ASTM D4435-2008 Standard Test Method for Rock Bolt Anchor Pull Test《石栓锚定拉力试验的标准试验方法》.pdf

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1、Designation: D 4435 08Standard Test Method forRock Bolt Anchor Pull Test1This standard is issued under the fixed designation D 4435; 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

2、 indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 The objective of this test method is to measure theworking and ultimate capacities of a rock bolt anchor. Thismethod does not measure the entire roof suppo

3、rt system. Thismethod also does not include tests for pretensioned bolts ormine roof support system evaluation.1.2 This test method is applicable to mechanical, cementgrout, resin, (epoxy, polyester, and the like), or other similaranchor systems.1.3 The values stated in inch-pound units are to be re

4、gardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.4 All observed and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D 6026.1.4

5、.1 The method used to specify how data are collected,calculated, or recorded in this standard is not directly related tothe accuracy to which the data can be applied in design or otheruses, or both. How one applies the results obtained using thisstandard is beyond its scope.1.5 This standard does no

6、t 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 limitations prior to use.2. Referenced Documents2.1 ASTM Standard

7、s:2D 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD 4436 Test Method for Rock Bolt Long-Term Load Re-tention TestD 6026 Practice for U

8、sing Significant Digits in Geotechni-cal DataD 6167 Guide for Conducting Borehole Geophysical Log-ging: Mechanical Caliper3. Terminology3.1 See Terminology D 653 for general definitions.3.2 Definitions of Terms Specific to This Standard:3.2.1 displacementThe movement of the rock bolt head.3.2.2 fail

9、urethe inability of the anchor system or rock tosustain increased load without rapidly increasing deformation.In some instances, the peak load itself cannot be sustained.3.2.3 loadthe total axial force on the rock bolt.3.2.4 pressure, stressthe force per unit area.3.2.5 ultimate capacitythe maximum

10、load sustained bythe anchor system.3.2.6 working capacitythe load on the anchor system atwhich significantly increasing displacement begins.4. Summary of Test Method4.1 A rock bolt is installed in the same manner and in thesame material as its intended construction use. The bolt ispulled hydraulical

11、ly and the displacement of the bolt head ismeasured concurrently. The bolt is pulled until the anchorsystem or rock fails. The ultimate and working capacities of thebolt are calculated from the plot of load versus displacement.5. Significance and Use5.1 Rock bolts are used for support in a variety o

12、f miningand civil engineering situations.3The pull test may be used toprovide a quantitative measure of the relative performance ofdifferent anchor systems in the same rock type.Anchor systemsmay be different mechanical anchors or different bond materi-als or lengths for grouted anchors. Such data c

13、an be used tochoose an anchor type and determine bolt length, spacing, andsize.5.2 The objective of the method is to measure anchorperformance, and not the performance of the rock bolt itself.Thus, to ensure that the bolt response during the test is minimaland predictable, high strength, short-lengt

14、h (6 to 8 ft (1.8 to 2.51This 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 edition approved July 1, 2008. Published July 2008. Originally approvedin 1984. Last previous edition approved in

15、 2004 as D 4435 04.2For referenced ASTM standards, visit 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.3For additional information see, “Suggeste

16、d Method for Determining theStrength of a Rock Bolt Anchor (Pull Test),”Suggested Methods for Rock BoltTesting, International Society for Rock Mechanics Commission on Standardizationof Laboratory and Field Tests, 1974.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM

17、International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.m) bolts have been specified. The bolt should be just longenough to ensure that no failure of the rock mass occurs.5.3 Ideally, the rock bolt anchor should fail by shear at theanchor-rock interface or

18、bond. Therefore, the local character-istics of the rock, such as roughness and induced fractures, aresignificant factors in the anchor strength. To obtain realisticstrength values, the test holes should be drilled using the samemethods as the construction rock bolt holes.5.4 Rocks with significant t

19、ime-dependent behavior, such asrock salt or shale, may respond to the anchor system itself andchange the anchor strength. In these cases, considerationshould be given to testing bolts over a period of time.5.5 In establishing a testing program, the following factorsshould be considered:5.5.1 Anchor

20、pull tests should be conducted in all rock typesin which construction bolts will be installed. If the rock isanisotropic, for example, bedded or schistose, the tests shouldbe conducted in various orientations relative to the anisotropy,including those at which the construction bolt may be installed.

21、5.5.2 In each rock type, at each orientation, and for eachanchor system, a sufficient number of tests should be con-ducted to determine the average bolt capacities within a fixeduncertainty at the 95 % confidence level. The allowable uncer-tainty band depends on the project and involves such factors

22、 asthe rock quality, expected project lifetime, and importance ofthe areas to be bolted. Its determination will require consider-able engineering judgment. As a rough guideline, at least 10 to12 pull tests for a single set of variables have been foundnecessary to satisfy the statistical requirements

23、.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 the suitability of theequipment and facilities used. Agencies that meet the criteria of PracticeD 3740 are g

24、enerally considered capable of competent and objectivetesting. Users of this test method are cautioned that compliance withPractice D 3740 does not in itself assure reliable testing. Reliable testingdepends on many factors; Practice D 3740 provides a means of evaluatingsome of those factors.6. Appar

25、atus6.1 Loading SystemThe system for pulling the rock boltsshall consist of a hollow-center hydraulic ram and mounting/reaction frame. The hydraulic ram shall be of sufficientcapacity to fail the anchor and shall have a travel range of atleast 2 in. (50 mm). The mounting/reaction frame shall beusabl

26、e against uneven rock surfaces. The loading system shallapply a force that deviates by no more than 5 from the longaxis of the bolt during the test.6.2 Load TransducerAn electronic load cell is recom-mended to measure the load on the rock bolt. The cell shallhave an accuracy of at least 6200 lbf (68

27、90 N), includingerrors introduced by the excitation and readout system, and aresolution of at least 100 lbf (445 N). Other types of loadtransducers may be used if their performance meets thesespecifications. Alternatively, a pressure gauge or electronictransducer may be used to measure the pressure

28、applied to theram, provided that the load measurement requirements aboveare satisfied, including the effects of friction in the hydraulicram, and the like.6.3 Displacement TransducerA dial gauge is recom-mended to measure the displacement of the rock bolt head. Itshall have an accuracy of at least 6

29、0.001 in. (0.025 mm), aresolution of at least 0.0005 in. (0.013 mm), and a range of atleast 2 in. (50 mm). It shall be mounted along the axis of therock bolt within 5. The end of the rock bolt, or pulling rod ifused, shall be smooth with a counter-sink area approximately14 in. (6 mm) in diameter to

30、accommodate the measuring tip ofthe dial gauge. Other types of displacement transducers may beused provided they satisfy the requirements of this section.6.4 Displacement Transducer SupportThe displacementtransducer shall be supported from a point no closer than 3 ft(0.9 m) to the reaction frame, if

31、 attached to the same rock face.The support shall be sufficiently rigid that no deflection orinstability occurs during testing.6.5 Anchor SystemsThe anchors used for testing shall befrom the manufacturers standard production stock. Mechani-cal anchors shall be inspected to ensure that no defectivean

32、chors are tested. Mechanical anchors should be of correctsize for the hole diameter and the anchorage size should beknown. Grout or resin shall be fresh (within the shelf life) andobtained from unopened containers. If grouted anchors are tobe tested, ensure resin cartridge sizes are compatible with

33、holediameter, rock bolt bar diameter and length of anchoragerequired. For anchorages utilizing injected grout, ensure mix-ing and injection equipment and systems are compatible withmanufacturers recommendations.6.6 Rock Bolt and AccessoriesThe rock bolt shall be ofsufficient diameter and strength th

34、at its elastic range is notexceeded during testing. Standard bearing plates, washers, andthe like may be used as required.6.7 Drilling EquipmentThe same type of drilling equip-ment and drill bits that will be used for installing rock boltsduring the construction phase of the project shall be used as

35、 faras possible to drill the test holes.6.8 Torque WrenchIf expandable shell mechanical an-chors are used, a torque wrench shall be used to set them. Thewrench shall have a capacity at least 20 % greater than themanufacturers recommended anchor-setting torque. Thetorque wrench shall have an accuracy

36、 of at least 62 % of thefull-scale reading, and a resolution of at least 1 % of thefull-scale reading.6.9 Borehole Diameter Measuring GaugeA gauge shallbe used to measure the diameter of the borehole at the anchorlocation. It shall have an accuracy of at least 60.02 in. (0.5mm) and resolution of at

37、least 0.01 in. (0.25 mm)6.10 ThermometerA thermometer shall be used to mea-sure temperature in the borehole, within the anchor zone ifresin or cement grout anchorages are being tested. The tem-perature of the resin or grout shall also be measured at the timeof injection. The thermometer should have

38、an accuracy of atleast + 0.5F (0.28C) and a resolution of at least 1F (0.56C).6.11 Fig. 1 shows a typical test setup.7. Procedure7.1 Drilling the Test Hole:7.1.1 Drill the test hole using the same procedure that willbe used during construction. Wash or blow the borehole cleanof all cuttings.D4435082

39、7.1.2 The hole need not be as deep as the proposed length ofthe rock bolts. It shall, however, be deep enough to set theanchor past the zone of disturbance caused by the excavationand the zone of stress concentration caused by the reaction ofthe pulling frame. For mechanical shell anchors, drill the

40、 hole1 ft (0.3 m) past the end of the anchor. A hole approximately 6ft. (1.8 m) in length has generally been found to be adequate.7.1.3 Inspect the test hole visually using a flashlight ormirror to reflect sunlight down the hole. If more than one halfof the bottom of the hole cannot be seen, the hol

41、e is notsufficiently straight for a pull test and shall not be used.7.1.4 Measure the test hole diameter in two perpendiculardirections at the top and bottom of the anchor location boreholeusing a diameter measuring gauge for a total of four measure-ments.7.2 Preparation of AnchorsIf any anchor prep

42、arations,such as degreasing or rust removal, will be done duringconstruction, prepare the test anchors in the same way. If nospecial preparation will be done during construction, do notprepare the test anchors.7.3 Setting the Anchor:7.3.1 If mechanical anchors are used, lightly lubricate thedownhole

43、 end of the rock bolt and screw on the anchor. Whenin position, torque the bolt to the manufacturers recommendedlevel to set the anchor. A pair of jam-nuts on the upper end ofthe rod may be used to apply torque without producing axialload in the bolt. If the manufacturers torque cannot beachieved be

44、cause of anchor rotational slippage due to shearfailure in the rock, note the maximum torque reading andinstall subsequent anchors to 80 % of this value. Do not testanchors where rotation occurs between the rock surface and theanchor. In all cases, record any slipping or other anomalousbehavior as s

45、hown in Fig. 2.7.3.2 Install cement grout or resin anchors according to themanufacturers recommendations.7.4 Test Method:7.4.1 All tests are performed on untensioned bolts. Recordthe temperature in the borehole within the anchor zone; thetemperature of the resin or grout at the time of injection and

46、 theambient air temperature. Ideally the test anchorages should beinstalled under the same temperature conditions as expectedduring construction. The time required for resin or groutanchorages to reach their design strengths is temperaturedependent and may vary significantly. Consult the resin orgro

47、ut manufacturers literature for recommended curing timesunder various temperature conditions. Curing times may bevaried between 1 to 5 days under similar temperature condi-tions to assess the effects of curing time on strength. Toevaluate the influence of grouted bond length on anchorstrength, sever

48、al anchorage lengths should be tested, ideallyunder similar temperature conditions and curing times.7.4.2 On at least half of the tests, perform three loading andunloading cycles to check for pre-failure anchor movements.Apply the load with the hydraulic ram in cycles to14,12, and34 of the estimated

49、 failure load. Load the bolt in ten equalincrements and unload it in ten equal decrements.7.4.3 Apply the load smoothly and rapidly.7.4.4 After the third cycle, pull the bolt in the sameincrements as used during the last cycle or in 500 lbf (2.2 kN)increments, whichever is less, until the anchor system fails orthe limit of the loading system is reached.7.4.5 Test non-cycled bolts to failure in 20 equal loadincrements or increments of 500 lbf (2.2 kN), whichever isless.7.4.6 Read and record displacement and load after eachpressure increment or decre