1、Designation: D 4554 02 (Reapproved 2006)Standard Test Method forIn Situ Determination of Direct Shear Strength of RockDiscontinuities1This standard is issued under the fixed designation D 4554; the number immediately following the designation indicates the year oforiginal adoption or, in the case of
2、 revision, the year 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. Scope*1.1 This test method covers the measurement of peak andresidual direct shear strength of in situ
3、rock discontinuities asa function of stress normal to the sheared plane. This shearedplane is usually a significant discontinuity which may or maynot be filled with gouge or soil-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.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 standa
5、rd 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:2D 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 3740 Practice for Minimum Requirements for AgenciesEngaged in the
6、 Testing and/or Inspection of Soil and Rockas Used in Engineering Design and Construction3. Terminology3.1 Definitions: See Terminology D 653 for general defini-tions.3.2 Definitions of Terms Specific to This Standard:3.2.1 discontinuitiesthis includes joints, schistosity,faults, bedding planes, cle
7、avage, and zones of weakness, alongwith any filling material.3.2.2 peak shear strengththe maximum shear stress in thecomplete curve of stress versus displacement obtained for aspecified constant normal stress.3.2.3 residual shear strengththe shear stress at whichnominally no further rise or fall in
8、shear strength is observedwith increasing shear displacement and constant normal stress(Fig. 1). A true residual strength may only be reached afterconsiderably greater shear displacement than can be achievedin testing. The test value should be regarded as approximateand should be assessed in relatio
9、n to the complete shear stress- displacement curve.3.2.4 shear strength parameter, c (see Fig. 2)the projectedintercept on the shear stress axis of the plot of shear stressversus normal stress (see Note).3.2.5 shear strength parameter, f (see Fig. 2)the angle ofthe tangent to the failure curve at a
10、normal stress that isrelevant to design.3.2.5.1 DiscussionDifferent values of c and f relate todifferent stages of a test (for example, c8, cr8, fa, and fb,ofFig. 2).4. Summary of Test Method4.1 This test method is performed on rectangular-shapedblocks of rock that are isolated on all surfaces, exce
11、pt for theshear plane surface.4.2 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
12、 (see 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 can be employed
13、 in stability analysis of rockengineering problems, for example, in studies of slopes,underground openings, and dam foundations. In applying the1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics.C
14、urrent edition approved May 1, 2006. Published June 2006. Originallyapproved in 1985. Last previous edition approved in 2002 as D 4554 02.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume
15、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.test results, the pore water pressure cond
16、itions and the possi-bility of progressive failure must be assessed for the designcase, as they may differ from the test conditions.5.3 Tests on intact rock (free from planes of weakness) areusually accomplished using laboratory triaxial testing. Intactrock can, however, be tested in situ in direct
17、shear if the rockis weak and if the specimen block encapsulation is sufficientlystrong.NOTE 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 Pr
18、actice D 3740 are generally considered capable of competentand objective testing/sampling/inspection/etc. Users of this standard 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 ev
19、aluating some of those factors.6. Apparatus6.1 Equipment for Cutting and Encapsulating the TestBlockThis includes rock saws, drills, hammer and chisels,formwork of appropriate dimensions and rigidity, expandedpolystyrene sheeting or weak filler, and materials for reinforcedconcrete encapsulation.6.2
20、 Equipment for Applying the Normal Load (see Fig.3)This includes flat jacks, hydraulic rams, or dead load ofsufficient capacity to apply the required normal loads.NOTE 2If a dead load is used for normal loading, precautions arerequired to ensure accurate centering and stability. If two or morehydrau
21、lic rams are used for loading, care is needed to ensure that theiroperating characteristics are identically matched and they are in exactparallel alignment.6.2.1 Each ram should be provided with a spherical seat.The travel of rams, and particularly of flat jacks, should besufficient to accommodate t
22、he full anticipated specimen dis-placement. The normal displacement may be estimated fromthe content and thickness of the filling and roughness of theshear surfaces. The upper limits would be the filling thickness.6.2.2 Hydraulic SystemA hydraulic system, if used,should be capable of maintaining a n
23、ormal 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 asimilar low friction device to ensure that at any given normalload, the resistance to shear displacement is less than 1 %
24、ofthe maximum shear force applied in the test. Rock anchors,wire ties, and turnbuckles are usually required to install andsecure the equipment.6.3 Equipment for Applying the Shear Force (see Fig. 3):6.3.1 One or More Hydraulic Rams, of adequate totalcapacity with at least 150-mm travel.6.3.2 Hydraul
25、ic Pump, to pressurize the shear force system.6.3.3 Reaction SystemA reaction system to transmit theshear force to the test block. The shear force should bedistributed uniformly along one face of the specimen. Theresultant line of applied shear forces should pass through thecenter of the base of the
26、 shear plane at an angle approximatelyFIG. 1 Shear Stress Displacement GraphsD 4554 02 (2006)2NOTE 1In this case, intercept cron shear axis is zero.fr= residual friction angle,fa= apparent friction angle below stress sa; point A is a break in the peak shear strength curve resulting from the shearing
27、 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 obtained for smooth surfaces of rock on rock, andi = inclination angle of surface asperities.fb= apparent friction an
28、gle 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 = cohesion intercept of peak shear strength curve; it may be zero.c = apparent cohesion at a stress level corresp
29、onding 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 In Situ Direct Shear TestD 4554 02 (2006)315 to the shear plane with an angular tolerance of6 5. Theexact angl
30、e should be measured to 61.NOTE 3Tests where both shear and normal forces are provided by asingle 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 ForceTh
31、isincludes one system for measuring normal force and anotherfor measuring applied shearing force with an accuracy betterthan 62 % of the maximum forces reached in the test. Loadcells (dynamometers) or flat jack pressure measurements maybe used. Recent calibration data applicable to the range oftesti
32、ng should be appended to the test report. If possible, thegages should be calibrated both before and after testing.6.5 Equipment for Measuring Shear, Normal, and LateralDisplacementDisplacement should be measured (for ex-ample, using micrometer dial gages) at eight locations on thespecimen block or
33、encapsulating material, as shown in Fig. 4(Note 4). The shear displacement measuring system shouldhave a travel of at least 100 mm and an 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 me
34、asuring reference system (beams,anchors, and clamps) should, when assembled, be sufficientlyrigid to meet these requirements. Resetting of gages during thetest should be avoided, if possible.NOTE 4The surface of encapsulating material is usually insufficientlysmooth and flat to provide adequate refe
35、rence for displacement gages;glass plates may be cemented to the specimen block for this purpose.These plates should be of adequate size to accommodate movement of thespecimen. Alternatively, a temperature calibrated tensioned wire andpulley system with gages remote from the specimen may be used. Th
36、esystem, as a whole, must be reliable and must conform with specifiedaccuracy requirements. Particular care is needed in this respect whenemploying electric transducers or automatic recording equipment.7. Procedure7.1 Preparation of Test Specimen:7.1.1 Outline a test block such that the base of the
37、blockcoincides with the plane to be sheared. The direction ofshearing should correspond, if possible, to the direction ofanticipated shearing in the full-scale structure to be analyzedusing the test results. To inhibit relaxation and swelling and toprevent premature sliding, it is necessary to apply
38、 a normalload to the upper face of the test specimen as soon as possibleafter excavation of the opening and prior to sawing the sides.The load, approximately equal to the overburden pressure,may, for example, be provided by screw props or a system ofrock bolts and crossbeams. Maintain the load until
39、 the testequipment is in position. Saw the test block to the requireddimensions (usually 700 by 700 by 350 mm) using methodsthat avoid disturbance or loosening of the block. Saw a channelapproximately 200 mm deep by 80 mm wide around the baseof the block to allow freedom of displacements during test
40、ing.The block and particularly the 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 permissib
41、le, if, for example,the surface 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 dis
42、turbanceduring preparation. Irregularities that would limit the thickness or em-placement of encapsulation material or reinforcement should be removed.7.1.2 Apply a layer of weak material at least 20 mm thick(for example, foamed polystyrene) around the base of the testblock, and then encapsulate the
43、 remainder of the block inconcrete or similar material of sufficient strength and rigidity toprevent collapse or significant distortion during testing. Designthe encapsulation formwork to ensure that the load bearingfaces are flat (tolerance 63 mm) and at the correct inclinationto the shear plane (t
44、olerance 62).7.1.3 Carefully position and align reaction pads, anchors,etc., if required to carry the thrust from normal and shear loadsystems to adjacent sound rock.Allow all concrete time to gainadequate strength prior to testing.7.2 Consolidation of Test Specimen:7.2.1 The consolidation stage of
45、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 7.
46、3.3).7.2.2 Check all displacement gages for rigidity, adequatetravel, and freedom of movement, and record a preliminary setof load and displacement readings.7.2.3 Raise normal load to the full value specified for thetest, recording any consequent normal displacements (consoli-dation) of the test blo
47、ck as a function of time and applied loads(Fig. 5 and Fig. 6).7.2.4 If consolidation occurs, it may be considered completewhen the rate of change in normal displacement recorded ateach of the four gages is less than 0.005 mm/min for at least 10min. Shear loading may then be applied.7.3 Shear Testing
48、:7.3.1 The purpose of shearing is to establish values for thepeak and residual direct shear strengths of the test plane.Corrections to the applied normal load may be required to holdthe normal stress constant (see 8.5). A shear determinationshould preferably be comprised of at least five tests per b
49、lock,tested at different but constant normal stress. If conditionswarrant, test more than one block for each shear plane.NOTE 1Gages S1 and S2 are for shear displacement, L1 and L2 forlateral displacement, N1 through N4 for normal displacement.FIG. 4 Arrangement of Displacement GagesD 4554 02 (2006)47.3.2 Apply the shear force either incrementally or continu-ously.7.3.3 Take approximately 10 sets of readings before reach-ing peak strength (Fig. 1 and Fig. 3). The rate of sheardisplacement should be less than 0.1 mm/min in the 10-minperiod before taking
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