1、Designation: D 5607 08Standard Test Method forPerforming Laboratory Direct Shear Strength Tests of RockSpecimens Under Constant Normal Force1This standard is issued under the fixed designation D 5607; the number immediately following the designation indicates the year oforiginal adoption or, in the
2、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 reapproval.1. Scope*1.1 This test method establishes requirements and labora-tory procedures for performing dir
3、ect shear strength tests onrock specimens. It includes procedures for both intact rockstrength and sliding friction tests which can be performed onspecimens that are homogeneous, or have planes of weakness,including natural or artificial discontinuities. Examples of anartificial discontinuity includ
4、e a rock-concrete interface or a liftline from a concrete pour. Discontinuities may be open,partially or completely healed or filled (that is, clay fillings andgouge). Only one discontinuity per specimen can be tested. Thetest is usually conducted in the undrained state with an appliedconstant norma
5、l load. However, a clean, open discontinuitymay be free draining, and, therefore, a test on a clean, opendiscontinuity could be considered a drained test. During thetest, shear strength is determined at various applied stressesnormal to the sheared plane and at various shear displacements.Relationsh
6、ips derived from the test data include shear strengthversus normal stress and shear stress versus shear displacement(shear stiffness).NOTE 1The term “normal force” is used in the title instead of normalstress because of the indefinable area of contact and the minimal relativedisplacement between upp
7、er and lower halves of the specimen duringtesting. The actual contact areas during testing change, but the actual totalcontact surface is unmeasurable. Therefore nominal area is used forloading purposes and calculations.NOTE 2Since this test method makes no provision for the measure-ment of pore pre
8、ssures, the strength values determined are expressed interms of total stress, uncorrected for pore pressure.1.2 This standard applies to hard rock, soft rock, andconcrete.1.3 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are mathematicalconversions
9、to inch-pound units that are provided for informa-tion only and are not considered standard.1.4 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 pract
10、ices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 2216 Test Methods for Laboratory Determination of Wa-ter (Moisture) Content of Soil and Rock by MassD 3740 Practice f
11、or Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionE4 Practices for Force Verification of Testing MachinesE 122 Practice for Calculating Sample Size to Estimate,With Specified Precision, the Average for a Characteris
12、ticof a Lot or Process3. Terminology3.1 Definitions: For common definitions of terms used inthis standard, refer to Terminology D 653.3.2 Definitions of Terms Specific to This Standard:3.2.1 apparent stressnominal stress, that is, external loadper unit area. It is calculated by dividing the external
13、ly appliedload by the nominal area.3.2.2 Asperity:3.2.2.1 qualitythe roughness of a surface.3.2.2.2 featurea surface irregularity ranging from sharp orangular to rounded or wavy.3.2.2.3 asperitiesthe collection of a surfaces irregulari-ties that account for the surfaces roughness.3.2.3 Discontinuity
14、:3.2.3.1 An abrupt change, interruption, or break in theintegrity or physical properties of rock, such as a beddingplane, fracture, cleavage, crack, joint, or fault.3.2.3.2 A gapped discontinuity consists of opposing rocksurfaces separated by an open or filled space. A tight discon-tinuity consists
15、of opposing rock surfaces in intimate andgenerally continuous contact; it may be valid to treat such adiscontinuity as a single surface.1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics.Current e
16、dition approved July 1, 2008. Published July 2008. Originally approvedin 1994. Last previous edition approved in 2006 as D 5607 02 (2006).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume
17、information, refer to the standards Document Summary 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.3.2.3.3 A discontinuitys opposing rock sur
18、faces may beplanar to nonplanar and matching to misfit.3.2.4 intact shear strengththe peak shear resistance (inunits of stress) of an intact rock specimen or of a specimencontaining a completely healed discontinuity.3.2.5 nominal areaarea obtained by measuring or calcu-lating the cross-sectional are
19、a of the shear plane. It is calcu-lated after its relevant cross-sectional dimensions are deter-mined.3.2.6 residual shear strengththe shear stress, (see Fig. 1),corresponding to a specific normal stress, for which the shearstress remains essentially constant with increasing shear dis-placement. In
20、most cases, the shear stress after reaching PointA is the residual shear strength.3.2.7 shear stiffnessrepresents the resistance of the speci-men to shear displacements under an applied shear force priorto reaching the peak shear strength. It is calculated by dividingthe applied apparent shear stres
21、s by the resulting shear dis-placement (slope of the curve prior to peak shear strength, Fig.1).3.2.8 sliding friction shear strengththe peak shear resis-tance (in units of stress) of a rock specimen containing an opendiscontinuity.4. Summary of Test Method4.1 While maintaining a constant force norm
22、al to thenominal shear plane of the specimen, an increasing externalshear force is applied along the designated shear plane to causeshear displacement. The applied normal and shear forces andthe corresponding normal and shear displacements are mea-sured and recorded. These data are the basis for cal
23、culating therequired parameters.5. Significance and Use5.1 Determination of shear strength of a rock specimen is animportant aspect in the design of structures such as rock slopes,dam foundations, tunnels, shafts, waste repositories, cavernsfor storage, and other purposes. Pervasive discontinuities(
24、joints, bedding planes, shear zones, fault zones, schistosity) ina rock mass, and genesis, crystallography, texture, fabric, andother factors can cause the rock mass to behave as ananisotropic and heterogeneous discontinuum. Therefore, theprecise prediction of rock mass behavior is difficult.5.2 For
25、 nonplanar joints or discontinuities, shear strength isderived from a combination base material friction and overrid-ing of asperities (dilatancy), shearing or breaking of theasperities, and rotations at or wedging of the asperities. Slidingon and shearing of the asperities can occur simultaneously.
26、When the normal force is not sufficient to restrain dilation, theshear mechanism consists of the overriding of the asperities.When the normal load is large enough to completely restraindilation, the shear mechanism consists of the shearing off of theasperities.5.3 Using this test method to determine
27、 the shear strength ofan intact specimen may generate overturning moments whichcould result in an inclined shear break.5.4 Shear strength is influenced by the overburden ornormal pressure; therefore, the larger the overburden pressure,the larger the shear strength.5.5 In some cases, it may be desira
28、ble to conduct tests in siturather than in the laboratory to determine the representativeshear strength of the rock mass, particularly when design iscontrolled by discontinuities filled with very weak material.NOTE 3The quality of the result produced by this standard isdependent on the competence of
29、 the personnel performing it, and thesuitability of the equipment and facilities used. Agencies that meet thecriteria of Practice D 3740 are generally considered capable of competentand objective testing/sampling/inspection and the like. Users of thisstandard are cautioned that compliance with Pract
30、ice D 3740 does not initself assure reliable results. Reliable results depend on many factors,Practice D 3740 provides a means of evaluating some of those factors.6. Apparatus6.1 Testing MachineLoading device, to apply and registernormal and shear forces on the specimens. It must haveadequate capabi
31、lity to apply the shear force at a rate conform-ing to the specified requirements. It shall be verified at suitabletime intervals in accordance with the procedures given inPractices E4, and comply with the requirements prescribedtherein. The resultant of the shear force passes through thecenter of t
32、he intended shear zone or the centroid of the shearplane surface area to minimize adverse moments.NOTE 4There are many different direct shear device designs. Al-though details may vary concerning how to encapsulate specimens intoshear boxes as well as details for assembling the machine, the determi-
33、nations are usually similar.6.2 Fig. 2 is a schematic of an example shear box, anintegral part of the machine.6.3 Pressure-Maintaining DeviceA hydraulic componentthat will hold a pressure, within specified tolerances, within thehydraulic system.6.4 Specimen Holding RingsAluminum or steel holdingring
34、s (see Fig. 3) with internal dimensions sufficient to accom-modate specimens mounted in an encapsulating medium.6.5 Spacer Plates:6.5.1 Split Spacer PlatesPlastic (or other suitable mate-rial) plates of varying thicknesses for isolating an intactspecimens shear zone from the encapsulating compound (
35、seeFig. 3).6.5.2 Non-split Spacer PlatesPlastic (or other suitablematerial) plates of varying thicknesses that have a circular oroval hole in the center and are used for non-intact specimens.6.6 Displacement Measuring Device Linear variable dif-ferential transformers (LVDTs) may be used as normal an
36、dshear displacement measuring devices. Other devices such asFIG. 1 Generalized Shear Stress and Shear Displacement CurveD5607082dial indicators and direct current differential transformers(DCDTs), are satisfactory. Four devices are used to measurethe normal displacement and provide a check on specim
37、enrotation about an axis parallel to the shear zone and perpen-dicular to the shearing direction. Another device measures theshear displacement. These displacement devices should haveadequate ranges of travel to accommodate the displacements,613 mm (60.5 in.). Sensitivities of these devices should b
38、e0.025 mm (0.001 in.) for shear displacement and 0.0025 mm(0.0001 in.) for normal displacement. Ensure that the devicesare located away from the loading direction so as not to bedamaged in sudden failures.6.7 Data Acquisition EquipmentA computer may be usedto control the test, collect data, and plot
39、 results.7. Reagents and Materials7.1 Miscellaneous ItemsCarpenters contour gauge formeasuring joint surface roughness, roughness chart (see Fig.43), filler or modelling clay, calipers, spatula, circular clamps,utility knife, towels, markers, plotting papers, encapsulatingcompound, and camera.3Barto
40、n, N., and Choubey, V., The Shear Strength of Rock Joints in Theory andPractice, Rock Mechanics, 10, 1977.FIG. 2 Schematic Test SetupDirect Shear Box with Encapsulated SpecimenNOTE 1Note the split plastic plates for isolating the shear zone.FIG. 3 View Showing Pouring Encapsulating Material AroundUp
41、per Half of SpecimenFIG. 4 Roughness Profiles and Corresponding JRC ValuesAssociated With Each One5D56070838. Test Specimens8.1 Sampling:8.1.1 Intact SpecimenCare should be exercised in coredrilling, handling, and sawing the samples to minimize me-chanical damage to test specimens. No liquids other
42、than watershould be in contact with a test specimen.NOTE 5To obtain relevant parameters for the design, construction, ormaintenance of major engineering structures, test specimens should berepresentative of the host properties as nearly as practicable.8.1.2 Specimen with a Single DiscontinuityRock s
43、amplesare collected and shipped using methods that minimize distur-bance of test zones. A specimens dimensions and the locationof a discontinuity to be tested should allow sufficient clearancefor adequate encapsulation. The in situ integrity of disconti-nuities in a sample is to be maintained from t
44、he time ofsampling until the discontinuity is tested. Tape, plastic wrap, orother means may be utilized to preserve the in situ moisturecontent along the test zone. Plastic half rounds, core boxes,freezing, or other methods may be utilized to bridge thediscontinuities and prevent differential moveme
45、nt from occur-ring along the discontinuity. This is especially important fordiscontinuities containing any soft, or weak material.8.2 Size and ShapeThe height of specimen shall begreater than the thickness of the shear (test) zone and sufficientto embed the specimen in the holding rings. Specimens m
46、ayhave any shape such that the cross-sectional areas can bereadily determined. In most cases the least cross-sectionaldimension of the specimen should be at least 10 times thelargest grain size in the specimen. The test plane should havea minimum area of 1900 mm2(3 in.2).8.3 StorageSamples should be
47、 stored out of the weatherafter they are obtained at the work site (field) in order topreserve their integrity.8.4 Moisture ConditionIf specimens are to be tested nearthe natural moisture condition of the host material, they shouldbe stored and transported in moisture-proof containers, orcoated with
48、 thin sheets of plastic film and wax.9. Calibration and Standardization9.1 Load Monitoring DevicesThe load monitoring de-vices (such as load cells, proving rings, hydraulic gauges)should be calibrated according to Practices E4.9.2 Displacement Measuring Devices Measuring devicesare to be calibrated
49、at least once a year.10. Procedure10.1 Moisture ConditionIf required, the moisture condi-tion of the shear zone are determined and reported according toTest Method D 2216.10.2 Test Specimen:10.2.1 Measurements:10.2.1.1 Cross-Sectional Area of Regular GeometricalShapesThe relevant dimensions of the specimen at the shearzone cross section are measured to the nearest 0.025 mm(0.001 in.) using caliper or micrometer. Then, the apparentcross-sectional area of the intact specimen is calculated. Forinclined core the apparent area can be determined by m
