1、Designation: D7608 10Standard Test Method forTorsional Ring Shear Test to Determine Drained FullySoftened Shear Strength and Nonlinear Strength Envelopeof Cohesive Soils (Using Normally Consolidated Specimen)for Slopes with No Preexisting Shear Surfaces1This standard is issued under the fixed design
2、ation D7608; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or
3、 reapproval.1. Scope1.1 This test method provides a procedure for performing atorsional ring shear test under a drained condition to determinethe fully softened shear strength and nonlinear strength enve-lope of cohesive soils. The fully softened strength is used toevaluate the stability of slopes t
4、hat do not have a preexistingshear surface. In addition, the fully softened shear strengthcorresponds to the peak shear strength of a normally consoli-dated specimen. This test method focuses on the use of areconstituted specimen to measure the fully softened strength.This test method is performed b
5、y shearing a normally consoli-dated, reconstituted specimen at a controlled displacement rateuntil the peak shear resistance has been obtained. Generally,the drained fully softened failure envelope is determined atthree or more effective normal stresses. A separate test speci-men must be used for ea
6、ch normal stress to measure the fullysoftened strength otherwise a post-peak or even residualstrength will be measured if the same specimen is used becauseof the existence of a shear surface.1.2 The ring shear apparatus allows a reconstituted speci-men to be normally consolidated at the desired norm
7、al stressprior to drained shearing. This simulates the field conditionsunder which the fully softened strength develops in overcon-solidated clays, claystones, mudstones, and shales.1.3 A shear stress-displacement relationship may be ob-tained from this test method. However, a shear stress-strainrel
8、ationship or any associated quantity, such as modulus,cannot be determined from this test method because possiblesoil extrusion and volume change prevents defining the heightneeded in the shear strain calculations. As a result, shear straincannot be calculated but shear displacement can be calculate
9、d.1.4 The selection of normal stresses and final determinationof the shear strength envelope for design analyses and thecriteria to interpret and evaluate the test results are theresponsibility of the engineer or office requesting the test.1.5 The values stated in SI units are to be regarded as thes
10、tandard. The values given in parentheses are mathematicalconversions to inch-pound units that are provided for informa-tion only and are not considered 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 us
11、er 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:2D422 Test Method for Particle-Size Analysis of SoilsD653 Terminology Relating to Soil, Rock, and ContainedFluid
12、sD854 Test Methods for Specific Gravity of Soil Solids byWater PycnometerD2216 Test Methods for Laboratory Determination of Wa-ter (Moisture) Content of Soil and Rock by MassD2435 Test Methods for One-Dimensional ConsolidationProperties of Soils Using Incremental LoadingD2487 Practice for Classifica
13、tion of Soils for EngineeringPurposes (Unified Soil Classification System)D3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD4318 Test Methods for Liquid Limit, Plastic Limit, andPlasticity Index of
14、Soils1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.05 on Strength andCompressibility of Soils.Current edition approved May 15, 2010. Published July 2010. DOI: 10.1520/D760810.2For referenced ASTM standards, visit
15、 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 page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-295
16、9, United States.D6026 Practice for Using Significant Digits in GeotechnicalDataD6467 Test Method for Torsional Ring Shear Test to De-termine Drained Residual Shear Strength of CohesiveSoils3. Terminology3.1 DefinitionsFor definitions of technical terms used inthis test method, refer to Terminology
17、D653.3.2 Definitions of Terms Specific to This Standard:3.2.1 consolidatedsoil specimen condition after primaryconsolidation under a specific normal stress.3.2.2 fully softened shear forcethe shear force beingapplied to the specimen when the shear resistance begins todecrease with continued shear di
18、splacement.3.2.3 fully softened shear strengththe maximum shearresistance of normally consolidated and not presheared soil toshear and equals the fully softened shear force divided by thecross-sectional area of the specimen. The fully softened shearstrength should be used in an effective stress stab
19、ility analysisof slopes in overconsolidated clays with no pre-existing shearsurface. The shear strength can be represented by a failureenvelope and the strength parameters of c and F.4. Summary of Test Method4.1 This test method consists of placing the reconstitutedspecimen (slurry or paste) in the
20、annular specimen container,applying a predetermined normal stress through the top loadingplaten, providing for wetting and draining of the specimen(optional); consolidating the specimen under the normal stress;applying a constant rate of shear deformation; and measuringthe shearing force and displac
21、ement until a maximum shearresistance is reached.5. Significance and Use5.1 The ring shear apparatus maintains the cross-sectionalarea of the shear surface constant during shear and shears thespecimen continuously in one rotational direction for anymagnitude of displacement and along entire cross-se
22、ctionalarea.5.2 The ring shear apparatus allows a reconstituted speci-men to be consolidated at the desired normal stress prior todrained shearing. This simulates the field conditions underwhich the fully softened strength develops in overconsolidatedclays, claystones, mudstones, and shales because
23、the fullysoftened strength corresponds to the peak shear strength of anormally consolidated clay.5.3 The ring shear test is suited to the relatively rapiddetermination of drained fully softened shear strength becauseof the short drainage path through the thin specimen and failureoccurring near the t
24、op porous stone.5.4 The ring shear test minimizes the effect of initialdisturbance that may result from adjusting/creating a gapbefore starting shearing, especially in the direct shear device.5.5 The test results are primarily applicable to assess theshear strength of overconsolidated soils for drai
25、ned analysis inslopes that do not have a pre-existing shear surface, shearedbedding planes, joints, or faults.NOTE 1Notwithstanding the statements 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
26、the suitability of theequipment and facilities used. Agencies that meet the criteria of PracticeD3740 are generally considered capable of competent testing. Users ofthis test method are cautioned that compliance with Practice D3740 doesnot ensure reliable testing. Reliable testing depends on several
27、 factors;Practice D3740 provides a means of evaluating some of those factors.6. Apparatus6.1 Shear Deviceto hold the specimen securely betweentwo porous inserts. The shear device shall provide a means forapplying a normal stress to the faces of the specimen, formeasuring changes in thickness of the
28、specimen, for permittingdrainage of water through the porous inserts at the top andbottom boundaries of the specimen, and for submerging thespecimen in water. The device shall be capable of applying atorque to the specimen along a shear plane parallel to the facesof the specimen. A number of differe
29、nt ring shear devices arecommercially available, in practice, or are being developed soa general description of a ring shear device is presented withoutschematic diagrams. The location of the shear plane dependson the configuration of the apparatus. As a result, the shearplane may be located near a
30、soil/porous insert interface or atthe mid-height of the specimen if an upper ring can beseparated from a bottom ring as is done in a direct shear box.The device shall have low friction along the inner and outerwalls of the specimen container developed during shearing.Friction may be reduced by havin
31、g the shear plane occur at thetop of the specimen container, modifying the specimen con-tainer walls with low-friction material, or exposing the shearplane by separating the top and bottom portions of thespecimen container. The frames that hold the specimen shall besufficiently rigid to prevent thei
32、r distortion during shearing.The various parts of the shear device shall be made of amaterial such as stainless steel, bronze, or coated aluminumthat is not subject to corrosion by moisture or substances withinthe soil. Dissimilar metals, which may cause galvanic action,are not permitted.6.2 Specime
33、n Containera device containing an annularcavity for the soil specimen with an inside diameter not lessthan 50 mm (2 in.) and an inside to outside diameter ratio notless than 0.6. The container has provisions for drainage throughthe top and bottom. The initial specimen depth, before con-solidation an
34、d preshearing, is not less than 5 mm (0.2 in.). Themaximum particle size is limited to 10 % of the initialspecimen height as stated in the test specimen description.6.3 Torque Arm/Loading Platen Assemblymay have dif-ferent bearing stops for the proving rings, load cells, or force ortorque transducer
35、s to provide different options for the torquemeasurement.6.4 Porous Insertstwo bronze or stainless steel porousinserts mounted on the top loading platen and the bottom of thespecimen container cavity to allow drainage from the soilspecimen along the top and bottom boundaries. The inserts aidin trans
36、fer of shear stress to the top and bottom boundaries ofthe specimen. The inserts must be sufficiently serrated todevelop a strong interlock with the soil specimen. The perme-ability of the inserts shall be substantially greater than that ofthe soil, but shall be textured fine enough to prevent exces
37、siveD7608 102intrusion of the soil into the pores of the insert. The outer andinner diameters of the inserts shall be 0.1 mm (0.004 in.) less,and greater than those of the specimen annular cavity, respec-tively. The serration should have a depth of between 10 and15 % of the initial specimen height.N
38、OTE 2Exact criteria for porous insert texture and permeability havenot been established. For normal soil testing, medium-grade inserts witha permeability of about 5.0 3 104to 1.0 3 103cm/s (0.5 to 1.0 3 103ft/year) are appropriate for testing clays. It is important that the perme-ability of the poro
39、us insert is not reduced by the collection of soil particlesin the pores of the insert; hence frequent checking and cleaning (byflushing and boiling, or by ultrasonic cleaning) are required to ensure thenecessary permeability.6.5 Loading Devices:6.5.1 Device for Applying and Measuring the NormalForc
40、eNormal force is usually applied by a lever-loadingyoke that is operated by dead weights (masses). The deviceshall be capable of rapidly applying and maintaining thenormal force to within 61 % of the specified force.6.5.2 Device for Shearing the SpecimenThis device shallbe capable of shearing the sp
41、ecimen at a uniform rate ofdisplacement, without stick slip. The rate to be applied dependsupon the consolidation characteristics of the soil (see 9.5.1).The rate is usually maintained with an electric motor and gearbox arrangement.6.6 Shear Force Measurement Devicetwo proving rings,load cells, or a
42、 torque transducer with a readability/sensitivityof 0.2 N (0.05 lbf).6.7 Water Bathcontainer for the shear device and waterneeded to inundate the specimen6.8 Controlled High-Humidity RoomIf required, for pre-paring the specimen, such that the water content gain or lossduring specimen rehydration is
43、minimized.6.9 Deformation Indicatorsdial gauge, or other suitabledevice, capable of measuring the change in thickness of thespecimen, with a sensitivity of at least 0.0025 mm (0.0001 in.).Etched scale on circumference of the ring base to measure thedegrees traveled, and thus the shear displacement,
44、or othermethods capable of obtaining a sensitivity of at least 2.6.10 Equipment for Determination of Water Contentinaccordance in Test Method D2216.6.11 Miscellaneous Equipmentincluding timing devicewith a second hand, site-specific, distilled or demineralizedwater, mortar, pestle, spatulas, razor b
45、lades, straightedge, andso forth.7. Test Specimen7.1 The sample used for specimen preparation is to besufficiently large so that a ring shear specimen and specimensfor index property tests can be prepared.7.2 A reconstituted specimen can be obtained by pushing arepresentative sample, at the as-recei
46、ved water content,through the appropriate sieve. Soil with more than 25 %organic content is to be reconstituted without drying.7.3 Reconstituted clay specimens may be prepared bycrushing an air-dried representative sample and passing itthrough the appropriate sieve, for example, opening size lesstha
47、n or equal to 10 % of the initial specimen height. Air driedmethod should not be used for highly plastic soils, tropicalsoils, and organic soils.7.4 After sieving, the processed sample is mixed with sitespecific water/fluid or distilled water until a water content nearthe liquid limit is obtained. U
48、sing this water content minimizesthe amount of air trapped during placement of the soil pasteinto the annular cavity by increasing the degree of saturation.A water content between the liquid and plastic limits can beused if air will not be trapped in the annular cavity. Theprocessed sample should be
49、 allowed to rehydrate for at least 24h in a high-humidity room.7.5 Care is to be taken during crushing and mixing opera-tions to avoid introducing impurities into the sample.7.6 A spatula is used to place the reconstituted soil pasteinto the annular specimen cavity. The top of the specimen isplaned flush with the top of the specimen container.7.7 The liquid limit, plastic limit, and clay-size fraction ofthe specimens are measured using the soil used to create thetest specimen.8. Procedure8.1 Assemble the specimen container.8.2 Consolidation:8.2.1 Place and secu
