1).21.3 Three alternative procedures for classifying the dispers-ibility of clay soils are provided as follows:1.3.1 Method A and Method C, adapted from Ref (1),classify soils into six categories of dispersiveness a
5、s: dispers-ibility (D1, D2), slight to moderately dispersive (ND4, ND3),and nondispersive (ND2, ND1).1.3.2 Method B classifies soils into three categories ofdispersiveness as: dispersibility (D), slightly dispersive (SD),and nondispersive (ND).1.4 The values stated in SI units are to be regarded as
6、thestandard. The values given in parentheses are provided forinformation only.1.5 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 deter
7、mine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D 422 Test Method for Particle-Size Analysis of SoilsD 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 698 Test Methods for Laboratory Compaction Character-istics of Soil Using Stan
8、dard Effort (12,400 ft-lbf/ft3(600kN-m/m3)D 1193 Specification for Reagent WaterD 2216 Test Methods for Laboratory Determination of Wa-ter (Moisture) Content of Soil and Rock by MassD 2487 Practice for Classification of Soils for EngineeringPurposes (Unified Soil Classification System)D 2488 Practic
9、e for Description and Identification of Soils(Visual-Manual Procedure)D 3740 Practice for Minimum Requirements for AgenciesEngaged in the Testing and/or Inspection of Soil and Rockas Used in Engineering Design and ConstructionD 4221 Test Method for Dispersive Characteristics of ClaySoil by Double Hy
10、drometerD 4318 Test Methods for Liquid Limit, Plastic Limit, andPlasticity Index of SoilsD 4753 Guide for Evaluating, Selecting, and SpecifyingBalances and Standard Masses for Use in Soil, Rock, andConstruction Materials TestingD 6026 Practice for Using Significant Digits in Geotechni-cal Data3. Ter
11、minology3.1 Definitions:3.1.1 For definitions of terms in this test method, refer toTerminology D 653.3.2 Definitions of Terms Specific to This Standard:3.2.1 dispersive claysclays that diaggregate easily andrapidly in water of low-salt concentration, and without signifi-cant mechanical assistance.
12、Such clays usually have a highproportion of their adsorptive capacity saturated with sodiumcations.3.2.1.1 DiscussionSuch clays generally have a highshrink-swell potential, have low resistance to erosion, and havelow permeability in an intact state.1This test method is under the jurisdiction ofASTM
13、Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.06 on Physical-ChemicalInteractions of Soil and Rock.Current edition approved Nov. 1, 2006. Published December 2006. Originallyapproved in 1987. Last previous edition approved in 1998 as D 4647 93(2006).2The boldface
14、numbers in parentheses refer to the list of references at the end ofthis test method.3For 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 Document Summary
15、page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4. Summary of Test Method4.1 The test method is started with distilled water flowinghorizontall
16、y under a hydraulic head of 50 mm (2 in.) througha 1.0-mm (0.04-in.) diameter hole punched in the soil speci-men. The nature of the solution emerging from the specimenunder the intial 50-mm (2-in.) head provides the principledifferentiation between dispersive and nondispersive clays.Flow from disper
17、sive clays will be distinctly dark and the holethrough the specimen will enlarge rapidly, with a resultantincrease in the flow rate. Flow from slightly to moderatelydispersive clays will be slightly dark with a constant hole sizeand flow rate. Flow from nondispersive clays will be com-pletely clear
18、with no measurable increase in the hole size.4.2 Test results are evaluated from the appearance of theflowing solution emerging from the specimen, the rate of flow,and the final size of the hole through the specimen. Theseobservations provide the basis for classifying the soil speci-men.5. Significa
19、nce and Use5.1 The pinhole test provides one method of identifying thedispersive characteristics of clay soils that are to be or havebeen used in earth construction. The piping failures of anumber of homogeneous earth dams, erosion along channel orcanal banks, and rainfall erosion of earthen structu
20、res havebeen attributed to the colloidal erosion along cracks or otherflow channels formed in masses of dispersive clay (2).5.2 This test method models the action of water flowingalong a crack in an earth embankment. Other indirect tests,such as the double hydrometer test (Test Method D 4221), thecr
21、umb test (3, 4), that relates the turbidity of a cloud ofsuspended clay colloids as an indicator of the clay dispersivity,and chemical tests that relate the percentage of sodium to totalsoluble salt content of the soil are also used as indicator testsof clay dispersibility (2). The comparison of res
22、ults from thepinhole test and other indirect tests on hundreds of samplesindicates that the results of the pinhole test have the bestcorrelation with the erosional performance of clay soils innature.5.3 Method A and Method C of the pinhole test require theevaluation of cloudiness of effluent, final
23、size of the pinhole,and computation of flow rates through the pinhole in order toclassify the dispersive characteristics of the soil. Method Brequires only the evaluation of the cloudiness of effluent andfinal size of the pinhole to classify the dispersive characteristicsof the soil. The computation
24、 of flow rates through the pinholein Method A serves primarily as a guide to the properequipment and specimen performance under sequential pres-sures applied during the test. All methods produce similarresults and any method can be used to identify dispersive clays.5.4 The use of Method A or Method
25、C results in theaccumulation of data relative to sequential flow rates throughthe pinhole and consequent enlargement or erosion of the hole.The pinhole erosion test was developed for the purpose ofidentifying dispersive soils and is not intended to be ageometrically scaled model of a prototype struc
26、ture. Since thetheory of similitude was not used in the design of the pinholetest, quantitative data are not obtained. The quantity of flowthrough the pinhole, amount of soil erosion, or the rate of soilerosion should not be extrapolated to actual field conditions(3). However, such data may be usefu
27、l in performing qualita-tive evaluations of the consequences of such erosion in termsof dam failure, loss of life and property. They also may be usedin considering the cost effectiveness of defensive designmeasures necessary to minimize the effects of failure due todispersive clays. For example, the
28、 amount of colloidal erosionthat will occur in a soil classed as ND2 (very slightlydispersive) will be very small for a relatively long period oftime. Such erosion may not be significant in evaluating thecost-benefit relationships in projects where public safety is notinvolved or where normal mainte
29、nance procedures will handlethe problem. In such cases, classifying the soil as ND (nondis-persive) using Method B of the pinhole test should beadequate.5.5 Pinhole tests that result in classifying soil as slightlydispersive (ND3 by Method A or Method C or SD by MethodB) indicate high uncertainty ab
30、out the existence of significantproblems to be considered in the design or stability of astructure. In such cases, it is advisable to resample and test anumber of other soils from the same area to generate anadequate statistical sample for problem evaluation. The origi-nal slightly dispersive sample
31、 may come from an area on theedge of a more highly dispersive soil.5.6 In a few physiographic areas or geoclimatic conditions,or both, neither the pinhole test nor the other indicator testsprovide consistent identification of dispersive clays (5, 6, 7).Insuch cases, the results of the tests (8, 9) s
32、hould be evaluated interms of cost effectiveness and design judgment (7).5.7 For some projects, it may be desirable to perform thepinhole test using eroding fluids other than distilled water (8,10). In such cases, Method A, Method B, or Method C may beused to identify the dispersive characteristics
33、of the soil andcompare the results with those obtained using distilled water.NOTE 1Notwithstanding the statement on precision and bias con-tained in this test method: The precision of this test method is dependenton the competence of the personnel performing it, and the suitability of theequipment a
34、nd facilities used.Agencies which meet the criteria of PracticeD 3740 are generally considered capable of competent and objectivetesting. Users of this test method are cautioned that compliance withPractice D 3740 does not in itself assure reliable testing. Reliable testingdepends on several factors
35、; Practice D 3740 provides a means of evalu-ating some of those factors.6. Limitations6.1 Development of the test procedure to provide reproduc-ible results that differentiate between clay soils that wereknown to be erodible (dispersive) and nonerodible (nondisper-sive) in the field indicates the fo
36、llowing limitations in the useof this test:6.1.1 This test method is not applicable to soils with lessthan 12 % fraction finer than 0.005 mm and with a plasticityindex less than or equal to 4 (2, 11). Such soils generally havelow resistance to erosion regardless of dispersive characteris-tics.6.1.2
37、The most consistent results are produced when thenatural water content of the sample is preserved during thesampling, shipping, storage, and testing operations.D 4647 0626.1.3 A few instances have been reported in which thepinhole test did not identify some dispersive clays in which thepore water co
38、ntained less than 0.4 meq/L total soluble salts thatwere more than 80 % sodium salts.6.1.4 This test method was developed to test specimens ofdisturbed soil that are compacted into the test cylinder. This testmethod can also be used to test undisturbed specimens whenthey are properly trimmed and sea
39、led into the test cylinder;however, some investigators (6) have found that this testmethod is not applicable in evaluating the dispersive charac-teristics of undisturbed specimens of highly sensitive clays.Such clays may be classed as dispersive from the pinhole testresults but perform as nondispers
40、ive materials in nature.6.1.5 This test method is performed with distilled water, ata pH of 5.5 to 7.0, as the eroding fluid. The use of water withvarious ionic concentrations and combinations will alter theresults of the test (8, 10).7. Classification7.1 The observations of this test method provide
41、 the basisfor classifying the soil specimen into a category of dispersive-ness according to the following general criteria:7.1.1 Method A:D1, D2Dispersive clays that fail rapidly under 50-mm(2-in.) head.ND4, ND3Slightly to moderately dispersive clays thaterode slowly under 50-mm (2-in.) or 180-mm (7
42、-in.) head.ND2, ND1Nondispersive clay with very slight to nocolloidal erosion under 380-mm (15-in.) or 1020-mm (40-in.)head.7.1.2 Method B:DDispersive clays that erode rapidly under 50-mm (2-in.)head.SDSlightly dispersive clays that erode slowly under180-mm (7-in.) head.NDNondispersive clays that sh
43、ow very slight or nocolloidal erosion under 380-mm (15-in.) head.NOTE 2Method B for classifying dispersiveness of clay soils com-bines the categories of Method A as follows: D = D1, D2, ND4;SD = ND3; and ND = ND2, ND1.7.1.3 Method C:D1, D2Dispersive clays that fail rapidly under 50-mm(2-in.) head.ND
44、4, ND3Dispersive clays that erode slowly under50-mm (2-in.), 180-mm (7-in.), or 380-mm (15-in.) head.ND2, ND1Nondispersive clay with very slight to nocolloidal erosion under 380-mm (15-in.) head.8. Apparatus8.1 Pinhole Test ApparatusTypical pinhole test apparatusis shown in Fig. 1, Fig. 2, and Fig.
45、3. Various other types andsizes of specimen molds or containers and top and base platesmay be used provided the test specimen is 38 mm (1.5 in.)long, the pinhole is 1.0 mm (0.04 in.) in diameter, and the holethrough the truncated cone centering guide or other centeringdevice is 1.5 mm (0.059 in.) in
46、 diameter.8.1.1 It is important that the outlet drain be large enough toaccommodate the maximum inflow without creating a partialvacuum in the system. Partial vacuum may develop when smalldiameter outlet drains flow at full capacity and when longsegments of flexible tubing are attached to the outflo
47、w pipe.8.1.2 The development of partial vacuum in the systemproduces hydraulic heads greater than those specified for thetest in Section 10 and following.8.1.3 The installation of a 1.6-mm (116-in.) to 3-mm (18-in.)diameter breather hole in the center of the base plate, as shownin Fig. 1, generally
48、assures discharge from the system atatmospheric pressure without partial vacuum.8.2 Constant Head Tank, to supply distilled water with a pHof 5.5 to 7.0.8.3 Graduated Cylinders, of 10, 25, 50, and 100-mL capac-ity.8.4 Wire Screen, with holes smaller than 2 mm (0.08 in.),cut in circular shape to fit
49、inside the specimen tube.FIG. 1 Schematic Drawing of the Pinhole Test EquipmentD 4647 0638.5 Wire Punch, 1.0 mm (0.039 in.) in diameter by 50 to75-mm (2.5 to 3-in.) punch. (No. 19 veterinarian hypodermicneedle or 1-mm drill bit or stiff wire length.)8.6 Centering GuideTruncated cone centering guide with1.5-mm (0.059-in.) diameter hole (plastic, brass, steel, or othersuitable material).8.7 Coarse Sand, that has been washed and sieved throughNo. 10 to14-in. sieves (2 to 6 mm in diameter).8.8 Stop Watch, reading to 0.1 s.8.9 Manometer, pressure transducer, standpipe
