1、Designation: D 6128 06Standard Test Method forShear Testing of Bulk Solids Using the Jenike Shear Cell1This standard is issued under the fixed designation D 6128; 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 (e) 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 i
4、mpossible to classify ahead of timewhich bulk solids cannot be tested, but one example may bethose consisting of highly elastic particles.1.3 The values stated in SI units are to be regarded asstandard.1.4 The most common use of this information is in thedesign of storage bins and hoppers to prevent
5、 flow stoppagesdue to arching and ratholing, including the slope and smooth-ness of hopper walls to provide mass flow. Parameters forstructural design of such equipment also may be derived fromthis data.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with
6、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 Documents2.1 ASTM Standards:3D 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 3740 P
7、ractice for Minimum Requirements for AgenciesEngaged in the Testing and/or Inspection of Soil and Rockas Used in Engineering Design and Construction3. Terminology3.1 DefinitionsDefinitions of terms used in this testmethod are in accordance with Terminology D 653.3.1.1 adhesion test, na static wall f
8、riction test with timeconsolidation.3.1.2 angle of internal friction, fi, nthe angle between theaxis of normal stress (abscissa) and the tangent to the yieldlocus.3.1.3 angle of wall friction, f8, n the arctan of the ratio ofthe wall shear stress to the wall normal stress.3.1.4 bin, na container or
9、vessel for holding a bulk solid,frequently consisting of a vertical cylinder with a converginghopper. Sometimes referred to as silo, bunker, or elevator.3.1.5 bulk density, rb, nthe mass of a quantity of a bulksolid divided by its total volume3.1.6 bulk solid, nan assembly of solid particles handled
10、in sufficient quantities that its characteristics can be describedby the properties of the mass of particles rather than thecharacteristics of each individual particle. May also be referredto as granular material, particulate solid, or powder. Examplesare sugar, flour, ore, and coal.3.1.7 bunker, ns
11、ynonym for bin, but sometimes under-stood as being a bin without any or only a small vertical partat the top of the hopper.3.1.8 cohesive strength, nsynonym for unconfined yieldstrength.3.1.9 consolidation, nthe process of increasing thestrength of a bulk solid.3.1.10 critical state, na state of str
12、ess in which the bulkdensity of a bulk solid and the shear stress in the shear zoneremain constant.3.1.11 effective angle of friction, d, nthe inclination of theeffective yield locus (EYL).3.1.12 effective yield locus (EYL), nstraight line passingthrough the origin of the s, t-plane and tangential t
13、o the steadystate Mohr circle, corresponding to steady state flow conditionsof a bulk solid of given bulk density.3.1.13 elevator, nsynonym for bin, commonly used in thegrain industry.3.1.14 failure (of a bulk solid), nplastic deformation of anoverconsolidated bulk solid subject to shear, causing di
14、lationand a decrease in strength.1This testing method is under the jurisdiction of ASTM Committee D18 on Soiland Rock and is the direct responsibility of Subcommittee D18.24 on Character-ization and Handling of Powders and Bulk Solids.Current edition approved Dec. 1, 2006. Published January 2007. Or
15、iginallyapproved in 1997. Last previous edition approved in 2000 as D 6128 00.2This test method is based on the “Standard Shear Testing Technique forParticulate Solids Using the Jenike Shear Cell,” a report of the EFCE Working Partyon the Mechanics of Particulate Solids. Copyright is held by the Ins
16、titution ofChemical Engineers and the European Federation of Chemical Engineering.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 pag
17、e 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.3.1.15 flow, steady state, ncontinuous plastic deformationof a bulk solid at critical state.3.1.16
18、 flow function, FF, nthe plot of unconfined yieldstrength versus major consolidation stress for one specific bulksolid.3.1.17 granular material, nsynonym for bulk solid.3.1.18 hopper, nthe converging portion of a bin.3.1.19 major consolidation stress, s1, nthe major princi-pal stress given by the Mo
19、hr stress circle of steady state flow.This Mohr stress circle is tangential to the effective yield locus.3.1.20 Mohr stress circle, nthe graphical representation ofa state of stress in coordinates of normal and shear stress, thatis, in the s,t-plane.3.1.21 normal stress, s, nthe stress acting normal
20、ly to theconsidered plane.3.1.22 overconsolidated specimen, na condition in whichthe shear force passes through a maximum and then decreasesduring preshear.3.1.23 particulate solid, nsynonym for bulk solid.3.1.24 powder, nsynonym for bulk solid, particularlywhen the particles of the bulk solid are f
21、ine.3.1.25 silo, nsynonym for bin.3.1.26 shear test, nan experiment to determine the flowproperties of a bulk solid by applying different states of stressand strain to it.3.1.27 shear tester, nan apparatus for performing sheartests.3.1.28 time angle of internal friction, ft, ninclination ofthe time
22、yield locus of the tangency point with the Mohr stresscircle passing through the origin.3.1.29 time yield locus, nthe yield locus of a bulk solidwhich has remained at rest under a given normal stress for acertain time.3.1.30 unconfined yield strength, fc, n the major principalstress of the Mohr stre
23、ss circle being tangential to the yieldlocus with the minor principal stress being zero.Asynonym forcompressive strength.3.1.31 underconsolidated specimen, na condition inwhich the shear force increases continually during preshear.3.1.32 wall normal stress, sw, n the normal stress presentat a confin
24、ing wall.3.1.33 wall shear stress, tw, nthe shear stress present at aconfining wall.3.1.34 wall yield locus, na plot of the wall shear stressversus wall normal stress. The angle of wall friction is obtainedfrom the wall yield locus as the arctan of the ratio of the wallshear stress to wall normal st
25、ress.3.1.35 yield locus, nplot of shear stress versus normalstress at failure. The yield locus (YL) is sometimes called theinstantaneous yield locus to differentiate it from the time yieldlocus.4. Summary of Test Method4.1 Arepresentative sample of bulk solid is placed in a shearcell of specific dim
26、ensions. This specimen is preconsolidatedby twisting the shear cell cover while applying a compressiveload 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 reached.4
27、.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.4.4 A time shear test is run similarly to an instantaneousshear test, except that the specimen is placed in a consolidationbench between p
28、reshear and shear.4.5 A wall friction test is run by sliding the specimen overa coupon of wall material and measuring 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
29、thespecimen for a predetermined period of time, then sliding itagain to see if the shearing force has increased.5. Significance and Use5.1 Reliable, controlled flow of bulk solids from bins andhoppers is essential in almost every industrial facility. Unfor-tunately, flow stoppages due to arching and
30、 ratholing arecommon. Additional problems include uncontrolled flow(flooding) of powders, segregation of particle 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 properti
31、es of bulk solids, anddesigning bins and hoppers based on these flow properties,most flow problems can be prevented or eliminated.5.3 For bulk solids with a significant percentage of particles(typically, one third or more) finer than about 6 mm (14 in.), thecohesive strength is governed by the fines
32、 (-6-mm fraction).For such bulk solids, cohesive strength and wall friction testsmay be performed on the fine fraction only.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 us
33、ed. Agencies that meet thecriteria of Practice D 3740 are generally considered capable of competentand objective testing/sampling/inspection/etc. Users of this test methodare cautioned that compliance with Practice D 3740 does not in itselfassure reliable results. Reliable results depend on many fac
34、tors; PracticeD 3740 provides a means of evaluating some of those factors. PracticeD 3740 was developed for agencies engaged in the testing and/orinspection of soil and rock. As such it is not totally applicable to agenciesperforming this test method. However, users of this test method shouldrecogni
35、ze that the framework of Practice D 3740 is appropriate forevaluating the quality of an agency performing this test method. 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 consis
36、ts of abase (1), shear ring (2), and shear lid (3), the latter having abracket (4) and pin (5). Before shear, the ring is placed 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) an
37、d weights (7). Ahorizontal force is applied to the bracket by a mechanicallydriven measuring stem (8).D61280626.2 It is especially 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 dimensio
38、ns of the Jenike shear cells supplied byJenike thus, for the purpose of this testmethod, they are ignored.NOTE 19Points to the left of Point A are ignored because theyrepresent a state where tensile stresses can occur in the shear cell. This canbe seen by considering the yield point on Fig. 14 marke
39、d by S(), belowPoint A. If a Mohr circle 3 is drawn through this point, which is tangentialto the extrapolated yield locus, part of that circle will lie to the left of theorigin indicating negative normal stresses, that is, tensile stresses.8.2 Shear Testing Procedure for Time Consolidation:8.2.1 Wh
40、en a particulate solid is exposed to a normal orcompressive stress for some time it may gain strength. Thisgain in strength may be measured in the Jenike shear cell, andthe effect is called time consolidation.8.2.2 Time consolidation is carried out using a consolidatingbench, which consists of sever
41、al shear cells that can be loadedindependently. The time that the specimens sit at rest isspecified according to the application.NOTE 20As an alternative to using a consolidation bench, considerthe following: a critically consolidated specimen is prepared by preshear-ing with weight mWp. After attai
42、ning steady state flow the advance of theforce measuring stem is stopped but the stem is not retracted. The shearzone formed thus remains under the normal and shear stresses correspond-ing to steady state flow and is kept in this state for a definite time, t.Ifthestem is then retracted, the shear fo
43、rce will drop to zero, and the actualshear test may be performed in the usual way. It is found that withmaterials which gain strength during time consolidation, a higher shearstrength will be measured. In a s,t-diagram, the time yield locus for timeconsolidation will lie above the instantaneous flow
44、 yield locus. If theeffect of time consolidation in the Jenike shear cell were measured in thismanner, one test would monopolize the shear cell for a very long time.Also, creep of the specimen could cause a decrease in the applied shear4This method of constructing the steady state Mohr circle is spe
45、cified by theEFCE and Jenike. Alternative methods of construction have been proposed. See forexample, Peschl.FIG. 11 Yield Locus and Data PointsD6128069force during the resting phase.8.2.3 Specimen preparation and preshear time effectsAfter completion of instantaneous testing and evaluation,perform
46、time tests at the same preshear normal stress levels.NOTE 21For a selected preshear normal stress, specimen preparationand preshear are the same as for the instantaneous test.8.2.4 Time Consolidation:8.2.4.1 Perform the test for time consolidation in the fol-lowing way. Using the shear tester, prepa
47、re and preshearsamples with weight mWpin the normal manner and then retractFIG. 12 End Point Above Fitted LineFIG. 13 End Points on Fitted LineFIG. 14 Yield Locus Showing Valid Shear PointsD61280610the stem after preshear. Remove the hanger with weights. Thentransfer the shear cells (base, shear rin
48、g, shear lid, andmaterial) to the consolidating bench. In order to prevent theevaporation or take up of moisture from the ambient environ-ment, place a flexible cover over each cell, and then load eachby placing a weight mWteither directly on the lid or by meansof a loading rod.NOTE 22When the shear
49、 cell is transferred from the shear tester to theconsolidating bench, care should be taken that the ring is not movedrelative to the base.As the weight carrier is lowered on the shear lid, greatcare must be taken in adjusting the position of the shear cell on theconsolidation bench to ensure that the weight carrier acts centrally on theshear lid or on a similarly sized compression plate when the weight carrieris lowered.8.2.4.2 Select the weight mWtin such a way that the stressstate in the specimen during time consolidation is the same asd
