1、Designation: D4554 12Standard Test Method forIn Situ Determination of Direct Shear Strength of RockDiscontinuities1This standard is issued under the fixed designation D4554; 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 () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers the measurement of peak andresidual direct shear strength in a drained condition of in sit
3、urock discontinuities as a function of stress normal to thesheared plane. This sheared plane is usually a significantdiscontinuity that may or may not be filled with gouge orsoil-like material.1.2 The measured shear properties are affected by scalefactors. The severity of the effect of these factors
4、 must beassessed and applied to the specific problems on an individualbasis.1.3 The values stated in SI units are to be regarded as thestandard. No other units of measurements are included in thisstandard.1.4 All observed and calculated values shall conform to theguidelines for significant digits an
5、d rounding established inPractice D6026.1.5 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 applica-bility of regulatory
6、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 ContainedFluidsD2216 Test Methods for Laboratory Determination of Water(Moisture) Content of Soil and Rock by MassD3740 Practice for Mi
7、nimum 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 SoilsD6026 Practice for Using Significant Digits in GeotechnicalDataD6913 Test Methods for Part
8、icle-Size Distribution (Grada-tion) of Soils Using Sieve Analysis3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this test method referto Terminology D653.3.2 Definitions of Terms Specific to This Standard:3.2.1 discontinuitiesany surface across which some prop-erty of the rock
9、mass is not continuous. Discontinuities includejoints, schistosity, faults, bedding planes, cleavage, and zonesof weakness, along with any filling material.3.2.2 peak shear strengththe maximum shear stress in thecomplete curve of stress versus displacement obtained for aspecified constant normal str
10、ess.3.2.3 residual shear strengththe shear stress at whichnominally no further rise or fall in shear strength is observedwith increasing shear displacement and constant normal stressas shown in Fig. 1. A true residual strength may only bereached after considerably greater shear displacement than can
11、be achieved in testing. The test value should be regarded asapproximate and should be assessed in relation to the completeshear stress displacement curve.3.2.4 shear strength parameter, capparent cohesion; theprojected intercept on the shear stress axis of the plot of shearstress versus normal stres
12、s as shown in Fig. 2.3.2.5 shear strength parameter, friction angle; the angleof the tangent to the failure curve at a normal stress that isrelevant to design as shown in Fig. 2.3.2.5.1 DiscussionDifferent values of c and relate todifferent stages of a test, for example, c, cr, a, and b,ofFig.2.4. S
13、ummary of Test Method4.1 This test method is performed on rectangular-shapedblocks of rock that are isolated on all surfaces, except for theshear plane surface.1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.12 on
14、Rock Mechanics.Current edition approved Aug. 1, 2012. Published November 2012. Originallyapproved in 1985. Last previous edition approved in 2006 as D4554 02 (2006).DOI: 10.1520/D4554-12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at servicea
15、stm.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 C700, West Conshohocken, PA 19428-2959. United St
16、ates14.2 The blocks are not to be disturbed during preparationoperations. The base of the block coincides with the plane to besheared.4.3 A normal load is applied perpendicular to the shearplane and then a side load is applied to induce shear along theplane and discontinuity. A typical equipment con
17、figuration isshown in Fig. 3.5. Significance and Use5.1 Because of scale effects, there is no simple method ofpredicting the in situ shear strength of a rock discontinuityfrom the results of laboratory tests on small specimens; in situtests on large specimens are the most reliable means.5.2 Results
18、can be employed in stability analysis of rockengineering problems, for example, in studies of slopes,underground openings, and dam foundations. In applying thetest results, the pore water pressure conditions and the possi-bility of progressive failure must be assessed for the designcase, as they may
19、 differ from the test conditions.5.3 Tests on intact rock that are free from planes ofweakness are usually accomplished using laboratory triaxialtesting. Intact rock can, however, be tested in situ in directshear if the rock is weak and if the specimen block encapsu-lation is sufficiently strong.NOT
20、E 1The quality of the result produced by this standard 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/sampling/i
21、nspection/etc. Users of this standard arecautioned that compliance with Practice D3740 does not in itself assurereliable results. Reliable results depend on many factors; Practice D3740provides a means of evaluating some of those factors.6. Apparatus6.1 Equipment for Cutting and Encapsulating the Te
22、stBlockThis equipment includes rock saws, drills, hammer andchisels, formwork of appropriate dimensions and rigidity,expanded polystyrene sheeting or weak filler, and materials forreinforced concrete encapsulation.6.2 Equipment for Applying the Normal LoadThis equip-ment includes flat jacks, hydraul
23、ic rams, or dead load ofsufficient capacity to apply the required normal loads as shownin Fig. 3.NOTE 2If a dead load is used for normal loading, precautions arerequired to ensure accurate centering and stability. If two or morehydraulic rams are used for loading, care is needed to make sure theirop
24、erating characteristics are identically matched and they are in exactparallel alignment.6.2.1 Each hydraulic ram should be provided with a spheri-cal seat. The travel of rams, and particularly of flat jacks,should be sufficient to accommodate the full-anticipated speci-men displacement. The normal d
25、isplacement may be estimatedfrom the content and thickness of the filling and roughness ofthe shear surfaces. The upper limits would be the fillingthickness.FIG. 1 Shear Stress Displacement GraphsD4554 122NOTE 1In this case, intercept cron shear axis is zero.fr= residual friction angle,fa= apparent
26、friction angle below stress sa; point A is a break in the peak shear strength curve resulting from the shearing off of major irregularities on theshear surface. Between points O and A, fawill vary somewhat; measure at stress level of interest. Note also that fa= fu+ i where:fu= friction angle obtain
27、ed for smooth surfaces of rock on rock, andi = inclination angle of surface asperities.fb= apparent friction angle above stress level sa(Point A); note that fawill usually be equal to or slightly greater than frand will vary somewhat withstress level; measure at the stress level of interest, r.c8 =
28、cohesion intercept of peak shear strength curve; it may be zero.c = apparent cohesion at a stress level corresponding to fb, andcr= cohesion intercept of residual shear strength which is usually negligible.FIG. 2 Shear Strength Effective Normal Stress GraphFIG. 3 Typical Arrangement of Equipment for
29、 In Situ Direct Shear TestD4554 1236.2.2 Hydraulic SystemA hydraulic system, if used,should be capable of maintaining a normal load to within 2 %of a selected value throughout the test.6.2.3 Reaction SystemA reaction system to transfer nor-mal loads uniformly to the test block includes rollers or as
30、imilar low friction device to make sure that at any givennormal load, the resistance to shear displacement is less than1 % of the maximum shear force applied in the test. Rockanchors, wire ties, and turnbuckles are usually required toinstall and secure the equipment.6.3 Equipment for Applying the Sh
31、ear ForceHydraulicrams of adequate total capacity with at least 150 mm of travel.6.3.1 Hydraulic PumpCapable of pressurizing the shearforce system.6.3.2 Reaction SystemA reaction system to transmit theshear force to the test block. The shear force should beuniformly distributed along one face of the
32、 specimen. Theresultant line of applied shear forces should pass through thecenter of the base of the shear plane at an angle approximately15 to the shear plane with an angular tolerance of 65. Theexact angle should be measured to 61.NOTE 3Tests where both shear and normal forces are provided by asi
33、ngle set of jacks inclined at greater angles to the shear plane are notrecommended, as it is then impractical to control shear and normalstresses independently.6.4 Equipment for Measuring the Applied ForceThisequipment includes one system for measuring normal force andanother for measuring applied s
34、hearing force with an accuracybetter than 62 % of the maximum forces reached in the test.Load cells, dynamometers or flat jack pressure measurementsmay be used. Recent calibration data applicable to the range oftesting should be appended to the test report. If possible, thegauges should be calibrate
35、d both before and after testing.6.5 Equipment for Measuring Shear, Normal, and LateralDisplacementDisplacement should be measured, forexample, using micrometer dial gauges, at eight locations onthe specimen block or encapsulating material, as shown in Fig.4 (Note 4). The shear displacement measuring
36、 system shouldhave a travel of at least 100 mm and accuracy better than 0.1mm. The normal and lateral displacement measuring systemsshould have a travel of at least 20 mm and an accuracy betterthan 0.05 mm. The measuring reference system (beams,anchors, and clamps) should, when assembled, be suffici
37、entlyrigid to meet these requirements. Resetting of gauges duringthe test should be avoided, if possible.NOTE 4The surface of encapsulating material is usually insufficientlysmooth and flat to provide adequate reference for displacement gauges;glass plates may be cemented to the specimen block for t
38、his purpose.These plates should be of adequate size to accommodate movement of thespecimen. Alternatively, a temperature calibrated tensioned wire andpulley system with gauges remote from the specimen may be used. Thesystem, as a whole, must be reliable and must conform to the specifiedaccuracy requ
39、irements. Particular care is needed in this respect whenemploying electric transducers or automatic recording equipment.7. Preparation of Test Specimens7.1 Outline a test block such that the base of the blockcoincides with the plane to be sheared. The direction ofshearing should correspond, if possi
40、ble, to the direction ofanticipated shearing in the full-scale structure to be analyzedusing the test results. To inhibit relaxation, swelling, and toprevent premature sliding, it is necessary to apply a normalload to the upper face of the test specimen as soon as possibleafter excavation of the ope
41、ning and prior to sawing the sides.Screw props or a system of rock bolts and crossbeams, may, forexample, provide the load approximately equal to the overbur-den pressure. Maintain the load until the test equipment is inposition. Saw the test block to the required dimensions,approximately 700 mm by
42、700 mm by 350 mm using methodsthat avoid disturbance or loosening of the block. See Note 5.Saw a channel approximately 20 mm deep by 80 mm widearound the base of the block to allow freedom of displacementsduring testing and also to facilitate possible required saturation.The block and particularly t
43、he shear plane should, unlessotherwise specified, be retained as close as possible to itsnatural in situ conditions during preparation and testing.NOTE 5A test block size of 700 by 700 by 350 mm is suggested asstandard for in situ testing. Smaller blocks are permissible, if, for example,the surface
44、to be tested is relatively smooth; larger blocks may be neededwhen testing very irregular surfaces. For convenience, the size and shapeof the test block may be adjusted so that the faces of the block coincidewith joints or fissures. This adjustment minimizes block disturbanceduring preparation. Irre
45、gularities that would limit the thickness or em-placement of encapsulation material or reinforcement should be removed.7.1.1 Apply a layer of weak material, such as foamedpolystyrene at least 20 mm thick around the base of the testblock, and then encapsulate the remainder of the block inconcrete or
46、similar material of sufficient strength and rigidity toprevent collapse or significant distortion during testing. Designthe encapsulation formwork to make sure the load bearingfaces are flat to a tolerance of 63 mm and at the correctinclination to the shear plane to a tolerance of 62.7.1.2 Carefully
47、 position and align reaction pads, anchors,and alike if required, to carry the thrust from normal and shearload systems to adjacent sound rock.Allow all concrete time togain adequate strength prior to testing.8. Calibration/Verification8.1 Equipment used to measure the normal and shear forcesshall b
48、e calibrated at least annually and verified before andafter testing.8.2 Equipment used to measure displacement shall be veri-fied annually.NOTE 1Gauges S1 and S2 are for shear displacement, L1 and L2 forlateral displacement, N1 through N4 for normal displacement.FIG. 4 Arrangement of Displacement Ga
49、ugesD4554 1249. Procedure9.1 Prepare the test block as described in Section 7.9.2 Consolidation of Test Specimen:9.2.1 The consolidation stage of testing is necessary in orderto allow pore water pressures, in the rock and especially in anyfilling material adjacent to the shear plane, to dissipate underfull normal stress before shearing. Behavior of the specimenduring consolidation may also impose a limit on permissiblerate of shearing. See section 9.3.3.9.2.2 Check all displacement gauges for rigidity, adequatetravel, and freedom of movemen
