1、Designation: D 6528 00Standard Test Method forConsolidated Undrained Direct Simple Shear Testing ofCohesive Soils1This standard is issued under the fixed designation D 6528; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、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 defines equipment specifications andtesting procedures for the measurement of constant volumestre
3、ngth and stress-strain characteristics of cohesive soils afterone-dimensional consolidation using a constant rate of simpleshear deformation mode of loading. The constant volumecondition is equivalent to the undrained condition for saturatedspecimens.1.2 This test method is written specifically for
4、devices thattest rectangular parallelepiped or cylindrical specimens. Othermore general devices, such as the torsional shear hollowcylinder, may be used to perform consolidated constant volumesimple shear tests but are beyond the scope of this test method.1.3 This test method is applicable to testin
5、g both undis-turbed and compacted soils, however, it does not includespecific guidance for compacting test specimens.1.4 It shall be the responsibility of the agency requestingthis test to specify the magnitude of the normal consolidationstress prior to constant volume shear and, when appropriate,th
6、e maximum normal consolidation stress, which will result inan overconsolidated specimen.1.5 The values stated in SI units are to be regarded as thestandard. Reporting test results in units other than SI shall beregarded as conformance with this test method.1.5.1 In the engineering profession it is c
7、ustomary practiceto use, interchangeably, units representing both mass and force,unless dynamic calculations (F=Ma) are involved. This implic-itly combines two separate systems of units, that is, theabsolute system and the gravimetric system. It is scientificallyundesirable to combine two separate s
8、ystems within a singlestandard. This test method has been written using SI units;however, inch-pound conversions are given in the gravimetricsystem, where the pound (lbf) represents a unit of force(weight). The use of balances or scales recording pounds ofmass (lbm), or the recording of density in l
9、b/ft3should not beregarded as nonconformance with this standard.1.6 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 establish appro-priate safety and health practices and determine the appli
10、ca-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:D 422 Test Method for Particle-Size Analysis of Soils2D 653 Terminology Relating to Soil, Rock and ContainedFluids2D 854 Test Method for Specific Gravity of Soils2D 1587 Practice for Thin-Walled Tube Geotechni
11、cal Sam-pling of Soils2D 2216 Test Method for Laboratory Determination of Water(Moisture) Content of Soil and Rock2D 2435 Test Method for One-Dimensional ConsolidationProperties of Soils2D 2487 Classification of Soils for Engineering Purposes(Unified Soil Classification System)2D 2488 Practice for D
12、escription and Identification of Soils(Visual-Manual Procedure)2D 3550 Practice for Ring-Lined Barrel Sampling of Soils2D 3740 Practice for Minimum Requirements for AgenciesEngaged in the Testing and/or Inspection of Soil an Rockas Used in Engineering Design and Construction2D 4220 Practices for Pre
13、serving and Transporting SoilSamples2D 4318 Test Method for Liquid Limit, Plastic Limit, andPlasticity Index of Soils2D 4452 Methods for X-Ray Radiography of Soil Samples23. Terminology3.1 DefinitionsThe terms used in this test method are inaccordance with Terminology D 653.3.1.1 shear modulus, na m
14、easure of a materials resis-tance to shear stress, equal to the ratio of the increment in theshear stress to the resultant increment in angle of deformationexpressed in radians. Also known as the modulus of rigidity.3.2 Definitions of Terms Specific to This Standard:3.2.1 active height control, na m
15、ethod of keeping theheight of the specimen constant during the shearing process in1This test method is under the jurisdiction of ASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.05 on StructuralProperties of Soils.Current edition approved Feb. 10, 2000. Publish
16、ed May 2000.2Annual Book of ASTM Standards, Vol 04.08.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.which the displacement control mechanism is physically ad-justed in response to the axial displacement measurement.3.2.2 passive he
17、ight control, na method of keeping theheight of the specimen constant during the shearing process inwhich the specimen and force measuring device are clampedby a mechanism that is much stiffer than the specimen.4. Summary of Test Method4.1 In this test method a specimen of cohesive soil isconstraine
18、d axially between two parallel, rigid platens andlaterally, such that the cross sectional area remains constant.4.2 The specimen is loaded axially and allowed to consoli-date one-dimensionally. Each normal load increment is main-tained until excess pore water pressures are essentially dissi-pated as
19、 interpreted from the axial displacement rate. Themaximum normal load is maintained until completion of onecycle of secondary compression or one day longer than the endof excess pore water pressure dissipation.4.3 The specimen is sheared by displacing one platentangentially relative to the other at
20、a constant rate of displace-ment and measuring the resulting shear force. The platens areconstrained against rotation and axial movement throughoutshear.4.4 The specimen volume is held constant during shear tosimulate undrained conditions. Constant volume is achieved bychanging the normal load appli
21、ed to the specimen to maintainconstant specimen height. Since the pore pressure is zerothrough shear, the change in normal stress is equal to thechange in effective stress and assumed to be equal to thechange in pore water pressure that would occur in a sealedspecimen confined by a constant total st
22、ress.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. Agencies that meet the criteriaof Practice D 3740 generally are considered capable of competent andobjective testing/sam
23、pling/inspection/etc. Users of this test method arecautioned that compliance with Practice D 3740 does not in itself assurereliable results. Reliable results depend on many factors; Practice D 3740provides a means of evaluating some of those factors.5. Significance and Use5.1 The shear strength of a
24、 specimen depends on the soiltype, normal consolidation stress, time of consolidation, rate ofstrain, and prior stress history of the soil.5.2 In this test, the shear strength is measured underconstant volume conditions that are equivalent to undrainedconditions for a saturated specimen; hence, the
25、test is appli-cable to field conditions wherein soils have fully consolidatedunder one set of stresses, and then are subjected to changes instress without time for further drainage to take place.5.3 The constant volume (undrained) strength is a functionof stress conditions. In this test method, the
26、strength ismeasured under plane strain conditions and the principlestresses continuously rotate due to the application of shearstress. This simple shear stress condition occurs in many fieldsituations including zones below a long embankment andaround axially loaded piles.5.4 The state of stress with
27、in the simple shear specimen isnot sufficiently defined nor uniform enough to allow rigorousinterpretation of the results. Expressing the data in terms of theshear stress and normal effective stress on the horizontal planeis useful for engineering purposes, but should not be confusedwith the effecti
28、ve stress parameters derived from other sheartests having better defined states of stress.5.5 The values of the secant shear modulus can be used toestimate the initial settlements of embankments built onsaturated cohesive soils due to undrained shear deformations.5.6 The data from the consolidation
29、portion of this test arecomparable to results obtained using Test Method D 2435provided that the more rigorous consolidation procedure ofTest Method D 2435 is followed.5.6.1 The axial displacements measured from Test MethodD 2435 are somewhat smaller than for the simple shear testbecause the specime
30、ns lateral confinement is less rigid and thetop platen is unable to rotate.5.6.2 The estimated preconsolidation pressure is compa-rable provided the specimen is loaded sufficiently into thenormally consolidated range.5.6.3 The rate of consolidation is comparable.6. Apparatus6.1 Fig. 1 presents a sch
31、ematic diagram of the essentialcomponents for the apparatus. The following sections specifythe component requirements.6.2 Normal Loading DeviceA suitable device for apply-ing normal force to the specimen. The device must be capableof maintaining constant force for the entire test duration,permit qui
32、ck application of force increments and allow con-tinuous adjustment of force when using active height control.6.3 Shear Loading DeviceA device for applying shearforce to the specimen with sufficient capacity and control todeform the specimen at the required displacement rate. Dis-placement should be
33、 smooth and continuous. As a minimum,the displacement rate should be within 6 15 % of the averagecalculated rate (12.3.7) from 50 % of the peak shear force tothe end of the test. Vibration due to operation of this deviceshould be sufficiently small so as not to cause visible ripples ina glass of wat
34、er placed on the loading platform.NOTE 2Screw driven systems typically apply an increase in displace-ment rate with increasing shear load application.6.4 Force Measuring DevicesTwo devices are required:one for measuring normal force and one for measuring shearforce. Each device shall have the necess
35、ary capacity and beaccurate to 6 2 % of the applied maximum force for a giventest. The devices shall be insensitive to eccentric loading orinstalled in a fashion to eliminate eccentric loading. Thecompressibility of the shear measuring device should not causethe deviation in shear displacement rate
36、to exceed6 15 % ofthe average rate. When using passive height control thecompressibility of the axial measuring device must satisfy thedeflection requirement of 6.9.6.5 Axial Loading RamThe axial loading ram must holdone platen parallel to the other while allowing axial displace-ment of the specimen
37、. If the piston resists the shear force, itmust do so with negligible rotation of the platen.6.6 Shear Slide TableThe shear slide table must hold theplatens parallel to each other and allow shear displacement ofD6528002the specimen. When using passive height control and the slidetable is within the
38、height control boundaries, its compressibil-ity must satisfy the deflection requirement of 6.9. The slidetable shall allow a sufficient displacement to provide a mini-mum of 30 % shear strain.6.7 Lateral Confinement DeviceThe specimen shall beconstrained laterally such that the cross-sectional area
39、at anylocation does not change by more than 0.1 % during shear. Inaddition, the confinement must allow uniform shear deforma-tion. Circular specimens are generally confined by a wirereinforced membrane or stacked rigid rings. Square specimensgenerally are confined by stacked hollow plates or hinged
40、solidplates. The thickness of the individual stacked rings or platesmust be less than110 of the specimen thickness in order toallow relatively uniform shear deformation. When the confin-ing device is within a water bath, it shall be constructed ofcorrosion resistant material.6.7.1 Specimen Size Requ
41、irements:6.7.1.1 The minimum specimen diameter (or lateral dimen-sion) shall be 45 mm.6.7.1.2 The minimum specimen height shall be 12 mm.6.7.1.3 The height to diameter, or minimum lateral dimen-sion, ratio shall not exceed 0.4.6.7.1.4 The specimen height shall not be less than ten timesthe maximum p
42、article diameter (see 9.4).6.7.2 PlatensThe top and bottom platens of the apparatusshall be constructed of corrosion resistant material and have acircular, rectangular or square cross-section to match thespecimen. The platens shall be designed to securely hold theporous disks and provide drainage fr
43、om the specimen to thewater bath and transfer shear to the specimen without horizon-tal slippage.6.7.3 Porous DisksThe porous disks shall be brass, siliconcarbide, aluminum oxide, or similar rigid corrosion resistantmaterial. The disks shall be flat, fine enough to preventintrusion of the soil into
44、the pores, and rough enough totransfer the shear stress. The disks must be at least ten timesmore permeable than the soil. Disks must cover at least 90 %of the specimen surface and when smaller than the specimen,must be recessed into the platen such that the surface in contactwith the soil is flush
45、with the platen.NOTE 3It is sometimes necessary to increase the surface roughness ofthe porous disks in order to prevent interface slippage. Short metallic pinscemented into the disks have been used successfully but introduce largeuncertainty in the shear strain calculations.NOTE 4Disks of ductile m
46、aterial, for example, brass, have been foundto warp due to the shear stress and need to be flattened on a regular basis.6.8 Displacement IndicatorsTo measure the change inspecimen height and the shear deformation (axial and lateralmovement of top platen relative to bottom platen) with areadability o
47、f 0.0025 mm.6.9 Volume Control EquipmentOne of the two followingmethods may be used to achieve constant volume during shear.With either method, the specimen is free to drain and themeasured change in normal total stress during shear is assumedto be equal to the pore pressure which would develop in a
48、sealed specimen confined by a constant total stress. In eithercase, the device shall not allow the specimen change in heightto exceed 0.05 % including the equipment deformation deter-mined in 10.1.6.9.1 Normal Force Adjustment DeviceActive height con-trol requires a mechanism to continuously adjust
49、the normalforce to prevent changes in the specimen height during shear.NOTE 5A variety of devices are used including manual adjustment ofa worm gear, computer control of a worm gear, and computer control ofa pneumatic cylinder.6.9.2 Axial Displacement ClampPassive height controlrequires a mechanism to lock the axial loading ram in placeduring shear. The normal force transducer must be momentinsensitive and located between the specimen and the clamp orthe specimen and the slide base.6.10 Specimen Trimming DeviceA trimming turntable ora cylindrical cutting ring may
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