1、Designation: D6128 16Standard Test Method forShear Testing of Bulk Solids Using the Jenike Shear Tester1This standard is issued under the fixed designation D6128; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last rev
2、ision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This method2covers the apparatus and procedures formeasuring the cohesive strength of bulk solids during bothcontinuous flow
3、and after storage at rest. In addition, measure-ments of internal friction, bulk density, and wall friction onvarious wall surfaces are included.1.2 This standard is not applicable to testing bulk solids thatdo not reach the steady state requirement within the travel limitof the shear cell. It is di
4、fficult to classify ahead of time whichbulk solids cannot be tested, but one example may be thoseconsisting of highly elastic particles.1.3 The most common use of this information is in thedesign of storage bins and hoppers to prevent flow stoppagesdue to arching and ratholing, including the slope a
5、nd smooth-ness of hopper walls to provide mass flow. Parameters forstructural design of such equipment also may be derived fromthis data.1.4 All observed and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D6026.1.4.1 The procedures used to
6、 specify how data are collected/recorded or calculated, in this standard are regarded as theindustry standard. In addition, they are representative of thesignificant digits that generally should be retained. The proce-dures used do not consider material variation, purpose forobtaining the data, spec
7、ial purpose studies, or any consider-ations for the users objectives; and it is common practice toincrease or reduce significant digits of reported data to becommensurate with these considerations. It is beyond the scopeof this standard to consider significant digits used in analysismethods for engi
8、neering design.1.5 UnitsThe values stated in SI units are to be regardedas standard. No other units of measure are included in thisstandard1.6 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
9、 establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D653 Terminology Relating to Soil, Rock, and ContainedFluidsD2216 Test Methods for Laboratory Determination of Water(Moisture) Conten
10、t of Soil and Rock by MassD3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD4753 Guide for Evaluating, Selecting, and Specifying Bal-ances and Standard Masses for Use in Soil, Rock, andConstruction
11、Materials TestingD6026 Practice for Using Significant Digits in GeotechnicalData3. Terminology3.1 DefinitionsFor common definitions of technical termsin this standard, refer to Terminology D653.4. Summary of Test Method4.1 A representative specimen of bulk solid is placed in ashear cell of specific
12、dimensions. This specimen is preconsoli-dated by twisting the shear cell cover while applying acompressive load normal to the cover.4.2 When running an instantaneous or time shear test, anormal load is applied to the cover, and the specimen ispresheared until a steady state shear value has been reac
13、hed.4.3 An instantaneous test is run by shearing the specimenunder a reduced normal load until the shear force goes througha maximum value and then begins to decrease.1This testing method is under the jurisdiction of ASTM Committee D18 on Soiland Rock and is the direct responsibility of Subcommittee
14、 D18.24 on Character-ization and Handling of Powders and Bulk Solids.Current edition approved Feb. 1, 2016. Published March 2016. Originallyapproved in 1997. Last previous edition approved in 2014 as D6128 14. DOI:10.1520/D6128-14.2This test method is based on the “Standard Shear Testing Technique f
15、orParticulate Solids Using the Jenike Shear Cell,” a report of the EFCE Working Partyon the Mechanics of Particulate Solids. Copyright is held by the Institution ofChemical Engineers and the European Federation of Chemical Engineering.3For referenced ASTM standards, visit the ASTM website, www.astm.
16、org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C
17、700, West Conshohocken, PA 19428-2959. United States14.4 A time shear test is run similarly to an instantaneousshear test, except that the specimen is placed in a consolidationbench between preshear and shear.4.5 A wall friction test is run by sliding the specimen overa coupon of wall material and m
18、easuring the frictional resis-tance as a function of normal, compressive load.4.6 A wall friction time test involves sliding the specimenover the coupon of wall material, leaving the load on thespecimen for a predetermined period of time, then sliding itagain to see if the shearing force has increas
19、ed.5. Significance and Use5.1 Reliable, controlled flow of bulk solids from bins andhoppers is essential in almost every industrial facility.Unfortunately, flow stoppages due to arching and ratholing arecommon. Additional problems include uncontrolled flow(flooding) of powders, segregation of partic
20、le mixtures, useablecapacity which is significantly less than design capacity, cakingand spoilage of bulk solids in stagnant zones, and structuralfailures.5.2 By measuring the flow properties of bulk solids, anddesigning bins and hoppers based on these flow properties,most flow problems can be preve
21、nted or eliminated.5.3 For bulk solids with a significant percentage of particles(typically, one third or more) finer than about 6 mm, thecohesive strength is governed by the fines (-6-mm fraction).For such bulk solids, cohesive strength and wall friction testsmay be performed on the fine fraction o
22、nly.NOTE 1The quality of the result produced by this test method isdependent on the competence of the personnel performing it, and thesuitability of the equipment and facilities used. Agencies that meet thecriteria of Practice D3740 are generally considered capable of competentand objective testing/
23、sampling/inspection/etc. Users of this test methodare cautioned that compliance with Practice D3740 does not in itselfassure reliable results. Reliable results depend on many factors; PracticeD3740 provides a means of evaluating some of those factors. PracticeD3740 was developed for agencies engaged
24、 in the testing and/or inspec-tion of soil and rock. As such it is not totally applicable to agenciesperforming this test method. However, users of this test method shouldrecognize that the framework of Practice D3740 is appropriate forevaluating the quality of an agency performing this test method.
25、 Currentlythere is no known qualifying national authority that inspects agencies thatperform this test method.6. Apparatus6.1 The Jenike shear cell is shown in Fig. 1. It consists of abase (1), shear ring (2), and shear lid (3), the latter having abracket (4) and pin (5). Before shear, the ring is p
26、laced in anoffset position as shown in Fig. 1, and a vertical force Fvisapplied to the lid, and hence, to the particulate solid within thecell by means of a weight hanger (6) and weights (7). Ahorizontal force is applied to the bracket by a mechanicallydriven measuring stem (8).6.2 It is especially
27、important that the shear force-measuringstem acts on the bracket in the shear plane (plane between baseand shear ring) and not above or below this plane.6.3 The dimensions of the Jenike shear cells that have in thepast been supplied by Jenike thus, for thepurpose of this test method, they are ignore
28、d.(2) Points to the left of Point A are ignored because theyrepresent a state where tensile stresses can occur in the shearcell. This can be seen by considering the yield point on Fig. 11marked by S(), below Point A. If a Mohr circle 3 is drawnthrough this point, which is tangential to the extrapola
29、ted yieldlocus, part of that circle will lie to the left of the originindicating negative normal stresses, that is, tensile stresses.4This method of constructing the steady state Mohr circle is specified by theEFCE and Jenike. Alternative methods of construction have been proposed. See forexample, P
30、eschl.FIG. 12 Yield Locus and Data PointsFIG. 13 End Point Above Fitted LineD6128 16119.1.3 Evaluate results separately for every chosen value ofthe preshear normal stress, although all points should be shownon one ,-diagram.9.1.4 Plot the preshear point, P, and all valid shear points forone given p
31、reshear normal stress level in ,-coordinates. Drawa smooth line through the valid points and extrapolate it to thepreshear normal stress. If this line passes above or throughPoint P, use it for further calculations. If it passes below PointP, plot a new line passing through Point P and fit it to all
32、 thevalid yield points.9.1.5 Draw a Mohr circle through the origin, tangential tothis smooth line, the instantaneous yield locus (YL in Fig. 15).NOTE 22The higher point of intersection of this Mohr circle with the-axis is the unconfined yield strength, fc. Calculate to three significantdigits.9.1.6
33、Draw a second Mohr circle through Point P, tangentialto the smooth line in such a way that the point of tangency isto the left of the preshear Point P.NOTE 23The upper point of intersection of this Mohr circle with thenormal stress axis is the major consolidation stress, 1. Calculate to threesignifi
34、cant digits. In this way, the pair of values, fcand 1, associated withthis particular yield locus are produced, these values all being associatedwith the major consolidation stress 1.NOTE 24The yield locus is normally found to show a small curvature,convex upwards.With many particulate solids, a str
35、aight line is a sufficientapproximation. If the yield locus is approximated as a straight line for allparticulate solids, then subsequent calculations are much simpler, but, insome cases, somewhat conservative results may be obtained, that is, ahigher fcvalue will be determined than when using a fit
36、ted curve.9.1.7 Determine to nearest 1 the angle of internal frictionof the particulate solid, i, at the major consolidation stress, 1,by measuring the angle between a yield locus and the -axis.9.1.7.1 Since this angle varies with when using a smoothline yield locus, its value should be read from th
37、e linearizedyield locus (LYL), which is the tangent to the two Mohr circlescharacterizing the major principal stresses 1and fc(Fig. 15).9.1.8 Draw a straight line through the origin, tangential tothe major principal stress Mohr circle. This line, which is theeffective yield locus (EYL), forms an ang
38、le with the axis,called the effective angle of friction. It should be determined toFIG. 14 End Points on Fitted LineFIG. 15 Mohr Circles, Angles of Friction and Yield LociD6128 1612nearest 1. For a given preshear normal stress and value of 1,determine a mean bulk density, bto four significant digits
39、.9.1.9 The preceding calculation produces values of fc, i, ,and bfor a given 1. By making measurements at severalpreshear normal stresses, the dependencies of fc, i, , and bon 1can be determined as shown in Fig. 16 ).9.1.10 Fit a smooth curve through the pairs of points (1,fc).See Fig. 16e). The 1an
40、d fccoordinates should be to the samescale. The dependency of fcon 1is called the Flow Function(FF) for instantaneous flow.NOTE 25The Flow Function usually has a slight curvature convexupwards.9.1.11 Fit a smooth curve through the points (1, )asshown in Fig. 16d. Also, plot in a similar way iand tas
41、shown in Fig. 16c and bas shown in Fig. 16a.NOTE 26For cohesive materials will decrease with increasing 1.9.2 Evaluation of Time Shear Test Data:9.2.1 Prorate the time shear stress values using the follow-ing equation:FIG. 16 Powder Properties as a Function of 1D6128 1613st5 st2FsSptp2 1DG(3)where:s
42、t= prorated time shear value of sts= prorated instantaneous shear value (Eq 2) for the sameshear normal stress,pt= preshear shear stress for the time test, andp= average of the instantaneous preshear shear stressvalues.9.2.2 Validity of Time Shear PointsPlot the time shearpoints in ,-coordinates (Fi
43、g. 17) and draw a straight linecalled the time yield locus, TYL, through the highest shearpoint and parallel to the instantaneous yield locus (for thatparticular preshear normal stress level). Draw a Mohr circlethrough the origin and tangential to this straight line.NOTE 27Those time shear points wh
44、ich lie to the right of this point oftangency Atof the Mohr circle to the straight line time yield locus areconsidered valid. The normal stress applied at shear for the highest timeyield point S3tis generally less than the normal stress applied at the endpoint, B, of the instantaneous yield locus.9.
45、2.3 Carry out evaluations separately for each preshearnormal stress level. Plot the valid time shear points for eachpreshear normal stress level in ,-coordinates (Fig. 18). Fit asmooth line through the points. This smooth line is called thetime yield locus.9.2.4 Draw a Mohr circle through the origin
46、 and tangentialto the time yield locus.9.2.4.1 The highest point of intersection of this Mohr circlewith the -axis is the time unconfined yield strength, fct.Calculate to three significant digits. This value, together withthe major consolidation stress for instantaneous flow, 1, foreach selected pre
47、shear normal stress gives the values 1, fctthatare used in plotting the time flow function, FFt.9.2.4.2 The angle between the time yield locus and the-axis is the time angle of internal friction, tfor that particular1(Fig. 18). It should be determined to nearest 1.9.2.5 Plot the time flow function,
48、FFt, by fitting a smoothcurve or a straight line to the pairs (1, fct) from each yieldlocus.9.3 Evaluation of Wall Friction Test Data:9.3.1 Plot the points wi, wion ,-coordinates and draw asmooth line through the points (Fig. 19).9.3.1.1 This is the wall yield locus (WYL) of the particulatesolid on
49、the specific wall material. The plot of the WYL will bea straight line or a curve convex upwards.9.3.2 If the wall yield locus is a straight line passing throughthe origin, then = constant. Otherwise, superimpose a steadystate flow Mohr circle associated with a yield locus and a majorconsolidation stress, 1,ontheWYL. Determine the upper pointof intersection of the WYL with the steady state flow Mohrcircle and draw a straight line through the origin and this pointof intersection. The angle tha
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